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Response Analysis of the

Deepwater Steel Lazy-Wave Riser for the

Turret Moored Floating Production Storage Off-loading System

By

Shangzhan Li

Bachelor of Engineering

College of Shipbuilding Engineering

Harbin Engineering University

Harbin, China

2011

A thesis submitted to Florida Institute of Technology

In partial fulfillment of the requirements

For the degree of

Master of Science

In

Ocean Engineering

Melbourne, Florida

December, 2014

We the undersigned committee hereby recommend that the attached document be

accepted as fulfilling in part of the requirements of the degree of

Master of Ocean Engineering.

“Response Analysis of the Deepwater Steel Lazy-Wave Riser for the Turret Moored

Floating Production Storage Off-Loading System,”

a thesis by Shangzhan Li

________________________________________

Dr. Stephen Wood

Professor and Ocean Engineering Program Chair, Marine and Environmental Systems

_________________________________________

Dr. Ronnal Reichard

Professor, Marine Environmental Systems

_______________________________________

Dr. Shengyuan Yang

Assistant Professor, Mechanical Aerospace Eng.

iii

Abstract

Response Analysis of the

Deepwater Steel Lazy-Wave Riser for the

Turret Moored Floating Production Storage Off-loading System

By

Shangzhan Li

Major Advisor: Stephen Wood, Ph.D., P.E.

With the continuous increase of exploration and development in deepwater (over 2,000

feet) and ultra-deepwater (over 5,000 feet) fields, technical challenges have arisen.

The environmental conditions in the Gulf of Mexico (GoM) make the development of

a traditional operation unit of a Floating Production Storage Off-loading (FPSO)

system with a simple Steel Catenary Riser (SCR) challenging. For example, the

pipeline would buckle at the touchdown zone due to the vessel motion caused by the

waves and the current. In recent years, the Steel Lazy-Wave Riser (SLWR) has been a

popular solution for deepwater operations, as it can improve the riser system’s fatigue

and strength response performance. In this paper, the feasibility, of developing a turret

moored FPSO-SLWR operation unit in the GoM, is investigated. The production risers

in the lazy-wave configuration are designed and analyzed in contrast with the simple

SCR design. Both designs are based on the same criteria and the same environmental

conditions. Using the Finite Element Analysis (FEA) software, Orcaflex, strength

iv

analysis, including static and dynamic analysis, for both in-place condition and

disconnection condition, is performed to simulate the response of the riser system to

different load cases. The robustness of the riser system is also demonstrated through

the sensitivity study. In addition, buoyancy module properties, which affect the global

performance of the riser system, are discussed and compared. The partial optimization

of the buoyancy module arrangement is also accomplished. The results of this study

indicate developing an FPSO-SLWR operation unit as feasible.

v

Table of Contents

Abstract ........................................................................................................................ iii

Table of Contents ...........................................................................................................v

List of Figures ............................................................................................................. vii

List of Tables .............................................................................................................. viii

Chapter 1 ........................................................................................................................1

INTRODUCTION .........................................................................................................1

1.1 Literature Review ......................................................................................................... 2

1.1.1 Riser ..................................................................................................................... 2

1.1.2 FPSO – Floating Production Storage Offloading ................................................. 2

1.1.3 SCR and Lazy-Wave SCR ................................................................................... 3

1.2 Statement of Problem ................................................................................................... 6

Chapter 2 ........................................................................................................................8

DESIGN BASIS AND ANALYSIS THEORY ..............................................................8

2.1 Design Basis ................................................................................................................. 8

2.1.1 General ................................................................................................................. 8

2.1.2 Riser System ........................................................................................................ 9

2.1.3 FPSO Vessel Data ..............................................................................................14

2.1.4 Internal Fluid Data, Design Pressure, and Temperature .....................................22

2.1.5 Environmental Data ...........................................................................................23

2.1.6 Hydrodynamic Coefficients ...............................................................................26

2.2 Analysis Software....................................................................................................... 28

2.3 Analysis Theory ......................................................................................................... 29

2.3.1 General ...............................................................................................................29

2.3.2 Load Case Matrix ...............................................................................................30

2.3.3 Analysis Methodology .......................................................................................33

2.3.4 Design Requirement and Acceptance Criteria ...................................................44

Chapter 3 ......................................................................................................................46

RISER DESIGN AND ANALYSIS .............................................................................46

3.1 Steel Catenary Riser Approach ................................................................................... 46

3.2 Lazy-Wave Steel Catenary Riser Approach ............................................................... 49

3.3 BM Analysis and Optimization .................................................................................. 52

3.4 SLWR Sensitivity Analysis ........................................................................................ 54

3.5 SLWR Disconnection Analysis .................................................................................. 55

vi

Chapter 4 ......................................................................................................................56

RESULTS AND DISCUSSIONS ................................................................................56

4.1 SCR Approach ............................................................................................................ 56

4.1.1 SCR configuration .............................................................................................56

4.1.2 SCR Strength Analysis .......................................................................................57

4.2 Lazy-Wave SCR Approach ......................................................................................... 62

4.2.1 SLWR Configuration .........................................................................................62

4.2.2 SLWR Strength Analysis....................................................................................63

4.2.3 SLWR Regular Wave Directional Analysis ........................................................70

4.3 Comparison of Two Design Approaches: SCR vs. SLWR ......................................... 79

4.4 BM Optimization ........................................................................................................ 81

4.5 Sensitivity Analysis .................................................................................................... 84

4.6 Disconnection Strength Analysis ................................................................................ 87

Chapter 5 ......................................................................................................................90

CONCLUSIONS AND RECONMMENDATIONS ....................................................90

5.1 Conclusions ................................................................................................................ 90

5.2 Recommendations ...................................................................................................... 93

REFERENCES ............................................................................................................94

APPENDIX A ..............................................................................................................96

vii

List of Figures

Figure 1.1.1 Free Hanging SCRs with and without intermediate buoys ....................... 4

Figure 1.1.2 Example configuration of Lazy-Wave Catenary Riser .............................. 6

Figure 2.1.1 Mooring System Layout .......................................................................... 15

Figure 2.1.2 Mooring System Configuration ............................................................... 16

Figure 2.1.3 STP Turret Buoy Geometry ..................................................................... 17

Figure 2.1.4 FPSO Coordinate System ........................................................................ 18

Figure 2.1.5 Wave Heading Convention ...................................................................... 19

Figure 2.3.1 FPSO Offset consideration ...................................................................... 31

Figure 2.3.2 Finite Element Model of a Line in Orcaflex ........................................... 35

Figure 2.3.3 Detailed Structure Model of Line in Orcaflex ......................................... 37

Figure 2.3.4 Frame of Reference for Stress Calculation in Orcaflex........................... 42

Figure 3.2.1 Snapshot of SLWR Orcaflex Model ........................................................ 51

Figure 3.5.1 Snapshot of SLWR Orcaflex Model in Disconnection Condition ........... 55

viii

List of Tables

Table 2.1.1 Thermal Performance Requirement ............................................................ 9

Table 2.1.2 Elevation of Riser Hang-off Location at FPSO .......................................... 9

Table 2.1.3 Riser Hang-off Arrangement ..................................................................... 10

Table 2.1.4 Flex Joint Rotational Stiffness .................................................................. 11

Table 2.1.5 Riser Line Pipe Material Properties .......................................................... 12

Table 2.1.6 Thermal Insulation Coating Properties ..................................................... 12

Table 2.1.7 VIV Strake Properties ............................................................................... 13

Table 2.1.8 Standard Rigid Joints Tolerances .............................................................. 14

Table 2.1.9 Main Particulars of the FPSO ................................................................... 14

Table 2.1.10 Segments Properties of Mooring System ................................................ 16

Table 2.1.11 FPSO Extreme Offset Data ..................................................................... 21

Table 2.1.12 Internal Fluid Properties and Design Pressures ...................................... 22

Table 2.1.13 Vertical Profile of Sea Water Temperature .............................................. 23

Table 2.1.14 Extreme Wave Data - Hurricane ............................................................. 24

Table 2.1.15 Extreme Wave Data - Winter Storm ........................................................ 24

Table 2.1.16 Extreme Loop Current Profiles ............................................................... 25

Table 2.1.17 Soil Friction Coefficients ........................................................................ 25

Table 2.1.18 Hydrodynamic Coefficients of Riser Pipe .............................................. 26

Table 2.1.19 Normal Drag Coefficients of Flexible Pipe ............................................ 27

Table 2.3.1 Load Case Matrix for the Production SLWR ............................................ 32

Table 2.3.2 Design Codes for Wall Thickness Sizing .................................................. 44

Table 2.3.3 Allowable Riser Stress Level .................................................................... 45

Table 2.3.4 Design Case Factor ................................................................................... 45

Table 3.3.1 Load Case Matrix for BM Arrangement Analysis .................................... 53

Table 4.1.1 Global Configuration for SCR .................................................................. 56

Table 4.1.2 Production SCR Nominal Static Analysis Results .................................... 58

ix

Table 4.1.3 Load Case Matrix for SCR Configuration Approach ................................ 58

Table 4.1.4 Riser Top Angular Response for simple SCR ........................................... 59

Table 4.1.5 Production SCR Combined Stress Results ................................................ 59

Table 4.1.6 Production SCR Stress Utilization Factors ............................................... 60

Table 4.1.7 Production SCR Effective Tensions and Bending Moments .................... 61

Table 4.2.1 Global Configuration of the designed SLWR ........................................... 62

Table 4.2.2 FPSO Vessel Offset for Different Load Case in Analysis ......................... 64

Table 4.2.3 Summary Results of Production Lazy-Wave SCR Nominal Static Analysis

...................................................................................................................................... 64

Table 4.2.4 Summary of SLWR Top Angular Response Results ................................. 65

Table 4.2.5 Summary of SLWR Stress Results – Riser Top ........................................ 66

Table 4.2.6 Summary of SLWR Stress Results – Arch Bend ...................................... 67

Table 4.2.7 Summary of SLWR Stress Results – TDP Area ........................................ 67

Table 4.2.8 Summary of Maximum SLWR Stress Utilization Factors ........................ 68

Table 4.2.9 Summary of SLWR Maximum Tension Results ....................................... 69

Table 4.2.10 Summary of SLWR Minimum Tension Results ...................................... 69

Table 4.2.11 Summary of SLWR Maximum Bending Moment Results ...................... 70

Table 4.2.12 Directional Riser Top Angular Response for Production SLWR ............ 71

Table 4.2.13 Directional Combined Stress Results of the SLWR– Riser Top ............. 72

Table 4.2.14 Directional Combined Stress Results of the SLWR– Arch Bend ........... 73

Table 4.2.15 Directional Combined Stress Results of the SLWR – TDP Area ............ 74

Table 4.2.16 Directional Stress Utilization Factors of the SLWR ............................... 75

Table 4.2.17 Directional Results of the SLWR – Maximum Tension .......................... 76

Table 4.2.18 Directional Results of the SLWR – Minimum Tension .......................... 77

Table 4.2.19 Directional Results of the SLWR – Maximum Bending Moment .......... 78

Table 4.3.1 Comparison Results of Riser Top Angular Responses .............................. 79

Table 4.3.2 Comparison Results of Von Mises Stress .................................................. 79

Table 4.3.3 Comparison Results of API Stress Utilization Factors ............................. 80

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Table 4.3.4 Comparison Results of Effective Tensions ............................................... 80

Table 4.3.5 Comparison Results of Bending Moments ............................................... 80

Table 4.4.1 BM Optimization Analysis Results – Effective Tension ........................... 81

Table 4.4.2 BM Optimization Analysis Results - Bending Moment ........................... 82

Table 4.4.3 BM Optimization Analysis Results - Von Mises Stress ............................ 82

Table 4.4.4 BM Optimization Analysis Results - Stress Utilization Factors ............... 83

Table 4.5.1 Sensitivity Analysis Results – Von Mises Stress ....................................... 84

Table 4.5.2 Sensitivity Analysis Results - API Stress Utilization Factors ................... 85

Table 4.5.3 Sensitivity Analysis Results - Effective Tensions ..................................... 86

Table 4.5.4 Contrast Results for Sensitivity Analysis .................................................. 86

Table 4.6.1 Disconnection Analysis Results of the SLWR - Stresses and Stress

Utilization Factors ........................................................................................................ 88

Table 4.6.2 Disconnection Analysis Results of the SLWR – Effective Tensions ........ 89

1

Chapter 1

Introduction

The environmental conditions in the Gulf of Mexico (GoM), such as seasonal

hurricanes and strong loop currents, make it very challenging to develop an operation

unit consisting of a Floating Production Storage Off-loading (FPSO) system with

simple Steel Catenary Risers (SCR). The weather-induced vessel motions can easily

cause the riser pipe to buckle at the touchdown area. In recent years, Steel Lazy-Wave

Risers (SLWR) have been considered as a popular solution to de-couple the vessel

motions with the riser responses at the touchdown area. However, it is not a

traditional option for offshore production facilities to develop turret moored FPSO

with SLWR in the GoM. An investigation is required to determine the feasibility of

developing an FPSO with SLWRs.

In this paper, the feasibility of developing an FPSO-SLWR in the GoM is investigated

and established. In order to obtain the riser response results, the static and dynamic

analysis is conducted for the specific design conditions, based on a water depth of

7000 ft. These results draw the basis for the riser performance analysis. The Buoyancy

Modules (BM) are attached onto a section of the riser pipe to provide lifting force for

the SLWR. The global performance of the SLWR is improved by optimizing the BM’s

arrangement. The riser responses, based on different BM material properties, total

attaching lengths, and buoyancy force ratios, are obtained and analyzed to achieve the

2

SLWR global configuration optimization. Additionally, the alternative SCR

configuration option is discussed as a comparison case. The SLWR responses, when

disconnected from the FPSO, are also investigated. Lastly, a sensitivity analysis is

conducted to check the robustness of the system.

1.1 Literature Review

1.1.1 Riser

A riser is a unique common element to many floating offshore structures. Risers

connect the floating drilling/production facility with subsea wells and are critical to

safe field operations. They are used to contain fluids for well control (drilling risers)

and to convey hydrocarbons from the seabed to the platform (production risers). Riser

systems are a key component for offshore drilling and floating production operations.

However, for deepwater operation facility development, riser design is one of the

biggest challenges [1].

1.1.2 FPSO – Floating Production Storage Offloading

Generally, the FPSOs are ship-shaped floaters with provisions for storing and

offloading oil simultaneously. Nowadays, FPSOs are the most prolific floating

production platforms, especially for fields in harsh environments and far away from

existing pipeline infrastructures [2]. The early FPSOs with the spread mooring

systems were developed in the 1970s to support the production in the smaller, remote

fields, where fixed structures would not be economical. They were restricted to mild

3

environments until the turret mooring system was introduced. This made it possible

for the FPSOs to operate in more severe environmental conditions [1].

One of the most important factors governing riser design is the vessel motion,

especially the heave motion, at the riser hang-off location. The vessel motion is a

combination resulting from environmental conditions and vessel responses to the

weather [3]. FPSO, a type of vessel with more dynamic motions, is typically used in

relatively less severe environmental conditions, such as in West Africa [3]. For this

study, the limited weather-vanning capacity of the vessel, provided by the turret

mooring system, makes it possible to adopt the FPSO in the GoM [1]. In addition, the

turret mooring system could allow the vessel to become disconnected from the SLWR;

thus, the FPSO does not have to be designed to accommodate the most critical

wave/current motions associated with hurricane and typhoon conditions [2].

The trend of using FPSOs for exploration and production in deepwater fields brought

to light the requirement for studying this type of offshore system [4], especially for

the fields in the GoM.

1.1.3 SCR and Lazy-Wave SCR

A simple steel catenary riser (SCR) is considered a cord of uniform density and

cross-section area hanging on two ends under gravity and buoyancy force in water

[10]. A typical SCR is characterized by downward wet weight along its length.

4

SCR has a free-hanging configuration with no intermediate BMs or floating devices,

as shown in Figure 1.1.1. It is now one of the most cost-effective alternatives for oil

and gas production and export in deepwater fields, where the large diameter, flexible

risers present technical and economic limitations [1]. SCRs are designed by referring

to the analytical results in accordance with the American Petroleum Institute (API)

codes, which includes API RP 1111 (2009) [5] and API RP 2RD (2006) [6], or the

DNV codes (DNV-OS-F101 [7] and DNV-OS-F201 [8]). In recent years, SCR has

been the preferred riser solution for deepwater floating production facilities in the

GoM [2].

Figure 1.1.1 Free Hanging SCRs with and without intermediate buoys [1]

However, there are some very critical design issues with the simple SCR application

5

in deepwater fields: the compression of the riser at the touchdown area; and, over

payload at the vessel’s riser hang-off location. SCR is very sensitive to vessel heave

motion, which may lead to the infeasibility of its application with FPSO in severe

environmental conditions [2]. One of the options to mitigate the compression at the

SCR touchdown area is to adopt a lazy-wave configuration of the riser by attaching a

set of buoyancy modules on a section of the riser pipe. SLWR has been considered to

mitigate the compression at the riser touchdown area due to the flexibility of

lazy-wave configuration [2]. So far, no such type of offshore production facility has

been developed in the GoM.

As shown in Figure 1.1.2, SLWR is similar to the traditional SCR with simple

catenary configuration, but with a section of riser pipe suspended. The suspended riser

section is attached with a set of BMs that can provide a certain amount of lifting force.

This provides a compliant arch bend at a specific water depth above the seabed [1].

A typical SLWR consists of three sections, which include hang-off catenary, the

buoyancy catenary, and the touchdown catenary [13], as illustrated in Figure 1.1.2.

The buoyancy catenary lies between the hang-off catenary and the touchdown

catenary. The buoyancy force provided by the BMs is around twice the submerged

weight of the flooded steel pipe with BMs attached [13].

6

Figure 1.1.2 Example configuration of Lazy-Wave Catenary Riser [4]

1.2 Statement of Problem

Based on the functional requirements of the riser, the design criteria and the design

data (including the data of the riser system, the environmental conditions, and the

FPSO vessel), the proposed study scope includes:

1. Riser Concept Selection

2. Riser Configuration Design

3. Strength Analysis:

i. Static Analysis

ii. Dynamic Analysis

7

4. API RP 2RD [6] code check

5. BM Optimization Analysis

6. Sensitivity Study

7. Disconnection Analysis

The optimization for the BMs is conducted according to the results of the above

analysis. It takes several variables into account:

1. Material properties of the buoyancy modules

2. Buoyancy force ratio vs. submerged weight of the riser pipe with buoyancy

modules attached

3. Total length of the riser pipe with BMs attached

4. Position along the riser pipe where the BMs are attached

In order to obtain the global response of the SLWR, the equivalent continuous model

of the riser pipe section with BMs attached is developed for analysis, which is more

conservative than the discontinuous model with single BMs attached in designated

positions on the riser pipe. However, for a detailed future design, the discontinuous

model is more suitable, because the local performance (such as the stress

concentration of the riser pipe with BMs attached) needs to be analyzed thoroughly

not only conservatively.

8

Chapter 2

Design Basis and Analysis Theory

2.1 Design Basis

In this section, the assumed environmental information and the FPSO data are

presented in detail. In addition, the design criteria and functional requirements, as

specified in API RP 2RD [6] are specified as well.

2.1.1 General

The assumed general design data for the production riser, including the water depth,

the riser design life, and the thermal performance requirements, are defined in the

following section.

Water Depth

In this study, the selected water depth is 7,000 ft.

Design Life

The design life for the production riser system is 25 years.

Thermal Performance Requirement

The production riser requires thermal insulation with the following assumed

requirements:

9

Table 2.1.1 Thermal Performance Requirement [11]

2.1.2 Riser System

This section presents a set of consistent data for developing the FPSO-SLWR system

used in this study, including riser pipe properties, FPSO and environmental data.

Riser Hang-Off System Data

The flexible jumpers are attached to the submerged turret located within the FPSO.

The elevation of the hang-off location is given in Table 2.1.2 for both the normal

operating and disconnection conditions.

Table 2.1.2 Elevation of Riser Hang-off Location at FPSO [11]

The assumed hang-off angles and azimuth angles of all export and production risers

are detailed in Table 2.1.3.

U-value (Inner Diameter based) 0.9 BTU/ft2/hr/°F

Cool down time 12 hrs from 100°F to 63°F

Buoy Condition Depth from MWL (ft)

Operating 69.3

Disconnected 232.9

10

Table 2.1.3 Riser Hang-off Arrangement [11]

Riser Description Exit Angle (deg) Azimuth Angle (deg)

1 Export 1 8 81.5

2 Production Riser 1 8 177.5




11

SCR Flex Joint Data

For this concept design, it is assumed that the flex joint will be used to terminate the

production SLWR at the top. The Table 2.1.4 presents the assumed rotational stiffness

of the flex joint.

Table 2.1.4 Flex Joint Rotational Stiffness [11]

Alternating Angle

degree

Max Design Rotational

Stiffness

ft-kips/deg

Max Design Rotational

Moment

ft-kips

0 0 0

0.01 93.33 0.93

0.02 76.28 1.70

0.03 67.79 2.37

0.04 62.35 3.00

0.05 58.43 3.58

0.06 55.41 4.14

0.07 52.98 4.67

0.08 50.96 5.18

0.09 49.24 5.67

0.1 47.76 6.15

0.2 39.03 10.05

0.3 34.69 13.52

0.4 31.90 16.71

0.5 29.90 19.70

0.6 28.35 22.53

0.7 27.11 25.24

0.8 26.08 27.85

0.9 25.20 30.37

1 24.44 32.82

1.5 21.72 43.67

2 19.97 53.66

3 17.75 71.41

4 16.33 87.74

6 14.51 116.75

8 13.34 143.44

10 12.50 168.45

12 11.86 192.16

14 11.34 214.84

17 10.72 246.98

20 10.22 277.64

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Rigid Riser Line Pipe Data

The API 5L X-70 [12] steel grade has been selected for the production Lazy-Wave

SCR. The properties of the standard rigid riser line pipe material are detailed in Table

2.1.5.

Table 2.1.5 Riser Line Pipe Material Properties [12]

Parameter Unit Production

Material Grade API 5L X-70

Material Yield Stress ksi 70

Ultimate Tensile Strength ksi 82

Young Modulus ksi 3.0E+04

Poisson Ratio -- 0.3

Steel Density lb/ft3 490

SCR Pipe Coating Data

1. Thermal Insulation Coating

The production riser insulation coating properties are assumed to be 5-layer PP. The

properties are listed in Table 2.1.6 below. The total thickness of the insulation coating

is 0.024 ft.

Table 2.1.6 Thermal Insulation Coating Properties [11]

Layer No. Parameter Density (pcf)

1 FBE 85.5

2 PP adhesive 55.6

3 PP solid 55.6

4 PP syntactic 40.0

5 PP solid 55.6

48.0Average Total

13

2. Corrosion Coating

The riser is protected by a cathode protection system in combination with a Fusion

Bonded Epoxy (FBE) coating system. For the SLWR in this study, it is assumed the

FBE is included in the insulation.

VIV Strake Data

Anti-VIV strakes are mounted on the rigid riser section. The assumed strakes

properties used in the analysis are shown below.

Table 2.1.7 VIV Strake Properties [11]

Description Unit Production Riser

Strake ID inch 11.54

Strake OD inch 12.54

Fin Height - 0.15D

Fin Period - 15D

Strake Part length inch 65.35

Weight in Air per part lbs 28

Weight in Seawater per part lbs -2.36

SCR Pipe Tolerance

The maximum and minimum weight tolerances for standard rigid riser joints [11] are

provided as in Table 2.1.8:

14

Table 2.1.8 Standard Rigid Joints Tolerances

Corrosion Allowance

The corrosion allowance of 3.0 mm is used for the riser pipe design.

2.1.3 FPSO Vessel Data

The FPSO data used in this riser study is based on assumptions of a typical FPSO in

the GoM.

FPSO Main Particulars

Main particulars of the FPSO are given in Table 2.1.9. Three vessel load conditions

are considered, i.e., ballast, intermediate, and fully loaded condition.

Table 2.1.9 Main Particulars of the FPSO

Wall Thickness Tolerance -8% / +12.5%

Weight Tolerance -5% / +6.5%

Description Unit Ballast Interm. Full

Overall Length ft

Length between Perpendiculars ft

Breadth Moulded ft

Depth ft

Draught, AP ft 22 36 46

Draught at Midship ft 19 32 45

Draught, FP ft 16 28 44

Vertical COG above baseline (free

surface included)ft 44 39 43

795

760

140

67

15

Submerged Turret Production System

As assumed, the turret location fore of midship is 295.3 ft. The cylindrical turret

extended below the vessel baseline has a height of 32.8 ft. and 44.3 ft. in diameter.

Mooring System

The mooring system is a 4+4+3 leg system comprised of chain segments, polyester

segments, wire rope segments, and a mooring line buoyancy element. Mooring line

directions are shown in Figure 2.1.1. The mooring line configuration is shown in

Figure 2.1.2. The properties of the individual segments of the mooring system are

provided in Table 2.1.10.

Figure 2.1.1 Mooring System Layout [11]

16

Figure 2.1.2 Mooring System Configuration [11]

Table 2.1.10 Segments Properties of Mooring System [11]

1 Studless Chain (R3S) 820 3.5 160963 0.9

2 Link 3 - - 7.5

3 Polyester Rope 8038 6.5 Nonlinear 0

4 Link 3 - - 7.5

5 Spiral Strand Wire Rope 1476 3.1 137133 0.2

6 Mooring Line Buoyancy Element 16 - - -60.5


8 Link 3 - - 9.6


10 Link 3 - - 9.6

11 Polyester Rope 33 6.5 Nonlinear 0

12 Link 3 - - 9.6


14 Link 3 - - 9.6


16 Link 3 - - 11.6

Segment

NumberSegment Type

Size

Diameter

[inch]

Axial

Stiffness

[kips]

Building

Length

[ft]

Equivalent

Submerged

Weight

(kips/ft)

17

STP Turret Buoy System

The geometry of the STP buoyancy, the jumper guide tubes, the umbilical guides, and

buoyancy element characteristics are shown in Figure 2.1.3.

Figure 2.1.3 STP Turret Buoy Geometry [11]

First Order Motion Transfer Function

1. Coordinate System

The coordinate system has the origin placed in the waterline level at midship. For

the right–handed system, the x–axis points forward towards the bow, the y–axis points

towards portside and the z–axis points upwards. Vessel axes relative to the global axis

are defined in Figure 2.1.4 [11].

18

Figure 2.1.4 FPSO Coordinate System [11]

2. Wave Directions

The heading convention is as follows, as shown in Figure 2.1.5:

Following Sea: 0° direction of the waves is defined as waves propagating along the

positive x–axis

Beam Sea: 90° direction of the waves is defined as waves propagating along the

positive y–axis

19

Head Sea: 180° direction of the waves is defined as waves propagating along the

negative x–axis

Figure 2.1.5 Wave Heading Convention [11]

3. RAO Definition

The RAOs refer to the origin of the coordinate system.

The wave is defined as

𝜁 = 𝐴 cos[𝜔𝑡 − 𝑘𝑥 cos(𝛽) − 𝑘𝑦 sin(𝛽)]

Where

A = wave amplitude

ω= wave frequency (rad/s)

20

t = time (s)

k = wave number

β= wave direction

x = position in x–direction

y = position in y–direction

The response X is defined as

𝑋 = 𝐴 × 𝑅𝐴𝑂 × cos(𝜔𝑡 + 𝜑)

Where

X = response

RAO = response amplitude operator

𝜑 = phase angle of response

Units are ft./ft. and rad./ft. for translational and rotational RAOs, respectively.

FPSO Vessel Offset

The maximum vessel offsets analysis for collinear wind and current loading are given

in Table 2.1.11.

21

Table 2.1.11 FPSO Extreme Offset Data [11]

The FPSO mooring system is required to be designed such that the turret offset shall

not exceed 6% of water depth for the intact mooring case and 8% of water depth for

the one-broken-mooring-line case. These requirements apply to both the 100-year

winter storm and the 1000-year loop current conditions. The actual offsets may be less.

However, this is depending on the mooring system design, asymmetry of the mooring

system, and the directionality of the environment.

1. Assuming a minimum offset of 1.5% of water depth and a maximum offset of 6%

of water depth for the intact mooring case for the 100-year winter storm and

1000-year loop current conditions, independent of the environment direction (i.e.,

assume that the FPSO offset magnitude is omni-directional).

2. Assuming a minimum offset of 2.0% of water depth and a maximum offset of 8%

of water depth for the one-broken-mooring-line case for the 100-year winter storm

and 1000-year loop current conditions, independent of the environment direction.

3. For less severe environmental conditions, deriving the minimum and maximum

offsets by linear interpolation.

Mooring Condition Percentage of Water Depth (%)

Intact 1.5 ~ 6

One Line Broken 2 ~ 8

22

Where the primary surface environment is wind driven, linear interpolation of FPSO

offset should be based on wind speed. Where the primary surface environment is

loop current, linear interpolation should be based on surface current speed. See the

examples below. Since the offsets are at this time assumed to be omnidirectional,

the interpolation should be calculated using the omnidirectional wind speed (or

current speed, as applicable). Analysis should be performed for both the minimum and

maximum FPSO offsets, if it is not clear which extreme will govern the design.

2.1.4 Internal Fluid Data, Design Pressure, and Temperature

As assumed, internal fluid density, pressure and temperature data for the SLWR are

presented in Table 2.1.12.

Table 2.1.12 Internal Fluid Properties and Design Pressures [11]

Component Unit Production

Max. Allowable Operating Pressure psi 10,000

Hydro-Test Pressure psi 20,000

Shut-In / Design Pressure psi 16,000

Location of pressure definition ft below MWL surface

Design Temperature, Maximum °F 230

Design Temperature, Minimum °F 35

Fluid density (lb/ft3, kg/m

3) pcf 55

23

2.1.5 Environmental Data

Seawater Data

1. Seawater Temperature

The seawater temperature profiles for the SLWR design are assumed as shown in the

following table. The extreme low temperature, annual average temperature, and

extreme high temperature are detailed.

Table 2.1.13 Vertical Profile of Sea Water Temperature [11]

2. Seawater Density

Seawater density is taken as 64 𝑙𝑏 𝑓𝑡3⁄ .

Seawater Kinematic Viscosity

The value of the kinematic viscosity is used to determine the value of the Reynolds

number and the corresponding hydrodynamic drag coefficients.

: 1.4 × 10−5 𝑓𝑡2 𝑠⁄

Marine Growth

Marine growth of 1.5 inches from the mean sea level to 150 ft water depth is

Extreme Low Annual Average Extreme High

Surface, 3 below MSL 48 76 88

-656 45 63 74

-1640 41 48 55

-3281 39 41 43

-7200 = seabed 37 40 41

Depth (ft)Temperature (°F)

24

considered. The densities of marine growth in air and in water are assumed to be

95.76 𝑙𝑏 𝑓𝑡3⁄ and 74.91 𝑙𝑏 𝑓𝑡3⁄ , respectively.

Wave Data

1. Extreme Wave Data

The assumed extreme wave data is given in Table 2.1.14 and Table 2.1.15.

Table 2.1.14 Extreme Wave Data - Hurricane [11]

Table 2.1.15 Extreme Wave Data - Winter Storm [11]

1 Year 10 Year 100 Year 1000 Year

m/s 10.4 20.2 31.2 46.4

Hs m 2.9 7 11.2 17.5

Tp s 9 11.9 13.7 15.8

Hmax m 5.5 11.3 21.3 33.3

Tmax s 8.3 10.9 12.6 14.5

Surface m/s 0.42 1.28 0.63 2.14

30m depth m/s 0.28 0.99 2.14 1.59

40m depth m/s 0.05 0.05 1.7 0.05

bottom m/s 0.05 0.05 0.05 0.05

Current Profile Should be Taken as Linear between Depths

Associated Wave

Conditions

Associated Current

Speed

Associated Wind Speed

1 Year 5 Year 10 Year 100 Year

m/s 17.3 22.2 23.7 28.3

Hs m 3.8 5.9 6.6 8.7

Tp s 9 10.4 10.8 11.9

Hmax m 7.2 11.2 12.5 16.5

Tmax s 8.3 9.6 9.9 10.9

Surface m/s 0.52 0.67 0.71 0.85

75m depth m/s 0.05 0.05 0.05 0.05

bottom m/s 0.05 0.05 0.05 0.05

Associated Current

Speed


Associated Wave

Conditions

Associated Wind Speed

25

Current Data

Extreme Currents:

Extreme current data is given in Table 2.1.16. Current profiles associated with 1-year,

10-year, and 100-year return periods are considered.

Table 2.1.16 Extreme Loop Current Profiles [11]

Soil Data

The friction coefficients, shown in Table 2.1.17, are used for the riser design and

analysis in this study.

Table 2.1.17 Soil Friction Coefficients [11]

Detailed analysis on soil stiffness is not planned for this study. Instead, a simplified

equation is used to estimate the soil stiffness K.

1 Year 10 Year 100 Year

m/s m/s m/s

Surface 1.1 1.7 2.1

50m depth 1.1 1.7 2.1

150m depth 0.7 1.1 1.4

300m depth 0.4 0.6 0.7

600m depth 0.2 0.3 0.4

800m depth 0.1 0.1 0.1

Bottom 0.1 0.1 0.1


Friction Coefficient Value

Longitudinal 0.3

Transverse 0.5

26

𝐾 = 40𝑁𝑐𝑆𝑢 (1)

In the equation (1) Su is the undrained shear strength of the soil and Nc is the

non-dimensional shape and depth factor. Since Nc is less than 7.5,

𝐾 ≤ 300𝑆𝑢 (2)

Using the undisturbed, undrained shear strengths at 0.25D below the mud line, the

vertical soil stiffness for the production riser is 10500 lb/ft/ft.

2.1.6 Hydrodynamic Coefficients

The riser system drag coefficients values selected, depend upon the Reynolds number

and the presence of vortex induced vibrations (VIV). Where unsuppressed VIV is

predicted to occur, the drag coefficients are modified accordingly.

For a stationary smooth circular cylinder, the drag coefficient is selected depending

upon the mean Reynolds number (Re) as defined in API RP 2RD [6], and shown in

Table 2.1.18.

Table 2.1.18 Hydrodynamic Coefficients of Riser Pipe [11]

Drag Coefficient Added Mass Coefficient

API RP 2RD

(Appendix C)1

1.4 1

Bare pipe

(depending on roughness)

Bare pipe

(VIV is anticipated)

27

The drag and added mass coefficients of the riser pipe are presented in the Table

2.1.19 [11]. Axial drag coefficient is set to zero.

Table 2.1.19 Normal Drag Coefficients of Flexible Pipe [11]

Reynolds Drag Coefficient

1000 1

10,000 1.2

200,000 1.2

300,000 0.6

1,000,000 0.6

4,000,000 0.8

100,000,000 0.8

Added mass coefficient Ca = 1, Where Cm = Ca + 1

28

2.2 Analysis Software

Orcaflex is utilized to accomplish all the configuration design, strength analysis,

sensitivity analysis, and buoyancy module optimization analysis of the SCR and

Lazy-Wave SCR.

Orcaflex is a marine dynamic program developed by Orcina for static and dynamic

analysis on a wide range of offshore systems, including all types of marine risers

(rigid and flexible), global analysis, moorings, installation and towed systems [9].

For this thesis research, fast and accurate analysis, of BMs attached catenary system

under wave and current loads and externally imposed motion, is provided by Orcaflex.

The program is operated in both single mode and batch mode, as needed, for routine

analysis work using Orcaflex; as well the special facilities for post-processing the

results.

Orcaflex is a fully 3D non-linear, time-domain, finite-element-based program, capable

of dealing with arbitrarily large deflections of the flexible structure from the initial

configuration [9].

29

2.3 Analysis Theory

2.3.1 General

Strength analysis, of the SCR and SLWR for the riser design, buoyancy module

optimization, and system robustness check, in both operation and disconnection

conditions, is conducted in accordance with the prescriptions specified in API RP

2RD [6]. In addition, the riser system design and the analysis conducted include:

Riser global configuration

Material selection and wall thickness sizing

Riser flex joint interface engineering

Design riser flex joint nipple extension dimension

Riser coating design

Riser VIV suppression device selection

This section outlines the analysis requirements for the production SLWR.

30

2.3.2 Load Case Matrix

To perform dynamic analysis, the load case matrix is set up first per the API RP 2RD

[6] definition, taking into consideration the different load conditions, to include:

1. Temporary condition

2. Operating condition

3. Extreme condition

4. Survival condition

For each load condition, several independent load cases are defined taking into

consideration environmental conditions, pressure, FPSO offset, mooring line

conditions (intact or broken) and FPSO turret buoy conditions (connected vs.

disconnected).

In addition, five directions of FPSO positions, including near, far, trans+, trans- and

270 degree, are considered in the analysis. Figure 2.3.1 below defines the NEAR,

FAR, TRANS directions with respect to the FPSO offset direction. NEAR is defined

as the FPSO offset in the riser plane and makes it slack. While the FPSO offset in the

riser plane and makes it taut, it is defined as FAR. TRANS is defined when the FPSO

offset in the plane 45 degree to the riser plane (+ taut; - slack).

It should be mentioned that the wave and current are conservatively assumed as

31

co-linear and applied in the same plane as FPSO offset direction. Wave, propagating

in direction of 270 degree, is identified associated the worst response of the FPSO.

Figure 2.3.1 FPSO Offset consideration [11]

The Production SLWR is analyzed according to the load case matrix defined in

Table 2.3.1.

32

1 HY01N N

2 HY01F F

3 HY02N N

4 HY02F F

5 OP01N N

6 OP01T T

7 OP01F F

8 OP02N N

9 OP02T T

10 OP02F F

11 EX01N N

12 EX01T T

13 EX01F F

14 EX02N N

15 EX02T T

16 EX02F F

17 EX03NN NN

18 EX03FF FF

19 EX04N N

20 EX04T T

21 EX04F F

22 EX05N N

23 EX05T T

24 EX05F F

25 EX06N N

26 EX06T T

27 EX06F F

28 EX07N N

29 EX07T T

30 EX07F F

31 SU01N N

32 SU01T T

33 SU01F F

34 SU02N N

35 SU02T T

36 SU02F F

37 SU03N N

38 SU03T T

39 SU03F F

40 SU04N N

41 SU04T T

42 SU04F F

43 SU05N N

44 SU05T T

45 SU05F F

Note: 1) Shut dow n pressure is 400 psig for production;

2) The reference elevation of internal pressure is MSL;

3) FPSO position relative to the riser should be interpreted as the turret buoy, and corresponding turret buoy motion at

particular w ater depth shall be used.

GoM FPSO Riser Strength Analysis Load Case Matrix

Wave

1 yr WS*

10 yr WS*

1 yr WS

Associated

10 yr WS*

100 yr H*

Load

Case

No.

NameAPI 2RD Load

Category

Mooring

Line

Condition

FPSO

Position

Pressure

(psig)

Temperature

(oF)

Density

(pcf)

FPSO -

Turret

Buoy

100 yr WS

10 yr WS*

Extreme

Yes

API 2RD

Allow able

Unity SUF

Associated

Associated

10 yr LC*

1 yr LC

100 yr LC*

Associated

Associated

100 yr H*

100 yr WS

Associated

Associated

10 yr WS*

Design Design Design Intact

Associated 10 yr LC*

Yes

Yes

0.67

Intact No

Design Damaged Yes

0.80

10 yr LC*

Shut Dow n 40 Dissel

Associated

Yes 1.0

Associated 100 yr LC*

Yes 1.0Damaged

Associated

Design

100 yr WS

Design Intact

Design Intact

Associated

Associated

Design Design

100 yr LC*

Design Design

1.0NoDamaged

Operating

Design Design

Design Design

Environmental Condition

Design Design Design Intact

Survival

Associated Dissel40.0Shut Dow n

Current

Hydrotest1.25 x

Design40 64 Intact Yes 0.90

Table 2.3.1 Load Case Matrix for the Production SLWR [11]

33

2.3.3 Analysis Methodology

1. Strength Analysis

For in-place condition, which means the FPSO turret buoy is connected with the

vessel and ready for operation, strength analysis is performed using Orcaflex to

establish the global configuration of riser in both SCR and SLWR approaches by

conducting static analysis. And in order to obtain dynamic results of hang-off

declinations, effective tensions at top connection, Von Mises stress, API RP 2RD [6]

stress utilization, bending moment, the riser system is analyzed dynamically for

different load cases and FPSO vessel offsets in different directions.

For static analysis, Orcaflex is used to perform the calculation, and determine the

nominal position and equilibrium of each line in two steps, of which the first step is

applying the Catenary Method [9] and the second step is applying the Full Static

Method [9].

Catenary Method

In Orcaflex, the equilibrium position of the line is calculated applying catenary

method, with including all effects, weight, buoyancy, axial elasticity, current drag and

seabed touchdown and friction, but ignoring the effects of bending and torsional

34

stiffness of the line or its end terminations, and the possible contact forces between

the line and any solid shapes in the model [9].

At this point, in the condition of no compression in the line, the robustness and

efficiency of the catenary algorithm is satisfying, while it cannot handle cases where

the line is in compression [9].

The Catenary algorithm calculate and determine the static position of the line based

on the iterative catenary calculation process, which is controlled by a number of

convergence parameters including Max Iterations, Tolerance, Min Damping and Mag.

of Std. Error, Mag. of Std. Change. These parameters are normally left default and can

be modified when the calculation fail to obtain converge [9].

Full Static Method

The Full Static Method is a line statics calculation process that includes all forces

modeled in Orcaflex, comparing to ignoring bending and torsional stiffness in The

Catenary Method. In particular, the effects of bending stiffness and interaction with

shapes are included in the calculation process, which will avoid the occurrence of

shock loads at the start of the simulation. Such shock loads are more likely to occur

when the bending stiffness is not included in the calculation [9].

Thus, the accurate equilibrium position of each line can be obtained in the second step

of static analysis applying the Full Static Method, which is based on the configuration

35

obtained in the first step as starting shape for the line [9].

Line Theory

A finite element model for a line is used in Orcaflex, as shown in the figure below.

Figure 2.3.2 Finite Element Model of a Line in Orcaflex [9]

The line is divided into a series of line segments which are then modeled by straight

massless model segments with a node at each end. The model segments only model

the axial and torsional properties of the line. The other properties (mass, weight,

36

buoyancy, etc.) are all lumped to the nodes, as indicated by the arrows in the figure

above. Nodes and segments are numbered 1, 2, 3 … sequentially from the top end of

the line to the other. So segment n joins nodes n and (n+1) [9].

Each node is effectively a short straight rod that represents the two half-segments

either side of the node. The exception to this is end nodes, which have only one

half-segment next to them, and so represent just one half-segment [9].

Each line segment is divided into two halves and the properties (mass, weight,

buoyancy, drag etc.) of each half-segment are lumped and assigned to the node at that

end of the segment [9].

Forces and moments are applied at the nodes – with the exception that weight can be

applied at an offset. Where a segment pierces the sea surface, all the fluid related

forces (e.g., buoyancy, added mass, drag) are calculated allowing for the varying

wetted length up to the instantaneous water surface level [9].

Each model segment is a straight massless element that models just the axial and

torsional properties of the line. A segment can be thought of as being made up of two

co-axial telescoping rods that are connected by axial and torsional spring+dampers

[9].

The bending properties of the line are represented by rotational spring+dampers at

each end of the segment, between the segment and the node. The line does not have to

37

have axial symmetry, since different bend stiffness values can be specified for two

orthogonal planes of bending [9]

38

Structure Model

In the calculation and analysis conducted by Orcaflex, the detailed structure model of

line, as shown in the figure below, includes various spring + dampers that model the

structural properties of the line, as well the coordinates frame of reference and the

angles that are used in the calculation theory [9].

Figure 2.3.3 Detailed Structure Model of Line in Orcaflex [9]

39

There are 3 types of spring + dampers in the model: axial spring + damper, bending

spring + damper and torsion spring + damper.

The axial stiffness and damping of the line are modelled by the axial spring + damper at

the center of each segment, which applies an equal and opposite effective tension force

to the nodes at each end of the segment [9].

The bending properties are represented by rotational spring + dampers either side of the

node, spanning between the node's axial direction Nz and the segment's axial direction

Sz [9].

Tension Force

The tensions in the segments are calculated at first. Distance between the nodes at the

ends at the end of the segment, and the segment axial direction Sz are calculated by

Orcaflex to obtain the tension results [9].

Linear Axial Stiffness:

In the case of linear axial stiffness the tension in the axial spring+damper at the center

of each segment is calculated as follows. It is the vector in direction Sz whose

magnitude is given by:

𝑇𝑒 = 𝑇𝑤 + (𝑃0𝐴0 − 𝑃𝑖𝐴𝑖) [9]

mk:@MSITStore:C:/Program%20Files%20(x86)/Orcina/OrcaFlex/Demo/OrcaFlex.chm::/html/Line_Types__Stiffnesses_Data.htm#hcLineTypeAxialStiffness

40

Where,

𝑇𝑒 = effective tension

𝑇𝑤 = wall tension = 𝐸𝐴𝜀 − 2𝛾(𝑃0𝐴0 − 𝑃𝑖𝐴𝑖) + 𝐸𝐴𝑒 (𝑑𝐿 𝑑𝑡⁄ ) 𝐿0⁄

In this equation of Tw, the first term is the contribution from axial stiffness, the

second term is the contribution from external and internal pressure (via the Poisson

ratio effect) and the third term is the axial damping contribution. And the variables are

given by [9]:

EA = axial stiffness of line, as specified on the line types form (= effective

Young's modulus x cross-section area)

ε = total mean axial strain = (𝐿 − 𝜆𝐿0) 𝜆𝐿0⁄

𝐿 = instantaneous length of segment

λ = expansion factor of segment

𝐿0 = unstretched length of segment

ν = Poisson ratio

𝑃𝑖, 𝑃0 = internal pressure and external pressure, respectively

𝐴𝑖, 𝐴0 = internal and external cross sectional stress areas, respectively


mk:@MSITStore:C:/Program%20Files%20(x86)/Orcina/OrcaFlex/Demo/OrcaFlex.chm::/html/Line_Data__Structure.htm#Line_Structure_Expansion_Factor

mk:@MSITStore:C:/Program%20Files%20(x86)/Orcina/OrcaFlex/Demo/OrcaFlex.chm::/html/Line_Types__Stiffnesses_Data.htm#hcPoissonRatio

41

e = damping coefficient of the line, in seconds

𝑑𝐿 𝑑𝑡⁄ = rate of increase of length.

This effective tension force vector is then applied (with opposite signs) to the nodes at

each end of the segment. Each mid-node therefore receives two tension forces, one

each from the segments on each side of it.

Non-linear Axial Stiffness:

When the axial stiffness is non-linear then the tension calculation is as follows. It is

the vector in direction Sz whose magnitude is given by:

𝑇𝑒 = 𝑉𝑎𝑟𝑇𝑤(𝜀) + (1 − 2𝜈)(𝑃0𝐴0 − 𝑃𝑖𝐴𝑖) + 𝐸𝐴𝑛𝑜𝑚.𝑒 (𝑑𝐿 𝑑𝑡⁄ ) 𝐿0⁄ [9]

Where

𝑉𝑎𝑟𝑇𝑤 is the function relating strain to wall tension, as specified by the

variable data source defining axial stiffness.

𝐸𝐴𝑛𝑜𝑚. is the nominal axial stiffness which is defined to be the axial

stiffness at zero strain.

As in the linear case the effective tension force vector is then applied (with opposite

signs) to the nodes at each end of the segment. Each mid-node therefore receives two

effective tension forces, one each from the segments on each side of it [9].




42

Damping Coefficient e:

The damping coefficient e represents the numerical damping in the line. It is

calculated automatically based on the Axial Target Damping value specified for the

study:

𝑒 = 𝑒(𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙) ∙ (𝑇𝑎𝑟𝑔𝑒𝑡 𝐴𝑥𝑖𝑎𝑙 𝐷𝑎𝑚𝑝𝑖𝑛𝑔)/100 [9]

Where

𝑒(𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙) = (2 × 𝑆𝑒𝑔𝑚𝑒𝑛𝑡 𝑀𝑎𝑠𝑠 × 𝐿0 𝐸𝐴⁄ )1

2 [9]

is the critical damping value for a segment and Segment Mass includes the mass of

any contents but not the mass of any attachments [9].

Pipe Stress Calculation

The stress calculation in Orcaflex based on the assumption that the loads on the line

are taken by a simple cylinder, made of uniform material, whose inside and outside

diameters are given by the stress diameters specified before calculation [9].

As shown in the following figure, a cross-section through a mid-segment point in the

frame of reference is being considered. The origin O of the frame of reference is at the

pipe centerline, Oz along the pipe axis (positive towards End B) and Ox and Oy

normal to the pipe axis (and so in the plane of the cross-section) [9].

mk:@MSITStore:C:/Program%20Files%20(x86)/Orcina/OrcaFlex/Demo/OrcaFlex.chm::/html/General_Data__Numerical_Damping.htm#hcGeneral_Data_Target_Damping

43

Figure 2.3.4 Frame of Reference for Stress Calculation in Orcaflex [9]

At this cross-section, Orcaflex calculates the following values [9]:

i. Internal and external pressures, Pi and Po respectively.

ii. Effective tension and resulting wall tension. These are both vectors in the

z-direction, with magnitudes Te and Tw respectively.

iii. Curvature, which is a vector in the xy-plane, with components Cx and Cy in the

Ox and Oy directions, respectively.

iv. Bend Moment, which is a vector in the xy-plane, with magnitude M and

components Mx and My in the Ox and Oy directions, respectively.

v. Shear force, which is also a vector in the xy-plane, with magnitude S and

components Sx and Sy in the Ox and Oy directions, respectively.

vi. Torque, which is a vector in the z-direction with magnitude τ.

44

2. BM Arrangement Analysis and Optimization

Generally, SLWR has been proven that it could improve the fatigue and strength

performance of traditional SCR at touchdown area by decoupling the vessel motion

with riser. In addition, the payload on support vessel can be adjustable by utilizing the

lazy-wave configuration on steel catenary riser.

Besides, the current trial and error or iterative procedures to determine a lazy-wave

configuration of riser has been widely adopted in industry, even it’s not the most cost

effective approach. For this thesis research, this approach is also adopted for the BM

arrangement optimization analysis.

A variety of input parameters, which include equivalent pipe outer diameter of riser

pipe section with BM attached, total mass per unit length of the riser pipe with BM

attached, total length of riser pipe section with BM attached and the position along the

riser where BM attached, corresponding to the arrangement, position and material

properties of buoyancy modules, are investigated in the analysis to accomplish the

optimization of BM arrangement. Driving factors that make a major influence on the

vessel payload, Von Mises stress, declination angle and bending moment of the riser

pipe are analyzed and summarized.

45

2.3.4 Design Requirement and Acceptance Criteria

The riser is designed in order to satisfy all the design criteria listed in Table 2.3.2. For

Von Mises Stress check, the stress is calculated in accordance with the requirements

in API RP 2RD [6].

1. Wall Thickness Criteria

Wall thickness design of the risers shall be in accordance with the following codes, as

shown in Table 2.3.2 below:

Table 2.3.2 Design Codes for Wall Thickness Sizing

Criteria Design Code

Burst API RP 1111[5]

Collapse due to external pressure API RP 2RD [6]

Please note that pipe is not sized to withstand buckle propagation. The Pipe is needed

to be replaced if a buckle is observed.

2. Strength Criteria

Strength performance of the SLWR shall comply with API RP 2RD [6]. The allowable

stress levels and the design case factor Cf are given in Table 2.3.3 and Table 2.3.4.

46

Table 2.3.3 Allowable Riser Stress Level

Note: y = SMYS, a = basic allowable stress =2/3 y

Table 2.3.4 Design Case Factor

Load Category Design Case Factor, Cf Allowable Stress (% yield)

Operating 1 67

Extreme 1.2 80

Temporary 1.35 90

Survival 1.5 100

Installation 1.2 80

Stress Category Allowable Stress Reference

Primary membrane (Von Mises) Cf a API RP 2RD

Primary membrane plus bending 1.5 Cf a API RP 2RD

Primary membrane plus bending plus secondary 2 y 1 API RP 2RD

47

Chapter 3

Riser Design and Analysis

3.1 Steel Catenary Riser Approach

As a contrast approach, the simple SCR design approach for the same design

requirements and environmental conditions is performed and analyzed.

For the simple SCR configuration approach, the FPSO turret is in the in-place

condition, which means the turret is connected with the FPSO vessel during the whole

simulation period.

Dynamic strength analysis is performed for only 270 degree vessel position for each

load case, in time domain. For analysis simplification, only the 3 most critical extreme

load cases are selected and applied for the simulation.

First, the static analysis is performed to determine the global configuration of the SCR

system. This is done, in order to check the geometrical suitability of the riser system

before conducting the dynamic analysis. Next, the static analysis and the dynamic

strength analysis are conducted for the 3 most critical load cases, as stated above, with

corresponding regular wave loads, FPSO vessel offsets, current loads are applied to

each load condition. No directional cases with different vessel positions, hang-off

locations and departure angles are analyzed in the SCR approach. Only the most

critical load cases and the worst vessel positions are applied.

48

This is the same approach taken with the lazy-wave configuration, the static analysis

with and without mean FPSO offset and current loading has first been performed to

determine nominal tension at hang-off connection point, MBR and TDP location. A

detailed description includes:

1. Bending radius of curvature along the riser (touchdown area)

2. Declination angle at the top end of the riser

3. Maximum top tension

4. Touchdown Point (TDP) location (Arc length from top of riser)

For the dynamic analysis, the behavior of the riser configuration in the extreme

conditions is studied using the regular wave loads applied. Detailed results determined

and to be supplied include:

1. Maximum riser top tension at FPSO connection

2. Minimum bending radius and maximum bending moment along the riser

3. Maximum and minimum tension at TDP area

4. Maximum API RP 2RD [6] stress utilization factor along the riser

5. Minimum Effective Tension along the riser (likelihood of compression)

49

Orcaflex Model

The hang-off location in the model is taken as being the same with the STP turret,

which is located 295.3 ft. forward of midship, 32.8 ft. above the keel. The total length

of the modeled production SLWR is 12,790 ft.

The azimuth angle of riser is 304.5 degree in the computer model from the FPSO

north clockwise.

The mesh length varies from 0.5 ft. to 50 ft. Finer meshes are applied to the vicinity of

hang-off point and TDP area.

In the Orcaflex model, the top termination of the production SLWR is taken as

connected to the FPSO via a flexible joint. An articulation element is used to model

the flex joint with given bending stiffness. The SLWR extremity on seabed is fixed in

all translational direction with sufficient length on the seabed. This will eliminate the

boundary condition effect on critical riser response in the TDP area.

Flat seabed is selected at water depth of 7000 ft.

50

3.2 Lazy-Wave Steel Catenary Riser Approach

For in-place condition, which means the FPSO turret buoy is connected to the vessel,

strength analysis is performed for near, far, cross and 270 degree FPSO positions,

vessel offsets for each loading condition, in time domain.

The static analysis is performed in order to check the geometrical suitability of the

riser system before conducting the dynamic analysis. Considering the number of load

cases and computational efforts, the regular-wave-based dynamic analysis is

conducted first to identify the governing load cases for each load category. Then, the

directional analysis is performed, with 22.5 degree increments of FPSO position,

ranging from 0 to 360 degree. This is done to determine the worst result in

evaluating the riser response based on the vessel’s position. Thus, the governing load

cases with FPSO position corresponding with the worst riser motion response are

selected based on stress utilization, likelihood of compression, etc. As the regular

wave analysis is always more conservative compared to irregular wave analysis, the

irregular wave approach is not necessary to conduct if no compression occurs during

the regular wave analysis.

Static analysis taking into consideration mean FPSO offset and current loading has

first been performed to determine nominal tension at hang-off, MBR and TDP

location. Detailed description shall include:

1. Bending radius of curvature along the riser (Arch bend, and TDP)

51

2. Maximum top tension

3. TDP location (Arc length from riser top)

For the dynamic analysis, the behavior of the riser configuration in the extreme

conditions is studied using both the regular wave and irregular wave approach.

Detailed results determined and to be supplied include:

1. Maximum riser top tension at FPSO connection

2. Maximum and minimum tension at TDP

3. Maximum API RP 2RD [6] utilization factor along the riser

4. Minimum Effective Tension along the riser (likelihood of compression)

Orcaflex Model

The hang-off location in the model is taken being same with the STP turret, which is

located 295.3 ft. forward of midship, 32.8 ft. above the keel. The total length of the

modeled production SLWR is 12710 ft.

The azimuth angle of riser is 304.5 degree in the computer model from the FPSO

north clockwise.

The mesh length varies from 0.5 ft. to 50 ft. Finer meshes are applied to the vicinity of

hang-off point, suspended BMs attached riser pipe section and TDP area.

52

In the Orcaflex model, the top termination of the production SLWR is taken as

connected to the FPSO via a flexible joint. An articulation element is used to model

the flex joint with given bending stiffness. The SLWR extremity on seabed is fixed in

all translational direction with sufficient length on the seabed. This could eliminate

the boundary condition effect on critical riser response in the TDP area.

Flat seabed is selected at water depth of 7000 ft.

Figure 3.2.1 Snapshot of SLWR Orcaflex Model

53

3.3 BM Analysis and Optimization

SLWR has been considered as a popular solution in the deep and ultra-deepwater

operation due to the improvement performance of this type of riser in response to

vessel motions, especially the heave motion (motion in vertical direction), or saying,

to the harsh environmental condition. The improvement is achieved by suspending

part of the steel riser pipe in the seawater, by attaching a set of BMs on a section of

riser pipe, instead of adopting the simple catenary configuration. The material

property, arrangement and position along the riser where the BMs are attached, are the

major factors that influence the global response of the SLWR. Thus, the modification

range and values of input parameters for the BM optimization analysis are established

according to the input parameters matrix shown in the table below. The original load

case selected for the BM arrangement analysis is the most critical extreme case with

the worst load direction in 270 degree FPSO position, which can be referred in Table

3.3.1.

As shown in the load matrix table, for the first six cases, positions along the riser

where BMs are attached remain the same as in the original case. Among the other

three parameters, one is fixed, while the other two parameters increase or reduce by 5%

and 10%. For the last five cases, the first three parameters, equivalent outer diameter,

mass per unit length and the total length of the BM attached steel line pipe, are all

fixed, while the position of the BM attached on the steel pipe line varies -500 ft. to

54

+1000 ft. compared to the original case. Negative means that the starting point of the

BM attached zone further from the riser top than the original case, and vice versa.

Table 3.3.1 Load Case Matrix for BM Arrangement Analysis

In addition, all parameters vary to provide the same total buoyancy force as the

original case. With the equivalent outer diameter of the BMs attached pipe line being

fixed, and both total length and mass per unit length being variable, there are two

driving factors to consider: material property and stress concentration. With the mass

per unit length being fixed, and the other two parameters being variable, the driving

factors investigated are buoyancy force ratio and stress concentration. For the case No.

5 and No. 6, the total length of the BM attached pipe is fixed, thus the only factor

being investigated is the density of the BM material.

OD Mass per Unit Length BM Total Length Total Buoyancy Force Position

ft kpf/ft3 kp/ft kpf ft

0 2.8 0.198 1200 224.08 Original

1 2.8 0.22 1360 224.04 Original

2 2.8 0.2079 1267 224.05 Original

3 3.08 0.198 831 223.95 Original

4 2.52 0.198 2004 224.16 Original

5 3.08 0.2805 1200 224.39 Original

6 2.94 0.2385 1200 223.95 Original

7 2.8 0.198 1200 224.08 -200

8 2.8 0.198 1200 224.08 -500

9 2.8 0.198 1200 224.08 200

10 2.8 0.198 1200 224.08 500

11 2.8 0.198 1200 224.08 1000

Load Case: 5 Extreme 100Y Winter Storm 10Y Loop Current 270 degree

55

3.4 SLWR Sensitivity Analysis

A sensitivity study was conducted for the designed SLWR to prove the robustness of

the system to adverse uncertainties in the analysis data and tolerances in

manufacturing and installation. The following parameters are studied for sensitivity:

1. Hang-off angle increased by one degree.

2. Hang-off angle reduced by one degree.

3. FPSO offset increased by 10 percent.

4. Soil vertical stiffness increased by 10 percent.

Four load cases are considered in total, including: hydrotest, operation, extreme, and

survival load conditions. All four load cases, are analyzed and studied in the

sensitivity analysis.

56

3.5 SLWR Disconnection Analysis

For disconnection strength analysis, the STP and the mooring system are also

included in the Orcaflex model. A schematic of the computer model is shown in

Figure 3.5.1.

The disconnection strength analysis is performed for near, far, and transverse loading

conditions. For survival conditions, any one of the mooring lines is assumed to be

disabled for each load case.

Figure 3.5.1 Snapshot of SLWR Orcaflex Model in Disconnection Condition

Regular-wave-based strength analysis is conducted in time domain using Orcaflex.

The simulation duration is specified as 400 sec, and the motion responses of the last

100 sec are extracted and analyzed.

57

Chapter 4

Result and Discussion

4.1 SCR Approach

In this section, all analysis results from the SCR approach are detailed, including riser

configuration, static analysis results and dynamic results.

4.1.1 SCR configuration

Global configuration for the FPSO production SCR at in-place condition is obtained

and shown in Table 4.1.1.

Table 4.1.1 Global Configuration for SCR

Parameter Unit SCR

OD inch 8.625

Nominal Wall Thickness inch 1.725

Nominal Operating Top Tension kips 640

Top Hang Off Angle degree 8

Riser Heading Angle from FPSO North degree 304.5

Water Depth at Touchdown ft 7,000

Seabed Slope degree 0

Strake Length ft 4,570

Suspended Length from Hang Off to Nominal TDP ft 7,995

Horizontal Projection from Hang Off to Nominal TDP ft 2,883

Grounded Pipe Length from Nominal TDP to Transition Point ft 4,795

Total Riser Length from Analysis ft 12,790

58

4.1.2 SCR Strength Analysis

1. Static Analysis

Before performing global dynamic analysis, static analyses have been first conducted

in order to determine the global nominal configuration of the SCR and have better

understanding of the dynamic riser response to the main parameters of vessel and

weather below:

Offset directions

Current velocity

Load cases associated with all loading conditions in Table 2.3.1.

The vessel offset in 270 degree for different load conditions are derived according to

the method defined in section 2.1.3, as shown in Table 2.1.11. For different wave and

current load applied, vessel offsets varies and for conservatively considering, the

larger offset of both offsets corresponding to winter storm and loop current has been

taken to be used in the analysis.

The static analysis results for the SCR configuration approach with FPSO vessel in

the nominal position are presented in Table 4.1.2.

59

Table 4.1.2 Production SCR Nominal Static Analysis Results

Export Riser Units Values

Top Tension kpf 786.0

Hang-off Angle degree 7.95

TDP Location (Arc length from Riser Top) ft 7,995

TDP Area bend radius ft 1,151

TDP Tension kpf 108.26

Max Tension along line kpf 786.0

2. Regular Wave Analysis

The load cases studied for SCR configuration approach are listed in Table 4.1.3.

Table 4.1.3 Load Case Matrix for SCR Configuration Approach

Riser Top Motion

Riser top declination for various load cases are shown in Table 4.1.4. Maximum flex

joint rotation angles are highlighted.

X Y

1 100Y WS Associated 420 0 -420

2 10Y WS 100Y LC 351.73 0 -351.73

3 10Y WS Associated 468.98 0 -468.98

4 Associated 10Y LC 342.33 0 -342.33

Load Category: Extreme

Environmental Condition

Pressure

Design

Case

Factor

Mooring Total

Offset

Offset

Wave Current270

Design 1.2 Intact

Design 1.2 Damaged

60

Table 4.1.4 Riser Top Angular Response for simple SCR

Regular Wave Stress Results

Combined stress results of the analysis for the simple SCR are shown in Table 4.1.5.

Maximum stress of 128.2 ksi is observed at riser touchdown area in Extreme-A load

condition with 270 degree FPSO position. Several worst results are highlighted.

Table 4.1.5 Production SCR Combined Stress Results (ksi)

The API RP 2RD [6] utilization factor is the normalized factor of stress result vs.

stress limits according to API RP 2RD [6]. Stress utilization factor greater than 1

means the steel pipe structure would fail.

The API RP 2RD [6] utilization factor results at the SCR top and the touchdown area

are shown in Table 4.1.6. Maximum stress utilization of 2.31 is observed at the

Angular Deflection

Min Max Mean degree

1 Extreme A 270 156.02 176.54 168.37 15.98

2 Extreme B 270 149.56 171.80 161.21 22.44

3 Extreme C 270 161.29 176.62 170.50 10.71

4 Extreme D 270 166.27 172.23 169.61 5.73

Load CaseFPSO

Position

Top Angle (degree)

FPSO Direction TDP

degree Hoop Axial Bend VMS ft Hoop Axial Bend V M

1 EX A 270 34.0 40.3 43.1 46.3 7920 30.0 13.8 152.3 128.2

3 EX C 270 34.0 40.7 37.2 46.4 7612 30.0 11.4 150.6 123.5

4 EX D 270 33.9 37.5 26.0 39.4 7674 30.0 10.8 72.0 66.5

Load

Case

TOP Stress TDA Stress

61

touchdown area in Extreme-A load condition with 270 degree FPSO position, as

highlighted in red in the table below. All utilization factors greater than 1 are

highlighted in the Table as well.

Table 4.1.6 Production SCR Stress Utilization Factors

Effective Tensions and Bending Moments

The maximum and minimum effective tensions and bending moments for various

load cases are shown in Table 4.1.7. Maximum effective tension at riser top is 1194.9

kips in Extreme-C load condition with 270 degree FPSO position. Maximum bending

moment (BM) observed at the riser top is 414.7 kips-ft. for the Extreme-C load

condition with 270 degree FPSO position. Minimum effective tension observed at

touchdown area is -169.3 kips in Extreme-C load condition with 270 degree FPSO

position. Significant compression force is observed at riser touchdown area, which

means the riser pipe failed under such conditions.

FPSO Direction TDP

degree Top Ext TDP Max Top Ext TDP Max

1 EX A 270 45.2 46.3 128.2 128.2 7920 0.81 0.83 2.31 2.31

2 EX C 270 44.8 46.4 123.5 123.5 7612 0.80 0.83 2.30 2.30

3 EX D 270 33.0 39.4 66.5 66.5 7674 0.59 0.70 1.19 1.19

Utilization FactorLoad

Case

Max Von Mises Stress

(API Code/ksi)

62

Table 4.1.7 Production SCR Effective Tensions and Bending Moments

Min Ten Max Ten BM Min Ten Max Ten BM

kips kips kips-ft kips kips kips-ft

1 EX A 270 131.4 1179.1 414.7 -165.6 305.3 696

2 EX C 270 155.7 1194.9 358.2 -169.3 215.7 687.9

3 EX D 270 265.8 1073.9 249.6 -54.8 191.2 329.1

Load

Case

FPSO

Position

TOP TDP

63

4.2 Lazy-Wave SCR Approach

In this section, all analysis results according to SLWR approach are detailed,

including the riser configuration, static analysis results, and dynamic results.

4.2.1 SLWR Configuration

Global configuration of the designed SLWR for in-place condition is given in Table

4.2.1.

Table 4.2.1 Global Configuration of the designed SLWR

Parameter SLWR

OD inch 8.625

Nominal Wall Thickness inch 1.725

Nominal Operating Top Tension kips 640

Top Hang Off Angle degree 8

Riser Heading Angle from FPSO North degree 304.5

Water Depth at Touchdown ft 7000

Seabed Slope degree 0

Strake Length ft 4,570

Buoyancy Module Length ft 1,200

Starting Buoyancy Module Clearance with Seabed ft 1,486

End Buoyancy Module Clearance With Seabed ft 1,057

Suspended Length from Hang Off to Nominal TDP ft 10,060

Horizontal Projection from Hang Off to Nominal TDP ft 5,155

Grounded Pipe Length from Nominal TDP to Transition Point ft 2,650

Total Riser Length from Analysis ft 12,710

Final Riser Length Recommended ft 13,500

64

4.2.2 SLWR Strength Analysis

1. Static Analysis

Before performing global dynamic analysis, static analyses have been conducted in

order to determine the global nominal configuration of the designed SLWR and have

better understanding of the dynamic riser response to the main parameters of vessel

and weather below:

Vessel Position

Current velocity

Load cases associated with all loading conditions in Table 2.3.1.

The 5-direction vessel offset data for different load conditions are derived according

to the method defined in section 2.1.3, as shown in Table 2.1.11. For different wave

and current load applied, vessel offsets varies and for conservatively considering, the

larger offset of both offsets corresponding to winter storm and loop current has been

taken to be used in the analysis.

Table 4.2.2 presents the calculated FPSO vessel offsets applied in the analysis. The

static analysis results with the designed SLWR configuration and nominal FPSO

vessel position are presented in Table 4.2.3.

65

Table 4.2.2 FPSO Vessel Offset for Different Load Case in Analysis

Table 4.2.3 Summary Results of Production Lazy-Wave SCR Nominal Static Analysis

Wave Current ft

1 1Y WS Associated 257

2 Associated 1Y LC 257


4 1Y WS 10Y LC 257


6 10Y WS 100Y LC 352





Offset

Intact

Extreme design 1.2 Damaged

Survival design 1.5 Damaged

Hydrotest 1.25*design 1.35 Intact

Operation

design 1 Intact

design 1.2

Load

Category

Environmental ConditionPressure

Design

Case

Factor

Mooring

SLWR Units Values

Top tension kN 805

Riser Top Declination deg. 11.87

TDP Location (Arc length from Hang-off) ft 9866

TDP bend radius ft 3380

TDP Tension kN 165

Max Tension along line kN 805

66

2. Regular Wave Analysis

Riser Top Motion

Maximum riser top declination results for each load condition are shown in Table

4.2.4. And riser top declination results of all load cases are detailed in Appendix A.

Maximum flex joint rotation angles are observed in Extreme-B load case with 270

degree FPSO position, as highlighted in the table below.

Table 4.2.4 Summary of SLWR Top Angular Response Results

Min Max Mean

1 Hydro test A 270 169.71 174.59 172.37 2.59

6 Hydro test B 270 166.64 172.24 169.74 5.36

11 Operation A 270 159.13 176.13 169.16 12.87

16 Operation B 270 164.72 171.22 168.4 7.28

21 Extreme A 270 154.12 176.19 167.45 17.88

26 Extreme B 270 149.66 171.84 161.29 22.34

31 Extreme C 270 159.36 176.23 169.34 12.64

36 Extreme D 270 164.89 171.46 168.61 7.11

41 Survival A 270 154.31 176.2 167.35 17.69

46 Survival B 270 149.7 172.1 161.4 22.30

Load CaseFPSO

Position

Top Angle (degree) Angular

DeflectionNo.

67


Maximum stress results for each load condition in 3 catenary sections (riser top, arch

bend and touchdown area) are shown in the tables below. The stress results, of the

regular wave analysis with the SLWR approach, are detailed in Appendix A.

Maximum Von Mises Stress of 45.9ksi is observed at riser top for Extreme-A load

condition with 270 degree FPSO position. This most critical case occurs at the 1st

welding point under the flex joint taper tip. Bending stress governs the maximum

stress. The maximum results are highlighted in the tables as well.

Table 4.2.5 Summary of SLWR Stress Results – Riser Top (ksi)

Hoop Axial Bend V M

1 Hydrotest A 270 42.5 33.9 21.4 42.5

7 Hydrotest B Far 42.5 35.4 12.4 42.5

11 Operation A 270 34.0 35.6 39.5 43.7

17 Operation B Far 33.9 33.1 13.9 37.2

21 Extreme A 270 34.0 36.5 45.1 45.9

26 Extreme B 270 34.0 38.7 50.5 42.3

31 Extreme C 270 34.0 35.6 39.1 43.7

37 Extreme D Far 33.9 33.1 13.5 37.3

41 Survival A 270 34.0 36.5 44.8 45.9

46 Survival B 270 34.0 38.6 50.3 43.0

Load Case FPSO Position Riser Top (ksi)

68

Table 4.2.6 Summary of SLWR Stress Results – Arch Bend

Table 4.2.7 Summary of SLWR Stress Results – TDP Area

The maximum API RP 2RD Utilization Factors at the SLWR top and touchdown area

for each load condition are shown in Table 4.2.8. Maximum stress utilization of 0.936

Hoop Axial Bend V M

1 Hydrotest A 270 40.1 13.4 29.1 42.7

6 Hydrotest B 270 40.1 13.4 28.6 42.6

11 Operation A 270 30.9 10.9 32.9 38.7

16 Operation B 270 30.9 10.9 30.3 37.4

21 Extreme A 270 30.9 10.9 34.8 39.8

26 Extreme B 270 30.9 10.9 16.8 39.9

31 Extreme C 270 30.9 10.8 33.9 39.2

38 Extreme D Near 30.9 10.8 31.5 37.9

41 Survival A 270 30.9 10.8 36.2 40.6

46 Survival B 270 30.9 10.8 36.1 40.4

Load Case FPSO Position Arch Bend (ksi)

Hoop Axial Bend V M

1 Hydrotest A 270 39.4 10.2 14.4 37.5

6 Hydrotest B 270 39.4 10.2 14.1 37.4

11 Operation A 270 30.0 7.6 16.2 30.8

18 Operation B Near 30.0 7.5 14.9 30.3

21 Extreme A 270 30.0 7.5 16.9 31.0

26 Extreme B 270 30.0 7.5 17.1 31.1

31 Extreme C 270 30.0 7.5 16.7 30.9

38 Extreme D Near 30.0 7.5 15.6 30.5

41 Survival A 270 30.0 7.4 17.7 31.2

46 Survival B 270 30.0 7.4 17.7 31.3

TDP Area (ksi)Load Case FPSO Position

69

is observed at the flex joint extension in the Operation-A load case with 270 degree

FPSO position. The maximum stress and stress utilization factor results are

highlighted in the table.

Table 4.2.8 Summary of Maximum SLWR Stress Utilization Factors


The maximum effective tension, minimum effective tensions and maximum bending

moment at 3 sections (riser top, arch bend and touchdown area) of SLWR for each

load condition are shown in the following tables. The complete summary of effective

tensions and bending moments results with SLWR approach are detailed in Appendix

A. All the most critical results are highlighted in the tables. The maximum effective

tension at riser top is 1118.9 kips in the Extreme-B load condition with 270 degree

FPSO position. The maximum bending moment at riser top is 486.0 kips-ft in the

3 Hydro test A Near 29.9 41.9 42.7 37.5 48% 67% 68% 60%

6 Hydro test B 270 33.7 42.0 42.6 37.4 54% 67% 68% 59%

11 Operation A 270 39.4 43.7 38.7 30.8 84% 94% 83% 66%

16 Operation B 270 30.1 35.9 37.4 30.3 65% 77% 80% 65%

21 Extreme A 270 40.8 45.9 39.8 31.0 73% 82% 71% 55%

26 Extreme B 270 43.0 42.3 39.9 31.1 77% 76% 71% 51%

31 Extreme C 270 39.5 43.7 39.2 30.9 71% 78% 70% 55%

36 Extreme D 270 30.1 35.8 37.9 30.5 54% 64% 68% 54%

41 Survival A 270 41.0 45.9 40.6 31.2 59% 66% 58% 45%

46 Survival B 270 43.0 42.5 40.4 31.3 62% 61% 58% 45%

TDP

Max. Von Mises Stress

(API, ksi)Load Case

FPSO

PositionTop Ext Arch

Utilization Factor (%)

Top Ext Arch TDP

70

Extreme-B load condition with 270 degree FPSO position. Minimum effective tension

at riser touchdown area is 4.2 kips in Survival B load condition with 270 degree FPSO

position, which indicates no compression observed at the touchdown area at all.

Hence, the irregular wave analysis is not necessary to be conducted, as the regular

wave analysis has over predicted the compression at the touchdown area.

Table 4.2.9 Summary of SLWR Maximum Tension Results

Table 4.2.10 Summary of SLWR Minimum Tension Results

Riser Top Arch Bend TDP Area

2 Hydro test A Far 914.9 111.2 105.5

7 Hydro test B Far 914.2 122.7 101.3

11 Operation A 270 1005.8 109.9 71.6

17 Operation B Far 909.4 114.4 108.4

21 Extreme A 270 1040.2 113.8 70.8

26 Extreme B 270 1118.9 119.9 69.4

31 Extreme C 270 1004.3 104.3 67.9

37 Extreme D Far 912.7 137.3 115.1

41 Survival A 270 1038.8 107.8 66.1

46 Survival B 270 1116.3 117.2 65.9

Max Tension (kips)No. Load Case

FPSO

Position


1 Hydro test A 270 310.7 47.1 69.1

6 Hydro test B 270 294.2 46.7 70.6

11 Operation A 270 183.7 20.1 61.3

16 Operation B 270 278.4 42.7 66.6

21 Extreme A 270 169.8 7.7 58.4

26 Extreme B 270 134 4.5 57.2

31 Extreme C 270 185 19 58.7

36 Extreme D 270 278.4 41.1 64.3

41 Survival A 270 170.8 7.1 55.8

46 Survival B 270 135 4.2 55.1

Min Tension (kips)No. Load Case

FPSO

Position

71

Table 4.2.11 Summary of SLWR Maximum Bending Moment Results

4.2.3 SLWR Regular Wave Directional Analysis

In addition, the directional dynamic analysis considering different directions of vessel

positions (22.5 degree increment, range from 0 to 360 degree and all of near, far,

trans+ and trans- directions) is performed. The results are analyzed and compared to

identify the vessel position corresponding to the worst riser response (270 degree).

The load condition which is applied in the directional analysis is the Extreme-B

condition.


1 Hydro test A 270 205.7 132.9 65.7

6 Hydro test B 270 243.6 130.7 64.3

11 Operation A 270 380.2 150.2 73.9

16 Operation B 270 265.0 138.4 67.6

21 Extreme A 270 433.8 159.1 77.2

26 Extreme B 270 486.0 160.0 78.3

31 Extreme C 270 376.1 155.0 76.4

36 Extreme D 270 263.5 142.9 70.0

41 Survival A 270 431.3 165.6 80.8

46 Survival B 270 484.1 164.8 80.9

No. Load CaseFPSO

Position

Max Bending Moment (kips-ft)

72

Riser Top Motion

The riser top declinations results in the Extreme-B condition with all considered

FPSO position directions are shown in Table 4.2.12. Maximum flex joint rotation

angles are highlighted.

Table 4.2.12 Directional Riser Top Angular Response for Production SLWR


The directional combined stress results at 3 sections (riser top, arch bend and

touchdown area) of SLWR are presented in the following tables. The overall

Angular Deflection

Min Max degree

1 Extreme B 0 168.75 171.08 3.25

2 Extreme B 22.5 168.51 172.18 3.49

3 Extreme B 45 165.95 173.75 6.05

4 Extreme B 67.5 157.8 174.73 14.2

5 Extreme B 90 159.96 175.27 12.04

6 Extreme B 112.5 169.61 178.39 6.39

7 Extreme B 135 173.99 179.59 7.59

8 Extreme B 157.5 173.67 176.06 4.06

9 Extreme B 180 172.99 173.61 1.61

10 Extreme B 202.5 170.96 172.48 1.04

11 Extreme B 225 166.97 171.51 5.03

12 Extreme B 247.5 159.81 170.73 12.19

13 Extreme B 270 149.66 171.84 24.42

14 Extreme B 292.5 147.58 172.34 22.34

15 Extreme B 315 158.74 171.59 13.26

16 Extreme B 337.5 166.79 171.08 5.21

17 Extreme B Near 152.39 171.95 19.61

18 Extreme B Far 174.03 179.04 7.04

19 Extreme B Trans+ 167.89 173.01 4.11

20 Extreme B Trans- 169.33 171.96 2.67

Load CaseFPSO

Position

Declination (degree)

73

maximum stress of 46.12 ksi is observed at the riser top (1st weld under flex joint

taper tip) in 270 degree FPSO position. The maximum results of each riser are

highlighted in the tables.

Table 4.2.13 Directional Combined Stress Results of the SLWR– Riser Top

Hoop Axial Bend V M

1 Extreme B 0 33.94 29.3 14.54 35.38

2 Extreme B 22.5 33.95 30.77 17.51 36.18

3 Extreme B 45 33.95 34.02 29.41 37.92

4 Extreme B 67.5 33.95 39.81 48.66 44.67

5 Extreme B 90 33.95 39.73 52.61 45.49

6 Extreme B 112.5 33.95 34.74 41.53 41.59

7 Extreme B 135 33.95 34.73 26.95 39.09

8 Extreme B 157.5 33.95 32.79 16.41 37.29

9 Extreme B 180 33.95 31.93 13.97 24.6

10 Extreme B 202.5 33.95 32.83 16.37 25.26

11 Extreme B 225 33.95 35.2 25.4 28.92

12 Extreme B 247.5 33.96 35.07 38.5 35.13

13 Extreme B 270 33.95 38.66 50.54 46.12

14 Extreme B 292.5 33.95 38.91 48.25 43.51

15 Extreme B 315 33.95 33.17 29 35.58

16 Extreme B 337.5 33.95 30.5 16.65 29.4

17 Extreme B Near 33.95 35.99 39.17 39.58

18 Extreme B Far 33.95 34.85 33.86 40.29

19 Extreme B Trans+ 33.95 32.31 22.41 36.98

20 Extreme B Trans- 33.95 34.07 20.21 26.44

Load CaseFPSO

Direction

Riser Top (ksi)

74

Table 4.2.14 Directional Combined Stress Results of the SLWR– Arch Bend (ksi)

Hoop Axial Bend V M

1 Extreme B 0 30.9 10.92 28.16 36.27

2 Extreme B 22.5 30.89 11.11 26.71 35.69

3 Extreme B 45 30.87 11.46 25.43 35.29

4 Extreme B 67.5 30.86 11.94 26.35 36.01

5 Extreme B 90 30.86 11.95 28.38 36.86

6 Extreme B 112.5 30.86 12.1 27.85 36.4

7 Extreme B 135 30.85 12.17 25.06 35.17

8 Extreme B 157.5 30.86 11.85 22.78 34.21

9 Extreme B 180 30.86 11.58 23.3 34.36

10 Extreme B 202.5 30.88 11.42 25.62 35.36

11 Extreme B 225 30.89 11.33 29.42 37.23

12 Extreme B 247.5 30.91 11.12 32.71 38.86

13 Extreme B 270 30.93 10.9 35.03 39.87

14 Extreme B 292.5 30.92 9.36 33.86 39.17

15 Extreme B 315 30.92 10.84 31.95 38.1

16 Extreme B 337.5 30.91 10.84 30.31 37.27

17 Extreme B Near 30.92 10.87 32.86 38.58

18 Extreme B Far 30.86 12.21 26.72 35.84

19 Extreme B Trans+ 30.88 11.27 26.03 35.49

20 Extreme B Trans- 30.88 11.36 27.46 36.25

Load CaseFPSO

Direction

Arch Bend

75

Table 4.2.15 Directional Combined Stress Results of the SLWR – TDP Area (ksi)

The directional results of API RP 2RD Utilization Factors [6] at SLWR top and

touchdown area are shown in the two tables below. The maximum stress utilization of

0.822 is observed at the flex joint extension with 270 degree FPSO position direction.

TDP

ft Hoop Axial Bend V M

1 Extreme B 0 10010 29.96 7.64 14.19 30.18

2 Extreme B 22.5 10050 29.96 7.8 13.4 29.99

3 Extreme B 45 10070 29.96 8.24 12.54 29.8

4 Extreme B 67.5 10140 29.96 8.66 12.05 29.73

5 Extreme B 90 10160 29.96 8.69 12.33 29.82

6 Extreme B 112.5 10150 29.96 8.93 11.89 29.72

7 Extreme B 135 10140 29.96 8.99 11.31 29.54

8 Extreme B 157.5 10120 29.96 8.69 11.05 29.5

9 Extreme B 180 10100 29.96 8.4 11.46 29.56

10 Extreme B 202.5 10060 29.96 8.2 12.63 29.81

11 Extreme B 225 10020 29.96 8.02 14.3 30.23

12 Extreme B 247.5 10000 29.96 7.78 15.95 30.7

13 Extreme B 270 10000 29.96 7.5 17.14 31.08

14 Extreme B 292.5 9990 29.96 7.47 16.82 30.99

15 Extreme B 315 9990 29.96 7.47 15.88 30.65

16 Extreme B 337.5 9990 29.96 7.51 15.22 30.45

17 Extreme B Near 10000 29.96 7.47 16.3 30.8

18 Extreme B Far 10150 29.96 9.02 11.43 29.61

19 Extreme B Trans+ 10050 29.96 8.04 12.89 29.87

20 Extreme B Trans- 10050 29.96 8.11 13.46 30

TDP AreaLoad Case

FPSO

Direction

76

Table 4.2.16 Directional Stress Utilization Factors of the SLWR


The directional results of the maximum effective tensions, minimum effective

tensions and max bending moments at 3 sections (riser top, arch bend and TDP area)

of SLWR are presented in the following tables. The maximum effective tension is

1 Extreme B 0 50.1% 63.2% 64.8% 53.9%

2 Extreme B 22.5 53.8% 64.6% 63.7% 53.6%

3 Extreme B 45 65.7% 67.7% 63.0% 53.2%

4 Extreme B 67.5 79.8% 80.1% 64.4% 53.1%

5 Extreme B 90 81.2% 80.3% 66.0% 53.2%

6 Extreme B 112.5 67.4% 74.3% 65.0% 53.1%

7 Extreme B 135 53.0% 69.8% 62.8% 52.8%

8 Extreme B 157.5 45.3% 66.6% 61.1% 52.6%

9 Extreme B 180 43.9% 65.3% 61.4% 52.8%

10 Extreme B 202.5 45.1% 66.5% 63.1% 53.2%

11 Extreme B 225 51.6% 69.5% 66.5% 54.0%

12 Extreme B 247.5 62.7% 72.0% 69.4% 54.8%

13 Extreme B 270 76.8% 82.2% 71.2% 55.5%

14 Extreme B 292.5 77.7% 79.4% 70.0% 55.4%

15 Extreme B 315 63.5% 66.7% 68.0% 54.7%

16 Extreme B 337.5 52.5% 64.1% 66.7% 54.4%

17 Extreme B Near 70.7% 72.9% 68.9% 55.0%

18 Extreme B Far 59.4% 72.0% 64.0% 52.9%

19 Extreme B Trans+ 58.7% 66.0% 63.3% 53.3%

20 Extreme B Trans- 47.2% 67.8% 64.7% 53.6%

Arch TDP

FPSO

Direction

degree

Load Case

Utilization Factor

Top Ext

77

1118.9 kips with 270 degree FPSO position direction. The maximum bending moment

at riser top is 486.0 kips-ft. with 270 degree FPSO position. The minimum effective

tension at touchdown area is 4.2 kips with 270 degree FPSO position. No

compression is observed at the riser touchdown area at all.

Table 4.2.17 Directional Results of the SLWR – Maximum Tension


degree kips kips kips

1 Extreme B 0 768.1 83.5 72.5

2 Extreme B 22.5 823.2 96.0 82.9

3 Extreme B 45 945.2 123.7 97.0

4 Extreme B 67.5 1107.2 156.2 112.6

5 Extreme B 90 1101.1 165.4 114.0

6 Extreme B 112.5 972.3 171.5 122.9

7 Extreme B 135 972.4 165.3 125.2

8 Extreme B 157.5 899.3 135.5 113.9

9 Extreme B 180 867.0 119.5 103.2

10 Extreme B 202.5 901.1 117.4 95.6

11 Extreme B 225 990.2 131.3 88.9

12 Extreme B 247.5 985.2 131.5 79.7

13 Extreme B 270 1119.0 119.9 69.4

14 Extreme B 292.5 1113.5 107.2 68.8

15 Extreme B 315 913.4 88.9 68.3

16 Extreme B 337.5 813.0 82.6 70.0

17 Extreme B Near 1019.3 95.5 68.7

18 Extreme B Far 976.9 174.5 126.3

19 Extreme B Trans+ 881.0 108.2 89.6

20 Extreme B Trans- 947.7 122.2 92.0

Load Case

Max. Effective TensionFPSO

Position

78

Table 4.2.18 Directional Results of the SLWR – Minimum Tension


degree kips kips kips

1 Extreme B 0 488.2 63.0 69.9

2 Extreme B 22.5 439.4 64.9 76.4

3 Extreme B 45 358.2 64.2 81.8

4 Extreme B 67.5 368.0 46.5 86.2

5 Extreme B 90 199.8 23.4 84.7

6 Extreme B 112.5 169.3 28.0 86.6

7 Extreme B 135 256.0 50.6 91.4

8 Extreme B 157.5 378.0 72.8 93.9

9 Extreme B 180 418.9 74.3 89.8

10 Extreme B 202.5 362.1 61.3 81.2

11 Extreme B 225 219.8 33.0 69.6

12 Extreme B 247.5 118.4 9.9 61.3

13 Extreme B 270 134.0 4.5 57.1

14 Extreme B 292.5 300.0 25.9 58.8

15 Extreme B 315 388.2 51.0 62.7

16 Extreme B 337.5 442.4 55.7 65.8

17 Extreme B Near 403.5 42.8 61.0

18 Extreme B Far 201.3 38.0 88.9

19 Extreme B Trans+ 396.4 64.2 79.0

20 Extreme B Trans- 298.1 48.7 75.3

Load Case

FPSO

Position

Min. Effective Tension

79

Table 4.2.19 Directional Results of the SLWR – Maximum Bending Moment


degree kips-ft kips-ft kips-ft

1 Extreme B 0 139.8 128.7 64.9

2 Extreme B 22.5 168.4 122.0 61.2

3 Extreme B 45 282.9 116.2 57.3

4 Extreme B 67.5 468.0 120.4 55.0

5 Extreme B 90 472.0 129.7 56.3

6 Extreme B 112.5 399.4 127.2 54.3

7 Extreme B 135 259.2 114.5 51.7

8 Extreme B 157.5 157.8 104.1 50.5

9 Extreme B 180 867.0 106.4 52.4

10 Extreme B 202.5 157.4 117.1 57.7

11 Extreme B 225 244.3 134.4 65.3

12 Extreme B 247.5 370.3 149.5 72.9

13 Extreme B 270 486.0 160.0 78.3

14 Extreme B 292.5 464.1 154.7 76.8

15 Extreme B 315 278.9 146.0 72.5

16 Extreme B 337.5 160.1 138.5 69.5

17 Extreme B Near 376.8 150.1 74.5

18 Extreme B Far 325.6 122.1 52.2

19 Extreme B Trans+ 215.5 118.9 58.9

20 Extreme B Trans- 194.3 125.5 61.5

Max Bending Moment

Load Case

FPSO

Position

80

4.3 Comparison of Two Design Approaches: SCR vs. SLWR

The comparison results, including the maximum and minimum effective tensions,

maximum bending moments, Von Mises stresses and API stress utilization factors [6]

according to both SCR and SLWR configuration approaches are presented in the

tables below. It can be established that the results obtained from analysis based on the

SCR approach indicates that the simple SCR configuration cannot satisfy the stress,

tension and bending moment requirements specified.

This is expected, since the environmental condition in the GoM is too harsh for the

simple steel catenary configuration riser with a turret moored FPSO facility.

Significant compressions are observed at touchdown area in all load conditions, which

leads to the explosively increase of the bending moment, Von Mises stress and stress

utilization factor. Thus, the pipe is very likely to clash or buckle locally.

Table 4.3.1 Comparison Results of Riser Top Angular Responses

Table 4.3.2 Comparison Results of Von Mises Stress

SCR SLWR

1 Extreme A 270 15.98 17.88

2 Extreme C 270 10.71 12.64

3 Extreme D 270 5.73 7.11

Load Case FPSO PositionAngular Deflection (degree)

Top Ext TDP Top Ext Hog TDA

1 Extreme A 270 81% 83% 231% 73% 82% 71% 55%

2 Extreme C 270 80% 83% 230% 71% 78% 70% 55%

3 Extreme D 270 59% 70% 119% 54% 64% 68% 54%

Load CaseFPSO

Position

API Stress Utilization Factor

SCR SLWR

81

Table 4.3.3 Comparison Results of API Stress Utilization Factors

Table 4.3.4 Comparison Results of Effective Tensions

Table 4.3.5 Comparison Results of Bending Moments

Top Ext TDP Top Ext Hog TDA

1 Extreme A 270 80.6% 82.8% 230.7% 72.9% 81.9% 71.1% 55.3%

2 Extreme C 270 80.0% 82.9% 229.6% 70.6% 78.0% 70.1% 55.2%

3 Extreme D 270 59.0% 70.4% 118.7% 53.8% 64.0% 67.6% 54.4%

Load CaseFPSO

Position

API Stress Utilization Factor

SCR SLWR

Top Max TDP Min Top Max Sag Min TDA Min

1 Extreme A 270 1179.1 -165.6 1040.2 7.7 58.4

2 Extreme C 270 1194.9 -169.3 1004.3 19 58.7

3 Extreme D 270 1073.9 -54.8 855.1 41.1 64.3

Load CaseFPSO

Position

Effective Tension (kips)

SCR SLWR

Top Max TDP Max Top Max Sag Max TDA Max

1 Extreme A 270 414.7 696.0 433.8 159.1 77.2

2 Extreme C 270 358.2 687.9 376.1 155.0 76.4

3 Extreme D 270 249.6 329.1 263.5 142.9 70.0

Load CaseFPSO

Position

Bending Moment (kips-ft)

SCR SLWR

82

4.4 BM Optimization

The angle deflections at riser top, clearances between the top of BMs attached riser

pipe and the seabed, maximum top effective tensions, maximum bending moment,

maximum Von Mises Stress and the API code utilization factors at three riser sections

(riser top, arch bend, TDP area) are considered and investigated for the BM

arrangement optimization. The load cases are selected based on the load matrix shown

in Table 3.3.1, Section 2.3.4. The results of analysis are presented in the following

tables.

Table 4.4.1 BM Optimization Analysis Results – Effective Tension

Angle Deflection TDP Seabed Clearance

degree ft ft TOP Sag TDP

0 5.878 10000 1097 1040.2 7.7 58.4

1 5.683 10130 1247 1036.0 4.6 55.3

2 5.795 10057 1160 1038.2 6.4 57.3

3 6.487 9731 779 1052.0 13.9 66.6

4 5.057 10704 1823 1025.2 -0.3 44.7

5 5.907 10000 1103 1039.5 4.2 58.3

6 5.892 10020 1100 1039.8 6.0 58.7

7 5.756 10390 946 1093.2 8.0 65.8

8 5.828 10180 1038 1061.8 7.9 61.7

9 5.951 9860 1162 1017.3 7.6 56.0

10 6.078 9630 1256 983.0 7.2 52.1

11 6.345 9215 1414 922.2 6.3 45.7

Effective Tension (kips)

83

Table 4.4.2 BM Optimization Analysis Results - Bending Moment

Table 4.4.3 BM Optimization Analysis Results - Von Mises Stress

Angle Deflection TDP Seabed Clearance

degree ft ft TOP Hog TDP

0 5.878 10000 1097 433.8 159.1 77.2

1 5.683 10130 1247 432.1 147.5 81.3

2 5.795 10057 1160 433.1 154.0 80.4

3 6.487 9731 779 439.2 199.1 67.1

4 5.057 10704 1823 426.3 120.8 98.6

5 5.907 10000 1103 434.1 161.8 79.4

6 5.892 10020 1100 434.0 160.5 78.9

7 5.756 10390 946 432.2 141.0 70.2

8 5.828 10180 1038 433.2 152.1 73.7

9 5.951 9860 1162 434.7 167.0 81.0

10 6.078 9630 1256 436.2 180.8 87.6

11 6.345 9215 1414 439.3 208.7 95.4

Bending Moment(kips-ft)

Seabed Clearance

ft Top Hog TDA

0 5.878 10000 1097 45.9 39.8 31.0

1 5.683 10130 1247 45.7 38.3 31.3

2 5.795 10057 1160 45.8 39.2 31.2

3 6.487 9731 779 46.1 45.4 30.4

4 5.057 10704 1823 45.6 35.3 32.8

5 5.907 10000 1103 45.9 40.2 31.2

6 5.892 10020 1100 45.9 40.0 31.1

7 5.756 10390 946 46.7 37.8 30.5

8 5.828 10180 1038 46.2 39.0 30.8

9 5.951 9860 1162 45.5 40.7 31.2

10 6.078 9630 1256 45.0 42.5 31.7

11 6.345 9215 1414 44.1 46.1 32.4

Angle Deflection TDPAPI RP 2RD Stress

84

Table 4.4.4 BM Optimization Analysis Results - Stress Utilization Factors

Seabed Clearance

ft Top Hog TDA

0 5.878 10000 1097 81.9% 71.1% 55.3%

1 5.683 10130 1247 81.7% 68.4% 55.8%

2 5.795 10057 1160 81.9% 69.9% 55.7%

3 6.487 9731 779 82.3% 81.0% 54.2%

4 5.057 10704 1823 81.4% 63.1% 58.5%

5 5.907 10000 1103 81.9% 71.7% 55.6%

6 5.892 10020 1100 81.9% 71.5% 55.5%

7 5.756 10390 946 83.4% 67.5% 54.5%

8 5.828 10180 1038 82.5% 69.7% 54.9%

9 5.951 9860 1162 81.2% 72.8% 55.7%

10 6.078 9630 1256 80.3% 75.8% 56.7%

11 6.345 9215 1414 78.7% 82.2% 57.9%

Stress UtilizationAngle Deflection TDP

85

4.5 Sensitivity Analysis

The sensitivity analysis results of the Von Mises stresses, stress utilization factors and

effective tensions are summarized and presented in the following tables. The

robustness of the designed system is established from the analysis results. In addition,

it is indicated based on the results that the Von Mises stress is the most sensitive to

Hang-off angle increase. The maximum change of 5.92% in Von Mises results is

caused by 1 degree increase of hang-off angle, as highlighted in Table 4.5.1. For this

same scenario, the maximum change in stress utilization factor results is observed as

well. Besides, Small changes (about 10%) in soil vertical stiffness and vessel offsets

influence the riser response results insignificantly.

Table 4.5.1 Sensitivity Analysis Results – Von Mises Stress

Top Arch TDP Top Hog TDP

Hydrotest A 42.5 44.9 38.7 0.1% 5.0% 3.2%

Operation B 36.1 39.6 30.9 0.6% 5.9% 2.0%

Extreme A 46.0 41.9 31.6 0.2% 5.1% 1.9%

Survival A 46.0 43.0 32.0 0.2% 5.9% 2.3%

Hydrotest A 42.7 43.6 37.8 0.6% 2.0% 0.8%

Operation B 35.9 38.8 30.8 0.2% 3.7% 1.5%

Extreme A 46.0 41.2 31.4 0.2% 3.4% 1.6%

Survival A 45.9 42.0 31.8 0.1% 3.6% 1.8%

FPSO Offset +10% Hydrotest A 42.7 42.9 38.2 0.4% 0.5% 1.9%

FPSO Offset +10% Operation B 35.9 37.5 30.4 0.1% 0.4% 0.1%

FPSO Offset +6% Extreme A 45.9 39.9 31.0 0.1% 0.1% 0.0%

FPSO Offset +10% Survival A 45.9 40.9 31.3 0.0% 0.7% 0.4%

Hydrotest A 42.7 43.1 38.2 0.4% 0.8% 2.0%

Operation B 35.9 37.4 30.3 0.0% 0.0% 0.0%

Extreme A 45.9 39.8 31.0 0.0% 0.0% 0.0%

Survival A 45.9 40.6 31.2 0.0% 0.0% 0.0%

Sensitivity Case Load CaseVon Mises Stress (ksi) Difference (%)

Soil Vertical Stiffness

+10%

Hang-off Angle

+1 degree

Hang-off Angle

-1 degree

86

Table 4.5.2 Sensitivity Analysis Results - API Stress Utilization Factors

Top Hog TDP Top Hog TDP

Hydrotest A 67% 64% 58% 0% 5% 3%

Operation B 77% 75% 64% 1% 6% 2%

Extreme A 82% 68% 54% 0% 5% 2%

Survival A 66% 55% 44% 0% 6% 2%

Hydrotest A 67% 68% 59% 1% 0% 1%

Operation B 77% 83% 66% 0% 4% 1%

Extreme A 82% 74% 56% 0% 4% 2%

Survival A 65% 60% 45% 0% 3% 2%

FPSO Offset +10% Hydrotest A 67% 68% 58% 0% 0% 2%

FPSO Offset +10% Operation B 77% 80% 65% 0% 0% 0%

FPSO Offset +6% Extreme A 82% 71% 55% 0% 0% 0%

FPSO Offset +10% Survival A 66% 58% 45% 0% 1% 0%

Hydrotest A 67% 67% 58% 0% 1% 2%

Operation B 77% 80% 65% 0% 0% 0%

Extreme A 82% 71% 55% 0% 0% 0%

Survival A 66% 58% 45% 0% 0% 0%

Soil Vertical Stiffness

+10%

Sensitivity Case Load CaseUtilization Fator % Change

Hang-off Angle

+1 degree

Hang-off Angle

-1 degree

87

Table 4.5.3 Sensitivity Analysis Results - Effective Tensions

Table 4.5.4 Contrast Results for Sensitivity Analysis

Top (kips) Difference (%)

Hydrotest A 859.9 0.4%

Operation B 873 1.8%

Extreme A 1047.2 0.7%

Survival A 1044.8 0.6%


Operation B 851.5 0.7%

Extreme A 1037.4 0.3%


FPSO Offset +10% Hydrotest A 844 1.4%

FPSO Offset +10% Operation B 856.7 0.1%

FPSO Offset +6% Extreme A 1040 0.0%

FPSO Offset +10% Survival A 1038.2 0.1%


Operation B 857.3 0.0%

Extreme A 1040.2 0.0%


Sensitivity Case Load CaseEffective Tension

Hang-off +1 deg

Hang-off -1 deg

Soil Vertical Stiffness +10%

Top Arch TDP Top Arch TDP Top ft

Hydrotest A 42.5 42.7 37.5 67.5% 67.8% 59.5% 856.4 9980

Operation B 35.9 37.4 30.3 76.8% 80.1% 65.0% 857.3 10000

Extreme A 45.9 39.8 31.0 81.9% 71.1% 55.3% 1040.2 10000

Survival A 45.9 40.6 31.2 65.5% 58.0% 44.6% 1038.8 9990

Tension

(kips)TDP

Load CaseVon Mises Stress (ksi) Utilization Fator

88

4.6 Disconnection Strength Analysis

Stress results of the disconnection analysis for the production SLWR are shown in

Table 4.6.1 and Table 4.6.2. Maximum stress of 42.247 ksi is observed at the riser

arch bend in survival near condition with mooring line 7 damaged.

The API RP 2RD Utilization Factors [6] at the riser top, arch bend and touchdown

area are presented in Table 4.6.1. The maximum stress utilization of 0.725 is observed

at the riser arch bend in the extreme near condition. At riser top, the maximum stress

utilization of 0.725 is observed at the stress joint extension in extreme far condition.

The maximum and minimum effective tensions results of the designed disconnected

SLWR for various load cases are shown in Table 4.6.2. Maximum effective tension of

788.3 kips is observed at riser top in the survival far condition with the mooring line

11 damaged, as highlighted in Table 4.6.2. The minimum effective tension of 76.1

kips is observed at the riser touchdown area in survival near case with the mooring

line six damaged. The overall minimum effective tension of 63.4 kips is observed at

the riser sag bend before arch section, which means no compression is not present at

the touchdown area in disconnection analysis.

89

Table 4.6.1 Disconnection Analysis Results of the SLWR - Stresses and Stress Utilization Factors

Top Arch TDP Top Arch TDA

1 EX03 Near 39.3 40.6 36.4 70.2% 72.5% 65.0%

2 EX03 Far 39.5 40.3 36.3 70.6% 72.0% 64.8%

3 SU05N#1 Near 40.7 40.9 36.4 58.1% 58.4% 51.9%

4 SU05T#1 Trans 40.7 40.1 36.2 58.2% 57.3% 51.7%

5 SU05F#1 Far 41.0 39.8 36.1 58.6% 56.8% 51.5%

6 SU05N#2 Near 40.6 41.0 36.4 58.0% 58.5% 52.0%

7 SU05T#2 Trans 40.7 40.2 36.2 58.1% 57.5% 51.7%

8 SU05F#2 Far 41.0 39.9 36.1 58.6% 56.9% 51.6%

9 SU05N#3 Near 40.6 41.0 36.4 58.0% 58.6% 52.0%

10 SU05T#3 Trans 40.7 40.3 36.2 58.1% 57.6% 51.7%

11 SU05F#3 Far 40.9 39.9 36.1 58.5% 57.1% 51.6%

12 SU05N#4 Near 40.5 41.1 36.4 57.9% 58.7% 52.0%

13 SU05T#4 Trans 40.6 40.4 36.2 58.0% 57.8% 51.8%

14 SU05F#4 Far 40.9 40.0 36.1 58.4% 57.2% 51.6%

15 SU05N#5 Near 40.2 42.2 36.8 57.4% 60.3% 52.5%

16 SU05T#5 Trans 40.4 41.4 36.5 57.8% 59.2% 52.1%

17 SU05F#5 Far 40.6 40.9 36.4 58.0% 58.4% 51.9%

18 SU05N#6 Near 40.2 42.2 36.8 57.4% 60.3% 52.5%

19 SU05T#6 Trans 40.4 41.4 36.5 57.8% 59.2% 52.1%

20 SU05F#6 Far 40.6 40.9 36.4 58.0% 58.4% 51.9%

21 SU05N#7 Near 40.2 42.2 36.8 57.4% 60.4% 52.5%

22 SU05T#7 Trans 40.4 41.4 36.5 57.8% 59.2% 52.1%

23 SU05F#7 Far 40.6 40.9 36.4 58.0% 58.4% 51.9%

24 SU05N#8 Near 40.6 41.0 36.4 58.0% 58.6% 52.0%

25 SU05T#8 Trans 40.7 40.3 36.2 58.1% 57.5% 51.7%

26 SU05F#8 Far 41.0 39.9 36.1 58.6% 57.0% 51.6%

27 SU05N#9 Near 40.6 40.9 36.4 58.0% 58.5% 52.0%

28 SU05T#9 Trans 40.7 40.2 36.2 58.1% 57.4% 51.7%

29 SU05F#9 Far 41.1 39.8 36.1 58.7% 56.9% 51.6%

30 SU05N#10 Near 40.7 40.8 36.4 58.1% 58.3% 51.9%

31 SU05T#10 Trans 40.7 40.1 36.2 58.2% 57.3% 51.7%

32 SU05F#10 Far 41.1 39.7 36.1 58.7% 56.8% 51.5%

33 SU05N#11 Near 40.7 40.8 36.3 58.2% 58.2% 51.9%

34 SU05T#11 Trans 40.8 40.0 36.1 58.2% 57.1% 51.6%

35 SU05F#11 Far 41.2 39.6 36.1 58.8% 56.6% 51.5%

Load CaseFPSO

Position

API RP 2RD Stress (ksi) API RP 2RD Utilization

90

Table 4.6.2 Disconnection Analysis Results of the SLWR – Effective Tensions

Riser Top - Max TDP Area - Min

kips kips

1 EX03NN Near 695.1 77.3

2 EX03FF Far 705.2 79.9

3 SU05N#1 Near 758.5 73.7

4 SU05T#1 Trans 770.2 80.8

5 SU05F#1 Far 784.4 85.1

6 SU05N#2 Near 757 73.1

7 SU05T#2 Trans 769.5 79.7

8 SU05F#2 Far 780.9 84

9 SU05N#3 Near 755.9 72.5

10 SU05T#3 Trans 768.5 78.7

11 SU05F#3 Far 778 82.9

12 SU05N#4 Near 755.2 72

13 SU05T#4 Trans 767.7 77.8

14 SU05F#4 Far 775.3 81.9

15 SU05N#5 Near 744.3 63.6

16 SU05T#5 Trans 748.1 69.4

17 SU05F#5 Far 758.2 73.2

18 SU05N#6 Near 744.1 63.4

19 SU05T#6 Trans 746.5 69.4

20 SU05F#6 Far 758.9 73.1

21 SU05N#7 Near 743.9 63.4

22 SU05T#7 Trans 745.3 69.5

23 SU05F#7 Far 759.8 73

24 SU05N#8 Near 756.1 73.4

25 SU05T#8 Trans 769.9 80.5

26 SU05F#8 Far 780.3 83.4

27 SU05N#9 Near 757.1 74

28 SU05T#9 Trans 772.9 81.3

29 SU05F#9 Far 782.7 84.5

30 SU05N#10 Near 758.3 74.6

31 SU05T#10 Trans 776 82.2

32 SU05F#10 Far 785.5 85.6

33 SU05N#11 Near 759.6 75.2

34 SU05T#11 Trans 779.7 83.2

35 SU05F#11 Far 788.3 86.8

FPSO

Position

Effective Tension

Load Case

91

Chapter 5

Conclusions and Recommendations

5.1 Conclusions

According to the calculation and analysis results obtained in this study, the following

conclusions can be drawn:

1. The simple SCR demonstrated it is not feasible for the FPSO to be developed

in the GoM. Based on the results obtained from the strength analysis,

including the static and regular-wave-based dynamic analysis, significant

compression forces are observed at the riser touchdown area and the combined

stresses are over the limiting design criteria.

2. The nominal global configuration of the SLWR is established by conducting

the static and the regular-wave-based dynamic analysis using Orcaflex. The

total length of the SLWR is 12,710 ft. and the suspended length of the SLWR

is 10,060 ft. All functional requirements and strength criteria specified in API

RP 2RD [6] are satisfied with the designed SLWR.

3. The strength responses of the in-place designed SLWR, to different

environmental factors and vessel motions in all load conditions, are

investigated by analyzing the designed FPSO-SLWR system dynamically with

the regular-wave-based method using Orcaflex. The maximum angular

92

deflection of the flex joint at the riser top is 22.34 degree. The maximum stress

and the maximum stress utilization factor along the riser are both observed at

the flex joint tip and with 270 degree of FPSO position. The maximum stress

is 45.7 ksi for extreme-A load condition, while the maximum stress utilization

is 93.6% for operation-A load condition. The maximum top tension is 1118.9

ksi for extreme-B load condition with 270 degree of FPSO position. The

minimum tension of 4.2 kips is observed at the riser section with BMs

attached and no compression force of the SLWR is observed at all. The

maximum bending moment of 486 kips-ft. is observed at top end of the

SLWR.

4. The extreme-B load condition is selected for SLWR directional analysis. 22.5

degree increment, ranging from 0 to 337.5 degree of the FPSO position, is

applied. The maximum results of the top angular deflection, stress, stress

utilization factor, top tension and bending moment of the SLWR are all

observed at the load case with 270 degree FPSO position. Thus, the FPSO

position of 270 degree is considered as associated with the most severe SLWR

responses.

5. The robustness of the FPSO-SLWR system is demonstrated by the sensitivity

analysis performed for SLWR. Four sensitivity factors are considered: riser

hang-off angle increased and decreased by 1 degree; FPSO offset increased by

93

10%; soil vertical stiffness increased by 10%. According to the analysis results,

the most sensitive factor for the riser response is the increased riser hang-off

angle.

6. In case the SLWR becomes disconnected from the FPSO, the dynamic

responses of the SLWR is investigated and analyzed using Orcaflex. The

integrity of the SLWR, during the disconnection period, is demonstrated. The

maximum stress observed along the SLWR is 42.2 ksi at the riser section

attached with the BMs. The maximum stress utilization factor observed along

the SLWR is 72.5% in extreme load condition, and the maximum top tension

is 788 kips, which is observed at the riser top in survival load condition.

7. The BM arrangement is partially optimized, by analyzing and comparing

the global performances of the SLWRs attached with the BMs in different

material properties, arrangements or attaching positions along the riser. All

arrangement factors vary correspondingly to achieve a constant total buoyancy

force.

In summary, the development, of the FPSO with SLWR in the GoM, is feasible as

indicated from the riser response results obtained in this study.

94

5.2 Recommendations

1. As one of the major conclusions of this study, the feasibility of developing

a FPSO-SLWR operation unit in the GoM is demonstrated according to the

analysis results obtained in the research. However, the feasibility is not

demonstrated conditionally. The fatigue analysis and the

Vortex-Induced-Vibration (VIV) analysis of the designed SLWR are not

conducted in this study. Additional research may be required to indicate

the feasibility of the development more comprehensively.

2. Besides considering the design and the long-term performance of the

SLWR, the uncertainties can also be significantly increased when

considering the risk caused by the SLWR installation in the GoM. For

example, when the entire riser section, with BMs attached, is deployed just

below the water surface, the bending moment and bending strain could

have very critical due to the current-induced force applied on the

large-diameter BMs. The limiting sea states for the SLWR installation in

the GoM could be too low (Hs lower than 1m) to be accepted. Future

corresponding investigations are required to establish the feasibility of

developing FPSO-SLWR in the GoM.

95

References

[1] Subrata K. Chakrabarti, “Drilling and Production Risers” HANDBOOK OF

OFFSHORE ENGINEERING, ISBN-10: 0-080044569-1, 2005, Volume 2, Chapter 9,

pp. 709-854.

[2] Jingyun Cheng, Peimin Cao, “Design of Steel Lazy Wave Riser for Disconnectable

FPSO,” Offshore Technology Conference (2013) 24166

[3] Bin Yue, David Walters, Weiwei Yu, Kamaldev Raghavan and Hugh Thompson,

“Lazy Wave SCR on Turret Moored FPSO,” ISOPE 2011

[4] Ana Lucia F. Lima Torres, Enrique Casaprima Gonzalez, Marcos Queija de

Siqueria, Claudio Marcio Silva Dantas, Marcio Martins Mourelle and Renato Marques

Correia DaSilva, “Lazy-Wave Steep Rigid Risers for Turret moored FPSO,”

Proceedings of OMAE’02-28124, 21st International Conference on Offshore

Mechanics and Artic Engineering pp. 1-2

[5] American Petroleum Institute, “Design, construction, operation and maintenance

of offshore hydrocarbon pipelines”, API RP 1111(3rd ed.), 2009, pp. 5-14

[6] American Petroleum Institute, “Recommended practice for design of risers for

floating production systems (FPSs) and Tension Leg Platforms (TLPs)”, API RP 2RD

(Second ed.), 2006, pp. 5-59

96

[7] Det Norske Veritas, “Submarine Pipeline System,s,” DNV-OS-F101, 2013

[8] Det Norske Veritas, “Dynamic Risers,” DNV-OS-F201, 2001

[9] Orcina Ltd, “OrcaFlex Manual, Version 9.6a,” 2013

[10] Hugh Howell, “Advances in Steel Catenary Riser Design: Advances in Steel

Catenary Riser Design”, DEEPTEC, 02/1995

[11] Ruxin Song, “Gulf of Mexico FPSO Riser System Design Basis Report,” 2013,

Unpublished document

[12] API, “Specifications for Pipe Line,” API 5L (43rd ed.), 2004

[13]Songcheng Li and Chau Nguyen, “Dynamic Response of Deepwater Lazy-Wave

Catenary Riser,” DEEP OFFSHORE TECHNOLOGY INTERNATIONAL, 12/2010

97

APPENDIX A

Results Summary of Regular Wave Analysis in SLWR Approach

1. Summary of SLWR Top Angular Response Results in All Load Cases

Table 1.1 SLWR Top Angular Response Results – Hydrotest A Load Condition

Table 1.2 SLWR Top Angular Response Results – Hydrotest B Load Condition

Table 1.3 SLWR Top Angular Response Results – Operation A Load Condition

Min Max Mean

1 Hydro test A 270 169.71 174.59 172.37 2.59

2 Hydro test A Far 171.24 172.4 171.81 0.76

3 Hydro test A Near 171.35 174.11 172.73 2.11

4 Hydro test A Trans- 171.99 172.78 172.41 0.78

5 Hydro test A Trans+ 172.23 172.69 172.47 0.69

Load CaseFPSO

Position


Deflection

Min Max Mean

6 Hydro test B 270 166.64 172.24 169.74 5.36

7 Hydro test B Far 173.13 174.37 173.71 2.37

8 Hydro test B Near 168.7 172.15 170.5 3.3

9 Hydro test B Trans- 171.69 172.64 172.21 0.64

10 Hydro test B Trans+ 172.24 172.55 172.42 0.55

Load CaseFPSO

Position


Deflection

Min Max Mean

11 Operation A 270 159.13 176.13 169.16 12.87

12 Operation A Far 167.34 178.11 172.8 6.11

13 Operation A Near 163.17 178.11 171.15 6.11

14 Operation A Trans- 171.57 172.94 172.21 0.94

15 Operation A Trans+ 171.17 174.58 172.64 2.58

Load CaseFPSO

Position


Deflection

98

Table 1.4 SLWR Top Angular Response Results – Operation B Load Condition

Table 1.5 SLWR Top Angular Response Results – Extreme A Load Condition

Table 1.6 SLWR Top Angular Response Results – Extreme B Load Condition

Min Max Mean

16 Operation B 270 164.72 171.22 168.4 7.28

17 Operation B Far 173.91 175.47 174.68 3.47

18 Operation B Near 167.11 171.39 169.37 0.61

19 Operation B Trans- 171.06 172.39 171.79 0.94

20 Operation B Trans+ 171.95 172.14 172.02 0.14

Load CaseFPSO

Position


Deflection

Min Max Mean

21 Extreme A 270 154.12 176.19 167.45 17.88

22 Extreme A Far 165.3 179.26 172.62 7.26

23 Extreme A Near 157.45 179.55 170.17 14.55

24 Extreme A Trans- 169.82 173.6 171.56 2.18

25 Extreme A Trans+ 170.23 175.82 172.38 3.82

Load CaseFPSO

Position


Deflection

Min Max Mean

26 Extreme B 270 149.66 171.84 161.29 22.34

27 Extreme B Far 174.03 179.04 176.11 7.04

28 Extreme B Near 152.39 171.95 163.35 19.61

29 Extreme B Trans- 169.33 171.96 170.68 2.67

30 Extreme B Trans+ 167.89 173.01 170.63 4.11

Load CaseFPSO

Position


Deflection

99

Table 1.7 SLWR Top Angular Response Results – Extreme C Load Condition

Table 1.8 SLWR Top Angular Response Results – Extreme D Load Condition

Table 1.9 SLWR Top Angular Response Results – Survival A Load Condition

Min Max Mean

31 Extreme C 270 159.36 176.23 169.34 12.64

32 Extreme C Far 166.68 177.69 172.28 5.69

33 Extreme C Near 163.47 178.41 171.3 8.53

34 Extreme C Trans- 171.56 172.94 172.22 0.94

35 Extreme C Trans+ 171.15 174.59 172.68 2.59

Load CaseFPSO

Position


Deflection

Min Max Mean

36 Extreme D 270 164.89 171.46 168.61 7.11

37 Extreme D Far 173.52 175.13 174.32 3.13

38 Extreme D Near 167.35 171.63 169.61 4.65

39 Extreme D Trans- 171.08 172.4 171.81 0.92

40 Extreme D Trans+ 171.97 172.16 172.04 0.16

Load CaseFPSO

Position


Deflection

Min Max Mean

41 Survival A 270 154.31 176.2 167.35 17.69

42 Survival A Far 164.52 179.63 172.43 7.63

43 Survival A Near 157.85 179.83 170.13 7.83

44 Survival A Trans- 169.8 173.68 171.6 2.20

45 Survival A Trans+ 170.27 175.84 172.35 3.84

Load CaseFPSO

Position


Deflection

100

Table 1.10 SLWR Top Angular Response Results – Survival B Load Condition

2. Complete Summary of SLWR Stress Results of 3 Riser Sections in All Load

Cases

Table 1.11 SLWR Stress Results at Riser Top – Hydrotest A Load Condition

Table 1.12 SLWR Stress Results at Riser Top – Hydrotest B Load Condition

Min Max Mean

46 Survival B 270 149.7 172.1 161.4 22.30

47 Survival B Far 173.37 179.57 176.07 7.57

48 Survival B Near 152.77 172.26 163.49 19.23

49 Survival B Trans- 169.35 171.99 170.74 2.65

50 Survival B Trans+ 167.94 173.06 170.67 4.06

Load CaseFPSO

Position


Deflection

Hoop Axial Bend V M

1 Hydro test A 270 42.5 33.9 21.4 42.5

2 Hydro test A Far 42.5 35.5 9.7 42.5

3 Hydro test A Near 42.5 34.5 10.9 41.9



Load Case FPSO Position Riser Top

Hoop Axial Bend V M

6 Hydro test B 270 42.5 34.2 25.3 42.0

7 Hydro test B Far 42.5 35.4 12.4 42.5

8 Hydro test B Near 42.5 34.5 12.8 41.9




101

Table 1.13 SLWR Stress Results at Riser Top – Operation A Load Condition

Table 1.14 SLWR Stress Results at Riser Top – Operation B Load Condition

Table 1.15 SLWR Stress Results at Riser Top – Extreme A Load Condition

Hoop Axial Bend V M

11 Operation A 270 34.0 35.6 39.5 43.7

12 Operation A Far 34.0 33.9 25.5 38.9

13 Operation A Near 34.0 35.1 27.2 39.9




Hoop Axial Bend V M

16 Operation B 270 33.9 31.7 27.5 35.9

17 Operation B Far 33.9 33.1 13.9 37.2

18 Operation B Near 33.9 31.9 15.0 36.0




Hoop Axial Bend V M

21 Extreme A 270 34.0 36.5 45.1 45.9

22 Extreme A Far 34.0 35.7 31.3 42.0

23 Extreme A Near 34.0 36.1 34.6 41.6

24 Extreme A Trans- 34.0 35.3 18.5 38.5

25 Extreme A Trans+ 34.0 34.6 20.7 37.9


102

Table 1.16 SLWR Stress Results at Riser Top – Extreme B Load Condition

Table 1.17 SLWR Stress Results at Riser Top – Extreme C Load Condition

Table 1.18 SLWR Stress Results at Riser Top – Extreme D Load Condition

Hoop Axial Bend V M

26 Extreme B 270 34.0 38.7 50.5 42.3

27 Extreme B Far 34.0 34.9 33.9 40.3

28 Extreme B Near 34.0 36.0 39.2 40.8

29 Extreme B Trans- 34.0 34.1 20.2 38.0

30 Extreme B Trans+ 33.9 32.3 22.4 37.0


Hoop Axial Bend V M

31 Extreme C 270 34.0 35.6 39.1 43.7

32 Extreme C Far 34.0 34.1 25.1 39.0

33 Extreme C Near 34.0 35.0 26.8 39.8

34 Extreme C Trans- 34.0 33.7 13.1 37.3

35 Extreme C Trans+ 33.9 32.5 13.3 36.4


Hoop Axial Bend V M

36 Extreme D 270 33.9 31.6 27.4 35.8

37 Extreme D Far 33.9 33.1 13.5 37.3

38 Extreme D Near 33.9 31.9 14.7 35.9

39 Extreme D Trans- 33.9 29.7 11.7 34.7

40 Extreme D Trans+ 33.9 28.0 10.1 34.1


103

Table 1.19 SLWR Stress Results at Riser Top – Survival A Load Condition

Table 1.20 SLWR Stress Results at Riser Top – Survival B Load Condition

Table 1.21 SLWR Stress Results at Arch Bend – Hydrotest A Load Condition

Hoop Axial Bend V M

41 Survival A 270 34.0 36.5 44.8 45.9

42 Survival A Far 34.0 35.9 30.7 42.2

43 Survival A Near 34.0 36.1 34.1 41.5

44 Survival A Trans- 34.0 35.1 18.4 38.5

45 Survival A Trans+ 34.0 34.6 20.6 37.9


Hoop Axial Bend V M

46 Survival B 270 34.0 38.6 50.3 43.0

47 Survival B Far 34.0 35.0 33.4 40.5

48 Survival B Near 34.0 35.9 38.9 40.7

49 Survival B Trans- 34.0 34.1 20.1 38.0

50 Survival B Trans+ 33.9 32.3 22.2 37.0


Hoop Axial Bend V M

1 Hydro test A 270 40.1 13.4 29.1 42.7

2 Hydro test A Far 40.1 14.1 22.6 40.5

3 Hydro test A Near 40.1 13.3 29.2 42.7



Load Case FPSO Position Arch Bend

104

Table 1.22 SLWR Stress Results at Arch Bend – Hydrotest B Load Condition

Table 1.23 SLWR Stress Results at Arch Bend – Operation A Load Condition

Table 1.24 SLWR Stress Results at Arch Bend – Operation B Load Condition

Hoop Axial Bend V M

6 Hydro test B 270 40.1 13.4 28.6 42.6

7 Hydro test B Far 40.1 14.0 23.3 40.8

8 Hydro test B Near 40.1 13.4 28.2 42.4




Hoop Axial Bend V M

11 Operation A 270 30.9 10.9 32.9 38.7

12 Operation A Far 30.9 12.0 25.0 35.2

13 Operation A Near 30.9 10.9 31.6 38.1




Hoop Axial Bend V M

16 Operation B 270 30.9 10.9 30.3 37.4

17 Operation B Far 30.9 11.7 22.5 34.1

18 Operation B Near 30.9 10.9 30.2 37.3




105

Table 1.25 SLWR Stress Results at Arch Bend – Extreme A Load Condition

Table 1.26 SLWR Stress Results at Arch Bend – Extreme B Load Condition

Table 1.27 SLWR Stress Results at Arch Bend – Extreme C Load Condition

Hoop Axial Bend V M

21 Extreme A 270 30.9 10.9 34.8 39.8

22 Extreme A Far 30.9 12.2 30.1 37.3

23 Extreme A Near 30.9 10.9 16.3 39.3

24 Extreme A Trans- 30.9 11.4 29.4 37.1

25 Extreme A Trans+ 30.9 11.4 27.7 36.4

Arch Bend Load Case FPSO Position

Hoop Axial Bend V M

26 Extreme B 270 30.9 10.9 16.8 39.9

27 Extreme B Far 30.9 12.2 26.4 35.8

28 Extreme B Near 30.9 10.9 32.9 38.6

29 Extreme B Trans- 30.9 11.4 27.4 36.3

30 Extreme B Trans+ 30.9 11.3 26.0 35.5


Hoop Axial Bend V M

31 Extreme C 270 30.9 10.8 33.9 39.2

32 Extreme C Far 30.9 12.2 24.7 35.0

33 Extreme C Near 30.9 10.8 33.4 38.9

34 Extreme C Trans- 30.9 11.3 27.2 36.1

35 Extreme C Trans+ 30.9 11.3 26.2 35.6


106

Table 1.28 SLWR Stress Results at Arch Bend – Extreme D Load Condition

Table 1.29 SLWR Stress Results at Arch Bend – Survival A Load Condition

Table 1.30 SLWR Stress Results at Arch Bend – Survival B Load Condition

Hoop Axial Bend V M

36 Extreme D 270 30.9 10.9 31.3 37.9

37 Extreme D Far 30.9 10.0 21.7 33.8

38 Extreme D Near 30.9 10.8 31.5 37.9

39 Extreme D Trans- 30.9 11.1 25.1 34.9

40 Extreme D Trans+ 30.9 11.1 24.7 34.7


Hoop Axial Bend V M

41 Survival A 270 30.9 10.8 36.2 40.6

42 Survival A Far 30.9 12.5 30.6 37.5

43 Survival A Near 30.9 10.8 35.9 40.3

44 Survival A Trans- 30.9 11.5 29.3 37.2

45 Survival A Trans+ 30.9 11.4 27.6 36.3


Hoop Axial Bend V M

46 Survival B 270 30.9 10.8 36.1 40.4

47 Survival B Far 30.9 12.5 26.7 35.8

48 Survival B Near 30.9 10.8 34.6 39.4

49 Survival B Trans- 30.9 11.4 27.4 36.2

50 Survival B Trans+ 30.9 11.3 25.9 35.4


107

Table 1.31 SLWR Stress Results at Touchdown Area – Hydrotest A Load Condition

Table 1.32 SLWR Stress Results at Touchdown Area – Hydrotest B Load Condition

Table 1.33 SLWR Stress Results at Touchdown Area – Operation A Load Condition

Table 1.34 SLWR Stress Results at Touchdown Area – Operation B Load Condition

TDP

Arc Length Hoop Axial Bend V M

1 Hydro test A 270 9980 39.4 10.2 14.4 37.5

2 Hydro test A Far 10060 39.4 11.0 11.1 36.9

3 Hydro test A Near 9970 39.4 10.1 14.6 37.5

4 Hydro test A Trans- 10020 39.4 10.4 12.2 37.1

5 Hydro test A Trans+ 10010 40.1 10.4 12.2 37.1

FPSO Position Touchdown Area

Load Case

TDP


6 Hydro test B 270 9990 39.4 10.2 14.1 37.4

7 Hydro test B Far 10050 40.1 10.8 11.4 37.0

8 Hydro test B Near 9980 39.4 10.2 14.0 35.9

9 Hydro test B Trans- 10010 39.4 10.4 12.3 37.1

10 Hydro test B Trans+ 10020 39.4 10.4 12.2 37.1

Load Case FPSO Position Touchdown Area

TDP


11 Operation A 270 10000 30.0 7.6 16.2 30.8

12 Operation A Far 10130 30.0 8.8 11.7 29.7

13 Operation A Near 10010 30.0 7.6 15.8 30.6

14 Operation A Trans- 10030 30.0 8.1 13.4 30.0

15 Operation A Trans+ 10060 30.0 8.0 13.0 29.9

Touchdown AreaLoad Case FPSO Position

TDP


16 Operation B 270 10000 30.0 7.6 14.8 30.3

17 Operation B Far 10100 30.0 8.5 10.7 29.4

18 Operation B Near 10010 30.0 7.5 14.9 30.3

19 Operation B Trans- 10060 30.0 7.9 12.2 29.7

20 Operation B Trans+ 10060 30.0 7.9 12.1 29.7


108

Table 1.35 SLWR Stress Results at Touchdown Area – Extreme A Load Condition

Table 1.36 SLWR Stress Results at Touchdown Area – Extreme B Load Condition

Table 1.37 SLWR Stress Results at Touchdown Area – Extreme C Load Condition

Table 1.38 SLWR Stress Results at Touchdown Area – Extreme D Load Condition

TDP


21 Extreme A 270 10000 30.0 7.5 16.9 31.0

22 Extreme A Far 10180 30.0 9.0 12.0 29.7

23 Extreme A Near 9980 30.0 7.5 16.5 30.8

24 Extreme A Trans- 10050 30.0 8.2 14.2 30.2

25 Extreme A Trans+ 10050 30.0 8.1 13.5 30.0

Touchdown AreaFPSO Position Load Case

TDP


26 Extreme B 270 9990 30.0 7.5 17.1 31.1

27 Extreme B Far 10150 30.0 9.0 11.4 29.6

28 Extreme B Near 9990 30.0 7.5 16.3 30.8

29 Extreme B Trans- 10040 30.0 8.1 13.5 30.0

30 Extreme B Trans+ 10060 30.0 8.0 12.9 29.9


TDP


31 Extreme C 270 9970 30.0 7.5 16.7 30.9

32 Extreme C Far 10140 30.0 9.0 11.1 29.5

33 Extreme C Near 9980 30.0 7.4 16.5 30.8

34 Extreme C Trans- 10030 30.0 8.1 13.3 30.0

35 Extreme C Trans+ 10070 30.0 8.0 13.0 29.9


TDP


36 Extreme D 270 9990 30.0 7.5 15.3 30.5

37 Extreme D Far 10140 30.0 8.7 10.3 29.4

38 Extreme D Near 9990 30.0 7.5 15.6 30.5

39 Extreme D Trans- 10060 30.0 7.9 12.1 29.7

40 Extreme D Trans+ 10050 30.0 7.9 12.1 29.7


109

Table 1.39 SLWR Stress Results at Touchdown Area – Survival A Load Condition

Table 1.40 SLWR Stress Results at Touchdown Area – Survival B Load Condition

3. Complete Summary of Von Mises Stress and Stress Utilization Results along

Riser Catenary in All Load Cases

Table 1.41 SLWR Von Mises Stress Results – Hydrotest A Load Condition

TDP


41 Survival A 270 9990 30.0 7.4 17.7 31.2

42 Survival A Far 10190 30.0 9.3 11.5 29.6

43 Survival A Near 9980 30.0 7.4 17.6 31.2

44 Survival A Trans- 10040 30.0 8.2 14.1 30.2

45 Survival A Trans+ 10080 30.0 8.2 13.4 30.0


TDP


46 Survival B 270 9970 30.0 7.4 17.7 31.3

47 Survival B Far 10170 30.0 9.3 10.8 29.5

48 Survival B Near 9970 30.0 7.4 17.2 31.1

49 Survival B Trans- 10040 30.0 8.1 13.4 30.0

50 Survival B Trans+ 10080 30.0 8.0 12.9 29.9


Riser Top TSJ Ext. Arch Bend TDP Area Max.

1 Hydro test A 270 35.5 42.5 42.7 37.5 42.7

2 Hydro test A Far 29.9 42.5 40.5 36.9 42.5

3 Hydro test A Near 29.9 41.9 42.7 37.5 42.7

4 Hydro test A Trans- 27.9 40.6 41.1 37.1 41.1

5 Hydro test A Trans+ 26.8 39.8 40.9 37.1 40.9

Max. Von Mises Stress(API, ksi)Load Case

FPSO

Position

110

Table 1.42 SLWR Von Mises Stress Results – Hydrotest B Load Condition

Table 1.43 SLWR Von Mises Stress Results – Operation A Load Condition

Table 1.44 SLWR Von Mises Stress Results – Operation B Load Condition

Table 1.45 SLWR Von Mises Stress Results – Extreme A Load Condition


6 Hydro test B 270 33.7 42.0 42.6 37.4 42.6

7 Hydro test B Far 28.6 42.5 40.8 37.0 42.5

8 Hydro test B Near 29.3 41.9 42.4 35.9 42.4

9 Hydro test B Trans- 27.4 40.6 41.1 37.1 41.1

10 Hydro test B Trans+ 27.7 40.0 40.9 37.1 40.9


FPSO

Position


11 Operation A 270 39.4 43.7 38.7 30.8 43.7

12 Operation A Far 35.4 38.9 35.2 29.7 38.9

13 Operation A Near 32.9 39.9 38.1 30.6 39.9

14 Operation A Trans- 29.1 37.3 36.1 30.0 25.0

15 Operation A Trans+ 28.0 36.4 35.6 29.9 36.4


FPSO

Position


16 Operation B 270 30.1 35.9 37.4 30.3 37.4

17 Operation B Far 25.7 37.2 34.1 29.4 37.2

18 Operation B Near 26.7 36.0 37.3 30.3 37.3

19 Operation B Trans- 24.1 34.7 35.0 29.7 35.0

20 Operation B Trans+ 25.2 34.1 34.7 29.7 34.7


FPSO

Position


21 Extreme A 270 40.8 45.9 39.8 31.0 45.9

22 Extreme A Far 37.8 42.0 37.3 29.7 42.0

23 Extreme A Near 36.7 41.6 39.3 30.8 41.6

24 Extreme A Trans- 32.5 38.5 37.1 30.2 38.5

25 Extreme A Trans+ 32.2 37.9 36.4 30.0 37.9


FPSO

Position

111

Table 1.46 SLWR Von Mises Stress Results – Extreme B Load Condition

Table 1.47 SLWR Von Mises Stress Results – Extreme C Load Condition

Table 1.48 SLWR Von Mises Stress Results – Extreme D Load Condition

Table 1.49 SLWR Von Mises Stress Results – Survival A Load Condition


26 Extreme B 270 43.0 42.3 39.9 31.1 43.0

27 Extreme B Far 33.3 40.3 35.8 29.6 40.3

28 Extreme B Near 39.6 40.8 38.6 30.8 40.8

29 Extreme B Trans- 26.4 38.0 36.3 30.0 38.0

30 Extreme B Trans+ 32.9 37.0 35.5 29.9 37.0


FPSO

Position


31 Extreme C 270 39.5 43.7 39.2 30.9 43.7

32 Extreme C Far 35.9 39.0 35.0 29.5 39.0

33 Extreme C Near 33.0 39.8 38.9 30.8 39.8

34 Extreme C Trans- 29.1 37.3 36.1 30.0 37.3

35 Extreme C Trans+ 27.9 36.4 35.6 29.9 36.4


FPSO

Position


36 Extreme D 270 30.1 35.8 37.9 30.5 37.9

37 Extreme D Far 25.5 37.3 33.8 29.4 37.3

38 Extreme D Near 26.5 35.9 37.9 30.5 37.9

39 Extreme D Trans- 24.0 34.7 34.9 29.7 34.9

40 Extreme D Trans+ 25.1 34.1 34.7 29.7 34.7


FPSO

Position


41 Survival A 270 41.0 45.9 40.6 31.2 45.9

42 Survival A Far 38.4 42.2 37.5 29.6 42.2

43 Survival A Near 36.4 41.5 40.3 31.2 41.5

44 Survival A Trans- 32.6 38.5 37.2 30.2 38.5

45 Survival A Trans+ 32.2 37.9 36.3 30.0 41.5


FPSO

Position

112

Table 1.50 SLWR Von Mises Stress Results – Survival B Load Condition

Table 1.51 SLWR API Stress Utilization Factor Results – Hydrotest A Load Condition

Table 1.52 SLWR API Stress Utilization Factor Results – Hydrotest B Load Condition

Table 1.53 SLWR API Stress Utilization Factor Results – Operation A Load Condition


46 Survival B 270 43.0 42.5 40.4 31.3 43.0

47 Survival B Far 33.0 40.5 35.8 29.5 40.5

48 Survival B Near 39.3 40.7 39.4 31.1 40.7

49 Survival B Trans- 26.4 38.0 36.2 30.0 38.0

50 Survival B Trans+ 32.8 37.0 35.4 29.9 37.0


FPSO

Position


1 Hydro test A 270 56.4% 67.5% 67.8% 59.5% 67.8%

2 Hydro test A Far 47.4% 67.5% 64.3% 58.6% 67.5%

3 Hydro test A Near 47.5% 66.5% 67.8% 59.6% 67.8%

4 Hydro test A Trans- 44.2% 64.4% 65.2% 58.9% 65.2%

5 Hydro test A Trans+ 42.6% 63.2% 64.9% 58.9% 64.9%

Utilization FactorFPSO

Position Load Case


6 Hydro test B 270 53.5% 66.6% 67.6% 59.4% 67.6%

7 Hydro test B Far 45.4% 67.5% 64.7% 58.7% 67.5%

8 Hydro test B Near 46.4% 66.5% 67.3% 59.4% 67.3%

9 Hydro test B Trans- 43.4% 64.4% 65.2% 58.9% 65.2%

10 Hydro test B Trans+ 44.0% 63.4% 64.9% 58.9% 64.9%

Utilization FactorLoad Case

FPSO

Position

113

Table 1.54 SLWR API Stress Utilization Factor Results – Operation B Load Condition

Table 1.55 SLWR API Stress Utilization Factor Results – Extreme A Load Condition

Table 1.56 SLWR API Stress Utilization Factor Results – Extreme B Load Condition

Table 1.57 SLWR API Stress Utilization Factor Results – Extreme C Load Condition


11 Operation A 270 84.3% 93.6% 83.0% 65.9% 93.6%

12 Operation A Far 75.9% 83.3% 75.4% 63.5% 83.3%

13 Operation A Near 70.6% 85.5% 81.5% 65.6% 85.5%

14 Operation A Trans- 62.3% 79.8% 77.3% 64.3% 79.8%

15 Operation A Trans+ 60.0% 78.0% 76.3% 64.1% 78.0%


FPSO

Position


16 Operation B 270 64.5% 76.8% 80.1% 65.0% 80.1%

17 Operation B Far 55.0% 79.7% 73.1% 62.0% 79.7%

18 Operation B Near 57.3% 77.1% 79.9% 65.0% 79.9%

19 Operation B Trans- 51.6% 74.3% 74.9% 63.6% 74.9%

20 Operation B Trans+ 54.0% 73.1% 74.4% 63.6% 74.4%


Position Load Case


21 Extreme A 270 72.9% 81.9% 71.1% 55.3% 81.9%

22 Extreme A Far 67.6% 74.9% 66.6% 53.0% 74.9%

23 Extreme A Near 65.4% 74.3% 70.2% 55.0% 74.3%

24 Extreme A Trans- 58.1% 68.7% 66.4% 51.6% 68.7%

25 Extreme A Trans+ 57.6% 67.7% 64.9% 53.6% 67.7%


FPSO

Position


26 Extreme B 270 76.8% 75.6% 71.2% 51.3% 76.8%

27 Extreme B Far 59.4% 72.0% 64.0% 52.9% 72.0%

28 Extreme B Near 70.7% 72.9% 68.9% 55.0% 72.9%

29 Extreme B Trans- 47.2% 67.8% 64.7% 53.6% 67.8%

30 Extreme B Trans+ 58.7% 66.0% 63.3% 53.3% 66.0%


FPSO

Position

114

Table 1.58 SLWR API Stress Utilization Factor Results – Extreme D Load Condition

Table 1.59 SLWR API Stress Utilization Factor Results – Survival A Load Condition

Table 1.60 SLWR API Stress Utilization Factor Results – Survival B Load Condition


31 Extreme C 270 70.6% 78.0% 70.1% 55.2% 78.0%

32 Extreme C Far 64.1% 69.6% 62.3% 52.7% 69.6%

33 Extreme C Near 59.0% 71.1% 69.4% 55.1% 71.1%

34 Extreme C Trans- 51.9% 66.5% 64.3% 53.6% 66.5%

35 Extreme C Trans+ 49.8% 65.0% 63.6% 53.4% 65.0%


Position Load Case


36 Extreme D 270 53.8% 64.0% 67.6% 54.4% 67.6%

37 Extreme D Far 45.5% 66.5% 60.3% 52.4% 66.5%

38 Extreme D Near 47.4% 64.2% 67.7% 54.5% 67.7%

39 Extreme D Trans- 42.9% 61.9% 62.4% 53.0% 62.4%

40 Extreme D Trans+ 44.9% 60.9% 62.0% 53.0% 62.0%


FPSO

Position


41 Survival A 270 58.6% 65.5% 58.0% 44.6% 65.5%

42 Survival A Far 54.9% 60.2% 53.6% 42.3% 60.2%

43 Survival A Near 52.0% 59.3% 57.6% 44.5% 59.3%

44 Survival A Trans- 46.6% 54.9% 53.1% 43.1% 54.9%

45 Survival A Trans+ 45.9% 54.2% 51.9% 42.8% 54.2%


FPSO

Position


46 Survival B 270 61.5% 60.8% 57.8% 44.7% 61.5%

47 Survival B Far 47.1% 57.8% 51.1% 42.2% 57.8%

48 Survival B Near 56.2% 58.1% 56.4% 44.4% 58.1%

49 Survival B Trans- 37.7% 54.3% 51.7% 42.9% 54.3%

50 Survival B Trans+ 46.9% 52.8% 50.6% 42.7% 52.8%


Position Load Case

115

4. Complete Summary of Von Mises Stress and Stress Utilization Results along

Riser Catenary in All Load Cases

Table 1.61 SLWR Maximum Effective Tension Results – Hydrotest A Load Condition

Table 1.62 SLWR Maximum Effective Tension Results – Hydrotest B Load Condition

Table 1.63 SLWR Maximum Effective Tension Results – Operation A Load Condition


1 Hydro test A 270 856.4 94.6 75.2

2 Hydro test A Far 914.9 111.2 105.5

3 Hydro test A Near 877.4 86.8 73.7

4 Hydro test A Trans- 790.3 95.6 84.9

5 Hydro test A Trans+ 731.2 86.5 84.3

Max Tension (kips)Load Case

FPSO

Position


6 Hydro test B 270 866.5 100.1 77.8

7 Hydro test B Far 914.2 122.7 101.3

8 Hydro test B Near 879.9 94.5 76.3

9 Hydro test B Trans- 791.4 95.6 85.3

10 Hydro test B Trans+ 730.5 90.2 84.4

Load CaseFPSO

Position

Max Tension (kips)

116

Table 1.64 SLWR Maximum Effective Tension Results – Operation B Load Condition

Table 1.65 SLWR Maximum Effective Tension Results – Extreme A Load Condition

Table 1.66 SLWR Maximum Effective Tension Results – Extreme B Load Condition


11 Operation A 270 1005.8 109.9 71.6

12 Operation A Far 942.3 153.9 117.2

13 Operation A Near 985.2 98.6 71.4

14 Operation A Trans- 934.8 119.3 91.2

15 Operation A Trans+ 888.1 109.3 89.5

Load CaseFPSO

Position

Max Tension (kips)


16 Operation B 270 857.3 96 73.4

17 Operation B Far 909.4 114.4 108.4

18 Operation B Near 866.3 88.8 70.4

19 Operation B Trans- 782.1 87.9 84.8

20 Operation B Trans+ 718.8 89.6 83.9

Load CaseFPSO

Position

Max Tension (kips)


21 Extreme A 270 1040.2 113.8 70.8

22 Extreme A Far 1007.2 174.2 123.7

23 Extreme A Near 1024.7 102.8 71

24 Extreme A Trans- 992.3 144.4 94.9

25 Extreme A Trans+ 966 130.2 93.7

Load CaseFPSO

Position

Max Tension (kips)

117

Table 1.67 SLWR Maximum Effective Tension Results – Extreme C Load Condition

Table 1.68 SLWR Maximum Effective Tension Results – Extreme D Load Condition

Table 1.69 SLWR Maximum Effective Tension Results – Survival A Load Condition

Table 1.70 SLWR Maximum Effective Tension Results – Survival B Load Condition


26 Extreme B 270 1118.9 119.9 69.4

27 Extreme B Far 976.9 174.5 126.3

28 Extreme B Near 1019.4 95.5 68.2

29 Extreme B Trans- 947.8 122.2 92

30 Extreme B Trans+ 881 108.2 89.6

Load CaseFPSO

Position

Max Tension (kips)


31 Extreme C 270 1004.3 104.3 67.9

32 Extreme C Far 946.3 165.5 127.1

33 Extreme C Near 983.1 92.9 66.7

34 Extreme C Trans- 934.7 119.3 91.6

35 Extreme C Trans+ 888.6 109.7 89.6

Load CaseFPSO

Position

Max Tension (kips)


36 Extreme D 270 855.1 91.8 70.5

37 Extreme D Far 912.7 137.3 115.1

38 Extreme D Near 864.6 85 67.3

39 Extreme D Trans- 782.2 95.5 85

40 Extreme D Trans+ 718.7 89.7 84.2

Load CaseFPSO

Position

Max Tension (kips)


41 Survival A 270 1038.8 107.8 66.1

42 Survival A Far 1013.9 191.6 137.1

43 Survival A Near 1022.3 95.8 64.3

44 Survival A Trans- 987.3 144.1 95.6

45 Survival A Trans+ 966.8 131 93.8

Load CaseFPSO

Position

Max Tension (kips)

118

Table 1.71 SLWR Minimum Effective Tension Results – Hydrotest A Load Condition

Table 1.72 SLWR Minimum Effective Tension Results – Hydrotest B Load Condition

Table 1.73 SLWR Minimum Effective Tension Results – Operation A Load Condition

Table 1.74 SLWR Minimum Effective Tension Results – Operation B Load Condition


46 Survival B 270 1116.3 117.2 65.9

47 Survival B Far 981.2 187.8 137.5

48 Survival B Near 1017.2 90.2 63.6

49 Survival B Trans- 947.8 123.2 92.4

50 Survival B Trans+ 881.6 109.4 89.5

Load CaseFPSO

Position

Max Tension (kips)


1 Hydro test A 270 310.7 47.1 69.1

2 Hydro test A Far 395.2 85.8 92.6

3 Hydro test A Near 412.0 57.9 68.9



Load CaseFPSO

Position

Min Tension (kips)


6 Hydro test B 270 294.2 46.7 70.6

7 Hydro test B Far 388.7 69.4 89.8

8 Hydro test B Near 414.4 57.1 71.2

9 Hydro test B Trans- 503.9 72.2 81.8


Load CaseFPSO

Position

Min Tension (kips)


11 Operation A 270 183.7 20.1 61.3

12 Operation A Far 235.2 49.3 87.7

13 Operation A Near 378.2 45.8 63.5



Load CaseFPSO

Position

Min Tension (kips)

119

Table 1.75 SLWR Minimum Effective Tension Results – Extreme A Load Condition

Table 1.76 SLWR Minimum Effective Tension Results – Extreme B Load Condition

Table 1.77 SLWR Minimum Effective Tension Results – Extreme C Load Condition

Table 1.78 SLWR Minimum Effective Tension Results – Extreme D Load Condition


16 Operation B 270 278.4 42.7 66.6

17 Operation B Far 381.0 86.6 94.6

18 Operation B Near 406.1 53.1 66.2



Load CaseFPSO

Position

Min Tension (kips)


21 Extreme A 270 169.8 7.7 58.4

22 Extreme A Far 199.1 25.5 86

23 Extreme A Near 351.4 37.3 60.4

24 Extreme A Trans- 226.2 28.9 71.1

25 Extreme A Trans+ 307.5 49 75.2

Load CaseFPSO

Position

Min Tension (kips)


26 Extreme B 270 134.0 4.5 57.2

27 Extreme B Far 201.3 38 89.2

28 Extreme B Near 403.4 42.8 61

29 Extreme B Trans- 298.1 48.7 75.3

30 Extreme B Trans+ 396.4 64.2 79

Load CaseFPSO

Position

Min Tension (kips)


31 Extreme C 270 185.0 19 58.7

32 Extreme C Far 239.4 52.4 92.7

33 Extreme C Near 375.0 42.9 59.8

34 Extreme C Trans- 310.1 51.6 76

35 Extreme C Trans+ 384.8 62.2 78.7

Load CaseFPSO

Position

Min Tension (kips)

120

Table 1.79 SLWR Minimum Effective Tension Results – Survival A Load Condition

Table 1.80 SLWR Minimum Effective Tension Results – Survival B Load Condition

Table 1.81 SLWR Maximum Moment Results – Hydrotest A Load Condition

Table 1.82 SLWR Maximum Moment Results – Hydrotest B Load Condition


36 Extreme D 270 278.4 41.1 64.3

37 Extreme D Far 383.9 77.4 99.1

38 Extreme D Near 404.6 50.6 63.4

39 Extreme D Trans- 493.7 71.7 81.6

40 Extreme D Trans+ 561.4 77.3 82.5

Load CaseFPSO

Position

Min Tension (kips)


41 Survival A 270 170.8 7.1 55.8

42 Survival A Far 203.5 26.9 90.6

43 Survival A Near 346.9 34.6 56.4

44 Survival A Trans- 226.6 29.1 71.4

45 Survival A Trans+ 307.0 49.1 76

Load CaseFPSO

Position

Min Tension (kips)


46 Survival B 270 135.0 4.2 55.1

47 Survival B Far 205.0 40.2 94

48 Survival B Near 399.3 40.2 57.7

49 Survival B Trans- 298.5 49 75.7

50 Survival B Trans+ 396.1 64.3 79.6

Load CaseFPSO

Position

Min Tension (kips)


1 Hydro test A 270 205.7 132.9 65.7

2 Hydro test A Far 93.6 103.4 50.7

3 Hydro test A Near 104.8 133.4 66.5



Load CaseFPSO

Position


121

Table 1.83 SLWR Maximum Moment Results – Operation A Load Condition

Table 1.84 SLWR Maximum Moment Results – Operation B Load Condition

Table 1.85 SLWR Maximum Moment Results – Extreme A Load Condition

Table 1.86 SLWR Maximum Moment Results – Extreme B Load Condition


6 Hydro test B 270 243.6 130.7 64.3

7 Hydro test B Far 118.9 107 51.9

8 Hydro test B Near 123.5 129 64.1

9 Hydro test B Trans- 88.2 113.6 56


Load CaseFPSO

Position



11 Operation A 270 380.2 150.2 73.9

12 Operation A Far 245.6 59.3 53.6

13 Operation A Near 261.4 144.6 72.1



Load CaseFPSO

Position



16 Operation B 270 265 138.4 67.6

17 Operation B Far 134.1 102.8 49

18 Operation B Near 144.6 138 68



Load CaseFPSO

Position



21 Extreme A 270 433.8 159.1 77.2

22 Extreme A Far 300.9 137.6 55.5

23 Extreme A Near 332.4 154.7 75.4

24 Extreme A Trans- 178.2 65.1 64.4

25 Extreme A Trans+ 199.1 126.5 61.7

Load CaseFPSO

Position


122

Table 1.87 SLWR Maximum Moment Results – Extreme C Load Condition

Table 1.88 SLWR Maximum Moment Results – Extreme D Load Condition

Table 1.89 SLWR Maximum Moment Results – Survival A Load Condition

Table 1.90 SLWR Maximum Moment Results – Survival B Load Condition


26 Extreme B 270 486 160 78.3

27 Extreme B Far 325.6 65.3 52.2

28 Extreme B Near 376.7 150.1 74.5

29 Extreme B Trans- 194.3 125.5 61.5

30 Extreme B Trans+ 215.5 118.9 58.9

Load CaseFPSO

Position



31 Extreme C 270 376.1 155 76.4

32 Extreme C Far 241 112.7 50.6

33 Extreme C Near 257.3 152.5 75.4

34 Extreme C Trans- 126.2 124.3 61

35 Extreme C Trans+ 128.1 119.9 59.3

Load CaseFPSO

Position



36 Extreme D 270 263.5 142.9 70

37 Extreme D Far 129.4 99 47.1

38 Extreme D Near 141.6 143.8 71.2

39 Extreme D Trans- 112.2 114.6 55.4

40 Extreme D Trans+ 97.5 112.7 55.2

Load CaseFPSO

Position



41 Survival A 270 431.3 165.6 80.8

42 Survival A Far 294.9 139.8 52.6

43 Survival A Near 327.9 164.1 80.2

44 Survival A Trans- 177.2 133.7 64.3

45 Survival A Trans+ 197.7 126.1 61.2

Load CaseFPSO

Position


123


46 Survival B 270 484.1 164.8 80.9

47 Survival B Far 321 110.4 49.5

48 Survival B Near 374.5 158 78.6

49 Survival B Trans- 193.3 125 61.1

50 Survival B Trans+ 213.8 118.5 58.8

Load CaseFPSO

Position
