Offshore Oil and Gas Platforms for Deep Waters · Offshore Oil and Gas Platforms for Deep Waters Atilla Incecik Department of Naval Architecture, Ocean ... • The number of drilling

ICNAME'2015_29th-30th June, 2015, Harbin_China

Offshore Oil and Gas Platforms for

Deep Waters

Atilla Incecik

Department of Naval Architecture, Ocean

and Marine Engineering

University of Strathclyde, Glasgow, UK

([email protected])

mailto:[email protected]


Summary of World Energy Demand


Energy Supply


Global Deep Water Discoveries






Deep Water Oil and Gas Platforms

Main Factors to be considered in Concept

Selection:

• Production Volume

• Environment

• Water Depth

• Distance to shore or infrastructure

• The number of drilling centres required to drain

the reservoir

• The well intervention frequency

• Cost

• Strategic reasons

Well Configuration and location options:

• Surface well completion

• Seabed Well Completion tied back to

o adjacent surface facility

o remote surface facility

Development Concept Options:

• TLP

• FPSO

• SPAR

• Semisubmersibles

• Subsea Tieback

Main Platforms Features

TLPs

• Custom designed for site application

• Single drilling centre

• Surface completed wells

• Integral Drilling / Workover Facilities

• No oil storage

• Tensioned rigid risers for production

• Flexible or steel catenary for import or export

• Sensitive to top side loads

• Relatively long development schedule

FPSOs

• New-build or tanker conversation

• Remote wells, normally completed subsea

• Drilling / workover requires specialist vessel

• Integral oil storage and offloading

• Flexible risers

• Insensitive to topside load

• Short development schedule

SPARs• Custom designed for site specific application

• Single drilling centre/surface completed

wells/integral workover, or

• Remote wells completed subsea/workover by

specialist vessel

• Integral oil storage or

• No oil storage

• Tensioned risers, flexibles or steel catenary

risers

• Medium development schedule

Semisubmersibles:

• New-build or conversion

• Remote subsea wells with workover by

specialist vessel

• Wells below with integral

drilling/workover facilities

• No oil storage

• Sensitive to topside load

• Flexible risers

• Short to medium development schedule

Subsea Tie back to Shallow Water• Custom designed for site specific applications

• Multiple drilling centres

• Remote subsea wells

• Well workover by specialist vessel

• No oil storage, oil is exported from host

platform

• Short development schedule

• Hydraulic performance of long flowlines is key

design issue

Floating offshore platforms

Page 118 Global Marine Trends 2030 | Offshore energy sector

Total platformsin 2010270

Fig. 100 Number of floating platformsSource: University of Strathclyde

2010

2

42

3

48

16

58

2

2

27

51

19




Challenges

Medusa Spar

Thunderhorse

Mars TLP

Typhoon TLP

Petronius tower


Hydrodynamic Design Challenges

Short crestedness Extreme waves/spatial wave characteristics Vortex Induced Vibrations/Vortex Induced Motions Multiple body interactions Coupled systems (offloading) Wave impacts Green water Non-linear wave effects Shallow water waves Dynamic Positioning CFD applications Model testing of Deep Water Offshore Platforms


Development of simulation tools for coupled systems


Development of simulation tools

for coupled systems



Development of simulation tools

for coupled systems



Development of analysis tools to predict the

occurrence and impact of ‘green seas’ on

FPSO’s and FPUs


Wave Impact Loading

Wave1

2

3

4

5

6

7

8 9

10

11

Wave Probe

Load Cell

Lower Deck Plan

LC CL


Prediction of Loading and

Response due to Non-linear Waves


Prediction of Loading and

Response due to Non-linear Waves


Experimental investigation into motion

control of Truss Spars


Numerical and experimental studies to

simulate loads and motions during installation

of SPARs


Model Testing of Deep Water Offshore

Platforms



Platforms



Platforms



Platforms


Excitation on Floating

Platforms

Waves

• 1st order forces at wave frequency (WF)

• 2nd order forces

mean wave drift forces

forces at sum frequencies (HF)

forces at difference frequencies



Platforms

Wind

• Mean wind forces

• Fluctuating wind forces due gusts in the wind field

• Vortex induced vibrations/motions (VIV/VIM)



Platforms

Current

• Mean current forces

• Fluctuating current forces




Platforms

Current

• Mean current forces

• Fluctuating current forces



Dynamic Responses

Motions

• Mean offset, WF, and LF

Mooring Forces

• Mean, WF, LF and HF (for TLPs)


Dynamic Responses

Vessel Natural periods (s)

Surge Sway Heave Roll Pitch Yaw

FPSO >100 >100 5-12 5-30 5-12 >100

SemiSub >100 >100 20-50 30-60 30-60 >100

Spar >100 >100 20-50 50-100 50-100 >100

TLP >100 >100 <5 <5 <5 >100


Dynamic Responses

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 10 20 30 40 50 60 70 80

Period (s)

He

av

e A

mp

litu

de

/Wa

ve

Am

plitu

de

(m

/m)

Spectrum

FPSO

SEMISUB

SPAR


Dynamic Responses

Horizontal Motion

WF

LF

WF

LF

M

W WF

M LF M M

Water Depth (m)

70 330 2000

Horizontal motions

are obtained from the

solutions of coupled

equations


Sources of Low Frequency

Damping

Wind Damping

Wave Drift Damping

Wave radiation

Viscous Hull Damping

Viscous mooring line and riser damping

Friction between the mooring lines and sea bed


Low Frequency Damping for an FPSO

0

10

20

30

40

50

60

70

80

90

1 2 3 4 5 6

Item

% o

f T

ota

l D

am

pin

g

Series1

Series2

Series3

ITEM:

1. Wind Damping 2. Wave Drift damping in 2.0 m/s current

3. Hull Damping in 2.0 m/s current 4. Mooring and riser damping in still water

5. Mooring and riser damping in 2.0 m current 6. Mooring and riser damping in 2.0 m/s current and

8 m regular waves

Series 1: 70 m water, mooring only

Series 2 : 860 m, mooring only

Series 3 : 860 m water, mooring and riser



Platforms



Platforms

Properly scaled system

• Prerequisites : All mooring lines to be included, correctly scaled with respect to mass, elastic and geometric properties.

• Results: Hull forces, motions, and mooring system loads can be obtained, including mooring line tension



Platforms

Simplified catenary modelling i.e. simplified or omitted lines • Prerequisites : Careful documentation of

modelling approximation by means of verified theoretical models or special calibration tests must be provided to demonstrate adequate damping and stiffness properties

• Results: Hull forces and motions can be obtained



Platforms

Catenary mooring lines replaced by horizontal lines • Prerequisites : Correct restoring force

characteristics needs to be documented

• Results: Since the mooring line damping is not modelled the motions will be too large. Wave drift forces on the hull can be obtained



Platforms

Dynamically controlled mooring lines • Prerequisites : Documentation of the winches

ability to simulate the dynamic mooring characteristics.

• Results: In principle it should be feasible but it will be very difficult to represent the instantaneous dynamic effect of wave frequency motions on line tensions. Hull forces and first order motions can be obtained but low frequency motions and mooring line tension cannot be obtained easily.



Platforms

Passive Hybrid SystemsTruncated parts of the mooring lines and risers are represented by a system of springs, masses and dampers.

In a passive hybrid system the horizontal mooring stiffness can be modelled correctly whereas damping due to mooring lines and mooring line dynamics cannot be obtained accurately.



Platforms

Active Hybrid SystemsTruncated parts of the mooring lines and risers are represented by computer controlled actuators that can work in model scale and in real time.

In an active hybrid system the dynamic mooring line behaviour can be simulated, including the damping and mooring line sea-bed friction characteristics


Concluding Remarks

For the offshore oil and gas industry, the challenge is to continue to provide for the future energy needs of the world’s consumers from resources in difficult locations in ways which are environmentally responsible, safe and economically viable.

This lecture presented the factors in the selection of a concept design for deep water offshore oil and gas field developments, and the recent research and development activities and challenges in hydrodynamics analysis of deep water platform designs.

Documents

Offshore Oil and Gas Platforms for Deep Waters · Offshore Oil and Gas Platforms for Deep Waters Atilla Incecik Department of Naval Architecture, Ocean ... • The number of drilling