2 - 2-phase Intro.pdf

Marine Pipelines - Hydraulics - 2

2-phase Flow Technology - Introduction

Gert van Spronsen - Pipelines

Shell Global Solutions International (SGSI) - Rijswijk

Email : [email protected] Tel : +31 70 447 3427

2009 Shell Global Solutions International B.V. All rights reserved. Do not distribute without consent of copyright owner

2

2-phase Flow - Introduction

2-phase Flow Technology - Introduction

Topics

Status Multiphase flow Two-phase parameters Models and validation

Dynamic simulation: when to use it

Session Objectives

Understand the potential of Multi-phase Transport Systems & the associated complexity

3


Two-phase Flow Definition

Crude oil - below bubble point

Natural gas below dew point (Retrograde condensation)

Simultaneous Flow of Hydrocarbon Liquid & Gas

through a Single Conduit

3-Phase flow - HC Liquid, Water & Gas

Increase Application range Production system modelling Transient simulations Transport untreated wellstream

Reduce costs Improve integrity / safety

Multiphase Applications in Production Systems


Two-phase Flow - the Key issues

Two-phase flow

Simultaneous flow of Hydrocarbon Gas & Liquid

Why bother

Centralize /reduce processing facilities

Key problem

Liquid arrival pattern (rate & quantity)

Technical Objective

Minimise liquid storage capacity at minimum operational constraints

Den Helder Slugcatcher 1000 m3

Slugcatcher - 5000 m3

8


Nigeria Slugcatcher, 1100 m3


Multiphase Flow Calculations

Thermodynamics Phase behaviour of HC Liquid & Gas

Multiphase Correlations Pressure drop & liquid Hold-up

Include:

and

10


Phase Diagram - Typical

0 %De

wPo

i nt

Criconden Bar

VapourRegion

CricondenTherm

Critical Point

A

B

LiquidRegion

Dense PhaseRegion

Temperature

Pres

sure

80%

60%

40%

Molar

Perc

ent L

iquid

20%

100% B

ub bl e P

oi nt

P/L Inlet

P/L Outlet

11


Phase Envelope - Example (2)

0

50

100

150

200

-100 -50 0 50 100 150

Temperature (DegC)

P

r

e

s

s

u

r

e

(

b

a

r

)

0 % Liquid 1 % Liquid 2 % Liquid 3 % Liquid 5 % Liquid 10 % Liquid 20 % Liquid 50 % Liquid100 % LiquidP&T - 6 mmNm3/dP&T - 4 mmNm3/dP&T - 2 mmNm3/d

3%5%

Liquid percentages

- all in Mol %

12


Phase Envelope - Example (3)

0

50

100

150

200

-100 -50 0 50 100 150

Temperature (DegC)

P

r

e

s

s

u

r

e

(

b

a

r

)

0 % Liquid

1 % Liquid

2 % Liquid

3 % Liquid

5 % Liquid

10 % Liquid

20 % Liquid

50 % Liquid

100 % Liquid

Hydrate Curve

Hydrate Curve

- all in Mol %

13


Multiphase Transport Concept

Gas is normally the demand variable

Gas flow - determined by pressure drop

Liquid flows - as result of gas/liquid interface forces

Less gas flow more liquid stays behind in pipeline

increase in hold-up

Annular dispersed

Stratified wavy

Slug / Intermittent flow

14


Two-Phase Parameters Total Pipeline Hold-up

Total hold-up Total liquid contained in the pipeline at any given time

Note: Normally calculated at steady state, but takes time to accumulate

HL = Total Pipeline Hold-up (m3)

15


Two-Phase Parameters - HL

Liquid hold-up (fraction) HL (Area of pipe segment filled with liquid) Fractional Hold-up is normally more than the Liquid Volume Fraction

Due to liquid friction losses & elevation effects (on top of P & T)

Varies along the pipeline

Fluid dynamics in addition to Thermodynamics

LHALA

=

- In general Vl < Vg- For homogeneous fluids (Vl = Vg) -> hold-up =

AL

16


Two-Phase Parameters - Liquid volume fraction - (liquid fraction of total fluid flowing)

Varies along the pipe with changing P & T

Liquid Volume Fraction is normally less than the fractional Hold-up

No liquid friction losses & elevation effects (on top of P & T)

Determined by Thermodynamic Equilibrium of the HC stream- No influence from Fluid dynamics

=GQ

=LQ

Flowing volume, actual m3/s of gas

Flowing volume, actual m3/s of liquid

17


Hold-up - Summary

Liquid flows mainly as a result of gas/liquid interface forces

Fractional Hold-up varies along the pipeline Thermodynamic effects (P&T) & Fluid Dynamics

Forces to move liquid Interfacial forces & gravity in down hill sections

Forces to slowdown liquid Friction with pipewall & gravity for uphill sections

Lower liquid velocity => increased liquid hold-up in the pipeline

Thus:

Lower gas velocities > higher liquid hold-up

Uphill sections > higher liquid hold-up

18


Two-Phase Flow Regimes & Flow pattern map

Annular Dispersed

Stratified Wavy

Slug (Intermittent)

Dispersed Bubble

/ Mist

Horizontal flow

Vertical flow

Fg

100

10-1

10-2

10-3

10-4

101

100

10-3 10-2 10-1 100 101 102 103

annular / mist dispersed bubble

stratified smooth

stratified wavy

intermittent(slug)GAS TRUNKLINES

FLOWLINES

Increased gas loading

Increased liquid loading

GASLIQUID X

19


Two-phase Flow Pipeline- Inlet Pressure - Outlet Pressure fixed at 65 bar

60

80

100

120

140

0 10 20 30 40 50 60

Flowrate (mmsm3/d)

P

r

e

s

s

u

r

e

(

b

a

r

)

36 inch

38 inch

40 inch

36 inch

38 inch

40 inch

Liquid head dominates the dP

Stability point, i.e. Minimum Flowrate

20


Two-phase Flow Pipeline- Liquid Volume in Pipeline - Steady Operation

6,000

8,000

10,000

12,000

14,000

0 10 20 30 40 50 60Flowrate (mmsm3/d)

L

i

q

u

i

d

H

o

l

d

-

u

p

(

m

3

)

36 inch 38 inch 40 inch

36 inch

38 inch

40 inchAt low flow more liquid to

manage

21


Pressure Loss - Model vs. Actual

L = 108 km

D = 20 inch

~10 % liquid

27.6

20.7

13.8

6.9

3.51.3 2.7 5.4 8.1

400

300

200

100

100 200 300 MMscf/d

m 3 x 10 6

PSIABarPressure loss

Gasflowrate

MeasuredCalculated KSLA

22


Liquid Hold-up - Model vs. Actual

L = 108 km

D = 20 inch

~10 % liquid

Measured

Calculated

6359

4769

3180

1590

7951.3 2.7 5.4 8.1

40

30

20

10

100 200 300 MMscf/d

m 3 x 10 6

bbl/ x 10 3m 3

Liquid volumein line

Gasflowrate

MeasuredCalculated KSLA

Bacton (UK) - Multi-Phase Testloop

24


Dimensions: 8 inch, 150 m

0, 1, 3 & 5 inclination

Fluids Gas & condensate

Flowrates: Gas 0 - 10 m/s

Liquid 0 - 2 m/s

Pressure - 70 bar

Liquid fraction 0 - 1

Model verificationat

field conditions

Bacton (UK) - Multi-Phase Testloop

25


Scientific Instruments in Test Section

Viewing Section Wave Characteristics Meter Hold-up Meter

PressureTap

Temperature(PT 100)

NeutronReflector

Detector

OpticalCable

SaphirePressureWindow

Video

LightSource

ReferenceProbe

NeutronSource

8 Conductivity probes with different lengthsarranged radially under different angles

3 Neutron backscattering probes.Equally spaced overthe circumference

Glass Liner

PressureEqualizer

26


Bacton Testloop - Flow visualisation

Gas flow

low high

2 m/s 7 m/s

Liquid flow

medium ~1 m/s

Gas flow

low - 1 m/s

Liquid flow

very low low

0.1 m/s 0.3 m/s

27


Bacton Testloop

Flow Visualisation

Gas flowrate

Liquid

flowrate

a specific operating window

28


Flow Visualisation a specific 450 km, 36 pipeline

Gas velocity (m/s)

3 5 7 10

- KP 450- 900 mmscf/d - 58 barg @outlet

6 m/s


- KP 200 - 650 mmscf/d- 58 barg @outlet

5 m/s3 m/s


8.5 m/s

- KP 320-960 mmscf/d- 47 barg @outlet

29


Liquid Distribution in a Pipe - Bacton Testloop

Accurate information on:

Friction losses

Liquid wetting - Corrosion

0.50.40.20.070.02

Vsl= 1.0 m/s

gas flow was constant at Vsg = 7.0 m/sliquid flows Vsl were at different rates as indicated

30


Improvements in Two-Phase Modelling

10

1

0.1

0.011010.1

Superficial gas velocity, m/s

S

u

p

e

r

f

i

c

i

a

l

l

i

q

u

i

d

v

e

l

o

c

i

t

y

,

m

/

s

intermittent

stratified

annular + mist

old boundary

Large scale Experiments

Improved theory

This removes conservatism and ensures:

Accurate Pressure drop & Hold-up prediction

Extended reach of multi-phase Pipelines

Smaller slugcatcher & less constraints

backed up by

31


Multiphase Modelling Aims

To reduce cost and maximise revenue by: Extending range of multiphase developments

Concentrating processing on one site

Minimising operational margins

Thorough understanding of Multiphase flow behaviour

- & developing modelling tools based on: First principle mathematical / physical models

Calibrating with experimental data

Validating with field data

32


Steady State & Dynamic Simulation- when to use what

Steady state modelling always essential: Allows rigorous checking of all options and concepts

Define operating window

Provide base case

Far simpler and quicker to use: cheaper

Use Dynamic Modelling to: Check steady state & transients assumptions

Develop operating envelopes

Train operators on how the pipeline system will respond

Off / On line tool for operation optimisation

33


Dynamic Simulation - Applications & Predictions

Design Sizing of pipeline & liquid handling facilities

Selection of thermal insulation

Operation Development of operational strategies

Liquid management systems off-& online

Safety and contingency analysis

TrainingPredictions:

Liquid production during a change of operation, depressurisation, etc Cooling during shut-down, depressurisation, etc Size of slugs (severe / hilly terrain) Spillage of fluids during pipeline ruptures

Applications:

34


Dynamic Modelling in the Project Phases

Conceptual Design Check key assumptions as made with steady state calculations

Detailed Design Detailed Steady State & Transient Calculations Pipeline System Principle Operational Modes Established

Project Execution - before start-up Pipeline Operational Envelope & Procedures completed, Operator training

Dedicated Pipeline Operational Model (off-line) required?

Operational Assistance during operations Maximise capacity, minimise start-up periods

On-line Operational Support should always be justified specifically

35


Point of Concern

Dont forget the basics

Use sophisticated simulations programs

only if justified by

standard calculation packages

36


Shell Global Solutions is a network of independent technology companies in the Shell Group. In this presentation the expression 'Shell' or 'Shell Global Solutions' is sometimes used for convenience where reference is made to these companies in general, or where no useful purpose is served by identifying a particular company.

Documents

2 - 2-phase Intro.pdf