Lys Ark Yang 2012

1 - Classification: Internal 2010-09-23

Challenges in offshore multiphase

viscous oil transport

Zhilin Yang

Guest lecture at NTNU, March 26, 2012


Outline

• Introduction

• Challenges for multiphase viscous oil transport

• Experimental programme and modeling of viscous oil-water flow

• Summary

Classification of viscous (heavy) oils

• American Petroleum Institute (API) gravity:

− Specific Gravity:

− At 60 ºF (15.5 ºC):

• Classification of viscous oils


oil

water

SG

141.5 131.5API gravity

SG

Light crude Medium oil Heavy crude Extra heavy crude

>31.1 ºAPI

(<870 kg/m3)

22.3 – 31.1 ºAPI

(870 – 920 kg/m3)

22.3 – 10 ºAPI

(920 – 1000 kg/m3)

<10 ºAPI

(> 1000 kg/m3)

Remaining World Oil Resources


Source: IEA

World Energy Outlook


0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

Years

Mill

bo

e/d

ay

Alternative Energy (mmboe/d)

Gas (mmboe/d)

Conv Oil (mmboe/d)

Heavy Oil (mmboe/d)

Coal (mmboe/d)

World Heavy Oil Basins


Statoil Heavy Oil areas

Heavy and Extra Heavy Oil Portfolio


API density scale

40o 30o 10o

Mariner

Oseberg

Grane

Alba

PetroCedeño

NAOSC

Peregrino

Bressay

HO / EHO

Statfjord

22 11 14 6+ 8.5

Troll

Viscosity (cp)* <1 10 1000 100000+

* Depending on temperature

Dalia

20o

19

Source HO definition: American Petroleum Institute

Light crude Medium oil Heavy crude Extra heavy crude

>31.1 ºAPI

(870 kg/m3)

22.3 – 31.1 ºAPI

(870 – 920 kg/m3)

22.3 – 10 ºAPI

(920 – 1000 kg/m3)

<10 ºAPI

(> 1000 kg/m3)

Statoil’s ambition for offshore multiphase

transport


Long distance transport ambitionFluid viscosity

0.1

1

10

100

1000

10000

100000

0 50 100 150 200 250 300 350 400 450 500 550 600

Transport distance [km]

Vis

co

sit

y@

20

C [

cP

]

50 km heavy oil

200 km oil

500 km gas-condensate

2009

2016+

Peregrino

Tyrihans

Snøhvit

Mikkel

Midgard

Troll

Kvitebjørn

Huldra

TOGI

Svale

Sygna

Vega

Peregrino


Brazil

BM-C-7

Brazil

BM-C-7

Rio de Janeiro

• Peregrino (BM-C-7) is located in the Southern

Campos Basin area, approximately 85 km

southeast of the nearest coastline (Cabo Frio).

• Water depth in Block BM-C-7 range from 95 to 135

meters.

• In the areas of planned field facilities, the water

depths will average 98 to 122 meters.

• Oil: 14 API

Peregrino Project • Statoil: Operator with 60% share

• Phase I: 1st oil in 29th of March, 2011

• Ambition for Phase II

− 20 km Tie-back


Technologies for long distance transport of

viscous oil


Pre-heating

0

5 000

10 000

15 000

20 000

25 000

0 20 40 60 80 100

Vis

cosity [

mP

a.s

]

Water Cut [%]

Water

continuous flow

Core annular

flow

Dilution: reduction of

oil viscosity

Major issues for water continuous flow

transport in offshore production pipeline

• Inversion point identification:

− Complex function of surface chemistry,

compositions of the crude and the way to

generate emulsion

• Emulsion viscosity

− Water-in-oil emulsion

− Oil-in-water emulsion

• Emulsion stability

− dP/dx for ST >> dP/dx (cw) for large oil

viscosity

• Shut-in and restart process


0

5

10

15

20

25

0 10 20 30 40 50 60 70

Water cut (%)

Rel.

vis

c.(

-)

No chemicals

With chemical

Pal&Rhodes model

PHASE

INVERSION

0

5

10

15

20

25

30

35

0 0.1 0.2 0.3 0.4 0.5

dP/

dx,

Pa/

m

Oil viscosity, Pa.s

90% WC - ST

90% WC -water continuous flow

95% WC - ST


Challenges from laboratory study to industrial

application - Inversion


• Three generally accepted mechanisms

− Normal to abnormal - Tightly packed

emulsion which spontaneously inverts at

the critical concentration

− Abnormal to normal – through the

formation of multiple emulsions

− Normal to abnormal – Through the

formation of a bicontinuous phase

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0 % 10 % 20 % 30 % 40 % 50 % 60 % 70 % 80 % 90 % 100 %

Pre

ssu

re g

rad

ien

t re

lati

ve to

sin

gle

ph

ase

mo

del o

il [

-]

Watercut

Model oil - water

Crude oil - waterDW

DWDW

DW

ST

DW

DWDW

DO

STST

DWDW

STSTST

DODO

STSTST

DO

DO

DO


applications - Emulsion


Different

emulsions

Lubrication of

unstable

emulsions

Emulsion

viscosity

variation


application - Emulsion

• Emulsion viscosity for laminar flow

− Well predicted if WC <30%

− Complicated for WC >30%


0

1

2

3

4

5

6

7

0 10 20 30 40 50 60 70 80

Water cut (%)

Re

lative

vis

cosity (

-)

Rheometer data, 16800 1/s

Rheometer data, 1000 1/s

Data multiphase flow loop

(approx 900 1/s)

Inversion water cut

from DCR experiments

• Emulsion viscosity for turbulent flow

− Valle (2000)

− Brinkmann (1956)

− Importance for relative viscosity?

• Water viscosity uncertainty?

• Umix=1, D=0.3m: Re>105

• May not be an issue for large

pipe flow


2.5

1rel d





• Emulsion stability under flowing condition:

− Water continuous flow normally generated by ESP

− Droplet formation due to ESP

• Droplet size and its distribution

− Droplet coalescence in turbulent flow condition

• Time and length scale

• From lab scale to real pipeline (D and L)

− Identification of flow stratification

• From lab to real pipe system

• Critical condition; miminal Umix

for dispersed flow


0

5

10

15

20

25

30

35

0 0.1 0.2 0.3 0.4 0.5

dP/

dx,

Pa/

m

Oil viscosity, Pa.s

90% WC - ST


95% WC - ST



application – shut-in and restart

• During the shut-in period

− Phase separation for unstable

emulsion

− Cooling process

− Status of fluid in pipeline before the

restart

• Phase distribution along pipe

• T distribution along pipe and

across the pipe section




• Restart process by flushing with hot water

or oil

− Initial condition

− Front velocity

− Thermal non-equilibrium

• Natural convection in large

diameter pipe




• CFD simulation of hot fluid propagation process:


How is this handled by classical 1D model?

Statoil’s response to these challenges

• Experimental study of different scales

− Systematic study of oil characterization – physical properties

− Small scale experiment: understanding emulsion and inversion

behavior:

• both model and crude oils

− Large scale experiment to mimic real production scenario

• Modeling of multiphase viscous flow

− CFD and classical 1D model

− From lab observations to field application - scaling

• Field tests

− Verification and validation


Statoil’s response to these challenges

• Current research activities - 2012

− Large scale experiment at Porsgrunn – real crude oils

• ESP, transport and separation

− Field tests at Peregrino-I

− Internal modeling work

− Experiment at SINTEF – model oil

− Cold shut-in and restart – TNO

− Modeling and experiment of multiphase viscous oil – Post-Doc and PhD at NTNU

− Viscous vertical flow –PhD at Nottingham University via TMF

− FACE program

− Summer internship, project work and Master Thesis work at NTNU


Large scale

experimental program

at Statoil


a

b

c

j

fd

e

h i

g

gas

oil

water

mixture

Baker Hughes 84-P75SXD Centurion

Centrifugal pump with 84 stages

Specifications of the experimental facility


Number of phases 3 (gas, oil, water)

Water flow rate 0-10 m3/h

Oil flow rate 0-15 m3/h

Liquid flow rate 0-25 m3/h

Gas flow rate Normal: GOR = 25

High: GOR = 100

Maximum pressure (except

ESP)

100 bar

Maximum pressure ESP 175 bar

Temperature range 4-110 ºC

Maximum temperature high

temp separation

170 ºC

Material Duplex Stainless steel 22Cr ( S31803)

Total liquid volume Ca 8.3 m3 (this test configuration)

Pipe internal diameter 0.05248 or 0.079m

Pipe length of test section 200 m

Pipe inclination -/+ 5 degrees

Main issues for modeling long distance

multiphase viscous oil flow • Emulsion formation

− Emulsion formation due to ESP: droplet size and its distribution

• Is the Hinze type of correlation applicable?

• Emulsion transportation (for unstable emulsion)

− Distance or time to reach fully-developed flow

• Droplet coalescence

− Flow regime transition – evolution

• Shut-in-and restart process

− What needs to be done?

• Classical 1D modeling


Summary

• The biggest challenge is:

− To find right people, to work on right problem, and to get right solution

• The key to solve this challenge is:

− Educate the people

• Welcome to work with Statoil

− Internship, Project, Master Thesis, PhD program, Post-Doc, and professional

career



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Presenters name

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E-mail address, tel: +00 00 00 00

www.statoil.com

Thank you

Lys Ark Yang 2012

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