Mobility Control Using FoamSnorre/WFB FAWAG Pilot Revisit

Arif Ali Khan (NTNU), Ying Guo (Total E&P Norge), Dag Wessel-Berg (SINTEF), Jon Kleppe (NTNU), Dennis Coombe (CMG)

Content

• Introduction– Project motivation and scope

• Snorre WFB pilot simulation – a revisit– Updated reservoir model– Porting from ECLIPSE to STARS and model validation– Full-field model vs sector model– Simulation benchmarking

• Simulation of FAWAG pilot– Sensitivity study with respect of foam parameters

• Summary, conclusions and recommendations

Introduction

• Project motivation– Start out as a master thesis– New Snorre reservoir model established in 2005 – Evaluate STARS as field simulator for FAWAG

• Project scope and ambition– Transfer the most recent reservoir model for Snorre WBF pilot to

STARS simulator– Re-evaluate the foam effect on the new Snorre WBF model– Establish a feasible workflow for FAWAG simulation– Recommend potential improvement for STARS simulator

A feasible workflow for FAWAG simulation

• Assumptions– Most of the FAWAG project will likely be implemented after a significant

period of water or gas flooding, and the oil saturation in the flooded areas is around Sorw or Sorg

– The reservoir model is well established• Pre FAWAG simulation

– Full-field simulation before FAWAG using Eclipse– Establish a sector model for the pilot region and validate using Eclipse

• FAWAG simulation (field + sector)– Port the models from Eclipse to STARS

• Use Petrel to export the grids, rock property, faults etc to STARS + manual adjustment of the data file for STARS

• Use Eclipse simulated saturation and pressure map before the FAWAG start to initialize the STARS simulation

– History-match the FAWAG data or predict the field behaviour using STARS

Snorre WFB pilot - history• Pilot time: November 1999 –

2001• Wells involved:

– P32 (inj)/P39 (prod), 1550 m – P32 (inj)/P42 (prod), 1450 m

• 2 FAWAG cycles after gas injection and WAG operation for about 3 years

• Total surfactant injected: ~140 tonn

– Slug 1: 15262 SM3 (0.49 wt%) for 9,5 days followed by 100 days gas injection

– Slug 2: 31733 SM3 (0.2 wt%) for 20.3 days followed by more gas injection

• Ref: SPE 75157 by A. Skauge et.al.

WAG/FAWAG history (well pair P32-39)

1. Surf slug: 0.49 wt%, 9.5 days, 15262 SM3 2. Surf slug: 0.20 wt%, 20.3 days, 31733 SM3

WAG FAWAG WAG

Snorre reservoir

From Eclipse to STARSSTARS

WFB – Full Field (2005 –Statoil)

ECLIPSE

WFB – sector (This work)

Establish the sector model for FAWAG using Frontsim

Water injection

Gas injection

Effect from nearby wells

Selected sector

SPE75157 vs this work

Geological Differences• Stochastic perm / porosity• Faults

PVT• Composional - 4 Component• Black oil - 5 ComponentRock Compressibility

Foam• Part never matches with old

parameters versus new model

New Eclipse Type Well Section

• New well Index• Deviated• Trans and skin included

AbsolutePermeability

Porosity

FAULTS

SPE75157 vs this work

Layer

# division

s

K (md)

Ф Layer height

(m)

Layer height

(mD*M)

4.2 14 700

2 480

1 120610

6.2

14.012.2

S1 5 3500 0.259

S2 7 400 0.236

S3 51

8090

0.2250.191

P- 39

Pdummy

P-32

25x21x20 = 10 500 grid blocks

P-32

P- 42

P- 39

Layer

# division

s

K (md)

Ф Avglayer height

(m)

Layer height

(mD*M)

1.69 -

-

S3 8 - - 4.06 -

S4 6 - - 4.06 -

2.77

S1 4 - -

S2 16 - -Stochastic values

29 x 26 x 34 = 25 636 grid blocks

Model porting from Eclipse to STARS

• Grid data – Use Petrel to export files with STARS format (trivial)– Grid coordinates and faults– Permeability and porosity values for each blocks– Transmissibility multipliers for each blocks– Pressure + Saturation values for each blocks

• Fluid data – Manual entering to STARS input files (trivial)• Well data - Convert Eclipse schedule files using with

CGM/IMEX to STARTS input files + 70% manual input file adjustment (tedious)

• Add foam in STARS (trivial)Arif – please review and change to match what you have done.

FAWAG pilot simulation workflow

EclipseField model

S + P profilein restart files

STARSField model

Field simulation results including

foam effect

STARSField model

EclipseField model

S + P profilein restart files

Field simulation results including

foam effect

WAG period FAWAG period

Eclipse vs STARS – Field model/NO FOAM

Poor match

Eclipse vs STARS – Field model/NO FOAMFULL FIELD SNORRE WFB, STARS

P-39P (PRODUCER)

Water Oil Ratio SC MEASUREDWater Oil Ratio SC ECLIPSEWater Cut SC STARSWater Cut SC STARS

Time (Date)

WaterO

ilR

1997 1998 1999 2000 2001 20020.00

0.20

0.40

0.60

0.80

1.00

WAG FAWAG

SLUG-1SLUG-2

FULL FIELD SNORRE WFB, STARSP-39P (PRODUCER)

Water Oil Ratio SC MEASUREDWater Oil Ratio SC ECLIPSEWater Cut SC STARSWater Cut SC STARS

Time (Date)

WaterO

ilR

1997 1998 1999 2000 2001 20020.00

0.20

0.40

0.60

0.80

1.00

WAG FAWAG

SLUG-1SLUG-2

WAG FAWAG

SLUG-1SLUG-2W

ater

cut

Eclipse vs STARS – Field model/NO FOAMFULL FIELD SNORRE WFB, STARS

P-39P (PRODUCER)

P-39P Blackoil, STARSP-39P Compositional, STARSWBHP_SIM_P-39P ECLIPSE

Time (Date)

Well

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 200615,000

20,000

25,000

30,000

35,000

WAG FAWAG

SLUG-1SLUG-2

FULL FIELD SNORRE WFB, STARSP-39P (PRODUCER)

P-39P Blackoil, STARSP-39P Compositional, STARSWBHP_SIM_P-39P ECLIPSE

Time (Date)

Well

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 200615,000

20,000

25,000

30,000

35,000

WAG FAWAG

SLUG-1SLUG-2

WAG FAWAG

SLUG-1SLUG-2

Wel

l Bor

ehol

e pr

essu

re (K

Pa)

Validation sector modelECLIPSE vs STARS (no foam)

WAG FAWAG

SLUG-1SLUG-2

WAG FAWAG

SLUG-1SLUG-2

WAG FAWAG

SLUG-1SLUG-2

Validation sector modelECLIPSE vs STARS (no foam)

WAG FAWAG

SLUG-1SLUG-2

WAG FAWAG

SLUG-1SLUG-2

WAG FAWAG

SLUG-1SLUG-2

Simulation benchmarking

• Full field model – Snorre– No of grid blocks: XYZ= 43 x 146 x 34 => 213 452 grid blocks– No of wells: 8 up to the end of FAWAG pilot– Total simulation run time

• Eclipse* up to FAWAG: ~ 20 hours• STARS** incl FAWAG ~ 18 hours• STARS** for FAWAG only: ~ 6 hours

• Sector model– No of grid blocks: XYZ= 29 x 26 x 34 => 25 636 grid blocks (~ 8 time

smaller than full field model)– No of wells: 3 up to the end of FAWAG pilot– Total simulation run time

• STARS** for FAWAG only: ~ 2 hours

* Unix / Solaris – 32 bits** High-End PC (Pentium4, dual processor, 3GHz/1.5GB RAM), 32 bits

Foam simulation – phenomenological approach

• The physical phenomenon included in the sensitivity studies1. Necessary surfactant concentration in order for foam to grow

(fsurfmin)2. Foam dry out when there is not sufficient water (Swmin)3. Foam killed by surplus of oil (Sof)4. Foam collapse due to viscous forces (Nc) – criticall capillary

number

Foam Model in STARS:

( ) FMskk wo

rgf

rg ×=

)11

654321 ⋅⋅⋅⋅⋅⋅⋅⋅⋅+=

FFFFFFMRFFM

• FM Dimensionless Interpolation Factor

FM = 1 (no foam)

FM = 0 (strong foam)

• MRF Reference mobility reduction factor

• F1 Surfactant concentration term

• F2 Water saturation term

• F3 Oil Saturation (foam killer)

• F4 Gas Velocity term

• F5 Capillary Number term

• F6 Critical Capillary Number term

Surfactant concentation effect

epsurf

s

fmsurfwF ⎥

⎦

⎤⎢⎣

⎡=1

Water saturation effect on foam

⎥⎦⎤

⎢⎣⎡ −×

+=π

)(arctan(5.02 fmdrySepdryF w

Oil saturation effect on foam

epoil

o

fmoilfmoilSF ⎥

⎦

⎤⎢⎣

⎡ −=3

F3: Oil Saturation Effect on FM

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 0.10 0.20 0.30 0.40 0.50

So

[FM

]

0

200

400

600

800

1000

12000.000.050.100.150.200.250.30 Sw

MR

F

FM- epoil = 0 FM- epoil = 0.25 FM- epoil = 1 FM- epoil = 2fmoil = 0.25 Sw MRF = 1000

Foam

Str

engt

h D

ecre

ase

Foam

No Foam

No Foam

Foam

Capillary number term

epcap

cNfmcapF ⎥

⎦

⎤⎢⎣

⎡=5

wgc

PKNσ∆

=

0,00

0,50

1,00

1,50

1,E-10

1,E-09

1,E-08

1,E-07

1,E-06

1,E-05

1,E-04

1,E-03

1,E-02

1,E-01

1,E+00

1,E+01

1,E+02

Nc

FM

0

200

400

600

800

1000

1200

MR

F

FM- epcap = -1 FM- epcap = 0 FM- epcap = 0,5 FM- epcap = 1 FM- epc

F5: Relative Capillary Number

F5: Relative Capillary Number Effect Term

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E-10 1.E-09 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03Nc

F5

epcap = -1 epcap = 0 epcap = 0.5 epcap = 1 epcap = 5 fmcap = 7.84E-08

epcap = 0(Viscous Effects Neglected on Foam Strength)

Slope = -1 (shear Thinning) Foam Degradation

Slope = +1 (shear Thickening)

Viscous Forces

Relative Permeabilities – After Foam Application

After Foam

Before Foam

MRF sensitivity MRF Sensitivity

SECTOR_WFB_MRF_10.irf SECTOR_WFB_MRF_20.irfSECTOR_WFB_MRF_50.irfSECTOR_WFB_MRF_70.irfSECTOR_WFB_MRF_100.irfSECTOR_WFB_MRF_200.irfSECTOR_WFB_MRF_300.irfSECTOR_WFB_MRF_400.irfSector, No FoamHistoryGas InjectionWater Injection

Time (Date)

Gas

Oil

Rat

io S

C (m

3/m

3)

Gas

Rat

e S

C (m

3/da

y)

Wat

er R

ate

SC

(m3/

day)

1998-12-1 1999-5-30 1999-11-26 2000-5-24 2000-11-200

200

400

600

800

0.00e+0

5.00e+5

1.00e+6

1.50e+6

2.00e+6

0

2,000

4,000

6,000

8,000

FAWAG

MRF = 50 (Ref SPE75157)

MRF =10MRF =20

MRF >100

Oil saturation sensitivity on foam

Weak foam

Strong foam

Foam sensitivity on critical capillary pressure

Foam sensitivity on critical capillary pressure

Foam sensitivity on water saturation

Foam sensitivity on water saturation

Sensitivity study on foam

This work SPE 75157

Base case Scale of influence

Base case

1 MRF ~10 - 50

fmdry = 0.12 – 0.2fpdry = 50000 – 500 000

2

2

No done ins this study. Not sure. (higly

dependent on permeability.

3 for block-block

2 for well-block

Scale of influence

Adsorption fmsurf = 0.0000058(0.01 wt%AOS??)epsurf = 1.0

4

Foam strength (MRF)

MRF = 70 1

Foam dryout fmdry = 0.6epdry = 100

2

Oil tolerance fmoil = 0.2-0.3epoil = 2

3

Shear Thinning

fmcap = 7.0E-05epcap = 1.5

N/A

Surfactant adsorption

Conclusions and recommendations

• The simulation exercises on the foam WFB FAWAG pilot demonstrate the feasibility STARS as a tool for field scale studies for FAWAG.

• More understanding and tuning of the reservoir simulation for FAWAG is needed in order to obtain trust-while results.

• Acquisition of lab data must be designed closely related to the planed field operation

• Refined grid analysis should be done in the close-well areas, but STARS must be made more robust for this.

• Hysteresis for WAG period should be included in the simulations• MRF as dependent on the FAWAG cycles, pressures, etc (input

table?)• Oil saturation plays important role for foam behaviour, specially in

the saturation ranges where foam is likely to be generated or killed and more sophisticated modelling is desired to capture the possible phenomena, e.g. Sw and its distribution, wettability, oil composition.

Thanks for your attention !Questions?