SPE DISTINGUISHED LECTURER SERIESis funded principally

through a grant of the

SPE FOUNDATIONThe Society gratefully acknowledges

those companies that support the programby allowing their professionals

to participate as Lecturers.

And special thanks to The American Institute of Mining, Metallurgical,and Petroleum Engineers (AIME) for their contribution to the program.

SPE Distinguished Lecturer Series

Viscous Oil EOR by Viscosity Viscous Oil EOR by Viscosity Reducing Immiscible (VRI) WAG Reducing Immiscible (VRI) WAG

ProcessProcess

Bharat S JhaveriBharat S Jhaveri

BP Exploration (Alaska) Inc.BP Exploration (Alaska) Inc.

Acknowledgements• SPE

• BP, Exxon Mobil, ConocoPhillips

• Alan Clark

• Frank Paskvan

• Jonathan Williams

• Katrina Yancey

• Pat McGuire †

• Rydell Reints

† SPE 93914Viscosity Reduction WAG: An Effective EOR Process for North Slope Viscous OilsP. L. McGuire, BP Exploration (Alaska) Inc., R. S. Redman, ConocoPhillips Alaska Inc., B. S. Jhaveri, K. E. Yancey, S. X. Ning, BP Exploration (Alaska) Inc.

• Motivation

• Miscible WAG* EOR

• Viscosity Reducing Immiscible WAG

• North Slope Situation

• Closing Remarks

* Water-Alternating Gas

Outline

Motivation For Gas EOR in Viscous Oil

• Conventional technology* not applicable⎯ Too deep

⎯ Offshore

⎯ Arctic

• Big projects with many high rate wells

• Available gas resource* e.g. Steam, Hot water flooding

• Motivation

• Miscible WAG EOR– Enriched Gas Drive

– Vaporizing Gas Drive

• Viscosity Reducing Immiscible WAG

• North Slope Situation

• Closing Remarks

Outline

Miscibility Mechanism

Low Viscosity Oil – 10 cp

5 10 15 20 25

Carbon Number

Mol

e %

0

2.5

5

Pseudo-Ternary Diagram

CH CI

CL

Critical point

Single Phase

C

PR = 2000 PSIA

Dew point

Bubble point

Two Phase

Enrichment Process

CH CI

CL

Critical point

Single Phase

C

PR = 2000 PSIA

Dew point

Bubble point

Two Phase

Oil

MI

MI - Oil Miscibility

CH CI

CL

Critical Composition

Single Phase

C

PR = 2000 PSIA

Dew point

Bubble point

Two Phase

Oil

MI

Pressure Dependence

CH CI

CL

Critical pointSingle Phase

C

PR = 1500 PSIA

Bubble point

Two Phase

Dew point

COil

MI

Pressure Dependence

CH CI

CL

Critical point

Single Phase

C

PR = 2500 PSIA

Two Phase

Oil

MI

Minimum Miscibility Pressure (MMP)

CH CI

CL

Critical Composition

Single Phase

C

PR = 2000 PSIA

Dew point

Bubble point

Two Phase

Oil

MI

Slimtube Recovery: Miscible

Pressure, PSIA

Rec

over

y @

1.2

PV

2000 3500

1.0

MMP (Minimum Miscibility Pressure)

Miscible Displacement Process

Transition

Zone

MI Oil

Phase Viscosities in Slimtube

0.01

0.1

1

10

100

0 200 400 600 800 1000

Oil ViscosityGas Viscosity

Inj. ---->Distance along slimtube (Grid-block no.) Prod.

Oil,

Gas

Vis

cosi

ty, c

p

Miscible WAG EOR Summary• Injection gas rich in (C2-C4)

hydrocarbons

• Fluid properties change by mass transfer

• MI composition a key design parameter

• WAG process to optimize gas sweep

• Motivation

• Miscible WAG EOR

• Viscosity Reducing Immiscible WAG

• North Slope Situation

• Closing Remarks

Outline

Moderate Viscosity Oil – 57 cp

5 10 15 20 25

Carbon Number

Mol

e %

0

2.5

5

VRI Mechanism

CHCI

CL

Oil

VRI

(Viscosity Reducing Injectant)

Critical point

1 Phase

2 Phase

PR = 2000 PSIA

Slimtube Recovery: Immiscible

Pressure, PSIA

Rec

over

y @

1.2

PV

2000 3500

1.0

MMPPR

VRI Displacement Process

VRITransition

ZoneViscous Oil

Reduced Viscosity Oil

0.01

0.1

1

10

100

0 0.2 0.4 0.6 0.8 1

Oil ViscosityGas Viscosity

Viscosity Reduction in Slimtube

Inj. ---->Distance along slimtube (Grid-block no.) Prod.

Oil,

Gas

Vis

cosi

ty, c

p

Viscosity Reduction in PVT Cell

1

10

100

1 2 30VRI Injected Moles/Mole

Oil

Vis

cosi

ty, c

p

VRI Reservoir Process (2D)I1 InjectorP1 Producer

Kx scale

• Vertical injector, horizontal producer

• Waterflood, WAG simulations

• Low and Moderate Viscosity Oils

• 1:1 WAG ratio, 30% HCPV Gas Injection

Injectant Description

• Low viscosity (10 cp) oil miscible with injected gas (MI)

• The same MI immiscible with moderate viscosity (57 & 117 cp) oils

• Injectant referred to as VRI for moderate viscosity oils

Slimtube Recoveries for 2 Oils

Pressure, PSIA

Rec

over

y @

1.2

PV

2000 3500

10 cp 57 cp

1.0

Injected Gas

Miscible for 10 cp

VRI for 50 cp

EOR Recoveries for MI & VRI (2D)

0

4

8

12

16

20

0 5 10 15 20 25 30Years

EO

R, %

OO

IP

10cp L-117 OBd

57cp Z-39 OBd

117cp Z-39 OBa

Miscible

VRI WAG

VRI WAG

EOR recovery similar for MI & VRI

Oil Rate for MI & VRI (2D)

0

200

400

600

800

1000

1200

0 2 4 6 8 10Years

Oil

Rat

e, S

TB/D

10cp_MI

10cp_wf

57cp_MI

57 cp_wf

117cp_MI

117cp_wf

Miscible

VRI WAG VRI WAG

Earlier EOR response for lower viscosity oils

117cp oil

45 cp oil

13 cp oil

117cp oil

45 cp oil

13 cp oil

Oil Viscosity Map (after 30 years)

117 cp oil

10 cp oil

57 cp oil

Miscible

VRI

VRI

VRI WAG Process

• Injectant not rich enough in (C2-C4) hydrocarbons

• Oil viscosity reduction and swelling by mass transfer

• Improved displacement by subsequent water injection

• WAG process to optimize gas sweep

• Motivation

• Miscible WAG EOR

• Viscosity Reducing Immiscible WAG

• North Slope Situation

• Closing Remarks

Outline

Map of Alaska North Slope

Prudhoe Bay Central Gas Facility• ~500 mmscf/d MI

North Slope Viscous Oil Resource

KUPARUK RIVER UNIT

PRUDHOE BAY UNIT

West Sak (non-core)W S/Schrader Bluff (core)

S-Pad

Polaris

Orion

West Sak 1J

W-203

NS Viscous Oil Opportunity• Huge Resource (Tens of BSTB)

• Current development targets ~5 BSTB in W. Sak/Schrader Bluff Formation

• Low primary & waterflood recovery

• Available Gas Resource

• Prudhoe MI not miscible with moderate to high viscous oil (>15 cp)

Schrader Bluff Oil Quality Variation

-

2

4

6

8

10

5 7 9 11 13 15 17 19 21 23 25 27 29Carbon Number

Mol

e %

40 cp W-203 Polaris

87 cp WS 1-01 D-Sand

61 cp WSP 8i D-Sand

10 cp Orion L117 OBd

57 cp Orion Z-39 OBd

117 cp Orion Z-39 OBa

52 cp Polaris W205 OBc

11 cp Milne S-12

C5+ fraction normalized to 100%

Miscible Target

VR-WAG Target

EOR Prediction Methodology

Reservoir Simulation- Type patterns

(based on reservoir description)

- EOR Type Curves (Oil, MI, RMI)

Reservoir Simulation- Type patterns

(based on reservoir description)

- EOR Type Curves (Oil, MI, RMI)

Liq

VapAdd MI

0%

5%

10%

15%

20%

0% 10% 20% 30% 40%MI INJECTED (TPV)

REC

OVE

RY

(%O

IIP)

Field Scaleup- Project area segments

(segment PV, well allocations)

- Tank model scaleup

Field Scaleup- Project area segments

(segment PV, well allocations)

- Tank model scaleup

Phase Behavior Model- PVT, Slimtube Data- EOS

Phase Behavior Model- PVT, Slimtube Data- EOS

Reservoir Simulation- Type patterns

(based on reservoir description)

- EOR Type Curves (Oil, MI, RMI)

Reservoir Simulation- Type patterns

(based on reservoir description)

- EOR Type Curves (Oil, MI, RMI)

Liq

VapAdd MI

Liq

VapAdd MI

Liq

VapAdd MI

Liq

VapAdd MI

0%

5%

10%

15%

20%

0% 10% 20% 30% 40%MI INJECTED (TPV)

REC

OVE

RY

(%O

IIP)

0%

5%

10%

15%

20%

0% 10% 20% 30% 40%MI INJECTED (TPV)

REC

OVE

RY

(%O

IIP)

Field Scaleup- Project area segments

(segment PV, well allocations)

- Tank model scaleup

Field Scaleup- Project area segments

(segment PV, well allocations)

- Tank model scaleup

Phase Behavior Model- PVT, Slimtube Data- EOS

Phase Behavior Model- PVT, Slimtube Data- EOS

KUPARUK RIVER UNIT

PRUDHOE BAY UNIT

West Sak (non-core)W S/Schrader Bluff (core)

S-Pad

Polaris

Orion

West Sak 1J

W-203

SPE 99569, “A New Scaleup Approach for Nonpattern Field Development Under Water or WAG Injection”, B. S. Jhaveri, BP Exploration (Alaska) Inc

NS Field Scaleup Example

0102030405060708090

100

Jan-06 Jan-11 Jan-16 Dec-20 Jan-26 Jan-31 Jan-36

MI I

nj m

msc

f/

0

5000

10000

15000

20000

25000

30000

35000

EOR

Rat

e B

PD

MI Inj WROM_BSJ_Update

EOR Oil Rate WROM_BSJ_Update

• Huge Development Target • 50 mmscf/d of VRI injection• 12 MBD EOR rate, 6% (OOIP) EOR• MI efficiency close to classical miscible

• Huge Development Target • 50 mmscf/d of VRI injection• 12 MBD EOR rate, 6% (OOIP) EOR• MI efficiency close to classical miscible

EOR

Rat

e

MI I

njec

tion

Rat

e

North Slope VRI Status• VRI project designed for Polaris & Orion fields

• IRS ruled VRI process as a qualified recovery method for EOR tax credit

• Alaska State approval to commence VRI injection in Polaris reservoir.– Injecting 2 mmscf/d MI in W-215

– 6% EOR recovery from 350 MSTB OOIP

• Application for Orion VRI injection approved– 1,000 MSTB OOIP target with similar EOR recovery

expected

Key Project Design Components• (Lean Gas, NGls, MI Capture)

• Surveillance (Gas Analysis, Well Intervention)

• Injectivity (Water/MI, Gas Trapping)

• Conformance (Zonal, Volumetric)

• Flood Management MI Resource (Voidage Replacement, Pressure Maintenance, WAG Ratio, MI Slug ,MI Allocation)

• Asphaltenes Dropout (Reservoir & Facility)

Closing Remarks• When conventional technology not applicable

• VRI technology can dramatically increase primary and waterflood recovery in viscous oil reservoirs

• Recovery enhancement by viscosity reduction and swelling

• Developed approach for the design, engineering, and evaluation of viscous oil gas EOR projects

SPE Distinguished Lecturer Series

Viscous Oil EOR by Viscosity Viscous Oil EOR by Viscosity Reducing Immiscible (VRI) WAG Reducing Immiscible (VRI) WAG

ProcessProcess

Bharat S JhaveriBharat S Jhaveri

BP Exploration (Alaska) Inc.BP Exploration (Alaska) Inc.