Phase Behavior Solid Organic Precipitation and Mobility

Characterization Studies in Support of Enhanced Viscous Oil Recovery On

Alaska North Slope22 -23rd January 2007

Outline

Introduction Prior work Present quarter Plan for next quarter Simulation study

ANS Heavy Oil

Heavy oil deposits of 20- 25 billion barrels Class A medium heavy oil e.g. Viscosity

~ 100cp or more Current production limited to 12000 -

15000 bbl/Day Monetize stranded (heavy) oil resources;

additional throughput for TAPS for sustained economic operation

Problems With ANS Heavy Crude Recovery Poor mobility and hence poor recovery Formation damage due to Asphaltene

deposition Injectivity limitations to solvent and gas

floods Emulsification and sand production

Objectives of the Project Understanding complex fluid phase behavior through compositional & PVT characterization. Phase behavior changes in presence of solvent

(CO2/Hydrocarbons). Study viscosity behavior in presence of solvents Solid deposition studies in pipeline and near well-

bore regions to provide insights into the molecular/pore-level mechanisms governing observed PVT behavior.

Phase behavior modeling using (CMG) WINPROP PVT Simulator and develop reliable numerical reference fluid model

Overview

Experimental Program

Characterization of reservoir hydrocarbon fluid Composition analysis of the system Constant composition expansion Differential liberation Batch separator tests

Special PVT tests Slim tube test Swelling test

Equipments Procured and Set up

Trace GC ultra Gas Chromatogram Temco PVT cell Anton Paar Densitometer DBR Recombination cell DBR Slim Tube Rig Cambridge Scientific SPL 440

Viscometer

Compositional Characterization

Recombined oil composition

(Representing the reservoir

oil composition )

Composition of Dead Crude oil on GC (FID)

By Simulated Distillation

Associated Gas Composition by GC (TCD)

Method System : Trace GC UltraColumn :TR-SIMDIST (10m , 0.53 mm ID )Injector : Split @ 350 °C ( Ratio 2:1)Temperature : Initial - 35 °C Ramp 1 - 5 °C /min till 175 °C Ramp2 - 7 °C /min Final - 350 ° For 5 Min Carrier Gas : HeInlet Pressure : 22kPa

Boiling Range Calibration for SIMDIST

Calibration Curve

Boiling point Vs RT y = 0.0695x - 21.32

R2 = 0.9979

0

10

20

30

40

50

60

0 200 400 600 800 1000 1200

Boiling Point F

RT

min

Results

Milne Point Crude

Composition

0

5

10

15

20

25

30

35

C7

C8

C9

C1

0

C1

1

C1

2

C1

3

C1

4

C1

5

C1

6

C1

7

C1

8

C1

9

C2

0+

SCN

wt %

Milne- Point Crude

Recombination

Component Mol %

N2 0.02

CO2 0.16

C1 98.33

C2 0.24

C3 0.31

i-C4 0.07

C4 0.12

C5 0.03

i-C5 0.03

C6 0.02

C7+ 0.02

Field GOR =230Scf/STB

Oil specific Gravity = 23.65 º API

Gas Composition for Recombination

Recombined Composition Recombined composition Milne -Point oil sample

0.0001

0.001

0.01

0.1

1

10

100

N2

CO

2

C1

C2

C3

i-C4

C4

C5

i-C5

C6

C7+

C8

C9

C10

C11

C12

C13

C14

C15

C16

C17

C18

C19

C20+

component

Wt %

Viscosity Behavior With Temperature(Brookfield Viscometer)

Milne-point oil sample

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Temperature C

Vis

co

sit

y c

p

Plan for Next Quarter Compositionally characterize heavy oil

samples and produce recombined oil composition

Perform PVT tests on heavy oil samples. Measurement of viscosity of crude oil sample

under pressure conditions. Test solubility of injectant gas in heavy oil

sample and study swelling behavior of oil.

Tuning of West Sak Heavy Oil DataAvailable West Sak Heavy Oil data was used to test the tuning procedure

Different tuning strategies like inclusion of BIP’s and splitting of plus fraction were tested

For the procedure adopted in the studyC21+ mole fraction was used as it isBIP’s were not included Regression was performed using the experimental values of saturation pressure, CCE and DLTuning was performed until a consistency between the experimental values and those predicted by the EOS was obtained

0.001

0.01

0.1

1

10

100

N2

CO

2 C1

C2

C3

C4

C5

C6

C7

C8

C9

C10

C11

C12

C13

C14

C15

C16

C17

C18

C19

C20

C21

+

Mol

e %

Compositional Analysis of West Sak Oil(Sharma 1989)

Dif. Lib. Calc.Regression Summary

0

200

400

600

800

1000

1200

0 500 1000 1500 2000 2500 3000

Pressure (psia)

Final Oil Visc. Init. Oil Visc.

Exp. Oil Visc.

Oil

Vis

cosi

ty c

P

CCE Calc.Regression Summary

50

60

70

80

90

100

110

0 1000 2000 3000 4000 5000 6000 7000 8000

Pressure (psia)

Final Liq. Vol. Init. Liq. Vol.

Exp. Liq. Vol.

Rel

ativ

e V

olum

e

Equation of State Tuning …Contd

Generalized strategy of EOS tuning applicable to heavy oils is developed

Three samples of heavy oils and four samples of light oils were evaluated

Saturation pressure and viscosity data were used for tuning purposes

Good fit between the experimental data and simulated values was obtained

Composition Distribution (mole %)

0

10

20

30

40

50

60

70

80

90

N2 CO2 C1 C2 C3 iC4 nC4 iC5 nC5 C6 C7+

Components

Mo

le %

Oil 1

Oil 2

Oil 3

Oil 4

Oil 5

Oil 6

Oil 7

Oil 8

Simulation results for Oil 5 at different temperaturesDif. Lib. Calc.

Regression Summary

0

20000

40000

60000

80000

100000

120000

140000

160000

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000

Pressure (kPa)

Oil V

isc

os

ity

(c

p)

Final Oil Visc.

Init. Oil Visc.

Exp. Oil Visc.

Dif. Lib. Calc.Regression Summary

0

20000

40000

60000

80000

100000

120000

140000

160000

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000

Pressure (kPa)

Oil

Vis

cosi

ty (c

p)

Final Oil Visc.

Init. Oil Visc.

Exp. Oil Visc.

T = 38 C

T = 60 C

Enhanced Oil RecoveryEnhanced Oil Recovery techniques with the main aim of improving declining production

Major point of focus is reduction in the viscosity of the heavy oils

Prudhoe Bay Gas as a miscible injectant will be tested due to its following characteristics

Promotes swelling

Reduces oil viscosity

Grid System and Petrophysical Properties

3D Cartesian grid system with a five spot injection pattern adopted for the study

25 X 25 X 9 grid system with a total of 5625 grid blocks

Distance between adjacent wells 1320 ft and between injection and production well 933 ft

Injection wells at the corners and production well at the center of the grid system

Layer No. Sand Interval (ft)Avg.

Porosity (%)

Avg. water saturation,

(%)

Net pay (ft)

9-topmost Upper 1 3544-3584 30 24 30

7 Upper 2 3614-3640 31 31 21

5 Lower1 3660-3686 23 45 3

3 Lower2 3695-3760 25 47 3

1-bottommost Lower3 3776-3814 27 41 17

Average Layer Properties (Bakshi et al 1991)

Plans for the next Quarter

Development of reservoir model with properties mentioned before has been accomplished

CMG GEM is proposed to be used for reservoir simulation tasks

Prudhoe Bay gas as a miscible injectant is to be tested initially

Simulation runs at 10%, 20%, 30%, 40%, 50% PV are proposed to be carried out

Thank You