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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