Phase Behavior Solid Organic Precipitation and Mobility Characterization Studies in Support of Enhanced Viscous Oil Recovery On Alaska North Slope rd January 2007

Outline Introduction Prior work Present quarter Plan for next quarter Simulation study

ANS Heavy Oil Heavy oil deposits of billion barrels Class A medium heavy oil e.g. Viscosity ~ 100cp or more Current production limited to 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 (CO 2 /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 Ultra Column :TR-SIMDIST (10m, 0.53 mm ID ) Injector : 350 °C ( Ratio 2:1) Temperature : Initial - 35 °C Ramp °C /min till 175 °C Ramp2 - 7 °C / min Final ° For 5 Min Carrier Gas : He Inlet Pressure : 22kPa Boiling Range Calibration for SIMDIST

Calibration Curve

Results Milne Point Crude

Composition

Recombination ComponentMol % N20.02 CO20.16 C C20.24 C30.31 i-C40.07 C40.12 C50.03 i-C50.03 C60.02 C Field GOR =230Scf/STB Oil specific Gravity = º API Gas Composition for Recombination

Recombined Composition

Viscosity Behavior With Temperature (Brookfield Viscometer)

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 Data Available 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 study  C21+ mole fraction was used as it is  BIP’s were not included  Regression was performed using the experimental values of saturation pressure, CCE and DL  Tuning was performed until a consistency between the experimental values and those predicted by the EOS was obtained

Compositional Analysis of West Sak Oil (Sharma 1989)

Oil Viscosity cP Relative Volume

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

Simulation results for Oil 5 at different temperatures T = 38 C T = 60 C

Enhanced Oil Recovery Enhanced 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-topmostUpper Upper Lower Lower bottommostLower 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