An Investigation of vaporization in the displacement of Swan Hills crude oil by rich gas

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The vaporization of Swan Hill Crude Oil in the displac ement process by enriched gas was investigated. This study mainly investigated the compositional effect and the displacement pressure effect on the interphase mass transfer when gas was introduced to mix with the crude oil at reservoir conditions. The study indicates that vaporization of c+ 5 material is directly proportional to the richness of the injected gas. Using ah enriched gas(SO mole% of c; ), the condensing drive vaporized about 40-50% of the c+ 5 from the crude oil after 2.5 pore volumes had been injected. The vaporization of the c+ 5 will decrease as the methane component increases in concentration in the injected gas. When the methane composition is increased to 95 mole%, the vaporization will amount to approximately 10% at an injected pore volumes of 2 . 5. Al so, this study indicates that displacement pressure has a dominating effect on the degree of vaporization. When the operating pressure is increased from 2,500 psia to 3000 psia ,the vaporization of the c+ 5 is increased from 32% to about 50% when an intermediate rich gas (37.32 mole per cent c+ 2 ) is used. In this study, composition of the twd phases at equilibrium were predicted, by a minimum free energy concept in conjuction with the modified Redlich-Kwong equation of state for the gas phase and the dilated Van Laar model for the liquid phase in the calculation of phase fugai cities as proposed by Prausnitz et al(l968) ~ The binary interaction constants or parameters for the heavy ends were calculated and adjusted based on the available compositional analysis of the equilibrium mixture of Swan Hill crude oil and injected gas at various gas oil mixing ratio. The predicted composition for the vapor and liquid in the equilibrium show an absolute deviation of less than 10% for the system mixture of Swan Hill crude oil and enriched gas at 2,500 psi and 225°F. In order to simulate the steady state displacement process, a multicell separation model was used. This model incorporates the constraint of constant volume for each cell and the option of fluid transport according to the phase mobility. Recovery calculated based on this simplified model shows a good agreement with avail able experimental data in the case of condensing gas drive. For condensing gas drive, two important factors are learned to be important: vaporization and condensation. Vaporization takes place for the heavy ends and condensation for the other components. Combination of these two mechanisms accounts for the high recovery in the order of 90 to 110% as experienced in the linear sand pack displacement test, where the methane composition used in the injected gas stream varies from 45 to 55 mole percent.
Bibliography: p. 200-204.
Yu, R. K. (1975). An Investigation of vaporization in the displacement of Swan Hills crude oil by rich gas (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from doi:10.11575/PRISM/16323