Abstract
An enhanced oil recovery laboratory program of miscible displacement has been carried out in order to determine the feasibility of using Farrud hydrocarbon gas as a solvent to increase oil recovery from Facha and Gir reservoirs of Ghani field. The study program included conventional PVT analysis, oil-swelling tests, and slim tube displacement tests. These data with dissolved gas and stock-tank oil analytical data were used in compositional, oil swelling, and oil recovery calculations. Swelling tests were performed by adding Farrud hydrocarbon gas to Facha and Gir reservoir oils. Eight mixtures were prepared containing 10, 20, 30, 40, 50, 60, 70, and 80-mole percentage of Farrud gas. From P-V relations of injection gas-oil mixtures at reservoir temperature; mixture saturation pressure, injection gas solubility, oil-swelling factor, and mixture densities were calculated. A detailed material balance of swelling test fluid hydrocarbon components were investigated, based on extended (C₁ to C₇) compositional analysis of the reservoir oil and injected gas. In order to determine Farrud gas minimum miscibility pressure (MMP), slim tube displacement tests at six gas injection pressures ranging from 1500 to 4000 psig were performed on Facha reservoir oil and at seven pressures ranging from 1000 to 4000 psig on Gir reservoir oil. The MMP for Facha reservoir oil was found to be 2445 psig and for Gir reservoir oil was found to be 2495 psig. Miscibility studies revealed that minimum miscibility pressures are extremely high and beyond the reservoir pressure (1347 psig for Facha and 1310 psig for Gir). The type of miscibility development is in agreement with the results of the swelling test indicating a condensing gas drive.