Gas methods of oil enhancement recovery allow to significantly increase the oil recovery in case of water-flooded depleted reservoirs at the late stage of oil fields development. Before implementation these methods at the oil field, it is necessary to substantiate efficiency of using gas agents in specific conditions of the production object. The aim of the research work was to determine the optimal regime of oil displacement with gas agents - carbon dioxide and associated petroleum gas (APG). An assessment of miscibility conditions at the Tsarichanskoye+Filatovskoye oil field in the Orenburg region with different gas agents in the pressure range, corresponding to the current values of the studied reservoir, was made. The object of the research was a wellhead oil sample of Dkt formation. The results of physical recombination, using a stable wellhead sample and recombination gas model, are three saturated systems with different gas contents, which simulate, in the first approximation, the processes of isothermal formation depletion. To confirm the efficiency of gas injection, physical simulation of the oil displacement process was carried out on the slim tube model using the recombined oil samples, carbon dioxide and associated petroleum gas of the Tsarichanskoye+Filatovskoye field.
A comprehensive analysis of the dynamics of oil displacement was carried out during laboratory studies. Based on a series of displacement experiments, the displacement regimes of carbon dioxide and associated petroleum gas injection have been determined. The highest displacement efficiency was observed when injecting carbon dioxide at pressure 19 MPa (displacement efficiency is 96.42%), when injecting APG at pressure 12.5 (displacement efficiency is 96.49%) and at pressure 9.5 MPa for the recombined sample with lower saturation pressure (displacement efficiency is 97.80%). The selected injection regimes for carbon dioxide and APG when the miscibility is achieved are the most effective in terms of residual oil recovery in the studied field.
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