A novel type curve for estimating oil recovery factor of gas flooding

Abstract

A novel type curve is presented for oil recovery factor prediction suitable for gas flooding by innovatively introducing the equivalent water-gas cut to replace the water cut, comprehensively considering the impact of three-phase flow (oil, gas, water), and deriving the theoretical equations of gas flooding type curve based on Tong’s type curve. The equivalent water-gas cut is the ratio of the cumulative underground volume of gas and water production to the total underground volume of produced fluids. Field production data and the numerical simulation results are used to demonstrate the feasibility of the new type curve and verify the accuracy of the prediction results with field cases. The new type curve is suitable for oil recovery factor prediction of both water flooding and gas flooding. When a reservoir has no gas injected or produced, the gas phase can be ignored and only the oil and water phases need to be considered, in this case, this gas flooding type curve returns to the Tong’s type curve, which can evaluate the oil recovery factor of water flooding. For reservoirs with equivalent water-gas cuts of 60%—80%, the regression method of the new type curve works well in predicting the oil recovery factor. For reservoirs with equivalent water-gas cuts higher than 80%, both the regression and assignment methods of the new type curve can accurately predict the oil recovery factor of gas flooding.

Keywords

• gas flooding reservoir
• equivalent water-gas cut
• type curve of gas flooding
• oil recovery factor
• prediction chart
• Tong’s type curve