Study On Development Technical Countermeasures Of Artificial Gas Cap Drive In Fault Block Reservoir

In the middle and late stage of fault block reservoir development,there is often "attic oil" in the high part of reservoir which is difficult to be used by water flooding,and artificial gas cap flooding is considered as an effective way to use such remaining oil.The structure of fault block reservoir is complex,the optimal mode of artificial gas cap is not clear,the mechanism of oil and gas water seepage is not clear,and the technical policy limit of gas cap flooding is not clear.Therefore,relevant studies on the above problems are conducive to the successful application of artificial gas cap flooding technology in fault block reservoirs,so as to effectively improve the recovery rate of fault block reservoirs.In this paper,the microscopic mathematical model of gas percolation is established by analyzing the process of gas percolation.Numerical simulation method is used to optimize the gas cap generation mode,and the optimal gas cap generation mode under different geological characteristics and well pattern distribution is determined.According to the main characteristics of different stages of artificial gas cap flooding,the parameter optimization and sensitivity analysis of artificial gas cap generation stage and artificial gas cap displacement stage were carried out respectively.Finally,the characteristics of residual oil distribution in a fault block N reservoir are analyzed,the technical countermeasures of different stages of artificial gas cap flooding are clarified,the development plan of artificial gas cap flooding in fault block N reservoir is designed,and the development effect is predicted.The main findings are as follows:(1)The formation of artificial gas cap needs to meet certain conditions.The formation of artificial gas cap is affected by interfacial tension,permeability,density difference,reservoir pressure and formation dip.(2)When the artificial gas cap flooding scheme is implemented in selected blocks,effective thickness is the most sensitive,followed by formation shape,formation dip,reservoir heterogeneity and development of interlayer.If there is no gas injection well at the top of the reservoir,the synergistic inducing effect between the lumbar Wells can be used to generate gas cap to reduce the time required for artificial gas cap generation.(3)The N fault block oil reservoir is divided into the parts with high degree of homogeneity and good physical properties,and the parts with injected water bursting,high degree of water flooding and poor physical properties are difficult to be affected by injected water and low degree of production.The water driving degree of the top of the reservoir is low and it belongs to the residual oil rich area.(4)When artificial gas cap is generated,it is necessary to reduce the gas injection speed,reduce the phenomenon of displacement gas finger and tongue,prevent the gas from breaking through prematurely and thus reduce the gas injection effect,and assist water injection to restore the formation pressure.The gas volume needs to be supplemented in the gas cap displacement stage.Compared with the continuous gas injection mode,the intermittent mode can effectively reduce the instability of the oil and gas interface and the penetration of the displacement leading edge.