高温高压气藏衰竭开发气水相渗变化规律探讨

Discussion on the change laws of gas-water relative permeability in the depletion development of HTHP gas reservoirs

气水相渗曲线一般在常温常压下利用非稳态气驱水实验获得,所得实验结果难以表征高温高压气藏衰竭开发过程中气水两相渗流变化规律。设计了不同温压条件、驱替方式、有效应力下气水相渗实验,结果表明,与地面条件相比,地层高温高压条件下水气黏度比、界面张力均降低,气驱水可使束缚水饱和度降低8%~13%,两相共渗区增加8%~15%;水驱气实验较气驱水实验相渗曲线整体偏左,分析认为高温高压水驱气实验能真实模拟实际气藏衰竭开发过程,结果更具代表性;不同有效应力下水驱气相渗实验,由于应力敏感的存在,相渗曲线整体下移,驱替效率降低约3.5%。在此基础上,统计分析了相渗曲线特征值及其形态参数变化规律,建立了衰竭开发过程气水相渗变化图版。本文研究成果可以应用到数值模拟中,指导高温高压气藏合理开发。

The gas-water relative permeability curve is generally obtained by unsteady gas drive water experiment under normal temperature and pressure,and the experimental results are difficult to characterize the change laws of gas-water two-phase percolation in the depletion development of HTHP gas reservoir.The experiments of gas-water relative permeability under different temperature and pressure conditions,displacement modes and effective stress are designed,and the results show that under the condition of in-situ HTHP,the viscosity ratio and interfacial tension of water and gas are both lower than that under the ground conditions.After the application of gas drive water,the irreducible water saturation has been reduced by 8%~13%and the two-phase infiltration area has been increased by 8%~15%.Compared with gas drive water experiment,the relative permeability curve of water drive gas experiment is generally on the left.The analysis suggests that the HTHP water drive gas experiment can simulate the actual depletion development process of gas reservoirs,and the results are more representative.Due to the existence of stress sensitivity,the relative permeability curve of water drive gas experiment migrates down as a whole and the displacement efficiency decreases by about 3.5%.On this basis,the characteristic values of relative permeability curve and the change laws of its shape parameters are statistically analyzed,and the change chart of gas-water relative permeability in depletion development is further established.The research results in this paper can be applied in numerical simulation to guide the reasonable development of HTHP gas reservoirs.