裂缝对岩石电阻率的影响及其在含气饱和度计算中的应用

摘要

裂缝性致密砂岩储层含气饱和度计算的准确性取决于岩石电阻率测量值的可靠程度,而岩石电阻率的测量值又受控于裂缝的导电性、产状、宽度和密度等参数.因此,研究裂缝对岩石电阻率测量值的影响是正确建立致密砂岩储层含气饱和度计算公式的基础.在数值模拟基础上详细观察裂缝的导电性、产状、宽度和密度等参数对岩石电阻率测量值的影响,通过岩电实验对数值模拟结果进行检验,提出了一个适用于裂缝性致密砂岩储层含气饱和度计算的归一化岩石电阻率公式,改进了目前常用的双重孔隙介质模型.最后,将改进的双重孔隙介质模型用于塔里木盆地克深地区裂缝性致密砂岩储层的含气饱和度计算.计算结果表明,改进的双重孔隙介质模型符合克深地区岩石裂缝内含气饱和度高的特点,且与试油结论吻合度更高.%The accuracy of gas saturation calculation in fractured tight sandstone reservoir depends on the reli-ability of rock resistivity measurement,and the measurement of rock resistivity is controlled by the conductivity, occurrence,width and density of fractures.Therefore,the study of the influence of fracture on rock resistivity measurement is the foundation for establishing a formula for calculating the gas saturation of tight sandstone reser-voirs.On the basis of numerical simulation,the influences of fracture conductivity,occurrence,width and density on the measurement of rock resistivity were observed.The results of numerical simulation were checked through rock resistivity experiment,and a normalized formula of rock resistivity suitable for calculating gas saturation of fractured tight sandstone reservoir was put forward,improving the dual porosity model commonly used for satura-tion calculation of fractured reservoirs.Finally,the improved dual porosity model was used to calculate the gas saturation of the fractured tight sandstone reservoirs in Keshen area of Tarim Basin.The calculation results show that the results of the improved dual porosity model are consistent with the characteristics of high gas saturation in rock fracture in Keshen area,and more consistent with the oil testing conclusion.