高温高压下地应力对电阻率影响实验研究

塔里木盆地克深地区白垩系巴什基奇克组致密砂岩储层具有高温高压和高强地应力特征,地应力对地层电阻率影响显著,导致电阻率测井曲线识别储层流体性质常存在多解性。开展岩样在高温高压下,围压大于轴压和围压小于轴压2种加载方式下的电阻率及其各向异性系数随水平应力差变化的实验研究。在弹性形变内,岩石电阻率随水平应力差的增大呈e的指数形式增大;电阻率随压力的变化呈明显的方向性特征;沿加压方向电阻率变化幅度小,垂直加压方向电阻率变化幅度大;不同加载方式下的电阻率各向异性系数随水平应力差变化关系不一样。为山前盆地高陡地层处于强挤压状态下,用地应力校正电阻率测井曲线值提供了可靠的实验理论依据和途径。

Experimental Study of the Stress Effect on Formation Resistivity under High Temperature and High Pressure

The tight sandstone reservoir in the cretaceous Bashijiqik formation of crusty region is in a state of high temperature and high pressure and high stress .Crustal stress has significant effect on formation resistivity , as a result , there are many possible explanations to the identification of reservoir fluid properties by resistivity logging curves .Therefore ,it is necessary to analyze the effect of stress on resistivity .In this paper we carried out an experiment to study the relationship between resistivity and anisotropy coefficient of rock with changing horizontal stress difference when the rock is under high temperature and high pressure and two different kinds of loading mode :the confining pressure is greater than the axial pressure but less than the axial pressure . The results are as follows :Within the elastic deformation , the rock resistivity increases in the form of e exponent with the increase of the horizontal stress difference ;The resistivity ,which has obvious directional characteristics , varies with the pressure along the direction of pressure ,the resistivity change is small ,and in vertical direction ,the variation of resistivity is large ;The resistivity anisotropy coefficient varies differently with the horizontal stress difference under different loading modes which provides valuable experimental theoretical basis and reliable way to correct resistivity logging curves with crustal stress in the high and steep strata in the foreland basin .