柴西地区变围压条件下储层物性变化规律

Reservoir Properties under Variable Confining Pressure in Western Qaidam Basin

利用柴达木盆地西部地区16个砂岩样品进行变围压实验,对砂岩储层中围压与孔隙度、渗透率及岩石孔隙压缩系数的关系进行研究。结果表明:当围压升高时,岩石颗粒重新排列,体积缩小;当围压降低时,岩石颗粒体积恢复,排列样式不会恢复;围压的变化对常规储层影响较大,对低渗透储层影响较小,渗透率变化幅度取决于喉道改变程度。岩石孔隙压缩系数随着围压的升高而降低,两者之间存在指数函数关系,建立了围压与岩石孔隙压缩系数的经验公式,该公式对柴达木盆地西部地区油藏工程研究具有一定的指导意义。

16 sandstone reservoir samples from Western Qaidam Basin are tested by laboratory variable confining pressure experiment to identify the effects of confining pressure on reservoir porosity,permeability and rock compressibility. Research shows that rock particles rearrange and the particle volumes decrease with the increase of confining pressure. When confining pressure decreases,rock particles gain original volumes without recovery of particle arrangement pattern. The conventional reservoir properties are more sensitive to confining pressure than that of low-permeability reservoir. Reservoir permeability rangeability is mainly dependent on the variation of throats. Reservoir rock compressibility decreases with the increase of confining pressure,which shows an exponential function. A empirical formula is established to model the relationship between confining pressure and reservoir rock compressibility. This empirical formula could provide certain guidance for the reservoir engineering researches in Western Qaidam Basin.