低渗岩心物性参数与应力关系的试验研究

RELATION OF GROUND STRESS WITH THE PROPERTIES OF LOW PERMEABLE CORE

地应力是影响低渗油气田地层参数的重要因素 ,尤其直接影响油层的渗透率、孔隙度等。通过室内试验 ,利用围压模拟地层应力 ,研究了有效应力与岩心的渗透率、孔隙度、岩石压缩系数之间的关系。研究结果表明 ,低渗岩心渗透率、孔隙度及压缩系数对有效应力变化较为敏感 ,随着有效应力的增大呈指数递减。试验发现 ,在有效应力的变化过程中发生了岩心弹塑性变形 。

The ground stress is an important influence factor on formation parameters of low permeability reservoir, especially, directly effecting reservoir porosity, permeability, compressibility, etc.. An experimental study in laboratory was carried out to determine the effect of ground stress on core porosity, permeability and compressibility by using confined pressure to simulate terra stress. The permeability confined pressure curve, the porosity (compressibility) confined pressure curve,and pressure gradient transformation curve are obtained. The state equations among rock porosity (compression coefficient), permeability and confined pressure are established. The testing results show that the core porosity, permeability, compressibility of low permeability core are sensitive to confined pressure, and there are exponential degression relation among them. It is found that core produces elastic distortion and plastic distortion with the change of confined pressure. The low permeability core has a start up pressure gradient in the course of fluid flow.