高围压条件下孔隙介质渗透特性试验研究

EXPERIMENTAL STUDY ON PERMEABILITY OF POROUS MEDIA UNDER HIGH CONFINING PRESSURE

为研究不同围压条件下孔隙介质的渗透性能,利用新研制的高压渗流仪,对大尺寸低渗透性软弱岩进行了系统的试验测试。试验渗透压差波动幅度仅为0.02MPa,渗出端溶液体积变化量测试精度可达0.03mL。通过溶液体积变化与时间的线性关系,稳定渗流量大小可以精确测定。以稳定压差、流量法(即稳压法),试验验证了岩石的渗透系数随着围压的增加而下降,当围压降低时,岩石渗透系数回升,但回升路径低于原始路径。根据轴向应变的变化情况,提出了室内试验应力-渗流耦合过程中渗透性的变化主要是侧向压力使孔隙、喉道产生压缩变形所致。

This paper examines permeability of porous media under different confining pressures. It uses unchangeable water pressure method. Large size soft rocks with low permeability have been systematically tested with a new equipment called high pressure permeability testing machine in laboratory. The penetration water pressure fluctuation scope is 0.01 MPa. The seepage exit water volume testing precision is 0.05 ml. According to a linear relationship of water volume and time, seepage quantity can be accurately calculated. The test results demonstrate that the permeability coefficient decreases with the increasing of confining pressure, and increase when unloading. The increasing rate during unloading is lower than that during loading. On the basis of the axial strain variation situation, it is found that the rock permeability change is mainly affected by the confining pressure during the coupling process of stress-seeping in rock samples at laboratory. The confining lateral pressure makes the porosity and seepage pipes to have compressive deformation.