低渗透软弱岩非达西渗流拟启动压力梯度试验研究

Non-Darcy flow quasi-threshold pressure gradient experimental study for low permeability soft rock

利用新开发的高压渗流仪,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0.01MPa,渗出端溶液体积变化量测试精度可达0.05ml。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),试验验证了低渗透岩石的非达西渗流现象。并根据非达西流线性段的渗流特点,采用三种方法推算了拟启动压力梯度值,并通过实例说明"二次平均法"是拟启动压力梯度推算的最有效方法。

With unchangeable water pressure method, big size and low permeability soft rocks have been systematically tested with the new equipment called High Pressure Permeability Testing Machine in Lab. The penetration water pressure fluctuation scope only is 0.01 MPa, and the seepage exit water volume testing precision is 0.05ml. According to linear relationship of water volume and time, seepage quantity can be accurately calculated. The test results demonstrate that the non-Darey flow phenomena are applicable for low permeability rocks. On the basis of the linearity seepage characteristics of non-Darcy flow, the quasi-threshold pressure gradient has been calculated with three methods. And it is proved that Averaged Two Times Method is the best one through examples.