变围压条件下低渗砂岩储层渗透率变化规律研究

试验研究了低渗透砂岩储层岩石的围压 -渗透率关系和围压 -松弛循环 -渗透率关系 ,试验结果表明 :随围压增加岩石的孔隙结构和骨架结构发生变化 ,引起岩石渗透率的下降 .通过对变围压条件下低渗透岩石渗透率变化规律分析 ,找到了一种新的表征围压 -渗透率关系的公式——指数函数线性组合 ,对 5个低渗透区块的 3 1组岩石样品试验数据进行对比和验证 ,该指数函数线性组合的拟合误差在± 5 %以内

Variation of the Permeability of the Low-permeability Sandstone Reservoir Under Variable Confined Pressure

The relationships between the permeability of the reservoir and confined pressure and confined pressure cycle are studied by experiments. The results show that when the confined pressure increases, the pore structure and the skeleton structure of the reservoir change, which results in the reduction of the permeability. Through the analyses of the varying law of the permeability under variable confined pressure, a new expression of presenting the relationship between the permeability and the confined pressure is found out, which is a linear combination of two exponential functions. The expression is verified by the testing data of 31 rock samples of 5 low-permeability blocks, and it is shown that the error of it is less than ±5%.