杂质盐岩渗透特性试验研究

利用四川大学THMC岩石三轴试验系统,针对中国天然气储库杂质盐岩开展全过程渗透试验研究,并通过试验结果拟合出同时考虑围压、扩容体积应变以及杂质含量的多因素耦合杂质盐岩渗透模型。研究表明:杂质含量、杂质分布及成分对盐岩渗透性均有显著影响,不同杂质含量盐岩损伤恢复后渗透率均有所降低,其塑性变形可分为2个阶段,I阶段渗透率增长迅速,II阶段渗透率增速减缓甚至渗透率下降,盐岩破坏后渗透率明显增大,残余阶段能维持在相对稳定的水平;低渗夹层制约盐岩垂向渗透性,而泥质成分盐岩较钙芒硝质盐岩渗透率更低。由拟合的多因素耦合渗透模型可得到:围压越高渗透率越低,扩容体积应变越大渗透率越高。当杂质含量大于0.46时,渗透率随杂质含量的增大而增大,当杂质含量小于0.46时,渗透率随杂质含量的增大而减小。

Experimental study on the permeability characteristics of impure salt rock

The percolation test of whole process to the impure salt rock of a natural gas reservoir in China was carried out using the THMC rock triaxial test system in Sichuan university. A multi-factor coupled percolation model considering simultaneously the confining pressure，dilation and impurity content was established by curve fitting the test results. The experimental research shows that the content，distribution and composition of the impurity all have the significant influence on the permeability of the salt rock. The permeability of salt rock with different impurity decreased after damage recovered. The plastic deformation can be divided into two stages. In stage one，the permeability increased rapidly，while in stage two，the permeability increased slowly and even decreased. The permeability increased significantly after the sample failure and the permeability maintained at a stable level in the residual phase. The low permeability interlayer restricts the vertical permeability. The salt rock with the mud component has the lower permeability than the salt rock with glauberite impurity. The multi-factor coupled percolation model shows that the higher the confining pressure，the lower the permeability，and the greater the volumetric strain dilation，the higher the permeability. When the impurity content is more than 0.46，the permeability increases with the increase of impurity content. When the impurity content is less than 0.46，the permeability decreases with the increase of impurity content.