基于原位渗透率试验反演岩石孔隙度的新方法

A new method for rock porosity inversion based on in-situ permeability test

为了获取岩石的原位孔隙度,在原位稳态渗透率试验的基础上,建立了以孔隙度和渗透率为主要参数的瞬态气体渗流模型,构造了基于遗传算法的孔隙度反演模型,分别采用原位渗透率试验中获取的岩石渗透率和瞬态压降数据作为已知量和观测数据,形成了基于原位渗透率试验反演岩石孔隙度的新方法。针对某场地的原位渗透率试验数据,分析了孔隙度对压降曲线的影响及孔隙度反演的可行性,编制了并行孔隙度反演程序,在大型计算机上对两个钻孔的孔隙度进行了反演并证明了反演结果的惟一性,最后通过数值模拟和实验室测量验证了反演结果的正确性。作为一种原位试验方法,对岩石及其孔隙结构破坏较小,其孔隙度反演结果比实验室测量法具有更好的区域代表性,反演结果可应用于气体泄漏行为模拟中。

To obtain the in-situ porosity of rock, a transient gas seepage model with main parameters of porosity and permeability is developed from an in-situ steady-state permeability test. A porosity inversion model is constructed based on genetic algorithm. Rock permeability and transient pressure decline data obtained from in-situ permeability tests are adopted as known variable and observational data respectively. Then a new method is formed to determine rock porosity inversion. The effect of porosity results from a typical site on the pressure decline curve and the feasibility of porosity inversion is analyzed. A parallel porosity inversion program is conducted, and then the porosities of rock at two holes are inversely calculated using the mainframe computer. Finally, the correctness of inversion results is verified by numerical simulation and laboratory measurement. As the in-situ test method has small damage to rock and its pore structure, the results of porosity by inversion method has better area representation than those by laboratory measurement, so that the inversion result can be applied to numerical simulation of gas leakage in rocks.