In a shale gas reservoir, the rock matrix has a relatively large porosity and gas in place, but extremely low permeability. Thus, the rock matrix is a bottleneck for shale gas flow from the reservoir to hydraulic fractures and then to the production well. We speculate that the next big thing after hydraulic fracturing for unconventional resources development is to enhance the matrix permeability in an economically feasible way. Consequently, the efficient and accurate characterization of rock matrix permeability in the laboratory is a critical task. The current laboratory techniques for source rock permeability measurement follow a “point-by-point” approach. They need multiple test runs to obtain a permeability-pressure curve, because they can only measure one permeability data point for one test run, and are thus time consuming. The root cause of this “point-by-point” approach is that these laboratory techniques are based on linearized gas flow theory requiring only small pore pressure disturbances to the experiment system. Liu et al. (2019) and this work introduce a new methodology that is based on the nonlinear gas flow theory and allows for direct measurement of the permeability-pressure curve with a single test run. This makes the approach highly time efficient. The feasibility and validity of the methodology are demonstrated in this work based on laboratory measurement results and their consistency with theoretical expectations and other independent measurements. The observed permeability exhibits a complex relationship with pore pressure as a result of the combined effects of Knudsen diffusion and mechanical deformation. For a given confining pressure, the observed permeability initially decreases with pore pressure because of Knudsen diffusion and then increases with pore pressure owing to the mechanical deformation. A rock sample with a lower permeability corresponds to a stronger Knudsen diffusion effect and weaker mechanical diffusion effect. This complex behavior highlights the need to accurately and efficiently measure the combined effects that may have important impacts on shale gas production.

在页岩气储层中，岩石基质具有相对较大的孔隙度和适当的天然气，但渗透率极低。因此，岩石基质是页岩气从储层流向水力压裂然后再流向生产井的瓶颈。我们推测，水力压裂之后非常规资源开发的下一件大事是以经济上可行的方式提高基质渗透率。因此，在实验室中高效，准确地表征岩石基质渗透性是一项关键任务。当前用于烃源岩渗透率测量的实验室技术遵循“逐点”方法。他们需要进行多次测试才能获得渗透率-压力曲线，因为它们一次只能测量一个渗透率数据点，因此非常耗时。这种“逐点”方法的根本原因是，这些实验室技术基于线性化气流理论，只需要对实验系统进行较小的孔隙压力干扰。刘等。（2019），这项工作介绍了一种基于非线性气体流动理论的新方法，可以通过一次测试直接测量渗透率-压力曲线。这使得该方法具有很高的时间效率。根据实验室测量结果及其与理论预期和其他独立测量的一致性，证明了该方法的可行性和有效性。由于Knudsen扩散和机械变形的共同作用，观察到的渗透率与孔隙压力表现出复杂的关系。对于给定的围压，由于Knudsen扩散，观察到的渗透率最初随孔隙压力而降低，然后由于机械变形而随孔隙压力而增加。渗透率较低的岩石样品对应于更强的努森扩散效应和较弱的机械扩散效应。这种复杂的行为凸显出需要准确，有效地测量可能对页岩气产量产生重要影响的综合影响的必要性。