Pore Accessibility and Competition for Pore Space between Light Alkanes in Petroliferous Shales at the Wet-gas Thermal Maturity

Understanding petroleum in shale reservoirs is broadly relevant given the current emphasis on these resources in the U.S. and developing interest worldwide. Petroleum in shale reservoirs is stored in organic matter and mineral pore space. However, the pore size distribution of methane vs. higher alkanes in shales is unclear. We propose to examine pore accessibility and competition for open pore space between methane and ethane in a shale sample at the wet-gas stage of thermal maturity. Competition for available pore space in the sample will be assessed by monitoring adsorption of a methane/ethane mixture and comparing the results to the adsorption of methane only. We hypothesize that methane will prefer smaller pores fractionating ethane within larger pores. If true, this suggests that when assessing shale reservoirs for C2+ alkanes an understanding of fine porosity may be unimportant.

针对页岩储层中油气赋存状态的研究具有广泛的应用价值，这是因为当前美国正重点开发这类资源，而全球范围内对其开发的兴趣也与日俱增。页岩储层中的油气赋存于有机质与矿物孔隙空间之中，但目前学界对于页岩中甲烷与高级烷烃的孔隙尺寸分布特征仍不明确。本研究拟针对处于热成熟湿气阶段的页岩样品，探究甲烷与乙烷之间的孔隙可及性差异，以及二者对开放孔隙空间的竞争行为。我们将通过监测甲烷/乙烷混合气体的吸附过程，并将其与纯甲烷吸附的实验结果进行对比，以此评估样品内对可用孔隙空间的竞争情况。我们提出如下假说：甲烷更倾向于优先占据更小的孔隙，从而使乙烷在较大孔隙中发生分馏。若该假说成立，则表明在针对页岩储层的C2+烷烃资源进行评估时，对细孔隙（fine porosity）的认知或许并非必要。