Abstract One of the biggest challenges in evaluating the transport and storage properties of shales is understanding how the pore structure and network evolve in the same stratigraphic shale during catagenesis. Using a combination of CO2 adsorption, mercury intrusion porosimetry, as well as scanning electron microscopy, we have described the evolution and the abrupt changes (jump) of pore characteristics in lacustrine shale at oil and gas maturation. With an increase maturity, our sample set exhibited abrupt changes in porosity-related characteristics. Porosity and surface areas presented a decline and then an increase, and a jump occurred due to hydrocarbon generation, with the minimum value in late maturity (i.e. vitrinite reflectance of ~1.3%). These changes were accompanied by corresponding changes in pore-size distributions, surface area percentage, and multi-scale pores volumes. The trends in porosity variation were related to different organic matter and mineral contents in our samples, to some extent, with the degree of maturation being the dominant influence. We found that inorganic pores were the main contributor to the porosity of less mature shales, while porosity in gas-mature shales was dominated by organic matter pores. In this work, we showed that organic matter transformation was a centric component of pore evolution. Our findings may fill significant gaps in understanding and predicting pore development, with respect to the maturity of lacustrine shales.

中文翻译：

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油气成熟期湖相页岩孔隙系统在退化过程中的突变

摘要 评估页岩输运和储存特性的最大挑战之一是了解在后成作用过程中同一地层页岩中孔隙结构和网络是如何演化的。结合 CO2 吸附、压汞孔隙度测定法和扫描电子显微镜，我们描述了油气成熟过程中湖相页岩孔隙特征的演化和突变（跳跃）。随着成熟度的增加，我们的样本集表现出孔隙度相关特征的突然变化。孔隙度和表面积呈先下降后上升的趋势，并因生烃而出现跳跃，晚熟时最小值（即镜质体反射率为~1.3%）。这些变化伴随着孔径分布的相应变化，表面积百分比和多尺度孔隙体积。孔隙度变化趋势与我们样品中不同的有机质和矿物质含量有关，在一定程度上，成熟度是主要影响因素。我们发现无机孔隙是较不成熟页岩孔隙度的主要贡献者，而气成熟页岩孔隙度以有机质孔隙为主。在这项工作中，我们表明有机质转化是孔隙演化的核心组成部分。我们的研究结果可能填补在理解和预测孔隙发育方面的重大空白，与湖相页岩的成熟度有关。成熟度是主要影响因素。我们发现无机孔隙是较不成熟页岩孔隙度的主要贡献者，而气成熟页岩孔隙度以有机质孔隙为主。在这项工作中，我们表明有机质转化是孔隙演化的核心组成部分。我们的研究结果可能填补在理解和预测孔隙发育方面的重大空白，与湖相页岩的成熟度有关。成熟度是主要影响因素。我们发现无机孔隙是较不成熟页岩孔隙度的主要贡献者，而气成熟页岩孔隙度以有机质孔隙为主。在这项工作中，我们表明有机质转化是孔隙演化的核心组成部分。我们的研究结果可能填补在理解和预测孔隙发育方面的重大空白，与湖相页岩的成熟度有关。