The study of pore network evolution is an important aspect of tight shale reservoir characterization. Pore spaces in shales consist of three major types: interparticle pores and intraparticle pores associated with mineral matrix and organic-matter pores. In this study, the evolution of pore networks for each pore type in lacustrine shales during thermal maturation was studied based on a suite of 19 Triassic Yanchang Formation shale samples from the Ordos Basin across a maturation gradient from immature to late mature (vitrinite reflectance (R_o) from 0.36 to 1.30%). The results show that different pore types follow systematic evolutions during thermal maturation and that the evolution of pore type and pore size is critically controlled by multiple diagenetic processes such as mechanical compaction, cementation, mineral dissolution, clay mineral transformation, and organic matter thermal maturation. Specifically, at immature and early mature stages (R_o < 0.55%), pores associated with mineral matrix are abundant and have moderate pore sizes. Interparticle pores exhibit preferential orientation along clay platelets. At the mature stage (0.55% < R_o < 1.15%), pores associated with mineral matrix have the smallest size, and interparticle pores become less common and show reduced preferential orientation because of mechanical compaction and cementation. Organic-matter pores start to develop at a maturity level of R_o 0.77% and higher. The total porosity and BET specific surface area show minimum values at R_o 1.12%, mainly because pre-existing matrix-related pores are destroyed by mechanical compaction and filled by migrated bitumen and liquid hydrocarbons, and then they increase when R_o exceeds 1.12%, which likely results from the development of secondary organic-matter nanopores due to the generation and expulsion of gaseous hydrocarbons. An increase in pore size of matrix-related pores at the late mature stage (1.15% < R_o < 1.30%) could be a result of dissolution by organic acid generated during organic matter thermal maturation.

孔隙网络演化的研究是致密页岩储层表征的重要方面。页岩中的孔隙空间主要由三种类型组成：与矿物基质和有机质孔隙相关的颗粒间孔隙和颗粒内孔隙。在这项研究中，基于鄂尔多斯盆地19个三叠系延长组页岩样品在从未成熟到晚熟的成熟梯度（玻璃质反射率（R _Ø）从0.36到1.30％）。结果表明，不同的孔隙类型遵循热成熟过程中的系统演化，并且孔隙类型和孔径的演化受到多种成岩过程的严格控制，如机械压实，胶结，胶结，矿物溶出，粘土矿物转化和有机质热成熟。具体而言，在未成熟和早熟阶段（R _o  <0.55％），与矿物基质相关的孔丰富且具有中等孔径。颗粒间的孔沿粘土薄片表现出优先的取向。在成熟阶段（0.55％<R _o 小于1.15％），与矿物基质相关的孔具有最小的尺寸，并且由于机械压实和胶结作用，颗粒间的孔变得不那么普遍并且显示出降低的优先取向。有机物毛孔的成熟度开始达到R _o 0.77％或更高。总孔隙率和BET比表面积在R _o 1.12％处显示最小值，这主要是因为预先存在的与基质相关的孔被机械压实破坏并被迁移的沥青和液态烃填充，然后在R _o时它们增加超过1.12％，这可能是由于气态碳氢化合物的产生和排出而导致的次级有机物纳米孔的发展。在成熟后期，基质相关孔的孔径增加（1.15％<R _o  <1.30％）可能是由于有机物热成熟过程中产生的有机酸溶解所致。