页岩有机孔成因演化及影响因素探讨

有机孔作为页岩孔隙系统的重要组成部分，形成于页岩生烃演化过程中，是页岩气生成、扩散和聚集留下的痕迹，也是页岩储层生气、储气能力的体现。在系统调研文献的基础上，结合已有的地质资料，首先，探讨了有机孔的成因，认为有机孔是有机质在生气膨胀力足够强时突破有机质表面大规模发育形成，属于生气膨胀力成因。其次，讨论了有机孔发育的影响因素。结果表明，有机孔发育除受TOC、R_o、有机质类型及显微组分等有机质地化属性影响外，还受有机质塑性特征、有机质赋存形式、次生沥青、压实作用及地层压力系数等的影响，变质阶段有机质的强烈压实变形不利于有机孔的保存，有机质黏附于矿物表面则有助于有机孔的后期保存，而地层压力系数与有机孔的发育具有较好的对应性。最后，以R_o作为主要划分指标，将有机孔的演化过程划分为未-低熟、成熟、高-过成熟及变质4个阶段，有机孔大量形成于高-过成熟阶段。

Formation Evolution and Influencing Factors of Organic Pores in Shale

Being an important constituent of the shale pore system, organic pores are formed during hydrocarbon generation in shale. They are traces of shale gas generation, diffusion, and accumulation, and they also reflect the gas generation and storage capacity of shale reservoirs. We explored the formation mechanism of organic pores based on the current literature and existing geological information. It is believed that organic pores form on a large scale when the expansive force of gas generation is sufficiently strong and organic matter breaks through its surface. Hence, organic pores form via the expansive force of gas generation. Factors influencing the development of organic pores are also discussed. The results show that organic pore development is not only influenced by the geochemical properties of organic matter, e.g., TOC, R_o, types of organic matter, and microscopic composition, but also by other factors, e.g., organic plasticity, forms of organic matter, secondary asphalt, compaction, and formation pressure coefficients. Intensive compaction deformation of organic matter does not favor preservation of organic pores during metamorphosis. Adhesion of organic matter onto mineral surfaces is conducive to late-stage preservation of organic pores, while formation pressure coefficients correspond relatively well to organic pore development. Finally, the organic pore evolution process is classified into four stages using Ro as the primary classification indicator, i.e., none to pre-mature, mature, highly to excessively mature, and metamorphosis. Many organic pores form during the highly to excessively mature stage.