Abstract: 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.

Key words: shale, organic pore, genetic, influencing factor, evolution process