Effect of Formation Pressure on Pore Structure Evolution and Hydrocarbon Expulsion in Organic-Rich Marine Shale

Exploring the relationship between formation pressure and shale pore evolution is helpful for enrichment development of marine gas accumulation theory. The thermal experiment was carried out on Xiamaling Formation (Pr3x) lowly matured shale, which has a similar sedimentary environment to Longmaxi (S1l) highly shale. Comparative experiments open semi-closed pyrolysis multiple structure characterization techniques, including CO2 N2 physisorption, mercury intrusion porosimetry, field emission scanning electron microscopy, were conducted. evolutionary model under proposed by characterizing evolution, hydrocarbon expulsion retention shales without fluid pressures. results show that existence increases percentage quartz reduces content clay minerals. change in no obvious effect maturity samples. With increase pressure, morphology gradually changes from narrow slit pores ink bottle-shaped pores. retained hydrocarbons mainly occupy mesopore space, promotes expulsion, especially mesopore. In addition, improves connectivity, high-over mature stage micropore volume decreases slightly, significantly, macropore have two stages.