川西地区二叠系火山岩异常高压演化与天然气成藏的关系

川西地区二叠系火山岩天然气藏发育较高的异常压力，异常压力的成因和天然气成藏的动力学过程较复杂，目前对研究区异常高压的演化过程及其对天然气成藏的影响规律仍认识不清。通过分析川西地区二叠系实测地层压力、测井响应资料和包裹体捕获压力，明确了异常高压的成因和演化过程。基于不同成藏期次形成的烃类包裹体中的含油流体包裹体颗粒（GOI）丰度，分析了地层压力演化与天然气成藏之间的关系。结果表明：寒武系筇竹寺组烃源岩的生-排烃作用和火山岩内部的原油裂解对异常高压的发育具有重要的贡献；储层内共发育3类包裹体，其形成对应3期大规模油气聚集，即二叠纪末期（距今256~251 Ma）形成碳质沥青包裹体、晚三叠世（距今230~208 Ma）形成油-水包裹体、侏罗纪中-晚期（距今175~152 Ma）形成气-水包裹体。在多期油气聚集过程中，古地层压力系数和烃类包裹体的GOI丰度逐渐升高，表明地层压力的变化为天然气大规模充注提供了充足的动力条件。

Relationship between abnormal high pressure evolution of Permian volcanic rocks and natural gas accumulation in the western Sichuan Basin

Abnormal high formation pressure is developed in Permian volcanic gas reservoirs in the western Sichuan Basin. As the cause of abnormal pressure and the dynamics of natural gas accumulation are very complex, the evolution process of abnormal high pressure and its influence on natural gas accumulation in the western Sichuan Basin still have not been clarified. Through analyzing the measured formation pressure, logging response data and inclusion trapping pressure in the study area, this paper makes clear the cause and evolution process of abnormal high pressure. Based on the abundance of grains with oil inclusions (GOI) formed in hydrocarbon inclusions at different accumulation stages, the relationship between formation pressure evolution and natural gas accumulation is analyzed. The results show that the hydrocarbon generation and expulsion of the Cambrian Qiongzhusi Formation source rocks and the crude oil cracking in the volcanic rocks have a significant influence on the development of abnormal high pressure. There are three types of inclusions developed in the reservoir, corresponding to three stages of large-scale oil and gas accumulation; carbonaceous asphalt inclusions, oil-water inclusions and gas-water inclusions were formed in the Late Permian (256-251 Ma), the Middle Triassic (230-208 Ma) and the Middle Jurassic (175-152 Ma) respectively. In the process of multi-stage oil and gas accumulation, the paleo-formation pressure coefficient and GOI abundance of hydrocarbon inclusions gradually increased, indicating that the change of formation pressure has provided sufficient dynamic conditions for large-scale natural gas charging.