湖南省保靖地区龙马溪组页岩气地质特征与成藏模式研究

湖南保靖地区为页岩气勘探新区块,其页岩气地质特征和富集规律有待进一步研究。通过对区内沉积环境、储层孔渗、地球化学特征及地层含气性等研究,总结区内龙马溪组页岩气的地质特征; 根据生烃发育史、裂缝发育特征、滑脱层运移特征以及断裂作用等研究,探索页岩气的成藏模式。研究结果表明: 湖南保靖地区龙马溪组页岩有机质丰度较高,热演化程度适中,脆性矿物含量较高,物性特征较好,具备页岩气富集成藏条件; 页岩从二叠纪开始进入生气阶段,并持续到中侏罗世; 中侏罗世末期研究区形成隔槽式断裂褶皱冲断带,龙马溪组储层中形成垂直层面多组网状裂缝及顺层滑脱层; 湖南保靖地区龙马溪组具有“滑脱层运移、裂缝聚集、孔隙残留、断层封堵、高位富集、箱状成藏”的页岩气富集成藏模式。

Shale gas geological characteristics and accumulation model of Longmaxi Formation in Baojing area of Hunan Province

Baojing area of Hunan Province is a new shale gas exploration block, and the geological characteristics and accumulation rule of shale gas are still worthy to be studied. The geological characteristics of Longmaxi Formation shale gas in the study area were summarized in sedimentology, porosity and permeability of the reservoir, geochemistry, gas content and other reservoir characters. According to the study of hydrocarbon generation history, fracture characteristics, detachment layer movement, and fault effect, shale gas accumulation mode was explored. The results show that Longmaxi Formation shale gas in Baojing area of Hunan Province has high organic matter abundance, moderate thermal maturity, high brittle mineral content, and good physical properties, which means this reservoir has shale gas enrichment conditions. The shale experienced the stage of gas generation from Permian to Middle Jurassic. At the end of Middle Jurassic, trough-like folds in a fold-and-thrust belt were formed and the multiple reticular cracks and bedding decollement layer in vertical dimension were formed in Longmaxi Formation reservoir. Therefore, the accumulation model of shale gas in Longmaxi Formation in Baojing area of Hunan Province can be briefly summarized as follows: migration in detachment layer, fracture accumulation, residual in pores, plugging by the fault, enrichment in higher areas and accumulation in box shape.