川东南涪陵地区五峰组-龙马溪组页岩气藏中的超压作用

Overpressure in shale gas reservoirs of Wufeng-Longmaxi formations, Fuling area, southeastern Sichuan Basin

王强 魏祥峰 魏富彬 燕继红 万梨

WANG Qiang WEI Xiangfeng WEI Fubin YAN Jihong WAN Li

中国石油化工股份有限公司 勘探分公司, 成都 610041

SINOPEC Exploration Branch Company, Chengdu, Sichuan 610041, China

中国南方海相上奥陶统五峰组-下志留统龙马溪组高产页岩气藏普遍发育超压，为分析超压对于页岩气藏的作用，选取川东南涪陵页岩气田典型钻井进行了系统解剖研究。超压是页岩气藏良好保存条件的直接表征，其中，有机质热演化生烃增压是造成该地区异常高压的主要因素；涪陵焦石坝主体龙马溪组页岩气高产层段地层均发育超压，页岩储层孔隙度高、含气量高。超压对页岩气藏的影响：一方面，超压能减缓作用在岩石骨架上的有效应力，使页岩储层保存相对较高的孔隙度，超压可形成页岩超压微裂缝，提高页岩储集层的渗流能力，同时超压意味着地层能量高，游离气含量高，页岩气藏含气性更好；另一方面，超压降低了作用在页岩储层的有效应力，同时超压微裂缝的发育有利于页岩压裂改造。

There commonly exists overpressure in shale gas reservoirs in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formations in marine strata in South China. Some typical wells in the Fuling Shale Gas Field were chosen to study systematically to reveal how the overpressure does on shale gas reservoirs. Overpressure is the direct shows of favorable preservation conditions for shale gas. Pressure increases when hydrocarbon generates from organic matter in thermal evolution, which is the main cause for abnormal high pressure in the region. Overpressure exists in all high yield intervals for shale gas in the Longmaxi Formation in Jiaoshiba of Fuling area. The shale reservoirs have high porosity and high gas content. The effect of overpressure on shale gas reservoirs was concluded. On the one hand, overpressure can slow down the effective stress on rock skeleton, so that the shale reservoirs preserve a relatively higher porosity, and overpressure can form shale overpressure micro-cracks, improving the seepage capacity of shale reservoirs. Overpressure indicates for high formation energy, high free gas content, and better gas content in shale gas reservoirs. On the other hand, overpressure reduces the effective stress on shale reservoirs, and the development of overpressure micro-cracks is conducive to shale fracturing.

国家科技重大专项“页岩气区带目标评价与勘探技术”（2017ZX05036）资助。

https://doi.org/10.11781/sysydz201903333