川东红星地区二叠系茅口组页岩气勘探突破及富集主控因素

Exploration breakthrough and main controlling factors for shale gas enrichment in the Permian Maokou Formation in Hongxing area in eastern Sichuan Basin

四川盆地二叠系页岩气具有良好的成藏条件和勘探潜力,继二叠系吴家坪组获得勘探突破后,将低勘探程度层系——茅口组“高灰”页岩气作为重要的勘探接替方向。利用HYM-1等井的岩心、测录井和分析化验资料,系统开展茅口组页岩气藏条件与富集特征的研究,认为茅口组四段一亚段页岩具有高碳、高灰、高孔隙度、高含气性、高杨氏模量、薄储层、多夹层的“五高一薄一多”的典型地质特征;与五峰组—龙马溪组等页岩相比,茅四段页岩碳酸盐矿物含量更高、黏土矿物含量更低,储集空间类型以有机质孔为主,无机孔较少,孔隙度平均4.27%,整体表现为高孔隙度;茅四段一亚段平均含气量为4.96m^(3)/t,具备较高的含气量。综合分析认为,富藻高碳页岩的发育、良好的储集能力和保存条件,以及页岩储层的可压裂性,是茅四段页岩气富集高产的主控因素。

The Permian shale gas in Sichuan Basin shows good hydrocarbon accumulation conditions and exploration potential.After obtaining breakthrough in the Permian Wujiaping Formation,the“high lime content”shale gas in Maokou Formation with a low degree of exploration has been regarded as a major orientation for exploration and replacement.The core samples,wireline and mud logging and experimental data in Well HYM-1 are used to systematically analyze the shale gas accumulation conditions and enrichment characteristics in Maokou Formation,and the study results indicate that the shale in the first sub-member of the fourth member of Maokou Formation has the typical geological characteristics of“five highs,one thin and one multiple”,i.e.,high carbon content,high lime content,high porosity,high gas content,high Yong’s modulus,thin reservoirs,and multiple interbeds;Compared with the shale in Wufeng-Longmaxi Formation,Maokou Formation shale has a higher carbonate mineral content but a lower clay content,and the reservoir space is dominated by organic pores,with few inorganic pores,and an average porosity of 4.27%,showing high porosity as a whole;The average gas content of the first sub-member of the fourth member of Maokou Formation is 4.96m^(3)/t,which shows a high gas content.The comprehensive analysis indicates that the development of algal-rich and high-carbon shale,good storage capacity and preservation conditions,as well as the good fracability of shale reservoir are the main controlling factors for the enrichment and high-yield production of shale gas in the fourth member of Maokou Formation.