川西北地区天井山古隆起规模微生物岩储层的成因及其地质意义

四川盆地西北部江油—剑阁地区中三叠统雷口坡组发育厚层微生物岩储层，但该储层发育的地质背景不清楚、对于主控因素的认识也存在着分歧。为了弄清该区规模储层发育区、指导天然气勘探开发工作，基于野外露头、钻井岩心和分析化验资料，在分析川西北地区天井山古隆起南段雷口坡组三段三亚段（以下简称雷三3亚段）微生物岩储层特征及其成因的基础上，评价了天井山古隆起对微生物岩储层规模形成的控制作用。研究结果表明：①天井山古隆起区雷三3亚段微生物岩储层岩性以藻屑云岩和藻纹层云岩为主，储集空间主要为藻黏结格架间溶孔、粒间和粒内溶孔、鸟眼孔、晶间溶孔以及裂缝；②古隆起区发育规模微生物岩储层，储层厚度介于20～70 m，面积约1×104 km2；③古隆起区发育规模储层主要是因其有利于微生物岩、准同生岩溶作用和表生岩溶作用的发育。结论认为，天井山古隆起区有利于微生物岩储层发育并能形成规模储层，是四川盆地雷口坡组值得关注的天然气勘探有利区带。

genesis and geological implications of large-scale microbialite reservoirs in the Tianjingshan paleouplift of the northwestern Sichuan Basin

A thick microbialite reservoir is developed in the Leikoupo Formation of Middle Triassic in Jiangyou-Jiange area of the northwestern Sichuan Basin. However, its geological background of reservoir development is not determined clearly, and the main control factors are not understood definitely. In order to determine the large-scale reservoir development area and guide natural gas exploration and development, this paper analyzed the characteristics and genesis of the microbialite reservoir in the third sub-member of the third Member of Leikoupo Formation (Lei33 sub-member) in the south section of Tianjingshan paleouplift in the northwestern Sichuan Basin and evaluated the control action of Tianjingshan paleouplift on the large-scale formation of microbialite reservoirs, based on outcrops, drilling cores and test data. And the following research results were obtained. First, the Lei33 sub-member microbialite reservoirs in the area of Tianjingshan paleouplift is lithologically composed of algal debris dolomite and algal laminar dolomite. The reservoir space is dominated by dissolved pores between algal binding grids, intergranular dissolved pores, intragranular dissolved pores, bird's eye pores, intercrystalline dissolved pores and fractures. Second, in the paleouplift area develops a large-scale microbialite reservoir, with a thickness of 20-70 m and an area of about 1×104 km2. Third, the main reason for the development of large-scale reservoirs in the paleouplift is that there are favorable conditions for the development of microbialite, penesyngenetic karstification and supergene karstification in this area. In conclusion, the Tianjingshan paleouplift area has favorable conditions for the development of microbialite reservoirs and the formation of large-scale reservoirs, so it shall be regarded as a favorable area for natural gas exploration of Leikoupo Formation in the Sichuan Basin.