Abstract：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.
