A study of the reservoir of Da’anzhai Member in Wenjing-Mingyue area of Sichuan Basin

Abstract：The Da’anzhai Member in Wenjing-Mingyue area is the major oil-producing horizon in central Sichuan, where the reservoir has apparent peculiarity and the reservoir rocks are mainly composed of shell limestone and muddy shell limestone. At the same time, the primary pores have died out because of the impact of intense compaction and cementation, but in the shell limestone, tectonic action in Xi’shan period created some structural fractures, in which a small number of dissolved pores and holes occurred during late dissolution. These structural fractures together with laminar fractures and calcite cleavages in rocks compose the chief reservoir space and percolating passage in Da’anzhai reservoir. In the study area, the reservoir is characterized by typical extremely low porosity-fracture, and the distribution of the reservoir is chiefly affected by the sedimentary facies and the development extent of fractures.