Abstract: Drilling core observation, imaging logging, seismic data and other data were used to comprehensively analyze the fracture properties and development mechanism of the Dengying-4 Member carbonate rock in Moxi of Central Sichuan by combining with uniform temperature test of inclusion. Result indicates that there is tensile fracture, small scale shearing fracture and small scale pressure-solution fracture in the Dengying-4 Member of Moxi, which is dominated by tensile fracture. There are four dominant fracture strikes, including NW, NE, WE and NS. The fractures show a high filling level and the corresponding filling materials are dolomite, muddy, asphaltene, calcite and a small amount of quartz. The fractures in the Dengying-4 Member result from three-stage tectonic movements. The first-stage fractures developed in the Act-II of Dengtongwan movement (522.0～508.0 Ma), which are dominated by NW, NS and WE fractures due to the northward subduction of the Indian plate and the eastward collision of the Eurasian plate, and the corresponding uniform temperature of inclusions is 116.6～146.3 ℃. The second-stage fractures developed in the Caledonian movement (425.0～420.0 Ma), which are dominated by NE fractures due to the collision between the Yangtze plate and the Cathaysia plate, and the corresponding uniform temperature of inclusions is 138.0～176.0 ℃. The third-stage fractures developed in the Yanshan-Himalaya movement (75.2~75.0 Ma), which are dominated by shearing micro-fractures due to the effect of Longmenshan thrust folds, and the corresponding uniform temperature of inclusions is 177.0~208.0 ℃. This research could provide certain theoretical reference and basis for the further understanding of carbonate reservoirs in the Dengying Formation.

Key words: carbonate rock, fracture property, development mechanism, Dengying-4 Member, Sinian, central Sichuan