Reservoir characteristics and main controlling factors of the Cambrian Xixiangchi Formation in the Sichuan Basin

The middle and lower Cambrian Xixiangchi Formation in the Sichuan Basin is a gas-bearing formation with a good potential. Its exploration degree is still very low at present, and the reservoir characteristics and main controls are not clear. Core, thin section and testing data were integrated to study the rock types, reservoir space, physical properties and controlling factors of the Xixiangchi reservoirs. The Xixiangchi reservoirs are mainly grain dolomites, followed by aplite-dolomites. The reservoir space includes pores, caves and fractures, and the reservoir type is fracture-pore type. The physical properties of the reservoirs are characterized by low porosity and low permeability, and locally high porosity and high permeability, showing a strong heterogeneity. For the distribution, the Xixiangchi reservoirs vertically stacked and have a poor lateral continuity. Thick reservoirs appear from the central Sichuan Basin to well GT 2 in the east, and then thinned in Wubaiti area. In Fengjie and Xishui areas at the basin edge, reservoirs distribute as belts, and are thinner compared to those in the basin center. Reservoir development was controlled by sedimentary facies obviously. In the grain shoal area, reservoirs have a high development degree. Besides, constructive diagenesis and tectonic fracture have positive effects on reservoir development.