Western Sichuan In Southern Shaximiao Group Exploration Target Selection Research

This paper regards the sandstone gas reservoir of Shaximiao formation of the mid-Jurassic of the Southwest of Sichuan Basin as its research object. On the foundation of the exploration analysis of success or failure, and by the study of sedimentation and diagenesis characteristics of sandstone rocks, think that the sandstones of Shaximiao Formation have two kinds of diagenetic facies. which one is from chlorite to silicrete to earlier calcite to latter calcite and the other is from earlier calcite to silicrete to latter calcite. The reservoirs of the two diagenetic facies have similar evolving characters with pores and both of their main erosion periods are corresponding to latter period of earlier diagenesis time and the ancient river-channel could control the sandstones-developed and distribution. On the basic of the analysing reservoirs of the Baiqian 110 well of Baimamiao gas reservoir and other 13 typical wells on the other gas-bearing structure, the basic geological rules of Shaximiao gas reservoir are unveiled, which conclude that the Shaximiao reservoir bed is essentially a transitional formation between Xujiahe 2 of upper-Triassic and Penglaizhen of upper-Jurassic with" fracture "and "concealment" of the gas bearing sand as its basic geological features. Pores developed in the reservoir are the material basis for gas production, and the level of developed pores and exposed reservoir fracture controls nature gas producing condition. Through the study of oil and gas migration and accumulation, think that the nature gas of Shaximiao reservoir mainly could come from the hydrocarbon source rocks of Xujiahe 5 of upper-Triassic. The key requirements in forming a gas reservoir with high productivity are source rocks with adequate thickness, the sandstone body with suitable thickness and good physical properties (H≥5m, φ >5%) and the existence of fractures. The envision on the next stage of exploration of the drilled gas-bearing structures and the concrete measures which should be adopted are put forward in the paper after this study.