Diagenetic and Sedimentary Controls on Porosity and Permeability in Upper Triassic Tight Gas Sandstone, Sichuan Basin

The reservoir quality prediction of tight gas sandstone is difficult due to the heterogeneity of porosity and permeability. Thus developing a better understanding of porosity and permeability in tight sands is critical for future gas exploration. In this paper study of the sedimentary and diagenetic controls on tight gas sandstone quality was conducted using the core data. the result shows: 1) Hydrodynamic condition is a controlling factor of Xujiahe tight sands quality in Southern Sichuan basin. Sandstone deposited with high energy tends to have higher porosity than low energy sandstones. 2) Within single channel sandstone, the porosity of middle and lower part are better than that of upper and bottom due to the energy change in channel deposition. Xujiahe tight sands quality is also controlled by burial diagenetic processes. The major factors of porosity loss are mechanical compaction in shallow burial depth (<2000m) and quart overgrowth in deeper burial period. Authigenic chlorite and illite mineral have greater influence on permeability than on porosity.