The Characteristics of Sedimentary and Packing and Reserves Development for Silurian Basin in the East Chongqing and West Hubei Area

The depositional evolution of Silurian Basin had undergone 4 stages:foreland depressional basin in early S1l,lifted depressional development at late S1l-early S1x,depressional packing at late S1x -S2h,depositional devolopment in S2x-S2hx in east Chongqing and west Hubei Area of Sichuan Basin.It was first revealed that the sandstones of S1x are shallow continent shelf tidal sand wave deposition controlled by tide,and the sandstones of S2h are tidal flat deposition.Due to succession changes of different surfaces,four 3rd sequences can be defined,such as SSQ1,SSQ2,SSQ3 and SSQ4.It is found from this study that there are sets of reservoirs with small porosity and low permeability,under the control of clasts supply from different directional provenances,specially linked up with the different fracture systems.The sandstone reservoirs are developed with different features,vertical positions are established by different depositional sequences,and their lateral distribution is controlled by the sedimentary facies belts.There are great prospects of exploration for the regional distribution of the Silurian formations in the study area.