The Basis Of Upper - Siltstones Of Transition Zone, River Group Must Be 2 Reservoir Geology Comprehensive Study

Clastic reservoir of the2nd member of Xujiahe formation, the Upper Triassic of Central-South Sichuan transitional belt is one of the key stratum series in the large-scale middle Sichuan basin. Due to the reservoir with low porosity, low permeability and heterogeneous, which is very hard to explore. Therefore, it is necessary to make research into Xujiahe formation of the Upper Triassic reservoir characteristics.Based on the theories and technologies of sedimentology, reservoir geology, petrology,geochemistry and reservoir evaluation, researches are carried out on several aspects such as reservoir petrologic characteristics, reservoir sandbody genesis types and distribution characteristics, diagenesis type, reservoir pore types, physical property characteristics and its controlling factors.Finally we confirmed the lower bound of physical property and studied the evaluation and forcasting of the reservoir.The Xujiahe Formation in studied area is a set of inland fluviolacustrine alternative terrigenous clastic deposit, and the main sedimentary microfacies is beach bar sandstone of shore-shallow lake.Reservoir rocks in higher levels of lithic and feldspathic,the lithology is mainly medium, fine-medium feldspathic detritus sandstone, lithic feldspathic sandstone and lithic sandstone, accessory is feldspar quartz sandstone and lithic quartz sandstone.The pore types are mainly intergranular pore,intragranular pore,matrix-pore and fractures.The diagenesis,which influences the pore development of the second segment of xujiahe,is mainly compaction,pressure solution,cementation and dissolution.The reservoir of the second member of xujiahe is typical hydrocarbon reservoir with low porosity and low permeablity.From the porosity and permeability relations display reservoirs is porous reservoir.fractures undeleloped in reservoir, but property of reservoir is better with fractures; Reservoir mainly by diagenesis,sedimentary microfacies and types of rocks factors.Based on predeeessor’previous research results on the effective reservior, according to reservoir lithology, physical properties, pore structure, casting thin sections as well as productivity data, the2nd member of Xujiahe formation can be divided into4classes.The results of reservoir evaluation and prediction show that the2nd member of Xujiahe formation is developed with bigger changes from both the vertical and horizontal. The studied area is the second reservoir and the third mostly.The most favorable sedimentary facies are beaeh bar sandstones that the best reservoirs in this area, and the property of reservoir vertical for lower-Xu2is better than upper, high value of porosity,reservoir thinkness and storage coefficient are in north east-south west45°irection a ribbon distribution around the Lei Koupo paleo-uplift, located in south-southwest of the studied area.