Influencing Factors And Quantitative Evaluation Of Reservoir Capacity Of Permian Shale Reservoirs In Central Hunan Depression

As a new clean energy source,shale gas has been highly valued by all countries in the world for its large reserves and wide distribution.At present,more and more scholars have devoted themselves to the exploration and development of shale gas,and have made certain recognition and breakthroughs in the marine shale strata in the Sichuan Basin and its surrounding areas of the Paleozoic in southern China.As one of the important petroleum basins in South China,the central Hunan depression has many sets of marine and transitional facies shales.According to previous studies,the Permian shale in the central Hunan depression has a wide distribution area and a large thickness,and has good shale gas formation conditions in geochemical characteristics and mineral composition.On the whole,the research on micro-pore structure of shale is relatively low,and the evaluation of reservoir capacity of shale reservoir is very weak,which restricts the process of exploration and development.Therefore,based on the field profile,core and well logging data in the central Hunan depression,the distribution and development of mudstone shale,organic geochemical parameters and reservoir characteristics of the Permian Longtan Formation are analyzed through geochemical analysis,FIB-SEM and other analysis tests.The study shows that the Permian Longtan Formation shale in the central Hunan depression is mainly composed of black shale of littoral marsh facies,moderate burial depth.The main type of kerogen is?_1—?₂.The average abundance of organic matter is 2.29%,and the thermal evolution degree is relatively high,with Ro averaging 2.43%,reaching the stage of high-over maturity.The main lithofacies is siliceous argillaceous shale.Reservoir pore space is well developed and has good adsorption performance.It has favorable geological conditions for shale gas accumulation and accumulation.The shale reservoir capacity of Longtan Formation is affected by terrigenous clastic injection,and the overall reservoir capacity is different.The development of laminae has a great influence on reservoir capacity.Certain laminae development is conducive to increasing pore volume and pore specific surface area and providing favorable reservoir space for shale gas reservoirs.Quantitative evaluation of shale reservoirs in the study area and other strata in China and North America by using two-factor evaluation method.The results show that although Longtan Formation shale is lower than Longmaxi Formation,it still has high reservoir capacity and has good prospects for exploration and development.