Characteristics Of Shale Reservoirs Of The Lower Cambrian Series Niutitang Formation In The Western Part Of Hunan And Hubei In The Middle Of Yangtze Area

Energy is the pulse of human society.From the early coal to oil,energy problems and environmental pollution have become the contradictions that today's society has to solve.For shale gas as a clean energy to some extent,humans solve this problem.Provides directions.Since the industrial exploitation of shale gas in the United States,Canada and other countries,China's exploration and development of marine shale in the South is also proceeding in an orderly manner.At present,it has made revolutionary breakthroughs in Changning and Weiyuan areas in the Sichuan Basin,but its main exploration horizon is the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation shale,well known in China's Sichuan Basin and its periphery.The Cambrian Niutitang Formation shale also has high exploration and development value.The western part of Hunan and Hubei is adjacent to the Sichuan Basin.The shale has good geological conditions and is the key relay area for shale gas exploration and development in China.In this paper,the shale deposits and reservoirs of the Lower Cambrian Niutitang Formation in the western Hunan and Hubei provinces are combined with the geological outcrops,logging data,analytical test results,and other knowledge theories of sedimentary petrology,geochemistry,and reservoir geology.Characteristics are systematically studied.The shale sedimentary environment and lithology distribution characteristics,geochemical characteristics,reservoir characteristics and influencing factors in the study area were determined,and the relevant evaluation parameters were used to optimize the favorable resources of the study area,which provided suggestions for the next exploration and development work.The shale of the Niutitang Formation in the study area develops a slope-soil-basin sedimentary system from north to south.The shale of the Niutitang Formation is mainly located in the sedimentary environment of clastic rock and shovel,and the shallow shoal in the vertical direction-semi-deep water shed-deep amphibious The shed is a transition.The shale of the Niutitang Formation is triad,and the shallow water shelf shed is dominated by gray mudstone,argillaceous limestone and silty shale.The water body gradually deepens from Yichang-Guzhang,and the carbonate content is reduced to clay.The main shale and silty shale are mainly composed of gray shale and carbonaceous shale;the deep water shelf is mainly composed of carbonaceous shale and siliceous shale.The thickness of the dark mudstone is the largest in the southwestern part of the study area,reaching more than 170 m.The organic matter content in the study area is relatively high,and the average TOC content is more than 3%.The organic matter type is mainly type I cheese heel,and its high value points are distributed in the Enshi-Guzhang area.The organic matter has a high degree of thermal evolution,and the average value of Ro is 3.52%,which is an over-mature stage.The rock mineral content in the study area is dominated by quartz + feldspar.The carbonate minerals develop very high in the north of Changyang,and the clay mineral content increases gradually from north to south on the plane.The porosity distribution of organic-rich shale reservoirs ranges from 0.6 to 8.43% with an average of 6.25%,with a large porosity in the southeastern part of the study area.The pore types are mainly organic pores,intergranular pores,intragranular pores and micro-cracks.The reservoir properties are mainly affected by organic matter content and organic matter abundance,followed by brittle minerals.According g to the relevant parameters of shale reservoir evaluation and the optimal selection index of favorable shale gas area of the bureau of land and resources,two favorable shale areas of the Niutitang formation were selected: the Enshi-Longshan-Guzhang area and the Hefeng-Zhangjiajie area.According to the relevant parameters of shale reservoir evaluation and the preferred index of shale gas favorable area of the Bureau of Land and Resources,one advantageous areas of shale in the Niutitang Formation are selected: Changyang-Wufeng area.