Study On Anoxic Deposit Of The Middle Permian In The Middle And Upper Yangtze Region

The Middle and Upper Yangtze Basin is the large oil and gas superimposed basin in the south of China,and the sedimentary cap rocks in the basin are relatively developed and have good prospects of oil and gas exploration and development.The predecessors have done a lot of research work on the petrology,sedimentary facies,source rocks,reservoirs,traps and accumulation rules of the Permian in the Middle and Upper Yangtze Region,and have obtained gratifying achievements in the field of oil and gas exploration,Found the ferry crossing,Luojiazhai,Puguang,Maoba,Longgang,Yuanba and other gas fields and a large number of oil and ancient reservoirs.Anoxic deposition is one of the main factors controlling the development of hydrocarbon source rocks,and the anoxic environment of the Middle Permian in the Middle and Upper Yangtze Region is more developed.Therefore,it is of great geological significance to explore the oil and gas exploration in the study of the Middle Permian anoxic deposition characteristics,to understand its mechanism and to assess its hydrocarbon generation potential.Based on the outcrop data of the Permian field,the identification data and the analytical data,Based on the study of sedimentary studies and petrology,the study of the Middle Permian anoxic deposition in the study area is carried out.Based on the analysis of the sedimentary characteristics of the Middle Permian in the Middle and Upper Yangtze Region,the characteristics of the anoxic sedimentation are summarized.The types of the rocks are mainly composed of black mud shale,black thin layer of siliceous rock,dark gray-gray black medium-Mudstone limestone and mud limestone.The first three types of rocks often form a dark shale-thin layer of siliceous-mudstone limestone assemblage,while mud-bearing limestone is mainly the "eyelid" part of the eyeball limestone.The petrological characteristics,paleontological features and geochemical characteristics of these two combinations were studied respectively,and their depositional environment and the causes of anoxic environment were analyzed.It is concluded that the dark shale-thin layer siliceous-mudstone limestone assembles is the product of basin,basin edge or slope environment.The anoxic environment is mainly large-scale transgression.The "eyelid" part of eyeball limestone should be Carbonate platform products,the anoxic environment should be the role of Uplift formation.Based on the correlation analysis and test data,the characteristics of the MiddlePermian source rocks formed by the anoxic deposition in the Middle and Upper Yangtze Region were evaluated.Based on the study of the distribution of anoxic deposition,we found that the distribution of the thickness of the Permian alluvial rocks along the Qianbei-Qianbei-western Hubei-eastern Chongqing-northeastern Sichuan-Sichuan has a certain law,Which is consistent with the distribution of anoxic deposition of the Middle Permian.The results show that the source rocks of the Middle Permian are dominated by?-?1and the maturity of the source rocks shows that the evolution of the Permian organic matter in the study area And it is believed that the development of hydrocarbon source rocks of Middle Permian in the Middle and Upper Yangtze Region is closely related to lithofacies palaeogeography,which mainly developed in anoxic environment,and the depositional environment is organic carbon distribution.Favorable control factors,high quality source rocks are mainly developed in the swamp environment and basin environment,the rock type is mainly carbonaceous mud(page)rock;carbonate platform is also a favorable environment for the development of hydrocarbon source rock.