Petroleum Geological Conditions And Exploration Prospects Of Upper Proterozoic To Lower Paleozoic In Northwestern Hunan

Northwestern Hunan is located in the Wuling folded fault belt--the junction of the Jiangnan axis and the upper Yangtze platformal fold belt which belongs to the southeastern margin of Yangtze para-platform. Northwestern Hunan was generally a inheritance of ancient slope structure from Cambrian to Triassic which was high in the northeast and low in the southwest. From the oil and gas zone partition, Northwestern Hunan is an important part of Western Hunan-Hubei area which is an oil and gas exploration prospect area of the lower Paleozoic Marine strata in South China. This thesis aims to investigate the oil and gas reservoir conditions of upper Proterozoic to lower Paleozoic of Northwestern Hunan, to optimal select the favorable accumulation area of hydrocarboncan, to serve for the next making and exploring decision.The upper Proterozoic to lower Paleozoic of Northwestern Hunan can be divided into a grade I source-reservoir-seal assemblage by analyzing the vertical evolution characteristics of sedimentary facies.This thesis preliminarily analyses the oil and gas accumulation conditions of upper Proterozoic to lower Paleozoic of Northwestern Hunan by a series of common technologies and methods, such as rock analysis, thin section observation and description and so on. The research figures out that Lower Sinian-Lower Silurian source rocks, with high abundance of organic matter, large thickness, and buried deep, which mainly can be divided into argillaceous rocks and carbonate rocks developed in non-high energy environment.These souces rocks mostly is medium-good source rocks (muddy source rocks take TOC>0.4%as the minimum standard and carbonate source rocks take TOC>0.2%as the minimum standard), Organic matter is mainly sapropel-type class (I type), which is made by original organic debris by invertebrates, algae, bacteria and other low biological composition, so it is believed that these souces rocks provide good material base for oil and gas formation; The upper Proterozoic to lower Paleozoic of Northwestern Hunan includes three major reservoirs, the Upper Sinian Dengying Formation, Cambrian, the LowerOrdovician Nanjinguan Formation-Honghuayuan Formation.These reservoirs developed dissolution pore, diagentic, intercrystalline solution pores and so on.so that it is easy to form favorable reservoirs. Two regional cap formations (Lower Cambrian, Silurian)and one direct cap formation(the Lower Ordovician dawan Formation)are developed in the upper Proterozoic to lower Paleozoic of Northwestern Hunan.On the basis of comprehensive analysis of reservoir geological conditions, calculating the resources of upper Proterozoic to lower Paleozoic of Northwestern Hunan with organic carbon method are about4058.77billion stere. Comprehensive evaluation of the cap rock condition, tectonism and hydrogeological conditions, point out that Sangzhi Shimen synclinorium is a better hydrocarbon preservation unit. Taking source reservoir cap conditions, trap conditions, preservation conditions, regional paleostructure position into consideration, combined with the evaluation results of the local structures, selected one favorable structural belt (yanziyan-tianzishan structural belt) and two relatively favorable (datongshan-siwangshan structural belt and guangdongshan structural belt) from seven secondary structural belt which belong to Sangzhi Shimen synclinorium.