| The upper Paleozoic in Linxing area in the Ordos Basin is rich in natural gas resources and has low exploration degree.With the comprehensive use of geological,seismic,logging,geochemistry and other datas,The geochemical characteristics of the source rocks,natural gas components,natural gas genetic types and natural gas source rock relationship are characterized.To a certain extent,it is of great significance to the exploration and development of natural gas in Lingxing area.Based on the analysis of gas composition and carbon isotope characteristics in different horizons,the characteristics of natural gas components and carbon isotopes in different horizons are analyzed and the gas generation intensity of three kinds of source rocks,coal,carbonaceous mudstone and mudstone,is calculated by means of hydrocarbon generation dynamics experiment.With the ability of hydrocarbon generation of three source rocks,a method for calculating the contribution rate of natural gas source rocks is established.The results show:Type III and II2 kerogen are the main types of parent material in source rocks,High abundance of organic matter,The source rocks in the whole region are mostly in the stage of thermal maturation.The carbon isotope value of natural gas is relatively heavy in Linxing area,it shows the characteristics of coal type gas.There is no differentiation in the process of vertical migration of alkane content,carbon isotopes did not reverse,it shows the characteristics of near source continuous injection.The natural gas mainly comes from Carboniferous Benxi formation and Permian Taiyuan formation source rocks,the contribution rates are 43.3%and 43.8%respectively.Coal is the main source rock of natural gas in Lingxing area.The natural gas has a good vertical matching relationship with source rocks,a combination of self generation and storage.The effective source rocks control the exploration of favorable areas of natural gas in Linxing area. |
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