Potential Analysis Of Carboniferous-Permian Coal Shale Gas Resources In Southwestern Shandong

Coal measures are deeply buried in Southwestern Shandong.After many years of exploration,coal measures shale gas may exist.Therefore,based on the detailed study of field data,drilling data,and organic geochemical data and other information in Southwestern Shandong,this paper studies the Carboniferous-Permian shale in Southwest Shandong by using the theories and methods of sedimentology,organic geochemistry,reservoir and petrology research,and clarifies the organic matter abundance and potential of the shale.The types of organic matter and maturity of organic matter are systematically analyzed.On this basis,the evaluation of shale gas resource optimization area is carried out.Based on the analysis of field data and drilling data,combined with the analysis of sedimentology and petrology characteristics,it is found that mudstones are mostly developed in tidal flat,lagoon and peat swamp sedimentary environments.According to the petrological and petrographic characteristics,the study area is divided into four sedimentary systems:tidal flat-lagoon,platform-lagoon,delta and meandering river.According to the average thickness and burial depth of mudstone in different boreholes,the isoline maps of mudstone thickness and shale burial depth are drawn.It is concluded that the thickness of mudstone in this area is mostly between 30 m and 140 m,and the burial depth is between 500 m and 3500 m.Based on the analysis of organic geochemical data and the theoretical knowledge of organic geochemistry,the organic geochemical characteristics of the study area are analyzed.It is found that the TOC content is mostly concentrated between 0.75%and 4%,the chloroform asphalt "A"content is between 0.0032%and 0.3044%,the hydrocarbon generating potential is between 0.0109 mg/g and 41.9908 mg/g,and the hydrocarbon source rock grade is generally poor to medium according to vitrinite and vitrinite.The triangular projection plots of vitrinite,inertinite and sapropelic group content and relative macerals content of source rocks show that the main types of organic matter are type ?2 and ?,with a small amount of type ?1 distribution.The vitrinite reflectance of shale ranges from 0.568%to 3.101%,which can be used to judge that the maturity of organic matter in shale is in the stage of low maturity to maturity.Based on the analysis of the occurrence conditions of Carboniferous-Permian shale gas in the area,the main factors such as organic carbon content,shale burial depth,shale thickness,organic matter maturity and structural complexity are combined,and the evaluation criteria of different selected areas are combined to delineate two favorable areas and five prospective areas.The research results of this paper have certain guiding significance for the exploration and development of shale gas in Western Shandong in the future.