| Shanxi Formatiom shale in Linfen-Hongdong area is taken as the research object.Mainly focus on reservoir characteristics,organic geochemical characteristics,pore fissure characteristics and shale gas occurrence.Research on four aspects of accumulation characteristics,the results show that:The Shanxi Formation is a sea-land interfacial sedimentary stratum,and it is a delta sedimentary system.The lithology consists of mud shale,silty sandy shale,sandstone,siltstone,coal seam,etc.The muddy component is mainly microcrystalline-cryptic clay.Mineral mineral aggregates,the clastic components are mainly quartz,feldspar and other particles.The dark mud shale has large thickness and good continuity,and is a favorable interval for shale gas development.The average clay mineral content can reach 57.4%,and the average quartz content can reach 34.5%.The content of clay minerals,quartz,feldspar,and carbonate rocks varies widely.Pyrite only appears in the bottom sample of the Shanxi Formation,indicating that the initial deposition was a strong reducing environment,which reflects the strong heterogeneity of the shale in the vertical direction.The shale brittleness coefficient is mainly concentrated between 0.3-0.4,indicating that the overall shale brittleness is generally low.The organic shale type of shale is type III kerogen,the main body of organic carbon content is between 1.0% and 4.0%,and the change is mainly controlled by the sedimentary environment.The Ro value of shale is between 1.17% and 1.67%,with an average of 1.39%,With the increase of depth,the reflectance of the vitrinite group increases slightly,which has good hydrocarbon generation conditions.The shale permeability value is between 0.0010727-0.0922997 mD,with an average of0.0210838 mD,and the permeability varies greatly.The shale pores and fissures of the Shanxi Formation are developed,and the porosity is mostly in the range of 1.40% to 1.80%.The overall distribution is relatively stable but low.The pore size range of mud shale in Shanxi Formation is mainly concentrated in small pores and micropores,and the pore volume can reach 6.8×10-4ml/g.The pore size is between 9.52?13.88nm,and the average pore size is 10.69nm.The comparison of the results of the carbon dioxide method and the liquid nitrogen method found that the pores and micropores above 2nm contributed a larger pore volume,while the micropores below 2nm contributed more total pore specific surface area,and the pore shape was wedge/V Type,better microporous connectivity.At 55?,the maximum content of adsorbed gas is 0.72-1.48m3/t,with an average of 1.19m3/t;The free mass is 0.658227-1.06962m3/t,and the average is 0.933861m3/t.The thermal maturation and hydrocarbon generation evolution of Shanxi shale shale in Linfen-Hongdong area can be divided into 4 stages.The most significant influence on the thermal evolution of organic matter is the Yanshan movement stage.Due to the magmatic thermal events of Yanshan,the geothermal gradient increases abnormally.The degree of thermal evolution of organic matter has been greatly improved.The main controlling factors for shale gas accumulation in the Shanxi Formation are as follows:tectonic effect promotes the migration and accumulation of organic hydrocarbon generation and shale gas;the sedimentary environment controls the material source,effective thickness,and organic matter abundance of shale gas accumulation.The adsorption gas content has a good positive correlation with the pore volume and specific surface area.The higher the porosity,the greater the shale gas content.The burial depth affects the production and accumulation of shale gas.Two-thirds of the study area has a buried depth of more than 2000m in the Shanxi Formation.The tectonic movement in the study area is frequent and the Shanxi formation After two settlements and two uplifts,the maximum burial depth exceeded 3000m.The larger burial depth is sufficient for the organic matter to undergo thermal evolution and generate a large amount of natural gas,which is beneficial to the formation of large-scale shale gas reservoirs.There are 47 figures,15 tables,and 146 references in this paper. |
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