Shale Reservoir Characteristics And Favorable Interval Selection Of Taiyuan Formation In Yushe Wuxiang Block,Shanxi Province

China's Shale Gas Technological recoverable resources rank first in the world,and the huge shale gas reserves provide reliable resources for promoting China's economic development.Through the analysis of 33 boreholes in Yushe Wuxiang block of Qinshui Basin,it is found that there is shale gas potential in Yushe Wuxiang block..The dark mudstone and coal seam of Taiyuan formation are well developed,which is one of the favorable gas producing intervals in Wuxiang,Yushe.In this paper,the shale reservoir of Taiyuan Formation in Yushe Wuxiang block is taken as the research object.Through data collection,experimental test and theoretical analysis,the characteristics of shale reservoir of Taiyuan Formation in the study area are studied,and the reservoir grade is divided according to logging evaluation parameters.The results show that:The Taiyuan Formation in the study area is a marine continental deposit.The early sedimentary environment is barrier coast-carbonate platform facies,and gradually becomes tidal flat lacustrine facies with relatively stable hydrodynamic environment.Finally,at the end of the Taiyuan formation,the sedimentary environment becomes shallow water delta facies.The thickness of shale in each section of Taiyuan Formation in the study area is affected by the sedimentary environment,and the sedimentary centers of shale in each section migrate with the change of sedimentary environment.The sedimentary center of the lower section of Taiyuan formation is located in the northwest of the study area,and gradually migrates to the North in the middle section,and finally migrates to the middle and north of the study area in the upper section of Taiyuan.The organic matter type of Taiyuan Formation shale reservoir is mainly type III kerogen,and the distribution of TOC in shale is uneven,ranging from 2.0%to 4.0%.In plane,the TOC increases from the middle of the study area to the South and North,and in vertical,the TOC gradually increases from shallow to deep.The maturity of organic matter is high,ranging from 2.33%to 2.79%,which is in the stage of high maturity to over maturity.The minerals in the shale are mainly composed of quartz and clay minerals,with a small amount of pyrite in some areas.The clay minerals are mainly composed of kaolinite,chlorite,illite and illite Mongolian mixed layer.Kaolinite,illite,chlorite and illite are 2%?74%,1%?54.6%,1%?10.8%and 0?94%respectively.The pore structure mainly consists of narrow parallel plate-shaped pores and wedge-shaped semi closed pores,with a small amount of ink bottle shaped pores.Sedimentary environment,diagenesis and tectonism have a certain influence on reservoir pore development.Sedimentary facies mainly affect reservoir physical properties by controlling rock type,mineral composition,pore permeability structure and clastic structure of sedimentary rocks.The influence of diagenesis on reservoir pore structure is mainly manifested in the diagenetic evolution of inorganic minerals and organic matter.Since the Permian,multi-stage structure has a certain impact on the reservoir.The Yanshanian tectonic movement has the strongest impact on the coal measures reservoir of Taiyuan formation.The shape of micro fractures in shale reservoir is related to the size of tectonic stress and the content of brittle minerals in the reservoir.The higher the content of brittle minerals,the easier the fractures bifurcate.Through the study of the reservoir characteristics and logging curve response characteristics of Taiyuan formation,it is found that the low shale reservoir in the study area is mainly located in the middle of Taiyuan formation,between K₄limestone and K₂ limestone,followed by the lower reservoir in the upper Taiyuan Formation siltstone mudstone section;the medium shale reservoir is mainly located in the upper Taiyuan Formation shale and coal seam combination section,and the effective thickness of shale in this section It is a good shale reservoir in the study area.There are 83 pictures,7 tables and 140 references in this paper.