Pore Structure Characteristics And Influencing Factors Of Inter-salt Shale Oil Reservoirs Of Eq₃ In Qianjiang Sag

Shale porosity is the main site for the accumulation and accumulation of shale oil and gas.Studying the characteristics of shale pore structure is of great significance for the evaluation of shale oil resource potential.In this paper,the inter-salt shale oil reservoir of Eq3₄¹⁰rhythm in the Qianjiang Sag,Jianghan Basin is taken as the research object,and the inter-salt shale oil in Eq₃of Qianjiang Sag is analyzed by means of XRD,FE-SEM,MICP,N₂adsorption and FIB-SEM three-dimensional imaging.The geological and geochemical characteristics of the reservoir and the pore structure characteristics finally identified the main controlling factors affecting the development of shale pores in the study area.Characteristics and pore structure characteristics,identified the main controlling factors affecting shale pore development in the study area.The results show that the sedimentary environment of study area is brackish water lake,and the water depth is semi-deep water lake.The mineral composition is mainly composed of carbonate minerals(dolomite and calcite),detrital minerals(feldspar,quartz,clay minerals)and salt minerals.(Calcerite,anhydrite,stone salt).The physical properties are characterized by"high porosity and low permeability".The average content of TOC in the shale oil reservoirs in the study area is 3.21%,and the average hydrocarbon generation potential(S₁+S₂)is 24.46mg/g.It has a good hydrocarbon-generating material foundation.The types of organic matter are mainly type I and type II.The degree of thermal evolution is relatively low.R_ois mainly between 0.3%and 0.8%.The study area of shale oil reservoirs has various types of pore reservoir space,including intercrystalline pores,intergranular pores,dissolution pores,and interlayer fractures.In terms of pore volume characteristics,macropores are the most developed,followed by mesopores,and micropores are the weakest.The overall connectivity of shale oil reservoirs in the study area is poor.In comparison,the pore volume,macropore development degree,and connectivity of argillaceous dolomite are better than those of argillaceous mudstone,indicating that argillaceous dolomite is widely developed in the study area.Regional pores are more developed.The main factors affecting the pore structure characteristics of intersalt shale oil reservoirs in the study area are organic matter content,mineral composition,and fluid erosion.Among them,the pore development degree of shale reservoir in the study area is negatively correlated with the TOC content,and the low thermal evolution degree of the study area makes its organic pore development not significant.The mineral components that affect the pore structure are mainly dolomite,calcite,clay minerals,and calcium mirabilite.Dolomite can promote the development of macropores,calcite and clay minerals can promote the development of mesopores,and calcium mirabilite can inhibit the study area Development of pores in shale reservoirs.Fluid simulation experiments show that the three fluids(H₂O,CO₂,H₂O+CO₂)have improved the pore structure and connectivity of the study area.Among them,the mixed fluid H₂O+CO₂has relatively improved the pore structure and connectivity of the study area.It is best to indicate that the modification effect of the mixed fluid is greater than that of a single fluid,but the proportion of slippery water in the mixed fluid needs to be paid attention to prevent its excess and thereby destroy the pores.