Study On The Evolution Of Oil Shale Thermal Simulation Reservoir Space Under An Open System

In recent years,the maturity of oil shale in-situ mining technology has given better prospects for the development and utilization of oil shale.During the in-situ pyrolysis of oil shale,the evolution characteristics of cracks and pores play a vital role in the heat and mass transfer process.In order to clarify the thermal evolution of oil shale,heating and expulsion of hydrocarbons has an impact on oil shale storage.For the influence of physical properties,the immature oil shale in the Minhe Basin is selected as the research object,and the thermal simulation is carried out by low-temperature dry distillation,using fracture threedimensional scanning imaging,CT scanning gray-scale imaging,high-pressure mercury injection experiment,low-temperature nitrogen adsorption experiment,X-ray diffraction Analysis and testing,combined with argon ion profiling technology and scanning electron microscopy,are used to analyze the storage properties of oil shale samples at different heating stages.From the macro to the micro system,the evolution characteristics of pores,fractures,chemical composition and clay composition of oil shale in each heating stage during the thermal simulation process are analyzed.The results show that the heating and dry distillation process of oil shale can be divided into three stages: low-temperature heating stage,a small amount of hydrocarbon expulsion,oil-water yield and semi-coke yield change little;medium-temperature heating stage,a large amount of hydrocarbon expulsion,oilwater yield rises sharply,The yield of semi-coke has dropped significantly;during the hightemperature heating stage,the residual hydrocarbon expulsion,the yield of oil and water and the yield of semi-coke basically do not change;during the heating process of oil shale,the number of cracks gradually increases,and the micro cracks gradually increase with the heating temperature.Widening and extending,communicating with each other to form large cracks,most of the cracks formed are parallel to the bedding plane,and no obvious cracks are generated in the direction of the vertical bedding plane;with the increase of heating temperature,the scale of the macropores in the pores of oil shale appears first After increasing,the “V”-shaped feature,which decreases and then increases,gradually changes from micropores to macropores,and some of the macropores communicate with each other to form microcracks;during the thermal simulation of oil shale,with heating As the temperature rises,the pores of oil shale gradually change from micropores to macropores.At the same time,as the hydrocarbon expulsion continues,organic matter is constantly being lost.The number of pores in the organic matter,pore size,and pore volume continue to increase.The connectivity of internal pores is also getting better;the adsorption capacity of oil shale semi-coke not only increases with the increase of relative pressure,but also increases with the increase of heating temperature;oil shale is in the thermal simulation process The smectite in the Imonite mixed layer gradually transforms into illite,the smectite structure collapses to remove the interlayer water,and the mineral particles are reduced,causing diagenetic shrinkage fractures in the oil shale.The increase of diagenetic shrinkage joints increases the porosity and permeability of oil shale,and provides storage space and migration channels for oil and gas generated during the thermal evolution of oil shale.