Study On The Mechanical Properties Of Oil Shale Pyrolysis And Percolation Law Under The Action Of Microwave

Oil shale is also known as " oleum shale",and the organic matter inside is known as casein,which can be pyrolyzed into hydrocarbon products at high temperatures.In the process of in situ extraction of oil shale,the evolution of physical and mechanical parameters of oil shale reservoir under the effect of high temperature has an important influence on the hydrocarbon production of the reservoir.In this paper,the physical-mechanical characteristics of oil shale after microwave pyrolysis were studied by using the experimental device of microwave pyrolysis,oil content tester,uniaxial compression tester,and CT scanner as the research object.The COMSOL software was used to numerically simulate the microwave pyrolysis of oil shale reservoirs and to study the changes of temperature,seepage and displacement of oil shale reservoirs during the microwave heating process.The details of the study and the main findings are as follows:The microwave pyrolysis experiment and oil content tester were used to pyrolyze oil shale at different microwave power and analyze the oil content of oil shale after pyrolysis.It was found that the internal structure of oil shale changed greatly under different microwave pyrolysis end temperatures,and with the increase of temperature,the pore fissures and fractures of oil shale were gradually developed and perfected,which was conducive to the infiltration of oil and gas.The percentage of oil shale semi-coke production gradually increases,and the percentage of remaining oil and gas gradually decreases with the increase of temperature.The oil shale before and after pyrolysis was scanned and reconstructed by X-ray micro-CT,and a appropriate REV model was selected for the three-dimensional reconstruction of the pore fracture,and a maximum sphere algorithm was used to construct a pore network model to quantitatively characterize the porosity and equivalent pore roar radius of the core,and to obtain the variation law of porosity with temperature,and it was found that the porosity inside the rock gradually increased with the rise of temperature.Based on Fourier’s law,the thermal conductivity of the cores was simulated to investigate the variation of thermal conductivity of oil shale at different microwave pyrolysis end temperatures.It was found that fractures in the oil shale would have an important effect on the heat transfer inside the oil shale.Finally,using COMSOL software,a multi-field coupled model of oil shale is established to numerically analyze microwave in situ pyrolysis of oil shale reservoirs.It is found that the size of microwave power affects the warming rate,the change of reservoir temperature field is closely related to the microwave pyrolysis time,the percolation rate inside the reservoir increases with the increase of microwave pyrolysis time,and the increase of reservoir porosity will promote the oil and gas percolation.The reservoir will produce larger displacement under high power,and comprehensively,600 W is the most suitable power under the three powers.