The Variation Law Of Deep Coal Measure Gas Reservoirs Physical Properties With The Increase Of Temperature And Pressure

Taking the marine-continental Transitional facies coal measure gas reservoirs from Shanxi-Taiyuan Formations in Yushe-Wuxiang block located in Qinshui coalfield as the key research object,No 15 coal seam from Taiyuan Formation is considered to have the higher CBM development potential than No 3 coal seam from Shanxi Formation from the perspective of thickness,buried depth and gas content while Taiyuan Formation mud shale has greater potential for shale gas exploration than Shanxi Formation mud shale from the perspective of gas logging display,organic matter abundance,hydrocarbon generating potential and source rock thickness(total thickness and single layer thickness).The pore characteristics of coal measure gas reservoirs are quantitatively characterized at full scale and the coal measure gas reservoirs are divided into four types according to the proportion of macropore and micropore volumes.Among which,middle rank coal mainly develops type III-micropore-macropore coexisting reservoir,high rank coal is type II-micropore dominant reservoir while mud shale is type IV-mesopore dominant reservoir.Additionally,the influence of organic matter abundance,thermal evolution degree and mineral composition on pore development of coal measure mud shale and the difference between coal shale and marine shale is pointed out.By comparing the fitting results of different empirical models and theoretical models,binomial function model is better to describe the relationship between porosity and effective stress while the power function model is better to describe the relationship between permeability and effective stress.There is a threshold between permeability and temperature.Before the threshold,temperature sensitivity has a great influence on permeability,but after the threshold,temperature sensitivity has a weak influence on permeability.The porosity stress sensitivity of coal measure gas reservoirs is coal>sandstone>shale,and the difference of stress sensitivity decrease with the increase of effective stress.Permeability sensitively also decreases with increasing effective stress.In the case of low confining pressure,the order of permeability stress sensitivity is transformed from shale>sandstone>coal to coal>shale>sandstone while in the case of low confining pressure,the permeability stress sensitivity order is transformed from coal>mud shale>sandstone to sandstone>mud shale>coal.The variation law of pore permeability of coal measure gas reservoirs with temperature and pressure is revealed.Furthermore,a three-compression test was carried out to investigate the relationships between confining pressure,maceral composition and coal quality with elastic parameters,mechanical strength parameters and energy parameters,the stress-strain criteria and constitutive model of coal are also initially constructed.The brittleness characteristics of various minerals in mud shale/compact sandstone and their influence on brittleness were determined,and the brittleness index calculation model based on the mineral composition method was determined.The brittleness of rock mass is evaluated from the perspective of rock mechanical strength,elastic parameters and energy dissipation.To overcome the defect of neglecting confining pressure in elastic parameter method,fracture toughness and strain energy density are introduced into the elastic parameter model as indicators of burial depth to reflect the influence of confining pressure on brittleness.The empirical formula between the difference of longitudinal wave time and shear wave time of different lithologies is established and the mechanical parameters,strength parameters and closed stress factors are explained by sonic logging and density logging.Additionally,the single well mechanics-brittle continuous section in the study area is established.The adsorption properties of coal measure gas reservoirs were compared from the perspectives of energy,adsorption potential,adsorption thermodynamics and adsorption kinetics.The adsorption prediction model of deep coal measure gas reservoirs was established.The ultimate heat of adsorption of coal is higher than that of mud shale.Additionally,the limit Gibbs free energy(U_L)is defined,and the variation law of adsorption difference of coal measure gas reservoirs is revealed.The limit Gibbs free energy of coal reservoir is greater than that of mud shale.The effect of temperature on coal saturation adsorption is more significant while its influence on limit Gibbs free energy of mud shale is more significant.There are 133 figures,38 tables,and 224 references in this dissertation.