Pore structure characterization of marine-continental transitional shale and seepage law simulation of shale gas
The marine-continental transitional shale reservoir in Daning-Jixian Block of Ordos Basin has strong heterogeneity,and the pore structure characteristics and the shale gas seepage laws of carbonaceous shale and pure shale have obvious differences.However,at present,the study on seepage laws of shale gas in pore structures of different lithologies is relatively lacking.Taking these two kinds of lithologic shale as the research objects and based on CT scanning and scanning electron microscopy physical experiment technology,the characteristic parameters of matrix pores and bedded fractures of these two lithologies are measured,the pore structure differences of these two lithologies are compared,a Lattice Boltzmann numerical stimulation method considering adsorption effects and slippage effects is constructed,and the influence of pore structures of these two lithologies on seepage laws of shale gas is analyzed.The results show that:(1)Fractures of carbonaceous shale show a spatial network structure,while fractures of pure shale are in parallel bedding direction.Compared with pure shale,carbonaceous shale has larger pore size,but fewer pores and lower porosity.(2)There are obvious slippage effects in shale pores.The slippage effects increase the flow velocity of gas,and the desorption of shale gas from pore walls alleviates the reduction of pore pressure and extends the production time.During the exploitation of pure shale layers,it is suggested that the production pressure difference should be reduced properly,and the slippage effects in small pores could be improved.During the exploitation of carbonaceous shale layers,the production pressure difference should be increased properly,and the shale gas yield could be improved by desorption.
marine-continental transitional faciesshalepore structureLattice Boltzmannseepage law
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