Research On Matrix Permeability Of Shale Based On Boltzmann Method And Digital Core

Shale gas exist in mud shales as adsorbent, free or dissolved state. When the pressure gradient or concentration difference functions shale gas in the matrix, it will cause the diffusion effect. As for the shale matrix, seepage passages are mainly nanometer and micron grade, its matrix permeability is greatly influnced by the diffusion effect.There are four main parts in the thesis:Laboratory measurement on permeability of LongMaXi Group in Sichuan Basin is carried out, two dimensional SEM images is disposed by using the ImageJ sortware.The conditional probability of two point neighborhood, four point neighborhood five point neighborhood, six point neighborhood and fifteen point neighborhood are calculated by using MCMC method, to reconstruct three dimensional digital core of shale rock, micro-scales of real shale can be more precisely simulated by the digital core.Pore distribution homogeneity and isotropy of shale are good.The LBM model is established based on the Lattice Boltzmann Method and the boundary conditions is set in terms of diffusion effect of gas micro flow in the porous media.The flow process of gas in microscopic pore can be more precisely simulated by this approach.provide scientific method for numerical simulation on the flowage of shale gas.Filtration law of gas in porous media is simulated with the variation of Kn. Theoretical calculations have shown that when the value of Kn rises, non-Darcy effect of gas in shale matrix is more obvious, permeability of the shale matrix declines. The permeability of the shale rock of our paper is around 0.0002 mD and the value of Kn is between 0.1 and 10.Based on the numerical simulation result from the connection with the pressure gradient and velocity of gas flow in digital core, the engineering model matrix on permeability of shale matrix is set. With the comparison between the calculation of this model and the result of laboratory measurement,the value of fractional error is around 2.17%.Compared with other methods, the relation between Kn and ? used in this thesis increased calculation accuracy of shale matrix permeability by 40%, providing theoretical base for permeability calculation of shale matrix.The study of this article can not only provide a theoretical basis for permeability calculation of shale matrix, but also have a guiding significance for later production forecasting and development project design of shale gas well, so it is meaningful for scientific method and valuable for engineering to some extent.