Study of apparent permeability in micro-scale shale reservoir pores using an improved porous media algorithm

One of the main challenges in modeling microscale shale gas flow is the limitations of low porosity porous media created by the Quaternary Structure Generating Set (QSGS) method. This leads to the inability to accurately calculate the relationship between porosity and shale gas flow. In addition, shale has a highly anisotropic and complex structure, and there is a lack of effective algorithm to solve the problem of poor connectivity between pores within anisotropic porous media. To address these challenges, this paper proposes a new image algorithm to improve the structure of shale porous media and to simulate microscale shale gas flow using the lattice Boltzmann method with regularized multiple-relaxation-time. Analysis via the maximum sphere algorithm reveals that the structural parameter variation rate of the porous medium sample, following optimization by the image algorithm, remains below 9%, effectively preserving the stability of the porous medium structure. Building upon this, pore velocity distribution was further calculated, and the influence of porosity on apparent permeability was analyzed. Simulation results demonstrate that this image algorithm overcomes the limitation of traditional QSGS models, which cannot effectively calculate permeability below approximately 0.45 porosity. Furthermore, this method is equally applicable to modeling anisotropic shale porous media, providing a reliable technical pathway for numerical studies of shale gas flow characteristics under varying anisotropy coefficients.