Unconventional Gas Mining: Insights from Pore to Mine Scale Simulations

Modern computational techniques are invaluable components of every engineer’s toolkit and every scientist’s laboratory. The main challenge for computational analysis of unconventional gas mining is to consider the multiscale heterogeneity and the related phenomena in natural and/or enhanced geo-materials. Heterogeneous materials typically possess a multitude of mechanically significant scales and each of these scales requires appropriate modeling. Heterogeneous structures on the microscale (i.e. mineral grains, pore space and micro-cracks) are often close in size to a characteristic length for the macroscopic pattern for such as subsurface flow and transport. Hence these structures strongly influence macroscale processes. To analyze and depict complicated unconventional gas behaviours across different scales in fractured porous media, an Enhanced Multiscale Heterogeneous Porous Media Computational Model (EMHPM) is proposed based on analytical solution for fluid flow in a nano pipe and lattice Boltzmann method (LBM), and implemented in PANDAS (i.e. PANDAS/LBM). We apply the conventional LBM (CLBM) algorithm for simulating the microscale processes based on a micro-structural high resolution X-ray/CT/MRI/SEM measurement data. Upon completion of a solution step, the micro models return with the upscale material properties such as permeability for macroscale analysis. The macroscale model which distinguishing fractures, solids and matrix with some certain permeability by stating its local physical properties from the microscale simulation will be simulated. PANDAS/LBM has been benchmarked and applied in analysis of unconventional gas mining, and the quantitative description of gas migration in porous media at extreme conditions has demonstrated advantages of the proposed algorithm for an improved understanding and assessing the unconventional gas flow phenomena in practical mining processes.