Direct Numerical Simulation of Suspended Particle Filtration in Geometrically-Complex Porous Media

Abstract: To stimulate coal seam gas extraction, a reservoir may be fractured via the injection of high-pressure fluids in a process known as hydraulic fracturing. Proppant particles can be injected to support the fractures and hold them open for extraction. During withdrawal, fines may become dislodged and flow back (or percolate) towards the main well, causing infrastructure damage. There exists limited work on the direct resolution of particle percolation during a flow-back, especially in non-ideal complex pore systems, and a more comprehensive understanding of realistic percolation could aid in the better design of extraction processes to reduce damage to critical infrastructure and improve the performance of gas wells. This work presents the development of a lattice Boltzmann and discrete element simulation framework to analyse the effect of non-uniform synthetic collector geometries on particle percolation. All synthetic structures showed exponential decay of deposited material with depth with correlates well with experimental observations in spherical systems. Packs of irregular particles had deeper retention with breakthrough rates approximately three times higher than packs of spherical collectors. All geometries exhibited linear-quadratic performance degradation dependent on deposit for low volumes of material. However, after a critical deposit threshold, the irregular pack diverged and achieved a 26.4% greater performance loss compared to an equivalent domain comprised of spherical collectors. This deviation was not captured by the analytical models considered, and has hitherto not been presented in the literature. Keywords: lattice Boltzmann method, discrete element method, straining, deep-bed filtration, population balance