Computational Modelling of Particle Straining in Porous Media

The understanding of formation damage in hydrocarbon reservoirs is extremely important to safe and cost-efficient reservoir exploitation. This thesis focuses on particle straining as a mechanism of formation damage, and investigates its effect on the permeability of porous media. Review of the current analytical models present in the literature show an incomplete understanding of particle straining as a method for porous media permeability reduction, and significant short-term deviation is seen in comparison to experimental results. This thesis approaches the problem of particle straining on the pore-scale using a computational approach, with the goal of quantifying the effect of particle straining on the permeability reduction of porous media. A methodology is introduced comprising of three main constituents in order to create a complete model; 1. The use of the Lattice Boltzmann Model (LBM) for modelling of fluid, 2. The use of the Discrete Element Method (DEM) for modelling the collision of particles, 3. The cohesion of the LBM and the DEM to create a total fluid and particle solver. Complex synthetic geometries representative of sandstone are created within Python to allow convergence of solution trials for varying mesh resolutions. Creation of these geometries is completely generalized, allowing for the application of these models to varying porous media, based on experimental measurements. The synthetic geometries are imported into both the fluid and particle solvers, allowing for testing using identical porous mediums. Simulation of fluids is performed through the open source software TCLB, a Lattice Boltzmann Method based solver suite. The underlying basis of the LBM is detailed, and validation of both simulation procedure and data analysis methods is achieved. Micro-CT scans of dolomite are obtained and imported to TCLB, showing application of the model to real-world porous media. Particle interactions are governed by the Discrete Element Method, simulated through ESyS-Particle. The selection process of major simulation parameters is put forth, and the synthetic geometries are successfully imported by the use of a modified marching-cubes algorithm to create a tessellated triangular mesh. Qualitative results of particle percolation through synthetic geometries are shown, giving validity to the DEM methodology utilised. A critical analysis of results is performed, and the cause of observed issues is reasoned. Extensive recommendations are put forth for the improvement of the methodology followed, allowing for the continued development of a pore-scale computational model of particle straining