Experimental investigation of permeability reduction due to migration of non-swelling clay minerals

Formation damage is being reported during the secondary and tertiary stages of reservoir lifespan. One of the unpleasant sequences of formation damage caused by fine particles is permeability reduction due to pore plugging and bridging. The fine particles might exist initially in a porous medium, or be introduced by the external sources. In addition, there is a variety of particle types and sizes. The current research focuses on the effects of non-swelling clay minerals motions, such as the laminar ones found in Iranian sandstone reservoirs, on permeability. For this purpose, sand packs in a variety of glass bead sizes and containing aluminium oxide as fine particles were designed to scrutinize the motion of fine particles under various pressure differences, flow rates, and fine concentrations. It was concluded that for each of the three sand packs considered as the porous media in this study and composed of fine glass beads with different sizes, there is a critical flow rate which is a function of glass bead size. For the flow rates less than critical flow rate, bridges form stably and lead to the highest formation damage. After reaching the critical flow rate, the bridges weaken and then break; thereafter, relative permeability would be independent of flow rate. All in all, it was deduced that permeability reduction and formation damage are directly proportional to particle concentration, and inversely proportional to glass bead size. The reason for using solid glass spheres in this study is their flow ability, great strength, chemical stability, low thermal expansion.