Experimental study of formation damage caused by clay with cyclic foam stimulation

Reservoir damage caused by clay is due to clay swelling or transport/deposition, which causes porous media blockage, drop of reservoir porosity and permeability, and reduce of oil and gas well production capacity. Foam plugging technology is proposed in this paper to remove the reservoir damage caused by clay, and cyclic foam stimulation test system is designed. In order to simulate formation damage caused by clay in different levels, 3 man-made sand producible cores invent firstly based on PVA film wrapped fine sand and calcium bentonite. Experiments results show that more weight percentage of clay in formation will cause lower of core permeability, the reservoir damage more seriously. Foam has good discharge effect on sand blockage and clay swelling. Permeability restitution coefficient is defined; the damage caused by the clay is severer than by the fine sand.