Micro-flow kinetics research on water invasion in tight sandstone reservoirs

The tight sandstone gas is a very critical unconventional gas resource. Nevertheless, liquid invasion may result in reduction of well productivity during the exploitation of tight gas. At present, the research on micro-flow kinetics in tight porous media is not very detailed, and there is no mathematical model for accurate description of liquid invasion in tight sandstone reservoirs. In this study, based on the micro-flow kinetics, the liquid invasion process is divided into two successive phases where the initial stage dominated by capillary and the pseudo steady stage influenced by pore pressure; a simplified kinetic model is proposed. The study shows that (i) the initial invasion stage is a transient process; (ii) during pseudo steady state, the key parameter becoming pore pressure drawdown, which should be considered in analysis of invasion in tight sandstone; (iii) the factor of permeability and static contact angle significantly influence invasion process, while viscosity has less impact on it.