Estimation of the Non-Darcy Coefficient Using Supercritical CO2 and Various Sandstones

Abstract

Non-Darcy flow (also known as high-velocity flow, inertial flow, etc.) often occurs in the near-well region of a reservoir during injection or production. This flow needs to be characterized and its origins fully understood, as it is a critical factor in reducing well productivity. The Forchheimer equation, which describes fluid flow considering an inertial effect, can be adopted to analyze non-Darcy flow. In particular, the non-Darcy coefficient in the equation represents inertial resistance in a porous medium and is an empirical value that depends on the pore geometry and fluid properties. This study, as part of research on geological CO2 storage, reports non-Darcy flow tests with a high flow rate and examines the non-Darcy coefficient by using supercritical CO2 and various sandstones. The dependence of the coefficient on the properties of the supercritical CO2 was also assessed in a series of non-Darcy tests under different pore pressures. The coefficient varied with the properties of the supercritical CO2 and sandstone. As the permeability of sandstone increased, the non-Darcy coefficient decreased nonlinearly and converged to a value. The results also indicate that the coefficient is reduced with a decreasing ratio of density to viscosity for the supercritical CO2. An equation predicting the coefficient was derived, having the advantage that both the hydraulic properties of rock and the fluid properties can be considered simultaneously in a dimensionally correct analysis.