Analytical Treatment of Transient Non-Darcy Flow

Abstract

Abstract Non-Darcy flow is an important factor affecting deliverability of gas and high-rate oil wells. An analytical model describing the transient non-Darcy flow is designed. The model is used to define a better interpretation approach. The new model has shown that the slope of the straight lines obtained from pressure drawdown and buildup tests are independent of the non-Darcy flow component as long as fluid properties remain constant The increase observed in the slope of semilog straight line for non-Darcy gas flow is due to large variations of gas properties with pressure. An explicit equation for the rate-dependent skin factor has been derived. Significant differences exist between the explicit equation and the empirical ones cited in the literature. A method is presented to qualify the size and permeability of mechanical skin region from a multirate test. The proposed equations are tested using a simulated test.