Decline-Curve Analysis Considering Nonlaminar Flow in Dual-Porosity Systems

Abstract

Summary Most of the theoretical work on decline-curve analysis with non-laminar flow in the reservoir considers either a dry gas or liquid flow in a homogeneous system. The purpose of this work is to analyze decline curves considering the non-Darcy flow effect in the reservoir for a slightly-compressible-liquid flow in dual-porosity systems at constant wellbore pressure. The transient and boundary-dominated flow periods are examined by means of computer results generated with a finite-difference simulator. Analytical expressions of velocity and wellbore rate are presented for the first time in this paper. These equations contain the laminar-flow solution as a particular case. A method is proposed to identify the presence of inertial effects by plotting d[log(q)]/d[log(t)] against log(t). The method for area calculation under laminar conditions produces a good approximation for a reservoir under nonlaminar flow. However, the presence of inertial effects distorts the shape of decline curves, resulting in erroneous estimates of wellbore and reservoir parameters by type-curve analysis with laminar decline curves. The utility of the methodology presented in this work is illustrated with synthetic examples.