New Results on Transient Well Tests Analysis Considering Nonlaminar Flow in the Reservoir

Abstract

Summary The aim of this work is to examine the wellbore pressure behavior in reservoirs with single-phase non-Darcy flow conditions produced at a constant sandface rate. The transient flow period is analyzed by means of results generated with a finite difference model. Analytical expressions of pressure drop and its semilogarithmic slope are presented for the first time. These equations contain the laminar flow solution as a particular case, and they provide means to evaluate the total skin factor. Another use of the analytical solution to the non-Darcy flow problem is to identify the presence of inertial effects by using a diagnostic plot, which consists of graphing the derivative of the pressure data vs. the inverse of the square root of time on a Cartesian paper. In this way, an analyst easily can predict the magnitude of the skin owing to nonlaminar flow under any condition of mechanical skin and rate. Furthermore, better stimulation jobs can be designed if non-Darcy flow conditions during a transient test are properly identified through the methodology presented in this study. The use of the methodology obtained in this work is illustrated with synthetic examples for homogeneous and naturally fractured reservoirs. Also, a field example of an undersaturated reservoir and a dry gas case (taken from the literature) shows the application of this technique. For the case of naturally fractured reservoirs, new insights are provided.