A New Approach to Multiphase Well Test Analysis

Abstract

Abstract This paper presents a new approach to analyze multiphase well tests. In this approach, multiphase flow is modelled using the diffusivity equation with p2 as the dependent variable. This approach is applied to analyze simulated and literature multiphase tests for a range of PVT properties. Results of this approach are compared to those obtained by the pressure (Perrine's) approach, which is shown to be a special case of the new approach. Fetkovich's empirical approach for isochronal oil-well testing has been in use since 1973 without theoretical derivation. His approach is derived here using the pseudosteady state solution of the diffusivity equation in terms of p2. The possibility of extending the isochronal testing to three phase systems is also discussed. This paper derives the pressure-saturation relation, reported by both Muskat and Martin. Assumptions made are also investigated. Martin's total compressibility is derived without assuming negligible pressure and saturation gradients. Finally, this paper explains the application of a new relative permeability technique, to estimate the absolute permeability of multiphase reservoirs. Two examples to verify this application are also reported.