Determination of In-Situ Reservoir Absolute Permeability Under Multiphase-Flow Conditions Using Transient Well Testing

Abstract

Summary A new method is presented that uses transient well testing to determine the in-situ absolute permeability of the formation when three phases of fluids are flowing simultaneously in the reservoir. The method was verified through simulation using synthetic data, and its applicability and practicality were confirmed through application to field data. Determining the absolute permeability over the reservoir scale using readily available transient testing data will have major benefits in accelerating history matching and improving reservoir-performance prediction. A recently developed method (Kamal and Pan 2010) to determine the in-situ absolute permeability under conditions of two-phase flow extended the applicability of transient well testing and has been adopted in commercial software. In this study, We extend the analysis method to determine the absolute permeability and fluid saturations when three phases are flowing in the reservoir. We show that an optimization procedure is needed to obtain the required results in this case. We show that the theoretical bases for the method presented to determine absolute permeability from transient tests under multiphase-flow conditions are the same as those used in obtaining relative permeability relations from core analysis and predicting reservoir performance in reservoir-simulation studies. The method presented in this study uses surface flow rates and the fluid properties of the three phases. It also uses the same relative permeability relations used in the simulation models, thus ensuring that the same permeability values calculated from field data are used in history matching and predicting the performance of the reservoir. It is assumed that the fluid saturations are relatively uniform in the region around the well at the time of the transient test. The method was verified by comparing the input values with the results obtained from analyzing several synthetic tests that were produced by numerical simulation. Data from a deepwater field were also used to test the practicality and validity of the method. For the field case, the method was verified by matching reservoir production and pressure using the calculated absolute permeability. Excellent agreements were obtained for both synthetic and field cases.