Numerical Well Testing: A Method to Use Transient Testing Results in Reservoir Simulation

Abstract

Abstract Transient testing is facing a challenge to have the information it provides incorporated in numerical simulators used to predict reservoir performance. Of greater importance, the lack of using the large number of dynamic in-situ reservoir parameters that can be determined from transient tests deprives operators from valuable data they can use to improve their reservoir management efforts. The main reason for the problem is that transient testing technology, developed largely via analytical solutions, provides average reservoir parameters not suited to the numerically discretized environment of current reservoir simulators. Previous efforts to include transient testing data in numerical reservoir simulation studies focused on history matching the pressure behavior during the test on a Cartesian-type plot just like matching stabilized production rates and pressures. Such approach neglects the wealth of information contained in the transient behavior of the tests. A method called Numerical Well Testing (NWT) is proposed in this paper to preserve the information obtainable from traditional well test analysis and deliver it in a form suitable for direct use in numerical reservoir simulation. By using this method petroleum engineers will not shy away from using transient testing results just because they do not know how to incorporate averaged values in their discretized reservoir model. NWT is a systematic method that consists of five steps starting with traditional well test analysis, locally refining grids based on the analysis results, modifying full field numerical models, upscaling, validating the updated model with production data, and predicting future reservoir performance. Details of how to accomplish each step are presented in the paper. NWT was applied to field cases to demonstrate the applicability of the method and proved that incorporating results from the proposed NWT procedure improved reservoir description. Descriptions enhanced by NWT matched not only well test data but also field production data, and predicted different reservoir performances from those obtained via matching only production data. The paper concludes by describing the software developments needed to make NWT a routine analysis method.