Practical Use of Simulators for Characterization of Shale Reservoirs

Abstract

Abstract Shale gas/oil wells are a challenge due to the complex reservoirs and well completion designs. Commercial simulators with new automatic features play an important role in shale reservoir characterization. These commercial simulators include special features for modeling horizontal, multi-fracked shale wells with simplified user interfaces. The primary goal of this paper is to compare the simulation of transient and boundary dominated flow with analytical solutions through specialized rate function plots. These comparisons provide a straightforward means for testing the accuracy of automatic gridding features and the simulation methodology. If simulators can match idealized reservoirs accurately, then confidence improves in the matching of actual field cases that may vary from idealized reservoir behavior. In this work, we tested the accuracy of these simulator features by making numerous simulation runs for various geological and geometric scenarios. We considered different simulation gridding and system models to correctly represent the transient linear flow and its effect on the analysis. Some general gridding rules were developed. This work investigates the use of an effective permeability equation from analytical solution and its application to several wells in reservoirs located in the Bakken, Barnett, and Eagle Ford formations. Simulation was used to confirm the equation’s accuracy and to show its applicability in fractured shale reservoirs. Results from this investigation should help engineers select the best automatic features to accurately represent shale wells and then cross check the results using the analytical solution. This study also expanded our understanding of flow behavior in production data which may be used to improve modeling shale wells for better agreement with the analytical solutions.