Reservoir performance analysis through the material balance equation: An integrated review based on field examples

The Material Balance Equation (MBE) has proved its versatility over a century because it has been adapted to include several production mechanisms identified in homogeneous, naturally fractured, and unconventional reservoirs. Thus, numerous field cases regarding the practical use of the MBE are found in the Petroleum Engineering literature. However, those cases have been analyzed by using diverse approaches introduced at different times, leading to a wide variety of analysis methods. Several field examples are revisited in this work through an integrated review that properly uses analysis techniques focused on diagnostics, straight-line analysis, and pressure-production history matching. This review provides additional insights about the reservoir performance compared to the results presented in the original papers. Thus, the conceptual model of the reservoir-aquifer system is consistently characterized by using several graphs along the process of analysis. The reasons related to the complementary role between the conventional straight-line analysis and the history matching technique are provided; the latter should confirm the results from the straight-line analysis, while this one should guide the history matching technique. Also, based on the observation that a good history match does not guarantee the correct characterization of the reservoir-aquifer model, the relevance of integrating the Material Balance analysis with other disciplines is discussed. The significance of the multidisciplinary approach to mitigate the non-uniqueness inverse problem is illustrated through the study of complex examples, such as a naturally fractured reservoir connected to an aquifer. Furthermore, scrutiny on the concept of total effective formation-water compressibility is provided to emphasize the similarities and differences in the analysis of homogeneous and naturally fractured reservoirs through the MBE.