Integrated Applications of Analytical, Empirical, and Reservoir Simulation Methods to Accurately Determine Original Oil In Place and Estimated Ultimate Recovery of a Mature Field

This thesis is a field data-driven research that focuses on the evaluation of a mature oil field in South Asia (LK-4). The investigation started with the evaluations of a variety of available surface and subsurface data. It is essential to quality check the geology, petrophysics, and production data in the existing geomodel before using it towards reservoir simulation. Significant efforts were devoted to estimate Original Oil in Place (OOIP) and Estimated Ultimate Recovery (EUR) by using various methods. Classical production diagnostic plots and material balance analysis were performed to understand the reservoir performance. The currently applied water injection was briefly evaluated to understand its benefit in improving field performance. Reservoir simulation studies were conducted to calibrate the reservoir properties with available production data. The main focuses of the simulation studies were to improve water production match in the field, to assist the determination of Oil-Water Contact (OWC), and to represent the behavior of the active producers better. Sensitivity studies were performed to understand the effect of various subsurface uncertainties to OOIP determination and history matching. Future production scenarios were developed based on different development strategies to increase production. Application of Rate Transient Analysis and Transient PI, in addition to other methods, successfully assisted in minimizing the OOIP range. Field EUR values were estimated based on calibrated simulation models, analytical methods, and empirical methods. Future development opportunities such as workovers, changes in operating procedures, and new drilling locations were identified.