Quantitative assessment of heterogeneity-controlled remaining hydrocarbon distribution in a mature sandstone reservoir using a detailed three-dimensional reservoir simulation model

Abstract Accurate estimation of remaining hydrocarbon resources in mature reservoirs is strongly affected by spatial reservoir heterogeneity, which can limit sweep efficiency and create poorly drained compartments. This study quantitatively evaluates the influence of reservoir heterogeneity on the distribution and accessibility of remaining hydrocarbons in a mature sandstone reservoir of the Marib–Al Jawf Basin. A three-dimensional black-oil reservoir simulation model was developed by integrating geological, petrophysical, and historical production and pressure data. The model incorporates spatial variations in porosity, permeability, and fluid saturation across multiple stratigraphic units and was calibrated through history matching to reproduce field production performance. The calibrated model was then used to analyze heterogeneity patterns and identify poorly swept reservoir zones. Simulation results reveal pronounced lateral and vertical heterogeneity characterized by strong permeability contrasts that control fluid flow behavior, generate preferential flow pathways, and create isolated compartments with limited connectivity. Consequently, approximately 35–45% of the original oil in place (OOIP) remains trapped within poorly connected reservoir compartments despite long-term production. The results demonstrate that spatial heterogeneity is the dominant control on the accessibility of remaining hydrocarbons and that pressure maintenance alone cannot ensure efficient reservoir sweep. Unlike previous studies that primarily focused on production optimization, this study integrates quantitative heterogeneity analysis with a calibrated three-dimensional reservoir simulation model to identify poorly drained hydrocarbon compartments, providing a transferable workflow for resource assessment and future development of mature heterogeneous reservoirs.