Revitalizing a Mature Oil Field in Libya's Sirte Basin: An Integrated Reservoir Simulation and Economic Optimization Study

The X oil field in Libya's Sirte Basin, with proven reserves exceeding 5 billion barrels in the basin, is experiencing a significant production decline due to insufficient natural aquifer support. This study presents an integrated reservoir simulation and economic optimization approach to revitalize this mature asset. Using the ECLIPSE 100 simulator, we developed a dynamic 3D black-oil model that accurately captured the field's weak aquifer drive through rigorous history matching (1999–present). The model evaluated multiple development scenarios, including hydraulic fracturing and infill drilling with vertical and horizontal wells. Results indicate that horizontal infill drilling in the structurally advantageous northern sector provided the best single-technique recovery (13.40%, 28.54 MMSTB). However, an integrated strategy combining northern horizontal wells with southern vertical exploratory drilling achieved superior outcomes: recovery factor of 17.65% and cumulative production of 37.60 MMSTB—a six-fold increase over the base "do-nothing" case (2.81%, 5.98 MMSTB). Economic evaluation, including detailed net present value (NPV) and sensitivity analysis, confirmed the financial viability of this optimal approach, generating an NPV of $671.84 million and a net cash flow of $2,294.63 million at a 10% discount rate. Sensitivity analysis demonstrated resilience to oil price fluctuations and discount rate variations. This study demonstrates that data-driven integrated modeling can unlock substantial unrealized potential in mature fields, providing a replicable framework for similar assets in the Sirte Basin and analogous carbonate reservoirs worldwide.