Geomechanical modelling and cap-rock integrity of one of the southwest Iranian giant carbonate oil field

Geomechanical modeling and simulation are introduced to accurately determine the combined effects of hydrocarbon production-injection scenarios and changes in rock properties due to geomechanical effects. Pore pressure and stress states vary during production and injection steps. These variations considerably affect reservoir and cap-rock integrity, faults reactivation, formation compaction and uplifting, and wellbore stability. Therefore, accurate pore pressure estimation is essential to maintain optimal conditions during injection and production operations. A series of data, including rock mechanical test data, well logs data, formation dynamic tester data, image logs data, leak-off tests (LOTs), drilling events, and regional geological studies were used in this work. In this study, a coupled geomechanical-fluid flow model was constructed to evaluate the cap-rock integrity during the injection-production scenario. The steps of the investigation are data audit, 1-D mechanical modeling (MEMs), 3D rock mechanical properties modeling, and 4D geomechanical simulation using a one-way coupling method. The results showed that throughout the production and injection scenario, the cap-rock was stable. Since there is a long distance between Mohr’s circle and the envelope, the cap-rock will not fail. Due to the low permeability of the cap-rock, there is no connection between its pore spaces, which leads to ignoring the variation in stress state due to variations in reservoir pressure.