Integrated Approach for 3D Complex Carbonate Reservoir Modelling: A Case Study of the Dahra Southeast Field, Sirte Basin

Abstract The study's main objectives are to create a representative static model to be used for the Dahra Southeast field development plan. Moreover, understands the tectonic history and characterizes the fault system by evaluating and modeling the fault system within the field. A structural framework approach using volume-based modeling (VBM) was employed to address the complexity of fault modeling. This approach ensures that all 35 faults are accurately modeled without compromise, and resulted grid cells maintain orthogonality with minimal distortion. Subsequently, structured stair-stepped griding was constructed from the Petrel Structural framework model. To model the Facies and the rock types, trend maps based on thickness fraction were employed to guide the distribution of facies and rock types. Additionally, the porosity and permeability distributions were biased by the rock types. Furthermore, the Saturation Height Function was utilized to estimate water saturation distribution, the uncertainty analysis was conducted. The Dahra reservoir which is one of the Great Mabruk field reservoirs, situated within a shallow marine, rimmed carbonate platform, primarily consists of limestone with occasional dolomite streaks. Diagenetic processes significantly impact porosity and permeability, further complicating the distribution of facies and petrophysical properties. In the NW part of the field, reef-derived limestone overlies back-reef shoal deposits. Cores from central wells reveal proximal shallow-water carbonates, suggesting deposition in a shallow lagoon occasionally interrupted by sub-aerial exposure. These cores also exhibit dolomite streaks. The 3D-created model aligns with the depositional conceptual model and observed trends. Additionally, the successful distribution of petrophysical properties enables precise estimates of hydrocarbon volume, and an excellent history match is achieved. This study was a part of a full field development plan for Dahra Southeast Reservoir. The static model paved the way for strategic prediction scenarios aimed at enhancing oil production in the field.