Potential Geomechanics Risks of the Proposed Field Development Strategy in a Faulted and Partially Fractured Stacked Carbonate Reservoir

A 4D geomechanics study was conducted in a heavily faulted and partially fractured stacked carbonate reservoir with the purpose of assessing the integrity risks associated to the field development campaign, characterized by different strategies of hydrocarbon production, and water and gas injection (WAG). The study focuses on the assessment of risks associated to intra-reservoir communication, caprock and reservoir integrity, reservoir deformation and compaction, surface subsidence and uplift, fracture and fault deformation and reactivation, and wellbore stability analyses. The integrity analysis was possible by building a calibrated 4D fluid-flow coupled geomechanical model, that uses the available dynamic models for each reservoir, from which changes in pressure were extracted along the history and forecast. The coupled simulation included stress-strain computations, deformation and failure analysis to assess the potential geomechanics risks of the proposed field development plan (FDP). The coupled geomechanics simulation showed no pore collapse in the different reservoirs but minor elastic deformation barely affecting the porosity and permeability of the intact rock, because of the high rock strength and relatively small pressure changes experienced during the history and FDP. Nonetheless, the fracture network shows a significant deformation, impacting aperture, hence fracture porosity and permeability. This phenomenon might eventually impact the flow patterns and repositioning of infill wells for both production and injection. Furthermore, some fault reactivation potential was observed in specific regions, characterized by heavy faulting, potential presence of natural fractures and subjected to drastic pressure changes. Reservoir deformation same as surface subsidence/uplift was minor, while drilling integrity might be affected by the reactivation of nearby critically stressed fracture networks and faults. Well and completions integrity seems not be at risk due to the high rock and cement strength, and casing design, limiting the amount of plastic deformation and potential failure to near zero, for the conditions of the proposed field development strategy.