Geomechanical Assessment of Fault Slip and Top Seal Integrity for a Deepwater Turbidite Field Development

Abstract Depletion and injection induced pore pressure changes will be accompanied by total stress changes in the reservoir and around faults which can cause fracture formation or fault activation that may result in fluid migration outside the reservoir. 3D geomechanical assessment of the Deep Water Turbidite (DWT field), located in the southern part of the Niger Delta in offshore Nigeria, was performed in line with subsurface process safety requirements, to determine the sealing integrity of the top seal and the likelihood of the major faults to slip under depletion/injection induced pore pressure changes during the production life of the field. The analysis was carried out using a proprietary Finite Element tool, based on TNO-Diana Finite Elements. A subsequent sensitivity study was performed to account for uncertainties in some of the material parameters used for the assessment. This paper presents the workflow and outcome of the geomechanical assessment carried out for the DWT field. Model results indicate that faults do not get triggered unless injection pressures can access the entire interval of the fault slip zone, including overburden and underburden sections. Analysis of planned injection pressures in the shallowest layers indicates a potential for hydrofracturing the shale caprock. A mitigation plan is currently being designed to address the issue.