3D Reservoir Geomechanical Modeling in Oil/Gas Field Production

Abstract

Abstract The pore pressure, stress state and geological structures as well as their evolution during an oil/gas field life have widespread influence on implications for wellbore stability, hydraulic fracturing, fault-reactivation, early water-cut, top surface subsidence, reservoir compaction and water/gas flooding. These events have a significant impact on reservoir performance and their effects need to be taken into account in production surveillance, analysis and forecasting. A coupled reservoir geomechanical modeling approach is developed, using the static and dynamic models of VISAGETM System, to compute the change in reservoir pore pressure and stress state, the evolution of reservoir properties, the development of potential fracturing and the reactivation of existing faults. This geomechanical modeling consists of an initial stress simulation prior to production and a coupled reservoir simulation due to depletion and/or injection activities. A very representative initial stress state can be simulated using this approach and can be well calibrated with stress measurements from wireline logs, borehole breakouts and regional stress. Based on the simulated initial stress state, the change in pore pressure due to depletion and/or injection is used to compute the change in effective stress and associated reservoir deformation. The production history and observed reservoir deformation in the past can be simulated. Reservoir performance and associated reservoir deformation can also be predicted in the future production. A full field study using the VISAGETM System was performed to help assess the integrity of the development plan in South Arne field, North Sea. The predicted stress and strain changes that were induced by production/injection were used to assess the wellbore stability, potential for faults reactivation, cap rock integrity and rock fracturing. This study demonstrates that coupled geomechanical modeling lends direct support to drilling operations and reservoir management.