Integrated Production System Modelling and Optimization for Advanced EOR Application in Pre-Salt Offshore Carbonate Reservoir

Applicability of Enhanced Oil Recovery (EOR) processes is gaining interest among offshore operators in recent years. CO2/miscible gas injection and Water Alternating Gas injection (WAG) are the most attractive EOR methods being considered by most offshore operators. Due to limitations imposed by the surface facility, any process optimization done through standalone reservoir simulation could be unreliable as the facility constraints and its effects are neglected. In order to minimize risk and reduce uncertainty, successful modelling and optimization of such projects requires integration of subsurface modelling with surface facility model.

In this work, field development and optimization of a complex offshore production system, from a Pre-Salt carbonate reservoir offshore of Brazil is studied. Different field development scenarios, including water flooding, miscible gas injection, and WAG injection, are considered. Compositional fluid model is used in order to correctly model the fluid mixing effects and miscibility. Pressure change and thermal effects are considered in all the facility equipment. The complexities of the surface network, including gas sweetening, compression, and fluid blending are included in the integrated model.

A new multi-user, multi-disciplinary Integrated Production System Modelling (IPSM) tool is used to fully-implicitly couple reservoir simulation with surface facility model. Production from the offshore asset is optimized for different development scenarios. The provided IPSM approach optimized operational schemes that were consistent with the constraints of the offshore facility. Additionally, with this new approach, all users from different disciplines were able to collaborate seamlessly, and any possible inconsistencies and discontinuities that could occur due to use of multiple decision making tools were removed.

The use of integrated production systems modelling for optimizing EOR schemes in offshore assets, particularly miscible WAG, is proved to provide more robust answers. The complexities and Uncertainties of such processes, for both reservoir and facility models, are successfully studied.