Integrated Modeling to Optimize Field Development of a Giant Oil Field

An integrated modeling approach was adopted to help optimize the full field development of a giant oil field. The integrated model implicitly couples simplified models of the reservoir, wells, surface flowlines, and facilities to dynamically represent the entire subsurface and surface production system all the way to the compressor inlet. The model is used to a) evaluate the impact of gathering system back-pressure, b) assess the impact of facility constraints, c) model facility expansion plans, d) identify facility de-bottlenecking opportunities, e) evaluate alternative well management methods and production allocation approaches, and f) quantify spare production capacity. For these objectives, the conventional sequential workflow of separate full-physics simulation models for reservoir, wells, and surface facilities does not adequately account for production system interactions, and complex coupled models are impractical for rapid scenario analysis.

The integrated model was constructed using the rate-and-pressure "Profile Generator" (PG) capability within ExxonMobil's proprietary reservoir simulator environment, EM^powerTM. The model can generate results for a 50-year forecast in a few hours on a single-processor desktop PC. Reservoir regions are represented by performance curves; wells are represented by inflow / outflow curves; and flowlines are represented by hydraulics flow models. The reservoir performance and well inflow curves are derived from standalone simulation results for each major development scenario via an automated workflow process. The integrated model uses well management controls to account for field operating guidelines, system back-pressure, facility operating conditions and capacity constraints.

Integrated modeling has been used previously in the industry. However, there are two distinguishing aspects of the PG model. First, the implicitly coupled solver is able to ensure computational robustness and efficient run time, enabling quick turnaround despite modeling a giant field from reservoir to central processing complex. Second, the PG model is fully integrated within the EM^power reservoir simulation environment. This integration enables seamless transfer of reservoir and well performance curves from the simulation models, sharing of all key input, and the use of EM^power's flexible, predictive well management methods. A streamlined workflow is also available to efficiently generate reservoir and well inflow performance curves from results generated by other reservoir simulators.

The overall workflow iterates between using the PG model and full-physics simulation models to rapidly converge on an optimized development plan. The PG model's fast run time enables numerous sensitivities to be run for broad scenario analysis. Results are then used to refine the development plan and narrow down to a few key cases for further study using full-physics reservoir simulation and facility network models or fully integrated simulation models. This paper discusses application of the PG model to conduct rapid screening studies and to help identify opportunities to optimize the field development plan. The results helped identify several opportunities to further improve the field development and expansion plans and reduce capital expenditure (CAPEX). These opportunities included optimizing the drilling schedule, altering the well management and production allocation methods, and/or understanding the impact of different plateau rate choices.