Optimized Reservoir Management With Mixed Linear Programming

Abstract

Summary Reservoir engineers face a large number of possible development plans for major offshore oil fields. Some of the factors affecting development include product-processing capacities, drilling-rig availability, extended use of existing platforms, enhanced-recovery options, and subsidence-avoidance requirements. Reservoir simulation is an accepted technique for estimating production from oil and gas fields. Each possible development scenario is simulated separately to obtain future oil- and gas-production estimates from wells included in the scenario. Simulation results are analyzed for each run, and the optimal plan is selected. Enumerating all the possible drilling schedules is a difficult task, and, even with clusters of advanced scientific workstations, the computational requirements of simulation can be overwhelming. This paper describes the application of linear mixed integer programming (MIP) to the combinatorial problem of generating the optimal redevelopment scenario for the Ekofisk field in the Norwegian sector of the North Sea. The MIP model determines the optimal redevelopment program and drilling schedule while maintaining operationally feasible product-processing requirements, drilling-rig use, and well/platform relationships. Optimality is based on the net present value (NPV) of the estimated production forecasts for the wells selected. Total recovered reserves is an alternative optimization criterion. Reservoir simulations generated the estimated production forecasts used in iterative runs of the optimized model. We discuss success of the approach and extensions.