An Integrated Approach to Optimize Field Development Plan Based on Uncertainty Analysis in a Giant Offshore Field

Abstract

With an increased maturity and complexity of the reservoir, an optimized field development plan implementation is critical to achieve the planned target and to ensure an optimum field recovery. The paper presents an optimized process with uncertainty analysis based on Monte Carlo Simulation for the purpose of optimizing the Medium Term Development Plan (MTDP) implementation. The five year development plan of this giant offshore field has been successfully assessed based on this optimized approach. The integrated workflow consists of four main parts, including actual field technical rate tracking, DBC optimization, simulation results, and effective capacity with Monte Carlo simulation embedded. The dynamic situations could be taken care with these seamless coupled tools. The actual field technical rate has been tracked on a monthly base through a systematic and automated process. The reference decline ratio has been assumed based on historical production decline analysis. Besides, a floating decline based on simulation results is also added in order to capture the well closure due to gas production limitation. Field technical rate is the fundamental input for field development plan to derive the field sustainable oil production rate. It is dependent on both existing wells' performance and future wells' planning. Both the expected gain and drilling schedule of the planned wells are crucial to achieve the production target with reservoir pressure appropriately supported. Voidage Replacement Ratio has been applied to balance production and injection. Drilling plan could be revised accordingly. The production and injection balance can be visualized in the effective capacity tool, which will be used to further optimize the producer and injector plans. The requirements of producers and injectors are summarized and imported into the DBC optimization tool to evaluate new drilling schedule, which will be used in the effective capacity tool for an iteration loop. Uncertainty analysis is critical to assure a field development plan. Uncertainties have been evaluated based on the factors' most probable range. Five major assumptions, including expected gain from new wells, drilling duration, decline ratio, put-on-production time, and operating efficiency, have been evaluated to assess the uncertainty. Mitigation actions could be proposed to assure the production plan.