Uncertainty Analysis in Simulation for Reservoir Management: Case Study from Niger Delta
The goal of an oil field development project is to accelerate the hydrocarbon production and maximize recovery at the lowest cost. Optimizing the production of oil from thin oil rim reservoirs poses a major challenge in the oil and gas industry because of the water and gas coning tendencies which limit the ultimate recovery from such reservoirs. Development of oil rims generally requires a lengthy study to unravel the complex interplay of the subsurface uncertainties and to determine technical feasibility, development concept and economic attractiveness. Simulations and experimental methods coupled with simple analytical solutions or correlations are typically used to identify the oil rate that minimizes coning and maximizes recovery. This research aims to optimize oil recovery from oil rims by generating models to be used to forecast production rates and increase the ultimate recovery over a range of uncertainties. In this work, a surrogate simulation model is developed to analyze oil rim dynamics and evaluate the impact of a range of subsurface uncertainties on the oil and gas recovery. Alternate development strategies have been considered, and the method of experimental design was used to obtain correlations for each development strategy. The lessons learned from the generic model were incorporated into a systematic study of an integrated reservoir management plan for developing an oil rim reservoir in the Niger Delta. Seven reservoir development strategies are evaluated using numerical reservoir simulation; and the optimum production strategy is selected. The evaluation of the best strategy includes optimization of well placement and economic analysis using the cumulative oil and gas recovery from the various development strategies. In the economic analysis several profitability indices such as net-present value, internal rate of return, and discounted payout period were utilized to identify the optimum development strategies. The results show that well placement has a significant impact on water and gas coningand on oil recovery. It is concluded that the development of thin oil rim reservoir requires an integrated reservoir management plan. Proper reservoir management is achieved when the reservoir producibility factors, operational constraints and economics of the project are considered in the field development planning.