Multi-objective reservoir production optimization: Minimizing CO2 emissions and maximizing profitability

Large amounts of energy are consumed and greenhouse gasses are emitted in the process of extracting oil and gas from offshore fields. We investigate methods for solving the multi-objective production optimization for minimizing the emissions of CO2 while maximizing economic profitability. Two scalarization methods for solving the multi-objective optimization problem - the weighted-sum method and the epsilon-constraint method - are evaluated for computational efficiency and interpretability of solutions on a simplified model of a North Sea oil field. The epsilon-constraint approach provided an easily interpretable optimization problem with the ability to specify a target reduction in CO2 emissions, but was relatively expensive to apply. The weighted-sum approach was easier to implement and the cost to obtain a solution was less than the cost for the epsilon-constraint approach by a factor of approximately three. For the injection rate controls in our example application, there were gaps in the Pareto optimal solutions obtained using the weighted sum approach when large weights were applied to the emissions reduction objective function.