As the demand for offshore oil platforms and eco-friendly oil production has increased, it is necessary to determine the optimal conditions of offshore oil production platforms to increase profits and reduce costs as well as to prevent environmental pollution. The Reid vapor pressure (RVP) of product oil is a key specification as an environmental consideration. To achieve a practical design for an offshore platform, it is necessary to consider environmental specifications based on an integrated model describing all units concerned with oil and gas production. In addition, an effective optimization strategy is required to determine the design variables. In this study, using Aspen HYSYS and a stochastic optimization strategy for simulation and optimization, the design variables for the crude oil separation process were simultaneously determined to maximize profits. The results of this research show that the condensate recycling train has an excellent capability to adjust the vapor pressure of crude oil, and an increase in the separation stage results in an improvement in the process performance. It is also important to consider the trade-off between the oil production and operating costs because an increase in the oil production rate and a decrease in the RVP of product oil can be achieved by an additional expenditure in the operating costs. This study can facilitate the design of efficient and eco-friendly offshore platforms.