Simulation-Based Optimization of Multistage Separation Process in Offshore Oil and Gas Production Facilities

Abstract

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.

Applied Process Simulation-Driven Oil and Gas Separation Plant Optimization using Surrogate Modeling and Evolutionary Algorithms

“…The optimization objective can be formulated in many different ways. The target can be to maximize oil/condensate production [2,[6][7][8], minimize power consumption [10], maximize profit (sales subtracted OPEX) [1,28] etc. Further, the variables are subject to bounds either external such as minimum flowing wellhead pressure (FWHP), flowing wellhead temperature (FWHT), practical/design limits on equipment such as cooling/heating medium design.…”

“…Further, the variables are subject to bounds either external such as minimum flowing wellhead pressure (FWHP), flowing wellhead temperature (FWHT), practical/design limits on equipment such as cooling/heating medium design. Finally, the process may be subject to a manifold of constraints [10,29] such as export specifications for crude oil, usually RVP/TVP [1,10], but also BS&W, salt content etc., gas export requirements such as max. dew point, combustion quality (HHV, Wobbe Index, Specific gravity) [10], minimum requirements to export pressure(s), restrictions on compressor performance (max, head, discharge temperature etc.).…”

“…The composition of the two fluids are based on the fluids from refs. [1] and [7] and the composition and fluid characterization in terms of hypotheticals/pseudo-components are shown in Table 1 and Table 2, respectively.…”

“…See implementation schematic in Figure 3. A similar black-box approach has been used by others [1,18,19] using either VBA or Matlab. For each sample in the sampling plan a corresponding simulation is made and the results recorded.…”

“…The challenge is to specify the operating conditions for the separation train which maximizes the profit, which is normally dominated by the export quantity of crude oil [1]. Having a relatively high pressure up to the final separation stage will result in a high quantity of C1/C2 being dissolved.…”