Automated Process Design in Oil and Gas Field Development
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Oil and Gas Processing plants require specialised equipment to effectively treat the hydrocarbons produced from the field. The processing equipment employed occupy a large amount of space and contribute a significant amount of weight to the platform which adds to the cost of offshore structures. The design of an offshore oil and gas field incorporates both technical and economic factors that must be considered throughout the project life. The development concept, design and selection of process equipment, energy consumption, carbon footprint, commodity prices, tax regime and profitability are some of the factors that are critically investigated at each stage of project development. These indicators inform the decision criteria which underpin the feasibility of an oil and gas field development. This master thesis presents an integrated automated model/tool that encompasses the technical and economic factors that can simplify the decision process. As a starting point, a hypothetical base case given a gas well composition and well parameters are used in this research. An offshore gas processing plant is modelled using ASPEN HYSYS in parallel with Microsoft Excel which was used to create equipment sizing calculators for each gas processing equipment. With such models, the impact to process design or to the entire project based on changes to technical and economic factors can be investigated. Different equations of state are also utilised to equally examine the influence on equipment design. The results from the base case showed that utilising different thermodynamic models can give up to ~ 3.5% difference in equipment weight and ~1.8% difference in footprint. The calculator developed was taken a step further to incorporate automation. Automation of the sizing calculator was performed using Aspen Simulation Workbook to link MS Excel to Aspen HYSYS as well as visual basic codes to create the functionality that allows for investigating the process design based on changing parameters. The calculator/tool also presents an analytical model that gives results of design indicators including equipment footprint/weight, energy consumption, carbon footprint and cashflow (Net Present Value) depending on the development concept. As a myriad of technical and economic factors can impact an oil and gas field development, the thesis focusses on three hypothetical production profiles. The results of the analyses using the automated tool showed that producing at a high rate and quickly does not necessarily give the optimum results and/or high profitability. Also, with the winning scenario changing the thermodynamic model for the process simulation from Soave Redlich Kwong to Peng Robinson gave a significant relative difference of approximately 3.5% in equipment weight amounting to 22 tons and 5% in NPV which amounted to USD $ 12 million. The research goes further to build on the three scenarios and shows methods to determine the optimum production profile with the objective of maximising NPV. A trend was shown where increasing the flowrate (plateau production) increases the profitability of the project; however, beyond the optimum flowrate the capital expenditure of the project increases and the profitability of the project declines. The optimum flowrate of 8MMsm3/d was determined. Essentially, the master thesis has presented an automated tool capable of examining gas processing project indicators for field development. It gives a preliminary design of gas processing equipment and provides the functionality of analysing the effect of different thermodynamic models to the design. Furthermore, it enables investigative analysis into changing parameters during the production lifecycle.