Life performance of oil and gas platforms for various production profiles and feed compositions

Oil and gas platforms present similar structural designs but process fluids with different thermo-physical and chemical properties, and with varying flowrates (variability of the gas-to-oil and water-to-oil ratios over time). It is therefore not possible to suggest a standard flow diagram of these facilities. Different processes and operating modes may be implemented to maximize the petroleum production and improve the overall system performance. The present work evaluates, in a first step, the variations of the heating, cooling and power demands over time, in terms of energy and exergy. The simulations were calibrated using actual field data (feed compositions and production profiles). In a second step, the minimum energy and exergy losses of the platform are assessed by performing a thermodynamic analysis, assuming an ideal scenario in which all processes are run at their design points. This approach proves to be useful for evaluating consistently different options for oil and gas production, and for determining, in a further step, the most promising solutions for minimizing the energy use over a field lifetime. The compression (natural gas and carbon dioxide) processes represent the major share of the total power demand (≥80%) for all feed compositions, at all stages of the field life. The power and heat generation system is responsible for about 60-70% of the total exergy destruction over time, followed by the gas treatment and membrane units. Efforts should therefore focus on a more efficient design and operation of the gas compression units, which are designed to handle the peak production of hydrocarbons, and on the valorisation of the turbine exhausts. Alternative CO2-treatment processes may also be of interest for feeds with high CO2-composition.