Energy Efficient Operation of Petroleum Production Plants

Abstract

Abstract The use of energy and the possibilities for energy recovery from pressurised fluid streams has been analysed for a petroleum production plant connected to an undersaturated oil field that was produced by water injection. The plateau production of oil was 15900 Sm3/d and water was injected at a rate of 20670 m3/d. The produced fluids arrived at the production plant at a relatively high pressure and temperature (70 bar and 82 °C). Produced oil and gas were continuously exported from the plant at 200 bara. The power consumption in the plant could be reduced by using equipment with high efficiency. The average power over the 27-year lifetime of the field was reduced from 19.95 MW to 14.78 MW for two scenarios using different equipment. This corresponds to a reduced energy consumption and reduced CO2 emissions of 986 million kWh and 692502 tonnes, respectively. Energy can be recovered from pressurized process streams. For the hydrocarbon streams in the plant turbogenerators were considered. Pressure from produced water could be recovered by use of pressure exchangers. On average 2 MW power was recovered over the lifetime of the field, saving 486 million kWh electric energy corresponding to 341166 tonnes CO2 emissions. All energy savings above apply both to plants powered by gas turbines and electrified fields. CO2 emissions per unit of potential combustion energy from produced petroleum was very low in the plateau phase of the production. Only late in the lifetime of the field the emissions approached and exceeded (depending on scenario) the average emissions of 5 g CO2/MJ for fields on the Norwegian Continental Shelf. The high potential for reduced energy consumption in the petroleum production plant and for energy recovery was due to the relatively high inlet pressures to the plant and high pressures of injected water. For lower inlet pressures and better water injectivity the potential will be lower, and fields should be studied case by case. Factors such as weight and space requirements of new alternative process equipment, cost and maintenance have not been considered in this work. In an electrified field the abundant supply of thermal energy from gas turbine exhaust will not be available. Thermal energy was available from the produced fluids and from the petroleum processing and could be sufficient e.g. for heating of housing areas and heating of process streams. If higher temperatures were needed heat pumps can be taken into use. Dedicated and field specific studies regarding use and recovery of thermal energy and possible applications of heat pumps must be done to find optimal solutions for the thermal energy demand of an electrified field, however.