Evaluating the energy consumption and air emissions of CO2-enhanced oil recovery in China: A partial life cycle assessment of extralow permeability reservoirs

Abstract

Carbon dioxide enhanced oil recovery (CO2-EOR) can capture, transport and store CO2 emitted by high energy consumption enterprises. Therefore, the use of CO2-EOR enhances oil recovery and is also an effective means of reducing CO2 emissions. Currently, energy and environmental assessments of CO2-EOR have been rare in China. In this study, partial life cycle assessment (LCA) is used to evaluate the energy consumption and air emissions gate to grave in a CO2-EOR test station for extralow permeability reservoirs in northern China. The gate to gate of CO2-EOR defines 5 stages: transportation, liquefaction, injection, oil production and recycling. Through the analysis of these stages, the results show that producing one metric ton of crude oil gate to gate consumes 2472.56 kW hours of electricity and emits 2532.63 kilograms of CO2, 74.18 kg of SO2 and 37.38 kg of NOx. Water flooding that occurs under similar geological conditions is selected and compared with CO2-EOR for energy consumption and air emissions. In the case of producing one metric ton of crude oil, CO2-EOR gate to gate consumes more electricity than water flooding gate to gate and emits more CO2, SO2 and NOx. Compared with the amount of CO2 injection, the net CO2 emissions of CO2-EOR gate to gate to produce one metric ton of crude oil are -1675.15 kg, and the net CO2 emissions of water flooding gate to gate to produce one metric ton of crude oil are 775.83 kg. When considering energy consumption in the downstream segments of CO2-EOR, the net CO2 emissions of CO2-EOR gate to grave to produce one metric ton of crude oil are 0.53 metric tons. The results of this study provide valuable insights into the policy implications and sustainable development of CO2-EOR in China.