New research by STRATEGY CCUS partners at the University of Zagreb in Croatia suggests that the use of carbon dioxide (CO2) in enhanced gas recovery (EGR) could result in carbon negative scenarios, whereby CO2 is permanently removed from the atmosphere.
The peer-reviewed study, published in Energies, presents findings from tests carried out at EGR operations at a gas condensate reservoir in Northern Croatia.
The researchers analysed all three elements of the CO2 life cycle within the EGR process: namely, the CO2 emitted by the combustion of gas from the start of production; the CO2 separated from the original reservoir gas at the processing plant; and the volumes of CO2 injected into the reservoir as part of EGR.
The test reservoir chosen represents a typical gas-condensate reservoir in Northern Croatia and, more specifically, in the Drava basin. The produced gas from this area usually contains around 50% of CO2.
The tests carried out by the University of Zagreb scientists converted a production well to a CO2 injection well in order to focus on CO2 storage rather than maximising hydrocarbon gas production.
Lucija Jukić, lead author, Faculty of Mining, Geology and Petroleum Engineering at the University of Zagreb, said: “Our studies have concluded that, even when the hydrocarbon gas in question has such high CO2 content, enhanced gas recovery using CO2 injection can be carbon negative. In almost all of our simulated CO2 injection scenarios, the process was carbon-negative from the time injection started. In the scenarios where CO2 injection begins earlier, it is carbon-negative from the start of gas production. This opens up the possibility of cost-effective storage of CO2 while producing natural gas with net negative CO2 emissions.”
Graphic: Contour map of formation top depths with gas/water contact. Credit: University of Zagreb