Optimizing oil productivity by immiscible CO2 and N2 injection comparison of the Asmari formation in southeastern Iraq.

Gas injection is a fundamental process for hydrocarbon recovery, whereby gas is injected into the reservoir to maintain pressure and increase production of oil or gas. This study was conducted to investigate the optimization of gas injection, differentiating between the behavior of CO2 and N2, as a potential alternative to water in southern Iraqi fields (the Abu-Ghirab field, particularly) to overcome the water supply shortage as a result of climate change. Techlog, Petrel, and CMG software were utilized to examine the CO2 and N2 behaviour. The increased percentages (CO2 and N2 injection processes) in the oil production rate are 139.45 and 66.6%, respectively. The wells located near the fault section show the best water cut (approximately 18%) among all the wells. The water cut percentages are 520 and 380 for CO2 and N2 injection, respectively, pointing out that the water cut produced by the N2 injection process is higher than that of CO2 by percentage of 36.8. An acute increase in the gas-oil ratio by N2 injection (more than 40 times on average) could result. The wells far away from the fault region have the best performance of gas-oil ratio among all the wells. For the entire field, the oil production rate for the CO2 injection process shows a significant increase in both ultimate and maximum production compared to N2. This could be due to the specifications of crude oil. The sensitivity analysis of the results from CO2 injection for the Asmari formation in Abu-Ghirab for production/injection percentage and water cut shows that the water cut percentage will be acceptable during the first 9 years of the process, with concerns of economic issues due to increasing gas-oil ratio (GOR).