Review on miscible, immiscible, and progressive nitrogen injection for enhanced oil recovery

Due to its relatively low cost, availability, safety, low environmental impact, and versatility, nitrogen emerges as a promising candidate for enhanced oil recovery. This article provides an overview of nitrogen injection applications within reservoirs, encompassing both miscible and immiscible conditions. Additionally, this work reviews unconventional nitrogen-based enhanced oil recovery methodologies, including the utilization of foamassisted nitrogen and cold nitrogen injection. To adapt miscible injection for reservoirs characterized by lower pressure, the combination of nitrogen with hydrocarbon gasses or CO2 presents a viable strategy. Notably, both miscible and immiscible nitrogen injection techniques demonstrate the potential to recover approximately 20 % of residual oil saturation. However, under conditions of high water cut, water alternating nitrogen injection surpasses regular immiscible nitrogen injection in terms of oil recovery. In the context of fractured rocks, foamassisted water alternating nitrogen injection yields a 15 % higher oil recovery compared to conventional water flooding approaches. Intriguingly, nitrogen-based foams have been effectively deployed in field conditions to enhance the recovery of 920 cp oil from heterogeneous reservoirs, resulting in a remarkable up to 2.6-fold increase in oil flow rate. These compelling outcomes instigate a comparative investigation of the method's efficacy against the conventional chemical flooding technique. Furthermore, nitrogen exhibits remarkable potential for oil recovery from ultra-low permeability (198 nD) rocks, owing to its low molecular weight that facilitates penetration even into very small pores. Moreover, the injection of cold nitrogen (-26 degrees C) induces a substantial enlargement of fractures in low permeability rocks, accentuating its efficacy in this context.