CO₂-Responsive Foam (CRF) for Mitigating CO₂ Channeling in Heterogenous Reservoirs

Abstract

CO2 foam has been identified as having significant applications in carbon capture utilization and storage (CCUS). This is attributed to its proven capability to mitigate channeling during CO2 injection effectively; meanwhile, the majority of injected CO2 can be safely stored in reservoirs through geo-sequestration. However, the high injection pressure and poor foam stability severely affect the wide employment of CO2 foam flooding. In this study, comprehensive investigations on a novel CO2-responsive foam (CRF) with desirable injectivity and noticeable longevity are presented. This novel foam system employs lauryl ether sulfate sodium (LES) and diethylenetriamine (DETA) as foaming agents, and it exhibits notable reversible CO2-responsive properties. This property enables the fluid to transit between low and high-viscosity states, enhancing foam injection performance and reducing the injection pressure. CRF is less detrimental to reservoirs compared to conventional polymer-enhanced foam (PEF) due to its ability to switch between gel-forming and gel-breaking phases using CO2/N2. In addition, rheological tests demonstrate that CRF exhibits superior high shear tolerance compared to PEF. Moreover, CRF shows greater stability and higher salt resistance compared to PEF. At a NaCl concentration of 5 × 104 mg/L, the half-life of CRF (152 min) was nearly 13 times longer than that of PEF (11 min). It is noted that CRF exhibits a higher resistance factor in high-permeability cores compared to low-permeability cores, indicating its outstanding capacity to block the channels and mitigate CO2 breakthrough. The results of the enhanced oil recovery (EOR) experiments indicated that CRF is capable of displacing more oil than PEF in fractured cores with identical experimental conditions. It is believed that CRF may be applied as a viable CCUS technique and may enlighten investigations on novel CCUS strategies.