Foam as Mobility Control for Integrated CO2-EOR in Fractured Carbonates

Miscible CO2 and CO2-foam laboratory injection tests were performed to study Enhanced Oil Recovery (EOR) processes in strongly water-wet fractured carbonate core material to evaluate the potential of foam for mobility control. The experimental results demonstrate a significant oil recovery potential during pure scCO2 injection in baseline unfractured cores: endpoint oil recovery was up to 98%OOIP and 80%OOIP was produced after 2PVof scCO2 injection starting at Swi. Recovery and production rates were significantly lower and slower for fractured cores where oil recovery was mainly driven by diffusion: 58-68%OOIP was recovered after 10PV injected. By switching to scCO2-foam injection after 1-2PV of pure scCO2, a viscous component was added to the oil displacement process, which increased oil recovery rates and final recoveries for all experiments. Integrated EOR (IEOR) schemes of waterfloods followed by tertiary CO2 and CO2-foam injection was also investigated for intricate fracture systems. Magnetic Resonance Imaging (MRI) provided in situ visualization of local development in oil saturations and fluid displacement fronts during waterflood and CO2 injection. It is shown that CO2 mobility control using CO2-foam significantly increase oil recovery during CO2 injection and will meet the challenges of low macroscopic sweep efficiency and the adverse water-shielding effect in CO2-EOR.