Experimental Study on Conformance Control Using Acidic Nanoparticles in a Heterogeneous Reservoir by Flue Gas Flooding

Flue gas flooding has been applied in many oilfields for its accessibility and low cost. However, the problem of gas channeling during flue gas flooding is significantly more serious due to reservoir heterogeneity and gravity override, and the traditional profile control agent is inapplicable because of flue gas acidity. In order to solve this challenge, a novel acidic nanoparticle was presented first; then, the profile control performance of both water slugs and this novel nanoparticle for flue gas flooding in heterogeneous reservoirs was studied using core samples with different rhythms. The results show that the stability of the acidic nanoparticles is good, and the viscosity of the nanoparticle solution increases as the pH decreases, which is suitable for acidic flue gas flooding. The oil recovery of flue gas flooding in a positive rhythm core is 5–10% greater than that in a reverse rhythm core. The water slug can improve oil recovery by 5% in the reverse rhythm core, and oil recovery was less than 2% in the positive rhythm core. The effect of a nanoparticle slug is much better than the water slug. It improved the oil recovery by 10% in the positive rhythm core by continuing flue gas flooding after nanoparticle slug treatment, which was more than the 20% in the reverse rhythm core. The ultimate oil recovery of both positive and reverse-rhythm cores by acidic nanoparticle slug treatment was around 50%, which was 10% greater than the water slug treatment. The conformance control using acidic nanoparticles is more suitable for reverse rhythm formation due to its plugging capacity, deformation characteristic, and viscosity increment in an acidic environment. This research demonstrated that these novel acidic nanoparticles could be effectively applied to conformance control during flue gas flooding in heterogeneous reservoirs.