Mitigating Asphaltene Deposition in CO 2 Flooding with Carbon Quantum Dots

Carbon capture, utilization, and storage (CCUS) technology has emerged as a pivotal measure in mitigating global climate change. Notably, CO 2 -EOR is esteemed for its dual function of sequestering CO 2 and enhancing oil recovery. However, this process presents challenges related to asphaltene deposition during CO 2 flooding, leading to reservoir damage, such as pore plugging. This study systematically manipulated the factors inducing CO 2 -induced asphaltene deposition, elucidating the mechanisms and magnitudes of asphaltene precipitation. Additionally, the study investigated the efficacy of carbon quantum dots (CQDs) in mitigating asphaltene deposition. Experimental findings indicated a positive correlation between asphaltene deposition and level of asphaltene content, CO 2 injection ratio, and temperature. Moreover, with an increase in experimental pressure, the asphaltene deposition rate demonstrated an initial increase followed by a subsequent decline. Leveraging their favorable compatibility with asphaltene, CQDs effectively suppressed the aggregation behavior of asphaltene. In the presence of CQDs, the onset of asphaltene precipitation was delayed from 45 V% to 55 V%, with the highest inhibition rate reaching approximately 36% at an optimal CQD concentration of 20 mg/L. This study proposes a novel approach to address asphaltene deposition issues in CO 2 -EOR processes, contributing to the enhancement of recovery rates in low-permeability reservoirs.