Experimental Investigation and Numerical Simulation of the Asphaltene Deposition Mechanism during CO2 Injection in Deep Reservoirs

Abstract Asphaltene precipitation induced by CO2 injection poses a severe challenge to flow assurance and oil recovery in deep, high-temperature, and high-pressure reservoirs. This study investigates the multiscale mechanisms of asphaltene deposition and its quantitative impact on production performance in the Lunnan Oilfield, Tarim Basin, using a combination of high-pressure visualized PVT experiments and compositional reservoir simulations. Experimental observations reveal that increasing pressure promotes the transition from immiscible to miscible states, accompanied by intensified mass transfer. SARA fractionation and high-resolution mass spectrometry (ESI/APPI) analyses indicate that elevated temperatures (140°C) enhance the extraction of light components and alter the stability of the colloidal system, where polar heteroatomic species (N1, O1, O2) act as key stabilizing agents. Field-scale numerical simulations further demonstrate that asphaltene deposition preferentially accumulates in the low-pressure near-wellbore region of production wells rather than injection wells. This localized damage severely impairs permeability and alters gas–oil flow dynamics, manifested as delayed initial gas breakthrough followed by accelerated late-stage GOR increase and gas channeling. Quantitative assessment over a 10-year production cycle shows that asphaltene precipitation results in a cumulative oil production loss of 13.89% and a reduction in the ultimate recovery factor by approximately 14% compared to the ideal no-precipitation scenario. These findings provide critical theoretical insights and practical guidance for optimizing CO2-EOR strategies in complex deep reservoirs.