CO₂驱油过程中的封存机制解析至关重要，因为众多碳捕集、利用与封存（CCUS）项目均与提高原油采收率（EOR）密切相关。CO₂在油藏中长期封存需经历驱油和关井两个阶段，涵盖注采同步、只注不采及注采停止等多重动态过程。由于不同阶段CO₂封存的控制机制尚不明确，其长期演化规律仍未被充分认知。本研究通过实验与理论分析，建立了低渗透致密砂岩油藏CO₂封存评价数学模型，涵盖构造/地层封存、残余气封存、溶解封存及矿物封存四大机制。基于华子坪油田精细地质模型，结合试井获得的储层渗透率和裂缝特征参数进行校准，模拟了连续注气和气水交替两种情景下全生命周期CO₂封存动态。结果表明：CO₂封存呈现"完全封存-动态封存-稳定封存"三阶段特征。连续注气方案（情景1）的CO₂封存总量和封存效率分别为6.34×10⁴吨和61%，气水交替方案（情景2）则为4.62×10⁴吨和46%。两种情景下构造/地层封存、残余气封存、溶解封存及矿物封存占比分别为33.36%、33.96%、32.43%、0.25%与15.09%、38.65%、45.77%、0.49%。CO₂封存机制演化呈现整体规律：构造/地层封存与残余气封存先增后减，溶解封存持续衰减，矿物封存稳步递增。基于此，研究构建了低渗透致密砂岩油藏CO₂封存机制长期演化图谱。

Understanding the storage mechanisms in CO₂ flooding is crucial, as many carbon capture, utilization, and storage (CCUS) projects are related to enhanced oil recovery (EOR). CO₂ storage in reservoirs across large timescales undergoes the two storage stages of oil displacement and well shut-in, which cover multiple replacement processes of injection–production synchronization, injection only with no production, and injection–production stoppage. Because the controlling mechanism of CO₂ storage in different stages is unknown, the evolution of CO₂ storage mechanisms over large timescales is not understood. A mathematical model for the evaluation of CO₂ storage, including stratigraphic, residual, solubility, and mineral trapping in low-permeability tight sandstone reservoirs, was established using experimental and theoretical analyses. Based on a detailed geological model of the Huaziping oilfield, calibrated with reservoir permeability and fracture characteristic parameters obtained from well test results, a dynamic simulation of CO₂ storage for the entire reservoir life cycle under two scenarios of continuous injection and water–gas alternation were considered. The results show that CO₂ storage exhibits the significant stage characteristics of complete storage, dynamic storage, and stable storage. The CO₂ storage capacity and storage rate under the continuous gas injection scenario (scenario 1) were 6.34 × 10⁴ t and 61%, while those under the water–gas alternation scenario (scenario 2) were 4.62 × 10⁴ t and 46%. The proportions of storage capacity under scenarios 1 and 2 for structural or stratigraphic, residual, solubility, and mineral trapping were 33.36%, 33.96%, 32.43%, and 0.25%; and 15.09%, 38.65%, 45.77%, and 0.49%, respectively. The evolution of the CO₂ storage mechanism showed an overall trend: stratigraphic and residual trapping first increased and then decreased, whereas solubility trapping gradually decreased, and mineral trapping continuously increased. Based on these results, an evolution diagram of the CO₂ storage mechanism of low-permeability tight sandstone reservoirs across large timescales was established.