CO₂驱油技术具有提高原油采收率和资源化利用与封存的双重目的，已在低渗-致密油藏得到广泛应用。为明确运移距离对CO₂混相驱油过程中密度差引起的重力超覆程度的影响规律，分别采用室内物理模型和数值模型开展研究。实验结果表明，混相条件下，由于岩心长度减小，重力超覆的扩展空间受限，但油气混相程度的降低，导致重力超覆程度降低幅度较小；当岩心长度继续减小时，混相程度降低对重力超覆的影响大于岩心长度对重力超覆扩展空间限制的影响，从而使重力超覆程度加剧。数模结果表明，随着运移距离的减小，重力超覆程度减弱，混相驱采收率提高。因此，结合油田现场情况，为减缓重力超覆，应适当减小井距，缩短CO₂气体运移距离，从而提高CO₂驱的波及效率。研究结果对于CO₂驱油现场试验方案设计和参数优化具有一定的指导意义。

CO₂ flooding technology has the dual purpose of improving oil recovery and resource utilization and storage, and has been widely used in low permeability tight reservoirs. In order to clarify the influence of migration distance on gravity overlap degree caused by density difference during CO₂ miscible displacement, indoor physical model and numerical model were used to conduct research. The experimental results show that under the condition of miscible phase, the expansion space of gravity overlap is limited due to the decrease of core length, but the decrease of oil and gas miscible degree leads to a small reduction of gravity overlap degree; When the core length continues to decrease, the influence of the decrease of miscibility on the gravity overlap is greater than the influence of the core length on the space limitation of gravity overlap expansion, thus intensifying the gravity overlap. The numerical simulation results show that with the decrease of migration distance, the gravity overlap degree weakens and the miscible flooding recovery increases. Therefore, in combination with the field situation of the oilfield, in order to reduce the gravity overlap, the well spacing should be appropriately reduced to shorten the CO₂ gas migration distance, so as to improve the sweep efficiency of CO₂ flooding. The research results have certain guiding significance for the design of CO₂ flooding field test scheme and parameter optimization.