A Review of the Percolation Mechanism in Low-Permeability Fractured Oil Reservoirs

Low-permeability fractured reservoirs represent a critical frontier for future oil and gas development, whose production performance heavily relies on the efficiency of imbibition in displacing oil from the rock matrix. This review aims to provide a systematic elaboration of the fundamental mechanisms of imbibition-driven oil recovery in such reservoirs and a comprehensive overview of the associated research advances and application prospects. The paper begins with a detailed analysis of the basic principles of imbibition, driven primarily by capillary and gravitational forces, and discusses the criteria (e.g., the inverse Bond number, NB<sup>−1</sup>) for distinguishing co-current and counter-current imbibition, along with their controlling factors. Subsequently, by synthesizing relevant domestic and international studies, it summarizes key findings from theoretical modeling, numerical simulation, and laboratory experiments (e.g., utilizing nanofluids for wettability alteration, optimizing imbibing fluid performance, and analyzing the impacts of fracture networks and temperature). The mechanisms by which chemical agents, such as surfactants and modified brine, enhance imbibition effects are also critically reviewed. Finally, based on the current state of research, this paper outlines promising future research directions. These include deepening the understanding of flow mechanisms in coupled fracture-matrix systems, promoting the synergistic application of imbibition with other enhanced oil recovery (EOR) techniques, establishing quantitative models that bridge laboratory results and field-scale practices, and developing novel, efficient, and low-damage imbibition fluids. This study serves as a valuable reference for enhancing the understanding of imbibition mechanisms and optimizing development strategies for low-permeability fractured reservoirs. 低渗透裂缝性油藏是未来油气开发的重要领域，其开发效果在很大程度上依赖于渗吸作用对基质中原油的动用效率。本文旨在系统阐述低渗透裂缝性油藏中渗吸驱油的核心机理，并全面综述其研究进展与应用前景。首先，文章详细分析了以毛细管力与重力为驱动力的渗吸基本规律，探讨了同向与逆向渗吸的判别准则（如Bond倒数NB−1）及其影响因素。进而，通过梳理国内外相关研究，总结了渗吸作用在理论模型、数值模拟及室内实验（如利用纳米流体调控润湿性、优化渗吸液性能、分析裂缝与温度影响等）方面的主要成果，并评述了表面活性剂、改性盐水等化学剂在强化渗吸效果方面的作用机理。最后，基于当前研究现状，本文展望了该领域未来的重点发展方向，包括深化裂缝-基质耦合系统的渗流规律研究、推动渗吸与其他提高采收率技术的协同应用、建立室内实验与矿场实践之间的定量关联模型、以及开发高效低伤害的新型渗吸工作液体系。本研究为深化理解渗吸机理及优化低渗透裂缝性油藏开发策略提供了有益参考。