【摘要】 为改善非常规油气藏低渗特性，水平井多级水力压裂技术得到了广泛应用。然而，在压裂过程中，部分水基压裂液会在毛细管压力的作用下自发渗吸进入基质，进而导致储层损害和采收率降低。因此，低渗油气藏水力压裂后的自发渗吸机理及其对采收率的影响是非常规油气藏开发的重要研究内容。首先，探讨了低渗油气藏复杂孔隙结构特征、黏土矿物组分和含量、水-岩界面特性等因素间的关系：复杂的孔隙结构会增加毛细管阻力；不同黏土矿物的不同吸附性能会影响水-岩界面张力，同时黏土含量升高会加快自吸速率；不同流体渗吸进入多孔介质时会制约自吸速率。上述研究结论揭示了水力压裂过程中自发渗吸的发生及演化机理对采收率的影响。其次，归纳了现有自吸标度模型，这些模型主要以无量纲自吸时间和自吸量为参数，定量探讨自发渗吸过程对采收率的影响规律。最后，对实际工程中不同自吸边界条件进行了探讨，明确了不同边界条件下的自吸采收效率。研究和探讨为提高低渗油气藏开采效率提供了理论依据。更多还原

【Abstract】 Due to the dense pore structures of unconventional oil/gas reservoirs, multi-stage hydraulic fracturing for horizontal wells were widely used to modify their permeability characteristics. However, some water-based fracturing fluids spontaneously imbibe into the matrix under capillary pressure, causing reservoir damage and a reduction in recovery rate during the fracturing process. Since the mechanism of spontaneous imbibition and recovery rate impact after hydraulic fracturing in low-permeability oil and gas reservoirs are the important research contents, this paper discusses the relationship among such factors as the complex pore structure characteristics, clay mineral composition and content, as well as water-rock interface properties, showing the complex pore structure would increase capillary resistance, differences in the adsorption properties of various clays affects the water-rock interface tension, the increase in content would accelerate the imbibition rate, and it would decrease when different fluids enter into porous medium. The research results indicate that the occurrence of spontaneous imbibition in the process of hydraulic fracturing and the evolution mechanism has both beneficial and detrimental impacts on the recovery, summarize the existing spontaneous imbibition scalar models, which take the dimensionless spontaneous imbibition time as well as spontaneous imbibition volume as the parameters and quantitatively explore the influence law of the spontaneous imbibition process on the recovery rate, discusses different spontaneous imbibition boundary conditions in actual projects, clarify the efficiency of spontaneous imbibition recovery. The research and discussion would provide theoretical basis for improving the recovery efficiency of low-permeability oil/gas reservoirs.更多还原