关键词: 致密油藏, 渗吸, 表面活性剂, 核磁共振, 纳流控, 数学模型

Abstract: The microscopic imbibition mechanism of surfactants is a key factor affecting imbibition recovery in tight oil reservoirs. At the nanoscale pore level, the coupling between solid-liquid interfacial characteristics and fluid transport behavior becomes increasingly complex, resulting in unclear imbibition behavior in tight reservoirs; therefore, it is essential to clarify the microscopic imbibition mechanisms and phase behavior evolution of surfactant systems. Taking tight reservoirs in Ordos Basin as the research subject, three imbibition systems with distinct solid-liquid interfacial characteristics, including brine, conventional surfactant (AES), and in-situ microemulsion (SDBS-APS), were constructed. Low-field nuclear magnetic resonance (NMR) and nanofluidic techniques were employed to systematically conduct core-scale imbibition experiments and nanoscale pore-scale visualization experiments. A mathematical model for microemulsion imbibition was subsequently established. The results indicate that:(1) The core imbibition recovery factors of brine, AES, and SDBS-APS are 14.5 %, 26.1 %, and 34.3 %, respectively. (2) SDBS-APS exhibits ultra-low interfacial tension and solubilization-emulsification capabilities, enabling more uniform vertical sweep in the core to effectively mobilize oil in deep reservoirs. (3) SDBS-APS can diffuse into the oil phase within nanopores, inducing the solubilization of interfacial films to form extensive microemulsion zones. (4) By incorporating solubilization coefficients and time parameters into the oil-water imbibition mathematical model, the relationship between oil saturation and imbibition distance under ultra-low interfacial tension conditions was established, achieving dynamic prediction of recovery efficiency.

Key words: tight oil reservoir, imbibition, surfactant, nuclear magnetic resonance, nanofluidic, mathematical model