【摘要】 碳捕集、利用与封存（carbon capture, utilization and storage, CCUS）技术是中国实现“双碳”目标的关键手段，CO₂驱油技术作为CCUS技术的重要组成部分，通过向地层注入CO₂以提高油气产量，而且实现部分CO₂封存，从而达到环境保护与经济效益双赢的效果。依托鄂尔多斯盆地X区块长8段低渗透油藏，探究CO₂驱油过程中原油与CO₂体系的相态特征。通过高压物性分析和原油与CO₂体系相态实验，获取原油的体积系数、黏度、密度和饱和压力，并从实验和模拟角度进一步探究了CO₂注入对其相态特征的影响。结果表明：鄂尔多斯盆地X区块长8段原油密度、体积系数和饱和压力随压力变化显著；CO₂的注入能改善油藏压力、降低原油黏度、改变原油与注入气体的相态行为和混相程度；孔隙尺度对CO₂与原油体系相态特征有显著影响，孔隙尺寸越小，孔隙内毛管力越大，对原油相态影响更显著；中值孔隙介质中，CO₂注入量增加使原油黏度下降明显，密度也逐渐减小，体积系数随之增大，表明CO₂驱油能够改善原油相态，有助于提升低渗油藏的开发效果，研究成果有望为CO₂提高原油采收率提供理论依据。更多还原

【Abstract】 Carbon capture, utilization and storage（CCUS） is recognized as a critical strategy for achieving China’s “dual carbon” goals. As a vital component of CCUS, CO₂-enhanced oil recovery（CO₂-EOR） improves hydrocarbon production through CO₂ injection into reservoirs while enabling partial CO₂ sequestration, thereby achieving synergistic environmental and economic benefits. The phase behavior characteristics of the crude oil-CO₂ system during CO₂ flooding in the low-permeability reservoirs of Block X, Ordos Basin was focused. High-pressure physical property analysis and phase behavior experiments were conducted to obtain key parameters, including crude oil volume factor, viscosity, density, and saturation pressure. Experimental and numerical simulation approaches were integrated to further analyze the effects of CO₂ injection on phase behavior. The results indicate that the density, volume factor, and saturation pressure of crude oil in Block X are significantly influenced by pressure variations. CO₂ injection is observed to enhance reservoir pressure, reduce crude oil viscosity, and modify the phase behavior and miscibility degree of the crude oil-CO₂ system. Pore size is identified as a critical factor affecting phase behavior: smaller pores with stronger capillary forces exhibit more pronounced impacts on crude oil properties. In median-sized pores, increased CO₂ injection reduces viscosity, decreases density, and enhances the volume factor. It is concluded that CO₂ flooding optimizes crude oil phase behavior and improves the development efficiency of low-permeability reservoirs. The research results provide theoretical insights into the phase behavior evolution during CO₂-EOR processes, offering guidance for enhancing oil recovery in similar reservoirs.更多还原