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Phase Behavior and Miscibility of CO2–Hydrocarbon Mixtures in Shale Nanopores
Industrial & Engineering Chemistry Research ( IF 3.8 ) Pub Date : 2021-03-31 , DOI: 10.1021/acs.iecr.1c00717 Yilei Song 1 , Zhaojie Song 1 , Jia Guo 1 , Dong Feng 1 , Xuya Chang 1
Industrial & Engineering Chemistry Research ( IF 3.8 ) Pub Date : 2021-03-31 , DOI: 10.1021/acs.iecr.1c00717 Yilei Song 1 , Zhaojie Song 1 , Jia Guo 1 , Dong Feng 1 , Xuya Chang 1
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The phase behavior of shale fluids is different from conventional reservoir fluids due to fluid adsorption and capillary pressure. The miscibility phenomenon between CO2 and oil in nanopores is also changed during CO2 injection for enhanced shale oil recovery (EOR). The objective of this work is to develop a general framework of a theoretical algorithm and model to study the phase behavior and miscibility of CO2–hydrocarbon mixtures in shale formations. First, an improved vapor–liquid equilibrium calculation model is proposed to determine the phase behavior of confined fluids by incorporating capillary pressure with an adsorption-dependent equation of state. Second, by introducing the critical point judgment, a novel vanishing interfacial tension algorithm is developed to calculate the minimum miscibility pressure (MMP) of the CO2–Bakken oil system in bulk and nanopores. The effect of fluid adsorption and critical property shifts is considered in nature in the model and algorithm. Results show that the nanopore confinement decreases the vapor–liquid composition and density difference, and thus induces the reduction of interfacial tension (IFT). With the decrease of pore size, the IFT decreases sharply, while the capillary pressure first increases under larger pore sizes and then decreases under smaller pore sizes. When fluid adsorption is considered, the IFT and capillary pressure will be further reduced. The MMP of Bakken oil and CO2 is reduced from 20.2 MPa at 50 nm pores to 17.5 MPa at 20 nm pores. Hence, the reduction of pore size leads to a decrease in MMP, which is beneficial for CO2-EOR.
中文翻译：
页岩纳米孔中CO 2-烃混合物的相行为和混溶性
由于流体的吸附和毛细压力，页岩流体的相态与常规的储层流体不同。在CO 2注入过程中，CO 2与油在纳米孔中的可混溶现象也发生了变化，以提高页岩油采收率（EOR）。这项工作的目的是开发一种理论算法和模型的通用框架，以研究CO 2的相行为和混溶性。–页岩地层中的碳氢化合物混合物。首先，提出了一种改进的气液平衡计算模型，该模型通过将毛细管压力与依赖于吸附的状态方程相结合来确定承压流体的相态。其次，通过引入临界点判断，开发了一种新颖的消失界面张力算法来计算CO 2的最小混溶压力（MMP）–散装和纳米孔的Bakken石油系统。在模型和算法中，自然考虑了流体吸附和临界特性转移的影响。结果表明，纳米孔限制减小了气液成分和密度差，从而导致界面张力（IFT）减小。随着孔径的减小，IFT急剧减小，而毛细管压力在较大孔径下先增大，然后在较小孔径下减小。当考虑流体吸附时，IFT和毛细管压力将进一步降低。Bakken油和CO 2的MMP从50 nm孔处的20.2 MPa降低到20 nm孔处的17.5 MPa。因此，孔径的减小导致MMP的降低，这对于CO 2 -EOR是有利的。
更新日期：2021-04-14
中文翻译：
页岩纳米孔中CO 2-烃混合物的相行为和混溶性
由于流体的吸附和毛细压力，页岩流体的相态与常规的储层流体不同。在CO 2注入过程中，CO 2与油在纳米孔中的可混溶现象也发生了变化，以提高页岩油采收率（EOR）。这项工作的目的是开发一种理论算法和模型的通用框架，以研究CO 2的相行为和混溶性。–页岩地层中的碳氢化合物混合物。首先，提出了一种改进的气液平衡计算模型，该模型通过将毛细管压力与依赖于吸附的状态方程相结合来确定承压流体的相态。其次，通过引入临界点判断，开发了一种新颖的消失界面张力算法来计算CO 2的最小混溶压力（MMP）–散装和纳米孔的Bakken石油系统。在模型和算法中，自然考虑了流体吸附和临界特性转移的影响。结果表明，纳米孔限制减小了气液成分和密度差，从而导致界面张力（IFT）减小。随着孔径的减小，IFT急剧减小，而毛细管压力在较大孔径下先增大，然后在较小孔径下减小。当考虑流体吸附时，IFT和毛细管压力将进一步降低。Bakken油和CO 2的MMP从50 nm孔处的20.2 MPa降低到20 nm孔处的17.5 MPa。因此，孔径的减小导致MMP的降低，这对于CO 2 -EOR是有利的。
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