Coupling of Modified Equation of State and Percolation Theory to Study Static and Dynamic Non-Equilibrium Phase Behavior of Heavy Oil in the Presence of Porous Medium

高粘度原油在一次枯竭过程中通常存在非平衡热力学相态。以前，稠油的相行为研究是在主体相中产生的；然而，它不能代表在多孔介质存在时的类似情况，这引起了人们对信息准确性的担忧。在这项研究中，提出了一种系统和比较的工作流程，将实验和数值方法结合起来，研究活稠油在多孔介质中的静态和动态非平衡相态行为。在实验部分，将对稠油体系进行高温高压相态试验，分别在与可视化压力室相连的充砂物理模型和自行设计制造的微观模型中进行。注入的复合活油将经历压力耗竭过程，通过改变降压速率来控制流体相的非平衡和平衡。在每个压力下，将直接或间接地测定和分析流体的总体积、析出的气相以及界面张力和界面面积、毛细压力等界面性质。用超声波仪对充砂模型进行扫描，确定试验条件下的流体相分布。对剩余的液相进行进一步降压，继续进行“差动释放试验”。在动态条件下进行上述充砂试验和模型试验。数值模拟将首先发展一个修正的状态方程，它结合了经典的统计力学势公式和考虑分子-分子相互作用的宏正则配分函数。为了更准确地描述非平衡稠油体系，提出了一种改进的热力学状态方程，并将其与物质/能量平衡和渗流理论相结合。在不同降压率下的每个时间步，在适当的初始条件和边界条件下，将体相的质量、动量和能量平衡以及界面物质交换结合到整体计算矩阵中。它将用全隐式和牛顿-拉夫森方法求解。将确定每一相中的组分分布和各自的流体性质。将实验测量数据与所建立的非平衡稠油体系数学模型进行了比较。总之，将状态方程和渗流理论结合起来，将发展一种新的方法来描述体相存在时非平衡态的相行为和性质变化。这一研究从宏观和微观两个层面捕捉了多孔介质存在下稠油体系流体相变从非平衡到平衡的全过程。

Non-equilibrium thermodynamic phase behavior normally exists for high viscous crude oil during the primary depletion process. Previously, phase behavior studies for heavy oil were generated in the bulk phase; however, it cannot represent a similar situation in the presence of porous medium, which creates cause for concern as to the accuracy of the information. In this research study a systematic and comparative workflow is proposed to combine experimental and numerical approaches to the study of the static and dynamic non-equilibrium phase behavior of live heavy oil in the porous medium. For the experimental part, the high temperature and high pressure phase tests will be performed for heavy oil systems in a sand-pack filled physical model connected to a visual pressure cell, and the self-designed and manufactured micromodel. The injected recombined live oil will go through the pressure depletion processes, and the fluid phase non-equilibrium and equilibrium will be controlled by varying the depressurization rate. At each pressure, the total fluid volume, evolved gas phase, and the interfacial properties such as interfacial tension and interfacial area, capillary pressure, etc. will be determined and analyzed directly or indirectly. The sand-pack model will be scanned by using an ultrasonic apparatus to determine the fluid phase distribution at the test conditions. The remaining liquid phase will be further depressurized to continue the "differential liberation test". The aforementioned sand pack and micromodel tests will be repeated in the scenario of dynamic condition. The numerical simulation will begin by developing a modified EOS which incorporates the classical statistical mechanical potential formulae and grand canonical partition function considering the molecule-molecule interactions. A combination of modified thermodynamic EOS with the material/energy balance and percolation theory is presented to facilitate the accurate description of non-equilibrium heavy oil systems. At each time step under different depressurization rate, the mass, momentum and energy balance of bulk phases and the interfacial material exchanges will be combined into the overall calculation matrix with appropriate initial and boundary conditions. It will be solved with fully implicit and Newton-Raphson methods. The component distribution in each phase and respective fluid properties will be determined. The experimentally measured data is compared to the formulated mathematical models of the non-equilibrium heavy oil system. In general, a new methodology will be developed to describe the phase behavior and property changes of non-equilibrium states in the presence of bulk phase by combining the equation of state with the percolation theory. This particular study captures the full journey of fluid phase transition from non-equilibrium to equilibrium at both macroscopic and microscopic levels for heavy oil systems in the presence of porous medium.