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

高粘度原油在一次衰竭过程中通常存在非平衡热力学相行为。以前，稠油的相行为研究是在体相中进行的；然而，在多孔介质存在的情况下，它不能代表类似的情况，这引起了对信息准确性的关注。在本研究中，提出了一种系统的、比较的工作流程，将实验和数值方法相结合，研究活体稠油在多孔介质中的静态和动态非平衡相行为。在实验部分，将对稠油系统进行高温高压阶段试验，试验将在一个与视觉压力单元相连的填砂物理模型和自行设计制造的微模型中进行。注入复合活油将经历压力衰竭过程，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，将直接或间接地确定和分析总流体体积、演化气相以及界面张力和界面面积、毛细压力等界面性质。将使用超声波设备扫描砂堆模型，以确定测试条件下的流体相分布。剩余的液相将进一步减压，继续进行“微分释放试验”。上述填砂和微模型试验将在动态条件下重复进行。数值模拟将从开发一个改进的EOS开始，该EOS结合了经典的统计力学势公式和考虑分子-分子相互作用的大正则配分函数。提出了一种将改进的热力学方程与物质/能量平衡和渗流理论相结合的方法，以促进对非平衡稠油体系的准确描述。在不同降压速率下的每个时间步长，将体相的质量、动量和能量平衡以及界面物质交换结合到具有适当初始条件和边界条件的整体计算矩阵中。它将用完全隐式和牛顿-拉夫森方法求解。将确定每个相中的组分分布和各自的流体性质。将实验测量数据与非平衡稠油体系的数学模型进行了比较。总的来说，将状态方程与渗流理论相结合，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。这项特殊的研究在宏观和微观层面上捕捉了多孔介质存在的稠油系统从非平衡到平衡的流体相变的完整过程。

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.