Reservoir simulation using high-fidelity fluid models is typically employed to study subsurface displacement processes that involve complex physics. Such processes are highly nonlinear and occur at the interplay of phase thermodynamics (phase stability and split) and rock/fluid interaction (relative-permeability). Due to its nonlinearity, relative-permeability is an important constitutive of the conservation equations, and has a significant impact on the simulation. Dependence of the phase relative-permeability on fluid compositions, pressure, and temperature is well-documented. In compositional reservoir simulation, however, relative-permeability is typically modeled as a function of phase saturation. Such an approach may lead to serious discontinuities in relative-permeability. To alleviate this issue, several authors proposed models based on phase state indicators (density, parachor, Gibbs Free Energy). However, such techniques cannot represent the complete degrees of freedom that are exhibited by compositional displacements. In this work, we present a relative-permeability model based on a parameterization of the compositional space. The model is independent of the hydrocarbon phase labeling as gas or oil. We show that our proposed model (1) applies regardless of the degrees-of-freedom of the compositional displacement problem, and (2) is guaranteed to yield a continuous relative-permeability function across the entire compositional space. We have implemented this model in our research simulator, and we present test cases using traditional relative-permeability models, as well as, numerical results that compare the nonlinear performance.

中文翻译：

---

用于成分模拟的连续相对渗透率模型

使用高保真流体模型的油藏模拟通常用于研究涉及复杂物理的地下置换过程。这种过程是高度非线性的，发生在相热力学（相稳定性和分裂）和岩石/流体相互作用（相对渗透率）的相互作用下。由于其非线性，相对渗透率是守恒方程的重要组成部分，对模拟有重大影响。相相对渗透率对流体成分、压力和温度的依赖性已得到充分证明。然而，在成分储层模拟中，相对渗透率通常被建模为相饱和度的函数。这种方法可能导致相对渗透率的严重不连续。为了缓解这个问题，几位作者提出了基于相状态指标（密度、降落伞、吉布斯自由能）的模型。然而，这些技术不能代表组合位移所展示的完整自由度。在这项工作中，我们提出了一个基于成分空间参数化的相对渗透率模型。该模型与标记为气体或油的烃相无关。我们表明，我们提出的模型 (1) 无论成分位移问题的自由度如何都适用，并且 (2) 保证在整个成分空间中产生连续的相对渗透率函数。我们已经在我们的研究模拟器中实现了这个模型，我们展示了使用传统相对渗透率模型的测试案例，以及比较非线性性能的数值结果。