Geologic Modeling of Spatial Variability in Sedimentary Environments for Groundwater Transport Simulation

地质介质的空间变异性，以及介质性质的空间变异性，是地下水输送研究的关键问题，然而，有关控制含水层结构形成的地质过程的重要信息尚未纳入水文地质模型。在以前的建模方法中，从少量测量数据的统计特征或假设的空间协方差模型推断出空间可变的含水层性质。通常情况下，人们忽视了解释性地质信息，即使这些信息很容易获得。现有的（空间）统计模型不太可能捕捉到实际含水层系统的许多基本要素，实际上可能产生地质上“不可能”的地下结构。因此，我们提出了一种基于沉积过程模型生成的综合地质的物理模拟方法来取代传统的随机模拟方法。我们将明确考虑控制含水层演化和导致含水层性质非均质性的地质过程。该方法结合了沉积过程模拟、岩石物理学、地质统计学和地下水建模。我们计划通过模拟生成三维合成含水层（几何和沉积地质），将非常精细尺度（如厘米）的地质信息转换为含水层水力特性，并利用大尺度数值流动模拟和颗粒跟踪模拟三维地下水运移。我们计划比较以地质过程为导向的方法与传统的随机/统计方法来模拟地下水流动。我们的方法将在一个复杂的油田区域（加州圣克拉拉谷）进行测试，并应用于代表各种沉积环境的假设含水层系统。

Spatial variability of geologic media, and consequently of media properties, is of key concern in ground-water transport studies, yet important information about geologic processes governing the creation of aquifer architecture has not been incorporated into hydrogeologic models. In previous modelling approaches, spatially variable aquifer properties have been inferred from the statistical characteristics of a few measured data or an assumed spatial covariance model. Typically there is a neglect of interpretive geological information, even when it is readily available. It is unlikely that existing (spatial) statistical models capture many of the essential elements of actual aquifer systems and may in fact produce a geologically "impossible" subsurface architecture. Therefore, we propose to replace the traditional stochastic simulation approach with a physically-based approach based upon synthesized geology which is generated by a sedimentary process model. We will explicitly consider the geologic processes which control aquifer evolution and which result in heterogeneity of aquifer properties. This approach combines sedimentary processes simulation, petrophysics, geostatistics, and groundwater modelling. We plan to use simulation to generate a three-dimensional synthetic aquifer (geometry and sedimentary geology), transform the geologic information at a very fine scale (i.e., centimeters) into aquifer hydraulic properties, and simulate three- dimensional groundwater transport using large scale numerical flow simulation and particle tracking. We plan to compare the geologic-processes oriented approach with the traditional stochastic/statistical approach to groundwater flow simulation. Our approach will be tested on a complex field area (Santa Clara Valley, CA) as well as applied to hypothetical aquifer systems representing a variety of sedimentary environments.