Modeling Flow in Porous Media with Vugular Meso-scale Heterogeneities

Arbogast0074310 沉积岩中有时含有比通常的粒间孔隙大得多的空洞区域，称为溶洞。 孔洞的不均匀性提出了实际和理论上的问题，以了解通过这样的岩石在现场规模的流体流动。 例如，标准采样方法的规模太小，无法解决这些不均匀性。 此外，它是不平凡的，以确定正确的物理形式主义建模流或解释流量测量，它是不清楚的，传统的均匀化方法是适用的。 在这个项目中，研究人员将包含厘米级溶洞的白垩纪碳酸盐岩大样本（约17，000立方厘米）的微观（CT扫描）和宏观测量直接与流场的高分辨率计算联系起来。 该框架允许测试不同的物理模型，用于样品几何形状中的流动。 具体目标是：（1）将样品的CT扫描像素映射到渗透率和孔隙度;（2）模拟微尺度系统中的流动;（3）确定单相流动的宏观尺度控制关系;以及（4）根据微尺度表征确定宏观模型参数。 算法和升级程序的研究进行，以实现第二和第三个目标。 随后的数值实验确定的替代沉积环境和成岩历史的影响，通过改变连通性的溶洞和渗透率分布的基质材料。 这最终导致在全场模拟中更有信心地预测空穴介质中的流动的能力。 流体通过多孔岩石的流动具有经济和环境意义。 例子包括石油和天然气生产，获得充足的水供应（地下水约占美国用水量的三分之一，许多城市完全依赖威尔斯），以及修复超级基金场地和许多能源部设施的地下污染。 这些流动所通过的沉积岩有时包含相对较大的洞或称为溶洞的空隙区域。 化石碎片的溶解是在碳酸盐岩中形成洞穴的常见机制，碳酸盐岩含有世界上一半以上的石油储量，并构成了美国许多最大的含水层。 溶洞比岩石颗粒之间的小得多的孔隙空间更有利于流体流动，这为理解大规模流动提出了实践和理论问题。 该项目旨在为这种类型的岩石构建模型，预测数百码至数英里的有效流动特性。 由于在这些距离上进行直接实验是不可行的，因此研究的一个重要组成部分是将中等规模的物理实验和大规模的计算实验相结合。 这项工作还依赖于数值算法和建模技术的基础研究。 建立正确的关系，控制这些岩石中的流体流动，使更有信心的预测，从全场模拟。

Arbogast0074310 Sedimentary rocks sometimes contain void regions called vugs that are much larger than the usual intergranular pores. Vugular heterogeneities raise both practical and theoretical problems for understanding fluid flow through such rocks at the field scale. For example, standard sampling methods are at a scale too small to resolve these heterogeneities. Moreover it is nontrivial to identify the correct physical formalism for modeling flow or interpreting flow measurements, and it is not clear that traditional homogenization approaches are applicable. In this project, the investigators tie microscopic (CT scan) and macroscopic measurements of a large sample (about 17,000 cubic cm) of Cretaceous carbonate rock containing centimeter-scale vugs directly to high-resolution computation of flow fields. This framework allows the testing of different physical models for flow in the geometry of the sample. The specific objectives are to: (1) Map CT scan pixels of the sample to permeability and porosity; (2) Simulate flow in the micro-scale system; (3) Determine the macro-scale governing relations for single phase flow; and (4) Determine the macroscopic model parameters in terms of the microscale characterization. Research in algorithms and upscaling procedures is conducted to achieve the second and third objectives. Subsequent numerical experiments determine the influence of alternative depositional environments and diagenetic histories by changing the connectivity of the vugs and the permeability distribution of the matrix material. This results finally in the ability to more confidently predict flow in vugular media in full-field simulations. The flow of fluids through porous rock is of economic and environmental interest. Examples include oil and gas production, obtaining adequate water supplies (groundwater accounts for about one third of the water used in the US, with many cities depending exclusively on wells), and remediating subsurface contamination at Superfund sites and many Department of Energy facilities. The sedimentary rocks through which these flows occur sometimes contain relatively large holes or void regions called vugs. The dissolution of fossil fragments is a common mechanism for creating vugs in carbonate rocks, which contain more than half the world's oil reserves and comprise many of the biggest aquifers in the US. Vugs are more conducive to fluid flow than the much smaller pore space between the rock grains, and this raises both both practical and theoretical problems for understanding large-scale flows. This project aims to construct models for this type of rock that predict the effective flow properties over hundreds of yards to several miles. Because direct experimentation over these distances is not feasible, an essential component of the research is the integration of intermediate-scale physical and large-scale computational experiments. This effort also relies on basic research in numerical algorithms and modeling techniques. Establishing the correct relations governing the flow of fluids in such rocks enables more confident predictions from full-field simulations.