Using a Well-Controlled Heterogeneous Permeability Field to Study Its Role on Miscible Density-Driven Convection in Porous Media

将二氧化碳（CO2）注入深层盐水层是减缓全球气候变化的一个有前途的解决方案。注入的CO2溶解在含水层水中，增加了其密度。增加的密度影响水的流动和注入的CO2的流动性。这种流动性还受到含水层渗透性的影响。深层含水层的渗透性在空间上变化很大，并影响流体移动的方式。这项研究使用3D打印技术建立实验装置，可以再现深层含水层的复杂特征，并研究可变渗透率如何影响多孔介质中流体的密度驱动运动。这项研究的结果将通过提供有效管理深层含水层中CO2注入所需的信息而造福社会。 这对于理解利用深层含水层的碳捕获和储存作为一项可行技术来减缓二氧化碳排放、全球变暖和气候变化的可行性至关重要。该项目还将扩大研究生和本科生的教育和培训，提高公众的科学素养，吸引妇女和少数民族学生，并与工业和当地企业发展伙伴关系。该项目的研究目标是使用高分辨率3D打印技术来克服传统实验方法所遇到的挑战，以便：1）验证渗透率对混相密度驱动对流的临界Rayleigh-Darcy数和临界时间的影响，2）构造已知且良好控制的非均质渗透率场以研究其对混相密度驱动对流的起始的作用，3）研究非均质渗透率场如何决定后期的流动模式和传质速率。具体而言，计算机建模用于生成颗粒集合体，其被称为“数字沉积物”块。将孔隙结构信息导入格子Boltzmann模拟器中，作为渗透率计算的流动模型的内部边界条件。然后，这些“数字沉积物”块将使用高分辨率3D打印来制造，以构建所需的渗透性结构。在本工程中，渗透率场的非均质结构由渗透率变化和相关长度来表征。一个实验模拟流体系统配备高速摄像机将被用来测量下的渗透率方差和相关长度的各种组合的对流传质速率。3D打印的“数字沉积物”块具有已知的和良好控制的渗透率，并且可重复用于不同的非均质渗透率场。这些优点有利于建设的非均质多孔介质，从而增加了实验室实验的总数，可以进行，这是至关重要的满足遍历性的要求，并使流体系统验证分析和数值结果的一个有价值的实验模拟。产生的知识是变革性的，将有助于研究其他密度驱动的对流过程中的非均匀多孔介质。在研究计划的支持下，该推广计划将针对不同的教育环境，以提高公众的科学素养，吸引女性和少数民族学生参与STEM，并为学生为现代劳动力做出贡献做好准备。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Injection of carbon dioxide (CO2) into deep saline aquifers is a promising solution to lessen global climate change. Injected CO2 dissolves in aquifer water and increases its density. Increased density affects the water flow and the mobility of the injected CO2. This mobility is also influenced by the permeability of the aquifer. The permeability of deep aquifers varies greatly in space and affects the ways in which the fluids move. This research uses 3D printing technologies to build experimental setups that can reproduce the complex characteristics of deep aquifers and study how variable permeability influence the density-driven movement of fluids in porous media. Results from this research will benefit society by providing needed information for efficient management of CO2 injection in deep aquifers. This is critical to understanding the feasibility of using carbon capture and storage in deep aquifers as a viable technology to mitigate CO2 emissions, global warming and climate change. The project will also serve to broaden the education and training of graduate and undergraduate students, increase public scientific literacy, engage women and minority students, and develop partnership with industry and local business.The research objective of this project is to use high-resolution 3D printing technologies to overcome the challenges encountered by conventional experimental methods, in order to: 1) validate the influence of permeability on the critical Rayleigh-Darcy number and critical time for the onset of miscible density-driven convection, 2) construct a known and well-controlled heterogeneous permeability field to study its role on the onset of miscible density-driven convection, and 3) investigate how heterogeneous permeability fields dictate the later-time flow patterns and mass transfer rates. Specifically, computer modeling is used to generate particle assemblies, which are referred to as "digital sediment" blocks. The pore structural information will be imported into a lattice Boltzmann simulator as internal boundary conditions of flow modeling for permeability calculation. These "digital sediment" blocks will then be fabricated using high-resolution 3D printing to construct the desired permeability structure. In this project, the heterogeneity structure of a permeability field is characterized by permeability variation and correlation length. An experimental analogue fluid system equipped with high-speed cameras will be used to measure the convective mass transfer rate under various combinations of permeability variance and correlation length. The 3D-printed "digital sediment" blocks have known and well-controlled permeabilities and are reusable for a different heterogeneous permeability field. These advantages facilitate the construction of heterogeneous porous media and thus increase the total number of laboratory experiments that can be conducted, which is critical for satisfying the ergodicity requirement and makes the fluid system a valuable experimental analogue for validating analytical and numerical findings. Generated knowledge is transformative and will contribute to the study of other density-driven convection processes in heterogeneous porous media. Reinforced by the research plan, the outreach plan will target different educational settings to increase public scientific literacy, engage women and minority students in STEM, and prepare students to contribute to a modern workforce.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.