Two-phase flows in open geological fractures: a combined experimental and numerical investigation

开放地质裂缝中的两相流：实验和数值研究相结合

• 批准号: 446379816
• 负责人: Professorin Dr. Insa Neuweiler
• 金额: --
• 依托单位: Institut für Strömungsmechanik und Umweltphysik im Bauwesen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/446379816?language=en
• 关键词: Two; phase; flows; open; geological

Many geotechnical and environmental engineering problems, such as geothermal energy production or storage of fluids in deep formations, involve flow processes in subsurface fractured media. When two immiscible fluids coexist, the flow involves the displacement of the interfaces between them. This so-called two-phase flow can result in very complex and intricate spatial distributions of the fluids, depending on the mean flow velocity, the viscosities and densities of the fluids, the mechanical properties of their interface, and the geometry of the permeable medium. For porous media, the rich phenomenology of two-phase flows has been investigated at length in the last 20 years. In geological fractures, on the contrary, the characterization of this rich phenomenology is still in its infancy. The first main objective of this project is to systematically investigate it, as a function of the fluids’ properties, flow conditions, as well as fracture geometry and closure.This objective will be tackled through a combination of (i) laboratory experiments on transparent setups reproducing a realistic fracture geometry but allowing for measurements of the spatial distributions of the two fluids and of their velocities, and (ii) numerical simulation of the two-phase flow in the fracture space, based on the first principles of fluid mechanics. The laboratory experiments will be set up and run at Géosciences Rennes, while the numerical study will be developed and run at University Hannover, thus building on the complementary expertise of the two groups. An innovative so called depth-averaged two-dimensional numerical simulation, which directly computes fluid velocities averaged over the fracture aperture, will also be developed jointly by the two groups. It is expected to provide an excellent compromise between prediction accuracy and computing efficiency. Systematic characterization of two-phase flow in rough fractures from the experimental and numerical data will be done jointly by the two groups.For practical applications, which involve length scales of tens to thousands of meters, the length scale of fluid-fluid interfaces cannot be resolved. To predict flow in field case studies, so-called continuum scale numerical models, which are not based on the first principles of fluid mechanics, are therefore used. These models are known to not often reproduce the spatial fluid distributions well. For example, the amounts of naturally-occurring fluid that remains in the subsurface after an injected fluid has displaced that previously-resident fluid, or the travel times of fluids over a given distance, are often poorly predicted. The second main objective of this project is to improve such large scale predictions by using the newly-acquired knowledge of two-phase flow phenomenology to find appropriate large scale model parameters that will optimize the prediction of large scale observables such as the amount of displaced fluid remaining in the geological formation.

许多岩土工程和环境工程问题，如地热能生产或深部地层中流体的储存，都涉及地下裂缝介质中的流动过程。当两种不混溶流体共存时，流动涉及它们之间界面的位移。这种所谓的两相流可以导致流体的非常复杂和错综复杂的空间分布，这取决于平均流速、流体的粘度和密度、它们的界面的机械特性以及可渗透介质的几何形状。对于多孔介质，在过去的20年里，两相流的丰富现象学已经被详细研究。相反，在地质断裂中，这种丰富的现象学的表征仍处于起步阶段。该项目的第一个主要目标是系统地研究它，作为流体性质、流动条件以及裂缝几何形状和闭合的函数。这一目标将通过以下组合来解决：（i）在透明装置上进行实验室实验，再现真实的裂缝几何形状，但允许测量两种流体的空间分布及其速度，（ii）基于流体力学第一性原理，对裂缝空间两相流进行数值模拟。实验室实验将在雷恩地质科学学院进行，而数值研究将在汉诺威大学进行，从而利用两个小组的互补专长。这两个小组还将联合开发一种创新的所谓深度平均二维数值模拟，它直接计算裂缝孔径上的平均流体速度。预计它将提供一个很好的折衷之间的预测精度和计算效率。两个研究小组将共同从实验和数值数据中对粗糙裂缝中的两相流进行系统的表征。对于实际应用，涉及几十到几千米的长度尺度，流体-流体界面的长度尺度无法解决。为了预测现场案例研究中的流动，因此使用了所谓的连续尺度数值模型，该模型不是基于流体力学的第一原理。已知这些模型通常不能很好地再现空间流体分布。例如，在注入的流体已经驱替先前驻留的流体之后，保留在地下的天然存在的流体的量，或者流体在给定距离上的行进时间，通常预测得很差。该项目的第二个主要目标是通过使用新获得的两相流现象学知识来改进这种大规模预测，以找到适当的大规模模型参数，从而优化大规模可观测量的预测，例如地质构造中剩余的驱替流体的量。