Field, laboratory and modelling constraints on fluid transport in fractured mudrocks with a focus on chemical self-healing

裂隙泥岩中流体输送的现场、实验室和建模约束，重点是化学自修复

• 批准号: 2891563
• 金额: --
• 依托单位: Heriot-Watt University
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2891563
• 关键词: Field; laboratory; modelling; constraints; fluid

One of the requirements for a Geological Disposal Facility (GDF) for radioactive waste is that itneeds to contain radionuclides away from the surface environment whilst they are still harmful, forsome radionuclides this can be many to tens of thousands of years. The containment function of ageological setting is affected by the presence of fault-fracture systems, which can create pathwaysfor the migration of radionuclides carried by gas and water. Mercia Mudrock Group (MMG) isconsidered as a potential host rock, and fault-fracture systems therein are potential conduits forfluid flow. The inshore, deep, saline setting considered for the GDF is further complicated by thefault-fracture system architecture and the complex mechanical stratigraphy of the interbeddedmudrock and evaporites of the MMG. Integral to this will be to demonstrate understanding of thefracture hosted (single and two phase) fluid flow and solute transport process.This broad scope of this research involves i) the observational description of MMG fault-fracturesystems from outcrops and cores including assessing the mechanical-stratigraphic controls onfracture network geometries; ii) the measurement of single (and multi-phase) flow in fractures as afunction of rock-fracture properties, effective stress and fracture / stress field orientations and; iii)measurement of adsorbing solute and fluid specific transport processes. All this information needsto be integrated in model frameworks focusing on flow and transport in fractures or the exchangebetween fractures and matrix. Given the need for models to describe flow at various length-scales,including regional scales, detailed numerical upscaling workflows are required to derive constitutiverelationships and effective properties for radionuclide and gas transport at decametre scales. Thisspecifically requires a strong interplay between observations done in outcrops (fracture networkand statistics thereof, understanding of fracture mineralisation versus stress directions etc) and thedevelopment of coupled hydro-chemical-mechanical models. This interplay, supported bylaboratory data, will be a key output of this project to advance the understanding of fluid flow alongfractures and to highlight the potential of multi-scale, multi-method approaches to evaluate thesafety case for radwaste storage in MMG formations.While the fracture characterisation can be determined in conventional laboratory studies,phenomenological understanding of fluid flow in faulted/fractured mudrock-evaporite sequencescan also be obtained by studying the fracture mineralization. The distribution of mineralisedfractures, fracture cross cutting relationships, fracture fill thickness, geochemistry, and isotopicages, can improve our understanding of paleofluid composition, preferential flow paths, time scalesand rates of fluid flow. Coupled hydro-chemical-mechanical modelling of fossil fluid flow systemscan provide process understanding and data sets to calibrate / validate models used for forwardpredictions over 103 to 106 year timescales. This information will directly inform modelling andlaboratory approaches to assess the potential for fracture self-healing due to mineralization by salts(e.g., gypsum, halite) in e.g., perturbed (i.e. reactivated) or excavated zones.

地质处置设施（GDF）对放射性废物的要求之一是，它需要在放射性核素仍然有害的时候远离地表环境，对某些放射性核素来说，这可能需要许多到数万年的时间。断裂断裂系统的存在影响了地质环境的遏制作用，为气体和水携带的放射性核素的运移创造了通道。麦西亚泥岩群（Mercia Mudrock Group， MMG）被认为是潜在的寄主岩，其中的断裂系统是潜在的流体流动管道。考虑到GDF的近海、深海、盐碱化背景，断裂-断裂体系结构和MMG的互层泥岩和蒸发岩的复杂机械地层使其进一步复杂化。这其中不可或缺的一部分将是展示对裂缝承载（单相和两相）流体流动和溶质输送过程的理解。这一广泛的研究范围包括：(1)从露头和岩心对MMG断裂-裂缝系统的观测描述，包括评估裂缝网络几何形状的机械地层控制；Ii)测量裂缝中的单相（和多相）流动作为岩石-破裂特性、有效应力和裂缝/应力场方向的函数；Iii)吸附溶质和流体特定输运过程的测量。所有这些信息都需要集成到专注于裂缝中的流动和输送或裂缝与基质之间交换的模型框架中。考虑到需要模型来描述各种长度尺度（包括区域尺度）的流动，需要详细的数值升级工作流程来推导出十米尺度上放射性核素和气体输送的本构关系和有效特性。这特别需要在露头观测（裂缝网络及其统计，对裂缝矿化与应力方向的理解等）和耦合水化学-力学模型的发展之间进行强烈的相互作用。这种相互作用得到实验室数据的支持，将成为该项目的关键成果，以促进对裂缝沿流的理解，并突出多尺度、多方法方法评估MMG地层中放射性废物储存安全案例的潜力。虽然裂缝特征可以通过常规的实验室研究来确定，但对断裂/断裂泥岩-蒸发岩层序中流体流动的现象学理解也可以通过研究裂缝的成矿作用来获得。矿化裂缝的分布、裂缝横切关系、裂缝充填厚度、地球化学和同位素可以提高我们对古流体组成、优先流动路径、时间尺度和流体流动速率的认识。化石流体流动系统的耦合水化学-力学建模可以提供过程理解和数据集，用于校准/验证用于103至106年时间尺度的预测模型。这些信息将直接为建模和实验室方法提供信息，以评估盐矿化导致裂缝自愈的可能性。（如石膏、岩盐）在扰动（即重新激活）或挖掘区。