How underground lithologies respond to thermo-mechanical coupling during energy extraction/storage.

地下岩性在能量提取/存储过程中如何响应热机械耦合。

• 批准号: 2893447
• 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-2893447
• 关键词: How; underground; lithologies; respond; thermo

On our quest to decarbonise our energy resources, underground heat energy storage is a key player. However, the impact of frequent cyclic thermo-mechanical (TM) stress changes over prolonged periods remains poorly understood and may threatened the longevity of the systems. This project aims to fill this gap by performing laboratory and numerical experiments under relevant cyclic TM loading conditions to investigate the stability of targeted lithologies in such systems. To address the energy transition challenges, new subsurface solutions focus either on new resources exploitation (geothermal) or storage (radioactive waste, heat and/or gas -underground gas storage, compressed-air energy storage, H, CO2). All these applications have in common to induce new, shallow, periodic, local thermo-mechanical stress changes. The scope of this PhD project is to use different-scale observations to model and predict the stability of targeted lithologies in underground complex systems when those are subjected to cyclic TM stress changes over prolonged periods. This research work seeks to understand how grain-scale deformation can contribute to the global response of the underground systems and how this response can be controlled to reduce any accompanied induced hazards. An innovative methodology, combining laboratory and numerical experiments, will be applied to extend the understanding of the thermo-sensitive brittle deformation processes in porous rocks. The data will provide information to support field-scale operational conditions involving periodic TM stress changes as well as shed light on potential cascading shallow geohazards.Objectives:O1: Examine the relationship between microstructural deformation and TM stresses.O2: Collect, analyse and model TM data together.O3: Transfer and improve existing DEM code from UDEC to open source and undertake grain size sensitivity analysis.O4: Provide relevant data to inform on risks associated to TM stresses in underground geological storage conditions.Laboratory experiments will be performed at different scales (from grain to sample scales). Core samples will be x-ray scanned at HWU to understand their internal 3D microstructure and assess their transport properties (porosity and permeability) at pre- and post-TM experiments (O1). TM experiments will be performed at BGS to simulate elevated environmental conditions. Several deformation scenarios will be investigated to cover different industrial field operations. This lab-scale global sensing data will be combined to petrographical analysis (O2) to correlate the spatiotemporal distribution of the lab-induced damage within the tested materials with the microstructural evolution. Moreover, similar grain-scale experiments with syn-deformation monitoring (x-rays) are possibly planned to unravel the micro-scale processes. Numerical modelling and machine learning techniques are nowadays used more frequently to predict the subsurfacesystem behavior. TM coupling calibrated Voronoi Grain Based Modelling (GBM) can capture micro-cracking as a mechanism of progressive damage, reproducing the stress-strain behavior of laboratory tests. Developing such models will help to understand how TM brittle damage develops across the scales, from grain-size cracking to rock mass fracturing, and its time dependency. This PhD project will build on the DEM developed by Woodman et al. (2021) to undertake notably a grain size and distribution sensitivity analyses in thermo-mechanical simulations (O3) to further assess the up scaling of laboratory data to field scale (O4).

在我们寻求脱碳的能源资源时，地下热量存储是关键参与者。但是，频繁的环状热机械（TM）应力变化在长时间的影响仍然很少，并且可能威胁到系统的寿命。该项目旨在通过在相关的环状TM加载条件下进行实验室和数值实验来填补这一空白，以研究此类系统中有针对性岩性的稳定性。为了应对能源过渡挑战，新的地下解决方案侧重于新的资源开发（地热）或存储（放射性废物，热量，热量和/或气体 - 地面气体储存，压缩空气储能，H，CO2）。所有这些应用都具有诱导新的，浅，周期性的局部热机械应力变化。该博士学位项目的范围是使用不同尺度的观测值对地下复合系统中靶向岩性的稳定性进行建模和预测，而这些岩性在长时间内经历了环状TM应力变化时。这项研究工作旨在了解谷物规模的变形如何有助于地下系统的全球响应以及如何控制这种响应以减少任何伴随的诱导危害。将实验室和数值实验结合的创新方法将应用于扩展对多孔岩石中热敏感的脆性变形过程的理解。数据将提供信息，以支持涉及周期性TM应力变化的现场尺度操作条件，并阐明潜在的级联浅层地质阵地。目标：O1：检查微结构变形与TM应力之间的关系。O2：收集，分析和模型TM一起数据。O3：将现有的DEM代码从UDEC转移和改进开源并进行晶粒尺寸敏感性分析。O4：提供相关数据，以告知地下地质存储条件下与TM应力相关的风险。实验室将在不同的尺度上进行实验（从谷物到样品比例）。核心样品将在HWU扫描X射线，以了解其内部3D微观结构，并在TM实验前和TM实验（O1）上评估其运输特性（孔隙率和渗透率）。 TM实验将在BGS上进行，以模拟升高的环境条件。将研究几种变形方案，以涵盖不同的工业现场操作。该实验室规模的全球感应数据将合并到岩岩分析（O2），以将测试材料中实验室诱导的损伤的时空分布与微结构进化相关联。此外，可能计划揭开微尺度过程的类似晶尺度实验（X射线）。如今，数值建模和机器学习技术的使用更频繁地预测亚面性系统行为。 TM耦合校准的基于Voronoi晶粒的建模（GBM）可以捕获微裂缝作为渐进损伤的机制，从而再现实验室测试的应力应变行为。开发此类模型将有助于了解TM脆性损伤如何在整个尺度上产生，从晶粒大小的裂纹到岩石质量压裂以及其时间依赖性。该博士学位项目将基于Woodman等人开发的DEM。 （2021）在热机械模拟中明显进行晶粒尺寸和分布敏感性分析（O3），以进一步评估实验室数据对现场尺度（O4）的提高缩放。