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).

在我们寻求能源脱碳的过程中，地下热能储存是一个关键因素。然而，人们对长时间频繁循环热机械 (TM) 应力变化的影响仍知之甚少，并且可能会威胁系统的使用寿命。该项目旨在通过在相关循环TM加载条件下进行实验室和数值实验来填补这一空白，以研究此类系统中目标岩性的稳定性。为了应对能源转型挑战，新的地下解决方案侧重于新资源开采（地热）或储存（放射性​​废物、热量和/或气体 - 地下天然气储存、压缩空气能量储存、H、CO2）。所有这些应用的共同点是引起新的、浅的、周期性的局部热机械应力变化。该博士项目的范围是使用不同尺度的观测来模拟和预测地下复杂系统中目标岩性在长期遭受循环 TM 应力变化时的稳定性。这项研究工作旨在了解颗粒尺度变形如何影响地下系统的整体响应，以及如何控制这种响应以减少任何伴随的诱发危害。将采用结合实验室和数值实验的创新方法来扩展对多孔岩石热敏脆性变形过程的理解。这些数据将提供信息来支持涉及周期性 TM 应力变化的现场规模操作条件，并揭示潜在的级联浅层地质灾害。目标：O1：检查微观结构变形和 TM 应力之间的关系。O2：一起收集、分析和建模 TM 数据。O3：将现有 DEM 代码从 UDEC 转移到开源并进行粒度敏感性分析。O4：提供相关数据以告知相关风险 地下地质储存条件下的TM应力。实验室实验将在不同规模（从谷物到样品规模）下进行。岩心样本将在 HWU 进行 X 射线扫描，以了解其内部 3D 微观结构，并评估其在 TM 实验前后的传输特性（孔隙度和渗透率）（O1）。 TM 实验将在 BGS 进行，以模拟升高的环境条件。将研究几种变形场景以涵盖不同的工业现场操作。该实验室规模的全球传感数据将与岩相分析 (O2) 相结合，将受测试材料内实验室引起的损伤的时空分布与微观结构演化相关联。此外，可能计划进行类似的具有同步变形监测（X射线）的晶粒尺度实验来阐明微观过程。如今，数值建模和机器学习技术更频繁地用于预测地下系统行为。 TM 耦合校准的 Voronoi 晶粒建模 (GBM) 可以捕获微裂纹作为渐进损伤机制，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 脆性损伤如何在从粒度开裂到岩体破裂的各个尺度上发展，及其时间依赖性。该博士项目将建立在 Woodman 等人开发的 DEM 的基础上。 （2021）特别是在热机械模拟（O3）中进行晶粒尺寸和分布敏感性分析，以进一步评估实验室数据到现场规模（O4）的放大。