High-resolution analysis of seismo-thermo-hydro-mechanical processes in fractured rocks during hydraulic stimulation: model development, validation and application

水力增产过程中裂隙岩石的地震-热-水-力过程的高分辨率分析：模型开发、验证和应用

• 批准号: 456376654
• 负责人: Dr. Mohammad Javad Afshari Moein
• 金额: --
• 依托单位: Fachrichtung Geophysik
• 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/456376654?language=en
• 关键词: resolution; analysis; seismo; thermo; hydro

Enhanced Geothermal Systems (EGS) aim at extracting the heat stored in the earth’s crust by circulating fluids between injection and production boreholes. Ideal conditions are typically found in formations at depths between 2-5 km, where the flow rate is not sufficient for commercial geothermal plants and where temperatures are high (i.e. >>100°C). Hence, high-pressure fluid injection, known as hydraulic stimulation, is a commonly adopted technique to generate a connected fracture network that facilitates the fluid circulation. Hydraulic stimulation is typically accompanied by induced seismicity that may be felt by the public and even cause damages. The objective of this project is to provide a fundamental understanding of induced seismicity in fractured rocks that improves the ability to forecast and control the seismic risk. This project adopts the hypothesis that seismicity is jointly controlled by the fracture network geometry and the activated thermo-hydro-mechanical (THM) processes in geological systems. We will apply Discrete Fracture Networks (DFN) to represent the structural discontinuities and model the THM processes at high resolution. This project employs the datasets from recent small‐scale (decameter) stimulation experiments at the Grimsel Test Site in Switzerland and state-of-the-art numerical models to achieve the following: 1) test the effectiveness of high-resolution models to capture the seismic, hydraulic and mechanical processes observed with small-scale experiments; 2) link the geometrical attributes of a fracture network (such as fracture intensity, connectivity, length and spatial distribution) to spatial, temporal and magnitude distribution of induced seismicity; 3) propose and test a novel maximum possible magnitude forecast model that regards the joint impact of multiphysics processes dominating at site-specific geological conditions and operational constraints; 4) assess upscaling of the small-scale (decameter) high-resolution DFN models to simulate the reservoir-scale (kilometer) experiments. This research project is novel in addressing the injection-induced seismicity by high-resolution physics-based models and high-quality datasets derived from unique in-situ experiments. The proposed research has significant implications to promote the transition policy towards a renewable energy supply and contributes to advancing our knowledge about the triggering mechanisms of induced earthquakes.

增强型地热系统（EGS）旨在通过在注入井和生产井之间循环流体来提取地壳中储存的热量。理想的条件通常在2-5 km深度的地层中找到，其中流速对于商业地热发电厂来说是不够的，并且温度很高（即>>100°C）。因此，高压流体注入，称为水力增产，是一种常用的技术，以产生一个连接的裂缝网络，促进流体循环。水力刺激通常伴随着诱发的地震活动，公众可能会感觉到，甚至造成损害。该项目的目的是提供对断裂岩石中诱发地震活动的基本认识，以提高预测和控制地震风险的能力。本研究假设地震活动性受地质系统中裂隙网络几何形态和活化的热-水-力学（THM）过程共同控制。我们将应用离散裂缝网络（DFN）来表示结构不连续性并以高分辨率对THM过程进行建模。该项目采用了最近小规模的数据集（十）在瑞士Grimsel试验场进行的模拟试验和最先进的数值模型，以实现以下目标：1）测试高分辨率模型的有效性，以捕捉通过小规模试验观察到的地震、水力和机械过程; 2）将裂隙网络的几何属性联系起来（如断裂强度、连通性、长度和空间分布）与诱发地震活动的时空和震级分布的关系; 3）提出并测试一种新的最大可能震级预测模型，该模型考虑了在特定场地地质条件和操作限制下占主导地位的多物理过程的联合影响; 4）评估小尺度（decoupling）高分辨率DFN模型的升级，以模拟小尺度（公里）实验。该研究项目通过高分辨率的基于物理的模型和来自独特的原位实验的高质量数据集来解决注入诱发的地震活动性。拟议的研究具有重大意义，以促进向可再生能源供应的过渡政策，并有助于推进我们的知识诱发地震的触发机制。