Low-enthalpy geothermal systems in the Western Canadian Sedimentary Basin

加拿大西部沉积盆地的低焓地热系统

• 批准号: RGPIN-2022-04502
• 负责人: Hollaender, Hartmut
• 金额: $ 3.13万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=749357
• 关键词: Low; enthalpy; geothermal; systems; Western

Canada has enormous geothermal resources which could supply the country with a renewable and clean source of power. Traditionally, fluid temperatures >150°C are used to produce electricity, which require deep boreholes in sedimentary basins such as the Western Canadian Sedimentary Basin (WCSB). However, low-enthalpy, low-temperature (<150°C) resources can also be used in binary cycle power plants, which circulate a secondary fluid with a low boiling point. These geothermal power plants have great potential in sedimentary basins to provide base load electricity. However, its current use is limited worldwide because the geothermal use of sedimentary basins is new and barely tested. As such, substantial knowledge gaps remain related to thermal, hydraulic, geomechanical, and (geo)chemical (THMC) behavior of fluids and reservoirs. Geochemical and temperature data from boreholes are often scarce or contain high uncertainties. This has led to complications and failures when deep geothermal reservoirs have been targeted in the past (e.g. Hesshaus et al. 2013). Additionally, the systems require significant financial investment so that field testing is limited, and knowledge development is based on numerical modeling. Unfortunately, several of the numerical models cannot be verified against measurements because such benchmarks are unavailable. A novel attempt is to use evaporite formations such as Prairie Evaporite in the WCSB for geothermal systems since these formations have positive thermal anomalies. However, these formations are highly soluble and salt minerals can self-heal so that the permeability of the geothermal reservoir will change throughout its operation. My envisioned research program aims for a better, natural science-based approach to model the development of geothermal energy, including from highly saline environments. My current proposed research will focus on three areas: i) develop physically based benchmarks for groundwater flow near evaporite formations, ii) assess impact of mineral dissolution and precipitation on reservoir permeability, and iii) assess impact of geomechanical processes on reservoir permeability. I will use coupled THMC modeling to better understand flow and transport occurring in deep geothermal wells. The highly saline systems require careful consideration of fluid density, dispersivity, geochemical reactions, and changes in permeability. The permeability of these formations must be increased by hydraulic stimulation. Past work from my group characterized host rocks, the physics involved in the breakthrough technology, and the fluid flow and heat transport in single fractures and at reservoir scale. The proposed research will expand our findings to evaporite formations and develop the physics to integrate self-healing to allow for fully coupled THMC modeling. The results will contribute to wider acceptance and deployment of this technology due to be higher predictability of processes in deep geothermal reservoirs.

加拿大拥有丰富的地热资源，可以为该国提供可再生和清洁的电力来源。传统上，>150°C 的流体温度用于发电，这需要在加拿大西部沉积盆地 (WCSB) 等沉积盆地中进行深钻孔。然而，低热函、低温（<150°C）资源也可用于循环低沸点二次流体的二元循环发电厂。这些地热发电厂在沉积盆地中具有提供基本负荷电力的巨大潜力。然而，它目前的使用在世界范围内受到限制，因为沉积盆地的地热利用是新的并且几乎没有经过测试。因此，在流体和储层的热、水力、地质力学和（地球）化学（THMC）行为方面仍然存在巨大的知识差距。来自钻孔的地球化学和温度数据通常稀缺或包含高度不确定性。当过去以深层地热储层为目标时，这会导致复杂化和失败（例如Hesshaus等人，2013年）。此外，这些系统需要大量的财务投资，因此现场测试受到限制，并且知识开发基于数值建模。不幸的是，一些数值模型无法根据测量进行验证，因为此类基准不可用。一项新颖的尝试是将蒸发岩地层（例如 WCSB 中的草原蒸发岩）用于地热系统，因为这些地层具有正热异常。然而，这些地层具有高度可溶性，并且盐矿物可以自我修复，因此地热储层的渗透率在其运行过程中会发生变化。我设想的研究计划旨在采用更好的、基于自然科学的方法来模拟地热能的开发，包括来自高盐环境的地热能。我目前提出的研究将集中在三个领域：i）为蒸发岩地层附近的地下水流开发基于物理的基准，ii）评估矿物溶解和降水对储层渗透性的影响，以及iii）评估地质力学过程对储层渗透性的影响。我将使用耦合 THMC 建模来更好地了解深层地热井中发生的流动和传输。高盐度系统需要仔细考虑流体密度、分散性、地球化学反应和渗透率的变化。这些地层的渗透性必须通过水力增产来增加。我的团队过去的工作描述了主岩、突破技术所涉及的物理原理，以及单裂缝和储层尺度的流体流动和热传输。拟议的研究将把我们的发现扩展到蒸发岩层，并开发整合自修复的物理学，以实现完全耦合的 THMC 建模。由于深层地热储层过程的可预测性更高，这些结果将有助于该技术的更广泛接受和部署。