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.

加拿大拥有巨大的地热资源，可以为该国提供可再生和清洁的能源。传统上，流体温度在150°C左右用于发电，这需要在沉积盆地（如西加拿大沉积盆地（WCSB））的深钻孔。然而，低焓、低温（<150°C）资源也可用于二元循环电厂，即循环低沸点的二次流体。这些地热发电厂在沉积盆地具有提供基负荷电力的巨大潜力。然而，目前在世界范围内的使用是有限的，因为沉积盆地的地热利用是新的，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，仍然存在大量的知识空白。钻孔的地球化学和温度数据往往很少或具有很高的不确定性。在过去，当深层地热储层被瞄准时，这导致了复杂性和失败（例如Hesshaus et al. 2013）。此外，该系统需要大量的财务投资，因此现场测试是有限的，并且知识开发是基于数值模拟的。不幸的是，由于没有这样的基准，一些数值模型无法根据测量结果进行验证。一种新颖的尝试是利用蒸发岩地层，如WCSB的Prairie蒸发岩作为地热系统，因为这些地层具有积极的热异常。然而，这些地层是高度可溶的，盐矿物可以自愈，因此地热储层的渗透率在整个开采过程中都会发生变化。我设想的研究项目旨在采用一种更好的、基于自然科学的方法来模拟地热能源的开发，包括从高盐环境中开发地热能源。我目前提出的研究将集中在三个方面：1)为蒸发岩地层附近的地下水流动制定基于物理的基准；2)评估矿物溶解和降水对储层渗透率的影响；3)评估地质力学过程对储层渗透率的影响。我将使用耦合THMC模型来更好地理解深层地热井中的流动和输送。高盐体系需要仔细考虑流体密度、分散性、地球化学反应和渗透率变化。这些地层的渗透率必须通过水力增产来提高。我的团队过去的工作描述了寄主岩石，突破性技术所涉及的物理特性，以及单个裂缝和储层尺度的流体流动和热输运。拟议的研究将把我们的发现扩展到蒸发岩地层，并发展物理学来整合自我修复，以允许完全耦合的THMC建模。由于深层地热储层过程的可预测性更高，该结果将有助于该技术的广泛接受和部署。