Low-enthalpy geothermal systems in the Western Canadian Sedimentary Basin

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电力来源。传统上，流体温度> 150 ° C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，低焓、低温（<150 ° C）资源也可用于双循环发电厂，该发电厂循环低沸点的二次流体。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是有限的，因为沉积盆地的地热利用是新的，几乎没有测试。因此，在流体和储层的热、水力、地质力学和（地质）化学（THMC）行为方面仍然存在大量知识空白。来自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。这导致了过去针对深层地热储层的复杂性和失败（例如Hesshaus等人，2013）。此外，该系统需要大量的财政投资，使现场测试是有限的，知识的发展是基于数字建模。不幸的是，一些数值模型无法根据测量结果进行验证，因为没有这样的基准。一种新的尝试是使用蒸发岩地层，如草原蒸发岩在WCSB的地热系统，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，并且盐矿物可以自我修复，使得地热储层的渗透性在其操作过程中会发生变化。我设想的研究计划旨在更好地以自然科学为基础的方法来模拟地热能的开发，包括从高盐环境中开发。我目前提出的研究将集中在三个领域：i）开发蒸发岩地层附近地下水流的物理基准，ii）评估矿物溶解和沉淀对储层渗透性的影响，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，以更好地了解流动和运输发生在深地热威尔斯。高含盐系统需要仔细考虑流体密度、分散性、地球化学反应和渗透性的变化。这些地层的渗透性必须通过水力刺激来增加。我的团队过去的工作描述了主岩，突破性技术中涉及的物理学，以及单个裂缝和油藏规模的流体流动和热传输。拟议的研究将扩大我们的研究结果，蒸发岩地层和发展的物理整合自我修复，允许完全耦合THMC建模。研究结果将有助于更广泛地接受和部署这项技术，因为它对深层地热储层中的过程具有更高的可预测性。

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.