Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada.
Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada.
J Contam Hydrol. 2021 Feb;237:103755. doi: 10.1016/j.jconhyd.2020.103755. Epub 2020 Dec 9.
In situ thermal recovery is utilized extensively for unconventional bitumen extraction in the Cold Lake-Beaver River (CLBR) basin in Alberta, Canada. Public health concerns have been raised over potable groundwater contamination and arsenic release adjacent to these operations within the CLBR basin, which have been linked to subsurface heating of aquifer sediments. Under localized heated conditions, As-bearing aquifer sediments have been shown to undergo water-rock interactions and release constituents at near neutral pH conditions; however, release mechanisms have yet to be conclusively reported. To investigate the hydrogeochemical processes of aquifer heating and solute transport in detail, this study applies a novel heated column design to mimic saturated aquifer materials in contact with a thermal recovery well while constraining flow and geochemical conditions. Two column experiment scenarios were considered using: 1) quartz [SiO] sand with 0.6 wt% pyrite [FeS]; and 2) aquifer sediments collected from the CLBR region. Heated temperature gradients between 50 °C and 90 °C were maintained within a 0.6 m section of the 3 m column with a flow rate of one pore volume per week. During heated low oxygen (<3 mg L) conditions, results generally show increases in pH, Al, As, B, Mn, Mo, Si and Zn concentrations within and downgradient of the column heating section. Constituent release is primarily attributed to thermal desorption from Fe oxides, clay and silicate mineral dissolution, competitive anion exchange, and increased mixing. Overall results suggest that these mechanisms are responsible for increasing constituent concentrations in groundwater adjacent to in situ thermal recovery operations.
原位热回收技术在加拿大阿尔伯塔省冷湖-比弗河（CLBR）盆地的非常规沥青开采中得到了广泛应用。由于 CLBR 盆地内这些作业区附近的饮用水地下水受到污染和砷释放，引起了公众健康方面的担忧，这与含水层沉积物的地下加热有关。在局部加热的条件下，含砷含水层沉积物已被证明会发生水岩相互作用，并在近中性 pH 条件下释放出成分；然而，释放机制尚未得到明确报告。为了详细研究含水层加热和溶质运移的地球化学过程，本研究采用了一种新颖的加热柱设计，模拟与热回收井接触的饱和含水层材料，同时约束流动和地球化学条件。本研究考虑了两种柱实验方案：1）含有 0.6wt%黄铁矿[FeS]的石英[SiO]砂；2）从 CLBR 地区采集的含水层沉积物。在 3 米长的柱体 0.6 米段内保持 50°C 至 90°C 的加热温度梯度，流速为每周一个孔隙体积。在加热低氧(<3mg/L)条件下，结果通常显示柱体加热段内及下游 pH、Al、As、B、Mn、Mo、Si 和 Zn 浓度增加。成分释放主要归因于 Fe 氧化物、粘土和硅酸盐矿物溶解、竞争阴离子交换和混合增加的热解吸。总体结果表明，这些机制是导致原位热回收作业区附近地下水中成分浓度增加的原因。
