Mathematical Modeling of the Fate of the Injected and In-Situ Generated Gases in Subsurface Geological Formations

在浅层油砂沥青的溶剂辅助热开采中，注入地下地质地层和溶剂的二氧化碳(CO2)泄漏的风险是主要的环境挑战之一。这些化学物质在地下的永久捕获可以通过几种捕获机制发生，如溶解、残留相和矿化。近年来，二甲醚等互溶于油酸和水相的生物衍生化学物质在溶剂辅助热回收沥青方面引起了人们的兴趣。此外，由于沥青在高于200摄氏度的高温下蒸汽，油砂中会产生或释放出大量的甲烷、二氧化碳和硫化氢。虽然为回收沥青而注入的溶剂与产出的流体一起被部分回收，但这些化学品中的一小部分将与产生的气体一起留在地下，长期存在泄漏到地下水的潜在风险。我的研究重点是开发模型，研究地下注入或原位生成的化学物质的长期命运。虽然在过去十年中取得了进展，但还需要进一步研究，以更好地了解捕获机制，并深入了解注入的二氧化碳和其他化学品的长期命运。我的研究计划旨在促进对基本捕获机制的了解，如对流溶解和二氧化碳以及地下注入的化学品或原位生成的化学品的长期归宿。特别令人感兴趣的是开发可供油砂行业、政府组织和政策制定者使用的计算工具，用于二氧化碳风险评估和现场从油砂中提取沥青的溶剂注入的环境影响评估。最近，已经开发了一些模型来估计压力卤水和二氧化碳从储存点的泄漏率。然而，估计注入和现场产生的化学品渗漏率的工具的开发仍处于非常初级阶段。特别是，应用于现场油砂开采过程的泄漏模型还很缺乏。此外，寻找通过加速对流溶解来加速二氧化碳的溶解捕获和降低泄漏风险的方法还需要进一步的研究。这项研究发展了知识，并提供了工具，帮助安全地实施二氧化碳和酸性气体封存，并在知情的情况下应用溶剂从油砂中就地提取沥青。特别是，对注入化学品的长期命运的新见解，潜在泄漏途径和机制的确定，以及加速溶解捕获的策略将是这项研究的新贡献。此外，该项目还为5名本科生、2名硕士和2名博士生提供培训。

Risk of leakage of carbon dioxide (CO2) injected into subsurface geological formations and solvents used in solvent-aided thermal recovery of bitumen from shallow oil sands is one of the major environmental challenges. Permanent trapping of these chemicals in subsurface may occur by several trapping mechanisms such as dissolution, residual phase, and mineralization. Recently, bio-derived chemicals such as dimethyl ether with mutual solubility in oleic and aqueous phases have gained interest in solvent-aided thermal recovery of bitumen. In addition, significant volumes of methane, carbon dioxide, and hydrogen sulfide are generated or liberated from oil sands as a result of steaming of bitumen at high temperatures greater than 200oC. While injected solvents for bitumen recovery are partially recovered with the produced fluids, a fraction of these chemicals along with the generated gases will remain in subsurface with potential risk of leakage to the groundwater in long term. The focus of my research is to develop models to study the long-term fate of the injected or in-situ generated chemicals in subsurface. While progress has been made in the past decade, further research is required to develop a better understanding of the trapping mechanisms and gain insight into the long-term fate of the injected CO2 and other chemicals. My research program aims to advance the knowledge of fundamental trapping mechanisms such as convective dissolution and long-term fate of CO2 and injected chemicals or in-situ generated chemicals in subsurface. Of particular interest is the development of computational tools that can be used by oil sands industry, governmental organizations, and policy makers for risk assessment of CO2 and environmental impact assessment of solvent injection for in-situ extraction of bitumen from oil sands. Recently, models have been developed for estimation of the rate of leakage of pressurized brine and CO2 from storage sites. However, development of tools for estimation of the rate of leakage of the injected and in-situ generated chemicals is still very much in its infancy. In particular, leakage models with applications to in-situ oil sands extraction processes are lacking. In addition, finding ways to accelerate solubility trapping of CO2 and reduce risk of leakage by acceleration of convective dissolution requires further research. This research develops knowledge and provides tools that help safe implementation of CO2 and acid gas sequestration as well as informed application of solvents for in-situ bitumen extraction from oil sands. In particular, new insights into the long-term fate of injected chemicals, determination of potential leakage pathways and mechanisms, and strategies to accelerate solubility trapping will be novel contributions of this research. In addition, this program provides training for 5 Undergraduate, 2 MSc, and 2 PhD students.