Impacts of stray gas migration on shallow groundwater: insights from laboratory experiments and numerical modelling

杂散气体运移对浅层地下水的影响：实验室实验和数值模拟的见解

• 批准号: 506784-2017
• 负责人: Mumford, Kevin
• 金额: $ 11.92万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Strategic Projects - Group
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=693933
• 关键词: Impacts; stray; gas; migration; shallow

The combination of horizontal drilling and multi-stage hydraulic fracturing has created a significant shift in global energy production, increasing the use and availability of natural gas through new technologies that allow the extraction of gas from previously inaccessible formations. Unconventional natural gas (shale gas) resources exist across Canada, but expansion has been accompanied by concern over potential threats to water resources. Research concerning these potential threats has not kept pace with the surge in development, and public concern, along with gaps in our understanding of controlling processes and the associated risks, is a significant impediment to further development in Canada. One potential risk is the leakage of gas (mostly methane) from deeper zones to shallow aquifers by gas flow outside the surface casing of an inadequately sealed or damaged wellbore. This free gas can dissolve into the surrounding groundwater leading to chemical and biological reactions that reduce groundwater quality. Focused research is needed to better understand factors influencing stray gas migration and dissolved gas transport to develop best practices for risk management and monitoring for potential effects on groundwater quality. This study will use a combination of high-resolution laboratory experiments and advanced numerical models to investigate the effects of stray gas migration on shallow groundwater. One-dimensional and two-dimensional experiments will track gas flow and dissolution using visual techniques as well as the analysis of gas and water samples. Analysis will include stable isotopes to assess reactions occurring in both the saturated and unsaturated zones. Numerical simulations using two different approaches will be compared to the experimental results and to each other, to assess model capabilities and develop new techniques. Additional simulations will investigate larger-scale, longer-term field scenarios to develop monitoring strategies and establish a framework for risk assessment under different geological and hydrogeochemical conditions.

水平钻井和多级水力压裂的结合使全球能源生产发生了重大转变，通过新技术增加了天然气的使用和可用性，这些新技术允许从以前无法进入的地层中提取天然气。 加拿大各地都有非常规天然气（页岩气）资源，但在扩张的同时，人们对水资源的潜在威胁感到担忧。 关于这些潜在威胁的研究没有跟上发展的步伐，公众的关注，沿着我们对控制过程和相关风险的理解上的差距，是加拿大进一步发展的重大障碍。 一个潜在的风险是，由于未充分密封或损坏的井筒的表层套管外的气体流动，气体（主要是甲烷）从较深的区域泄漏到浅层含水层。 这种游离气体可以溶解到周围的地下水中，导致化学和生物反应，降低地下水质量。 需要进行重点研究，以更好地了解影响杂散气体迁移和溶解气体迁移的因素，从而制定风险管理和监测对地下水质量潜在影响的最佳做法。 本研究将使用高分辨率的实验室实验和先进的数值模型相结合，调查杂散气体迁移对浅层地下水的影响。 一维和二维实验将使用可视化技术跟踪气体流动和溶解，以及气体和水样的分析。 分析将包括稳定同位素，以评估饱和区和非饱和区发生的反应。 使用两种不同方法的数值模拟将与实验结果进行比较，并相互比较，以评估模型能力和开发新技术。 更多的模拟将调查更大规模、更长期的实地情景，以制定监测战略，并建立不同地质和水文地球化学条件下的风险评估框架。