Free gas transport in the subsurface: Analogues and applications

地下自由气体传输：类似物和应用

• 批准号: RGPIN-2016-06509
• 负责人: Ryan, Cathryn
• 金额: $ 2.11万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=663967
• 关键词: Free; gas; transport; subsurface; Analogues

We know free gas transport occurs in the shallow subsurface because one can see its expression as bubbles in springs, wetlands, geysers, and as free gas ‘breakouts' during excavations and drilling. Yet we know little about free gas migration in the ‘shallow', or non-saline, groundwater zone. There is almost no mention of free gas transport in groundwater textbooks, and virtually no conceptual diagrams in either textbooks or the published literature. It is consequently difficult to design effective field approaches to identify, monitor, and mitigate gas fluxes. In essence we don't know what free gas transport ‘looks like' conceptually in the subsurface, nor do we know how to investigate or monitor for its occurrence.***Good scientific information on the nature and implications of free gas transport in the subsurface is hindering robust policy-making and public acceptability of development of two energy-related fields: carbon capture and storage (CCS) and fugitive methane gas migration (GM) around leaky petroleum wells***In CCS, supercritical phase CO2 is injected into deep geologic formations to curb anthropogenic releases to the atmosphere. Although a major environmental concern is free-phase gas leakage to surface, no field study has been conducted in this regard. More than 15 CCS operations exist, but none have been pushed to ‘failure', and hence no free gas escape observed. ***Unconventional oil and gas development has transformed the world's energy supply, but is impeded in many jurisdictions due to public opposition. Migration of fugitive gases (mainly methane) from the vertical section of oil and gas boreholes and into freshwater aquifers has been identified as the major concern for groundwater quality. The most common evidence for gas migration is either ‘surface casing vent flow' (inside the well casing) or surface-observable GM outside the casing. Regulators are currently struggling to define what GM means for water quality in freshwater aquifers that provide domestic well water supplies, and how GM be managed.***This work will study natural analogues where we know free gas transport in the shallow subsurface is occurring to improve our understanding of how to effectively detect, monitor, and remediate or manage free gases that are reaching fresh groundwater supplies and/or the ground surface. An extensive field program will be supported by specific lab studies. A parallel review of the distribution of non-hydrocarbon gases and abnormal pressuring in the Western Canadian Sedimentary Basin will provide regional context of free gas migration in recent geologic history.***The long term goals of this research are to develop a conceptual model that will guide free-gas migration investigations in the subsurface thus facilitating public understanding of energy industry activities, appropriate policy making, and efficient energy development that is environmentally responsible.*****

我们知道自由气体运输发生在浅层地下，因为我们可以看到它在泉水、湿地、间歇泉中的气泡表现，以及在挖掘和钻探过程中自由气体的“爆发”。然而，我们对“浅层”或不含盐的地下水区的自由气体运移知之甚少。地下水教科书中几乎没有提到自由气体输送，教科书和已发表的文献中也几乎没有概念图。因此，很难设计有效的现场方法来识别、监测和减轻气体通量。从本质上讲，我们不知道地下自由气体传输的概念“样子”，也不知道如何调查或监测它的发生。***关于地下自由气体运输的性质和影响的良好科学信息阻碍了两个能源相关领域的强有力的政策制定和公众可接受性的发展：碳捕集与封存（CCS）和泄漏油井周围的逸散甲烷气体迁移(GM) ***在CCS中，超临界阶段的二氧化碳被注入深层地质构造以抑制人为向大气释放。虽然一个主要的环境问题是自由相气体泄漏到地面，但在这方面还没有进行过现场研究。目前有超过15个CCS项目，但没有一个被推到“失败”的地步，因此没有观察到自由气体逸出。***非常规油气开发已经改变了世界能源供应，但由于公众的反对，在许多司法管辖区受到阻碍。从油气井垂直段向淡水含水层运移的逸出气体（主要是甲烷）已被确定为影响地下水质量的主要问题。天然气运移最常见的证据要么是“地面套管排气流”（在套管内），要么是套管外表面可观察到的GM。监管机构目前正在努力界定转基因对提供家庭井水供应的淡水含水层的水质意味着什么，以及如何管理转基因。***这项工作将研究自然类似物，我们知道浅层地下正在发生自由气体输送，以提高我们对如何有效检测、监测、修复或管理到达新鲜地下水供应和/或地表的自由气体的理解。广泛的实地计划将由具体的实验室研究支持。对加拿大西部沉积盆地非烃类气体分布和异常压力的平行回顾将为近期地质历史上的自由天然气运移提供区域背景。***本研究的长期目标是建立一个概念模型，该模型将指导地下自由天然气运移调查，从而促进公众对能源工业活动的理解，制定适当的政策，以及对环境负责的高效能源开发。*****