Localized buoyant convection in porous media: plumes and dispersion

多孔介质中的局域浮力对流：羽流和弥散

• 批准号: RGPIN-2019-04581
• 负责人: Flynn, Morris
• 金额: $ 3.35万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737714
• 关键词: Localized; buoyant; convection; porous; media

Examples of buoyancy-driven flow abound in nature, industry and everyday life from atmospheric convection to the steam that rises from a hot kettle on the stovetop. Less obvious, but equally important, is buoyancy-driven flow within a porous medium whereby hot/cold fluid navigates through the interstitial spaces between solid grains. Indeed, buoyant convection within porous media is relevant to energy systems e.g. thermal energy storage, methods of enhanced oil recovery such as steam-assisted gravity drainage or cyclic steam stimulation, and the geological sequestration of either carbon dioxide (CO2) or acid-gas (a mixture of CO2 and hydrogen sulfide), which result from the production of electricity and oil. The research proposed here, though fundamental in focus, is motivated most especially by this latter example. To this end, one must define the precise conditions under which the CO2 or acid-gas injected into formation will remain permanently sequestered. Although there are a variety of mechanisms that allow the injectate to become immobilized (capillary trapping, etc.), CO2 and acid-gas are more buoyant than, say, aquifer brine and tend therefore to rise from one geological layer to the next. The competition between immobilization and vertical migration, far from being of purely academic interest, determines whether the large outlays of public and private capital necessary for geological sequestration projects are, in fact, justified. In my research, I will use theory and laboratory experiment to advance our current understanding of buoyant convection in porous media. Three interconnected projects will be pursued. Firstly, I will consider the impingement of a buoyant plume on a sloping interface where the fluid has an easy and difficult time, respectively, flowing through the layers below and above. This mimics a scenario in which a plume of buoyant CO2 or acid-gas strikes a (possibly fractured) cap rock layer having a comparatively small permeability. To this base flow, and consistent with real geophysical scenarios, I will then allow some fraction of the injectate to dissolve into the ambient reservoir fluid. Although the volume of dissolving injectate is small, the impact on the flow dynamics is expected to be large. Finally, and again consistent with real flows, I will then specifically account for the limited miscibility of CO2 or acid-gas in aquifer brine. Doing so requires accounting for surface tension among other effects. Model predictions and measured data may be adapted into basin-scale geological algorithms that lack sufficient resolution to fully describe flow details at fine spatial scales. Instead, parameterizations of the tradeoffs between injectate drainage, advection and dissolution are required. To this end, a broader objective of the research is to collect, interpret and synthesize data in a way that is meaningful to other researchers, industry practitioners, regulators and policy makers.

浮力驱动流动的例子在自然界、工业和日常生活中比比皆是，从大气对流到从炉灶上的热水壶中升起的蒸汽。不太明显但同样重要的是多孔介质中的浮力驱动流动，热/冷流体通过固体颗粒之间的间隙空间航行。实际上，多孔介质内的浮力对流与能量系统相关，例如热能储存、诸如蒸汽辅助重力泄油或循环蒸汽刺激的提高石油采收率的方法，以及二氧化碳（CO2）或酸性气体（CO2和硫化氢的混合物）的地质封存，其产生于电力和石油的生产。这里提出的研究，虽然基本的重点，是最特别的动机是由后一个例子。为此，必须确定注入地层的CO2或酸性气体将保持永久隔离的精确条件。虽然有多种机制使注射物变得固定（毛细管捕获等），二氧化碳和酸性气体比含水层盐水更有浮力，因此倾向于从一个地质层上升到下一个地质层。固定化和垂直迁移之间的竞争远非纯粹的学术兴趣，它决定了地质固碳项目所需的大量公共和私人资本支出是否实际上是合理的。在我的研究中，我将使用理论和实验室实验来推进我们目前对多孔介质中浮力对流的理解。将进行三个相互关联的项目：首先，我将考虑浮力羽流在倾斜界面上的冲击，在该界面上，流体分别有一个容易和困难的时间，流过下面和上面的层。这模拟了一种情况，其中漂浮的CO2或酸性气体的羽流撞击具有相对较小渗透性的（可能断裂的）盖岩层。对于这个基流，并与真实的地球物理场景一致，我将允许注入物的一部分溶解到周围的储层流体中。尽管溶解注射物的体积小，但预期对流动动力学的影响大。最后，再次与真实的流量相一致，我将具体说明含水层盐水中CO2或酸性气体的有限溶解性。这样做需要考虑表面张力以及其他影响。模型预测和测量数据可能适用于盆地规模的地质算法，缺乏足够的分辨率，以充分描述流动细节在精细的空间尺度。相反，需要参数化的注射液排水，平流和溶解之间的权衡。为此，研究的一个更广泛的目标是以对其他研究人员、行业从业人员、监管机构和政策制定者有意义的方式收集、解释和综合数据。