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: 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=689311
• 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，从大气对流到炉灶上热水壶升起的蒸汽。不太明显但同样重要的是多孔介质内的浮力驱动的流动，其中热/冷流体通过固体颗粒之间的间隙空间。事实上，多孔介质内的浮力对流与能源系统有关，例如能源系统。热能储存、提高石油采收率的方法，例如蒸汽辅助重力排水或循环蒸汽吞吐，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，这些方法是由电力和石油的生产。*****这里提出的研究虽然是基础性的，但最受后一个例子的启发。为此，必须确定注入地层中的二氧化碳或酸性气体将保持永久封存的精确条件。尽管有多种机制可以使注射液固定（毛细管捕集等），但二氧化碳和酸性气体比含水层盐水更具浮力，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，它决定了地质封存项目所需的公共和私人资本的大量支出实际上是否合理。******在我的研究中，我将利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。将实施三个相互关联的项目。首先，我将考虑浮力羽流对倾斜界面的冲击，其中流体分别流过下面和上面的层有容易和困难的时间。这模拟了一种情况，其中一股浮力二氧化碳或酸性气体撞击具有相对较小渗透率的（可能破裂的）盖岩层。对于这个基础流量，并且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。尽管溶解注射液的体积很小，但预计对流动动力学的影响很大。最后，再次与实际流量一致，我将具体考虑含水层盐水中二氧化碳或酸性气体的有限混溶性。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以适应盆地规模的地质算法，这些算法缺乏足够的分辨率来充分描述精细空间尺度的流动细节。相反，需要对注入物排水、平流和溶解之间的权衡进行参数化。为此，该研究的更广泛目标是以对其他研究人员、行业从业者、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。 **