Darcy-scale dynamics of microscopically fluctuating interfaces

在最近的一份政府报告《英国石油和天然气-企业和政府行动》中，强调“到2040年代，英国70%的能源需求仍有可能由石油和天然气满足”，因此，从战略上讲，“最大限度地提高国内石油和天然气的供应量”。与进口相比，这将提高英国能源需求的弹性和安全性。与此同时，根据2014年世界能源展望报告，现有的二次采油方法在油田因“枯竭”而被放弃并转向新的勘探时仍有30%至60%的石油未被回收。这既低效又不环保。为了达到未采收的石油，并降低向新油田扩张的速度，直到可再生能源发电成为经济上可行的替代方案，有必要开发高效的提高石油采收率（EOR）方法。EOR的重点是回收被困在多孔岩石中的油滴，称为“神经节”，这些油滴在注水“二次开采阶段”后仍然被卡住。EOR的目的是通过一些额外的物理机制来动员神经节。相反的问题是二氧化碳封存;这是一个旨在减缓气候变化速度的过程。在那里，绝对必要的是，被泵入多孔层的二氧化碳体积保持在那里，而不会逃逸回大气中。在每种情况下，试错法评估回收或储存的效率是非常昂贵的，因此，在这里，理论家有一个独特的作用，发挥开发一个预测的数学模型，将可靠地描述动员的条件和动态的动员截留流体体积在不同的多孔基质。这项研究旨在解决这一双重问题。由于最近的两个事态发展，这一点成为可能：- 剑桥斯伦贝谢古尔德研究中心的一项实验发现，即使在外部强迫稳定的情况下，也可以通过单个孔隙的规模波动来调动多孔岩石中的神经节-该项目的研究人员开发了一个新的概念框架，用于描述湿润锋的传播，首次描述了极不寻常的（“异常”）液体侵入多孔固体的状态，这两个发展的协同作用开辟了一条道路，第一个可靠的预测模型描述了多孔固体中神经节的稳定性和动力学。油田改造变化的潜力已得到行业的认可，全球领先的石油和天然气行业技术解决方案供应商斯伦贝谢已通过发布其实验数据来支持该项目（保守估计为715，000英镑）以及其工作人员的帮助来解释它们（工作人员时间为15，000英镑）以及参与这项工作的PDRA的培训。在理论方面，所提出的工作解决了多相系统力学中的一些基础研究挑战，例如将孔隙尺度信息转化为宏观（达西尺度）模型的属性，以及流域拓扑结构中的过渡建模（神经节的破裂，它们的合并）。这方面的进展将对多相系统力学产生重大的方法论影响，远远超出多孔介质中流动的研究。拟议研究的新奇和冒险程度最好地说明了这一事实，即即使知道构成该项目基础的上述两项发展，仍然不可能甚至定性地预测其协同作用的效果。如果得到支持并取得成功，该项目将为我们对多相系统的理解提供一个飞跃性的进步，并通过斯伦贝谢立即应用结果。

In a recent Government report "UK Oil and Gas - Business and Government Action", it is stressed that "70% of British energy requirements [are] still likely to be met by oil and gas into the 2040s", so that strategically "maximizing domestic supplies of oil and gas [...] leads to increased resilience and security for the UK's energy needs when compared with imports". At the same time, according to the World Energy Outlook Report of 2014, existing methods of secondary oil recovery still leave from 30 to 60% of oil unrecovered when an oilfield is abandoned as 'exhausted' and the exploration moves to a new one. This is both inefficient and environmentally unfriendly. To reach the unrecovered oil and reduce the pace of expansion into new oilfields until renewable power generation becomes an economically viable alternative, it is necessary to develop efficient methods of Enhanced Oil Recovery (EOR). EOR is focused on recovering oil blobs trapped in the porous rock, known as 'ganglia', that remain stuck after the water-flooding 'secondary recovery stage'. The aim of EOR is to mobilize the ganglia by some additional physical mechanisms. The opposite problem is carbon dioxide sequestration; a process aimed at reducing the pace of climate change. There, it is absolutely essential that carbon dioxide volumes pumped into a porous layer remain there without escaping back into the atmosphere. In each case, the trial-and-error assessment of the efficiency of recovery or storage is prohibitively expensive, so that here theoreticians have a unique role to play by developing a predictive mathematical model that would reliably describe the conditions for mobilization and the dynamics of mobilized trapped fluid volumes in different porous matrices. The proposed research aims at addressing this dual problem. It has become possible as a result of two recent developments:- an experimental discovery at Schlumberger Gould Research Centre, Cambridge that the ganglia trapped in a porous rock can be mobilized by fluctuations on the scale of the individual pores which can be generated even when the external forcing is steady - a new conceptual framework for describing the propagation of wetting fronts, developed by the project's investigators, which for the first time describes highly unusual ('anomalous') regimes of invasion of liquids into porous solids, that were discovered experimentally two decades ago.The synergy of these two developments opens a way to the first reliable predictive model describing the stability and dynamics of ganglia in porous solids. The potential for the field-transforming changes has been recognized by industry, and Schlumberger, the world's leading supplier of technology solutions for the oil and gas industry, has offered to support the project by releasing its experimental data (conservatively estimated at £715,000 to generate) and the help of its staff to interpret them (£15,000 in the staff time) as well as training of the PDRAs involved in this work. On the theoretical side, the proposed work addresses a number of fundamental research challenges in the mechanics of multiphase systems such as the translation of the pore-scale information into the properties of a macroscopic (Darcy-scale) model and the modelling of transitions in the topology of the flow domain (breakup of ganglia, their coalescence). Advances here will make a significant methodological impact on mechanics of multiphase system well beyond the study of flows in porous media. The degree of novelty and adventure in the proposed research is best illustrated by the fact that, even knowing the two developments listed above that form the basis of the project, it is still impossible to even qualitatively predict the effect of their synergy. If supported and successful, the project offers a step-change advance in our understanding of multiphase systems and, via Schlumberger, an immediate application of results.