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——商业和政府行动》中，强调“到21世纪40年代，英国70%的能源需求仍有可能由石油和天然气来满足”，因此，从战略上讲，“最大限度地提高国内石油和天然气供应[…]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》，当一个油田因“枯竭”而被放弃，并转向新的勘探时，现有的二次采油方法仍有30%至60%的石油未采收率。这既低效又不环保。在可再生能源发电成为一种经济可行的替代方案之前，为了开采未开采的石油并减少新油田的扩张速度，有必要开发有效的提高石油采收率（EOR）的方法。EOR的重点是回收被困在多孔岩石中的油团，即所谓的“神经节”，这些油团在注水“二次开采阶段”后仍被困在岩石中。提高采收率的目的是通过一些额外的物理机制来调动神经节。相反的问题是二氧化碳的封存；旨在减缓气候变化速度的进程。在那里，泵入多孔层的二氧化碳体积保持在那里而不逃逸到大气中是绝对必要的。在每种情况下，对回收或储存效率的试错评估都是非常昂贵的，因此，理论家可以通过开发预测数学模型来发挥独特的作用，该模型可以可靠地描述不同多孔基质中被动员的流体体积的动员条件和动态。拟议的研究旨在解决这一双重问题。最近的两项进展使之成为可能：剑桥斯伦贝谢古尔德研究中心的一项实验发现，即使在外部压力稳定的情况下，单个孔隙规模的波动也能调动被困在多孔岩石中的神经节；该项目研究人员提出了描述湿润锋面传播的新概念框架；它首次描述了20年前通过实验发现的液体侵入多孔固体的极不寻常（“异常”）状态。这两个发展的协同作用为描述多孔固体中神经节的稳定性和动力学的第一个可靠的预测模型开辟了道路。行业已经认识到油田改造的潜力，世界领先的石油和天然气行业技术解决方案供应商斯伦贝谢提供了支持该项目的实验数据（保守估计为715,000英镑），并帮助其员工解释这些数据（员工时间为15,000英镑），以及培训参与这项工作的pdra。在理论方面，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）模型的特性，以及对流域拓扑中的转换建模（神经节的破裂，它们的合并）。这方面的进展将对多相体系的力学产生重大的方法学影响，远远超出对多孔介质流动的研究。所提议的研究的新颖性和冒险性的程度最好地说明了这样一个事实，即即使知道上面列出的构成该项目基础的两个发展，仍然不可能定性地预测它们协同作用的效果。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阶梯式的进步，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.