Darcy-scale dynamics of microscopically fluctuating interfaces

在最近一份名为《英国石油和天然气--企业和政府行动》的政府报告中，强调“到本世纪40年代，石油和天然气仍有可能满足英国70%的能源需求”，从而从战略上“最大化国内石油和天然气供应[……]，与进口相比，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》的报告，现有的二次采油方法仍有30%至60%的石油未被回收，即油田因已耗尽而被放弃，勘探转移到新的油田。这既是低效的，也不环保的。为了开采未开采的石油并减缓向新油田扩张的步伐，直到可再生能源发电成为经济上可行的替代方案，有必要开发有效的提高石油采收率(EOR)方法。提高采收率的重点是回收滞留在这种被称为“神经节”的多孔岩中的油块，这些油块在注水“二次采油阶段”后仍然滞留。EOR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，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。在每一种情况下，回收或储存效率的试错评估费用都高得令人望而却步，因此在这里，理论家可以通过开发一个预测数学模型来发挥独特的作用，该模型将可靠地描述动员的条件和不同多孔基质中动员的被困液体体积的动态。拟议的研究旨在解决这一双重问题。这是最近两项发展的结果：-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，也可以通过单个孔隙的波动来动员困在多孔岩石中的神经节-由该项目的研究人员开发的描述湿润锋面传播的新概念框架，首次描述了20年前通过实验发现的液体侵入多孔性固体的极不寻常的(异常)状态。这两项发展的协同作用为第一个描述多孔性固体中神经节的稳定性和动力学的可靠预测模型开辟了一条道路。行业已经认识到了改变现场的可能性，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已经提出支持该项目，方法是公布其实验数据(保守估计生成的数据为GB 715,000)，并帮助其工作人员解释这些数据(工作人员时间为15,000 GB)，以及对参与这项工作的PDRA进行培训。在理论方面，拟议的工作解决了多相体系力学中的一些基本研究挑战，例如将孔尺度信息转换为宏观(达西尺度)模型的性质，以及对流域拓扑中的转变(神经节的破裂及其合并)进行建模。这方面的进展将对多相系统的力学产生重大的方法学影响，远远超出对多孔介质中流动的研究。拟议研究的新颖性和冒险程度最好地说明了一个事实，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，该项目将在我们对多相系统的理解方面取得突破性进展，并通过斯伦贝谢立即应用成果。

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.