Multiphase fracturing of deformable media

近年来，水力压裂技术（俗称“fracking”）改变了美国的能源行业，而英国目前正处于大规模开发一种重要陆上页岩气资源的边缘。水力压裂包括注入加压压裂液，克服储层岩石的围压和抗拉强度，打破在不透水的页岩中充当导电通道的裂缝。水基压裂液与宿主流体混溶，注入速度必须快于其在页岩层内的耗散速度。拟议的项目解决了另一种压裂机制：多相压裂，其中气相穿透水饱和多孔介质。与传统压裂（单相过程）不同，作用于气/液/颗粒界面的毛细力预计将在裂缝生长动力学中发挥重要作用。该项目将侧重于详细了解控制多相裂缝生长的基本物理机制。一个定制的实验流动设备将用于研究向水饱和、可变形的多孔介质中注入加压气体后裂缝的生长动力学和裂缝网络模式的演变。我们试图回答的问题包括：表面张力、润湿特性和晶粒尺寸如何影响裂缝尖端的生长活性？是否可以使用实验参数（如毛细力、压缩率和注入速率）来控制不断变化的裂缝模式形成（以及延伸到裂缝带的渗透率）？第二个目标是开展CO2压裂的第一个基础研究，重点研究压裂过程与随后孔隙空间宿主流体中CO2的吸收和扩散运输之间的复杂相互作用。使用二氧化碳作为非常规压裂液有可能获得高渗透率的裂缝带，增加甲烷的采收率，因为二氧化碳优先与颗粒表面结合，并且是页岩气开采和大规模二氧化碳地质封存的结合过程。

Hydraulic fracturing, colloquially known as "fracking", has transformed the US energy sector in recent years, and the UK is now on the brink of a potential large scale development of a significant onshore shale gas resource. Fracking involves the injection of pressurized fracturing fluid that overcomes the confining pressure and tensile strength of the reservoir rock, breaking open fissures that act as conductive pathways in the otherwise impermeable shale. The water-based fracturing fluid is miscible with the host fluid, and must be injected at a faster rate than it dissipates within the shale play.The proposed project addresses an alternative fracturing mechanism: multiphase fracturing, where a gaseous phase penetrates a water saturated porous media. Unlike traditional fracking (a single phase process), the capillary forces acting at the gas/liquid/grain interface is expected to play a significant role in the fracture growth dynamics.This project will focus on developing a detailed understanding of the fundamental physical mechanisms that govern multiphase fracture growth. A custom made experimental flow rig will be used to study the fracture growth dynamics and the evolving fracture network pattern upon injection of a pressurized gas into a water-saturated, deformable porous media. Questions we seek to answer include: How does surface tension, wetting properties and grain size influence growth activity at the fracture tips? Can the evolving fracture pattern formation (and by extension the permeability of the fracture zone) be controlled using experimental parameters such as capillary forces, compressibility and injection rate?A second objective is to undertake a first fundamental study of CO2 fracturing, focusing on the complex interplay between the fracturing process, and the subsequent absorption and diffusive transport of CO2 within the pore space host fluid. Using CO2 as an unconventional fracturing fluid has potential for achieving high permeability fracture zones, increased methane recovery as CO2 binds preferentially to grain surfaces, and a combined process of shale gas recovery and large scale CO2 geo-sequestration.