Multiphase fracturing of deformable media

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.

The primary purpose of the proposed project is to uncover new knowledge of a fundamental nature, thereby contributing to the scientific advancement of several disciplines including complex/soft matter physics, geoscience, chemical and petroleum engineering. The establishment of the Complex Flow Lab and a new line of experimental research at Swansea University will generate new collaborative activity with academic research groups in the UK and locally in South Wales.

The project is expected to generate mid- to long term industrial/economic impact in the UK energy sector. The results will contribute to development of new unconventional technologies for shale gas recovery and CO2 geo-sequestration. Industrial R&D of these technologies will depend on a sound understanding of the basic physical mechanisms at play; the type of output that will be generated by this project. The UK sits on a large shale gas resource, some of which is geographically located in the South Wales region. Local industry involved in these projects will benefit from a strong academic activity in this field, with strong potential for future collaboration and joint projects, and access to educated graduates with highly relevant training and skills.

Positive environmental impact related to carbon geo-sequestration will result from gained knowledge of CO2 fracturing and migration. A future large scale implementation of such a technology would contribute to a reduction of CO2 emissions and associated global warming effects.

The research activity that the project generates will be used to motivate teaching at the college. Experimental rigs developed with funding from this project will later be utilized as demonstration and lab experiments and the project will as such impact positively on the education and training of Swansea University Environmental and Chemical Engineering students.

We have in the past had considerable success actively engaging with the wider community. The public interest in the topic of the study, and the inherent visual impact of the work, provide ample opportunity for outreach to the public via popular science media and other news and educational fora. Results, images and news will be shared on a web page we plan to set up for the Complex Flow Lab , and movies will be posted on a designated Youtube channel.