Multiphase fracturing of deformable media

Lead Research Organisation: Swansea University
Department Name: School of Engineering

Abstract

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.

Planned Impact

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.

Publications

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Ayaz Monem (2016) Two phase granular transport in cylindrical confinement in EGU General Assembly Conference Abstracts

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Campbell J (2017) Gas-Driven Fracturing of Saturated Granular Media in Physical Review Applied

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Campbell James (2015) Three-phase fracturing in granular material in EGU General Assembly Conference Abstracts

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Correas C (2018) Hydration induced morphological change on proppant surfaces employing a calcium-silicate cement system in Colloids and Surfaces A: Physicochemical and Engineering Aspects

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Dumazer G (2017) Self-Structuring of Granular material under Capillary Bulldozing in EPJ Web of Conferences

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Eriksen JA (2015) Bubbles breaking the wall: Two-dimensional stress and stability analysis. in Physical review. E, Statistical, nonlinear, and soft matter physics

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Eriksen JA (2015) Numerical approach to frictional fingers. in Physical review. E, Statistical, nonlinear, and soft matter physics

 
Description We developed new experimental techniques to study the gas driven fracturing of granular materials. We found that the fractures grow and divide by tip-splitting, forming spectacular branching tree-like structures. We discovered that the nucleation of a fracture event is determined by pore-scale fluid invasion, and that fracture expansion is limited by the frictional response in this system. We were able to develop new theoretical models that allowed us to predict the spatial density of the fracture pattern, a parameter that is of relevance to any industrial application aimed at permeability generation. Further, we discovered that the rate of gas injection is important as the system exhibits a dynamic transition at a critical rate. Below this rate, the fractures are rate-independent and dominated by frictional stick-slip dynamics. Above the critical rate the material fluidizes, and viscous forces dominate the pattern formation dynamics. We further looked into the micro-structure of the granular deformation, and together with partners at University of Oslo, Strasbourg and Sydney, where able to model the deformation process and measure the characteristic stress profiles within the granular compaction fronts surrounding fractures. The experimental work led us to discover new pattern formation processes in granular-fluid mixtures, including the effect of gravity on frictional fluid displacement patterns, and plug formation during multiphase flow and conveying in tubes.
Exploitation Route Our results on fracture growth in saturated granular materials provides new understanding of physical mechanisms which will help optimize pneumatic fracturing of sensitive hydrocarbon plays, e.g. by nitrogen of carbon dioxide as fracturing fluid. Gas-driven fracturing has the potential to significantly reduce the environmental impacts in terms of water usage for hydraulic fracturing in the industry. Future policy and regulatory development will require knowledge of the particular aspects of gas-driven fracturing that impact on risks to environment and public acceptance of the new technology. The concept of pneumatic fracturing for accelerated remediation of polluted soil is relatively new in the UK, and the obtained results have revealed the role of frictional interactions within the particle packing in shaping the complex fracture network. Future work is planned to devise optimal soil fracturing parameters, and to disseminate this new technique to UK soil remediation actors. An unexpected outcome of the project was the potential use of granular plug formation in capillaries and tubes as "scrubbers" to remove biofilms and stains in pharmaceutical and medical equipment.
Sectors Energy,Environment,Government, Democracy and Justice,Pharmaceuticals and Medical Biotechnology

URL https://complexflowlab.com/
 
Description Gas-driven (pneumatic) fracturing is a promising technology to replace hydraulic fracturing to stimulate certain hydrocarbon reservoirs. This "water-free" fracking technique has the potential to reduce negative environmental and societal effects associated with use of water-based fracturing fluids. The project led to new collaborations with industrial partners in the energy sector to explore the science of gas-driven fracturing further, and we have follow-up projects underway. An alternative usage of pneumatic fracturing to speed up flushing and decontamination of polluted soil emerged as a new avenue and is being explored as a future pathway to impact. The results of the project were disseminated widely and generated a lot of attention in the popular science press and on social media. A recent outreach effort saw publication of full page image in the Physics Today Back Scatter section. The American Physical Society main outreach site, Physics Central, featured the work resulting from the project in a Physics Buzz Blog post. The work was featured in numerous online news outlets and popular science blogs, as well as on social media (YouTube, Twitter, Google+). The experimental equipment developed by the project have been used locally as demonstrations for visitors, on open days and in teaching, and several summer project students and Masters students have been able to use the equipment for their final year projects.
First Year Of Impact 2016
Sector Education,Energy,Environment
Impact Types Cultural,Societal,Economic

 
Description National Research Network in Advanced Engineering and Materials
Amount £189,000 (GBP)
Organisation Higher Education Funding Council for Wales (HEFCW) 
Sector Public
Country United Kingdom
Start 07/2015 
End 12/2017
 
Description University of Bristol 
Organisation University of Bristol
Department School of Earth Sciences
Country United Kingdom 
Sector Academic/University 
PI Contribution The Bristol group came to Swansea to learn experimental techniques developed by us. We helped design their new rig and experimental protocols, and participated in the scientific development of the project.
Collaborator Contribution Experimental work on multiphase flows in the context of magma flow dynamics. Joint paper published in 2015.
Impact Joint papers Conference papers and presentations Multi-disciplinary: Physics, Engineering, Earth Science, Volcanology
Start Year 2012
 
Description University of Oslo 
Organisation University of Oslo
Department Department of Physics
Country Norway 
Sector Academic/University 
PI Contribution Project ideas, experimental results on pattern formation in frictional fluids. Hosting of guest researcher for 6 months.
Collaborator Contribution Experimental and theoretical results
Impact Published papers. Presentations at international conferences. New experimental methodologies. New numerical simulation programs. Joint PhD project (Jon Eriksen) Joint Postdoc project (Dr Guillaume Dumazer) Joint Postdoc project (Dr Benjy Marks)
Start Year 2011
 
Description University of Strasbourg 
Organisation University of Strasbourg
Department Institute of Physics of the Globe of Strasbourg
Country France 
Sector Academic/University 
PI Contribution Project ideas, experimental results.
Collaborator Contribution Development of numerical simulations and theoretical methods.
Impact Masters project, Swansea University Masters project, University of Strasbourg Presentations at international conferences PhD thesis (Dr Jon Alm Eriksen) Published joint papers Multi-disciplinary: Physics, Engineering, Geoscience
Start Year 2013
 
Description University of Sydney 
Organisation University of Sydney
Country Australia 
Sector Academic/University 
PI Contribution Development of experimental setups.
Collaborator Contribution Experiments and theoretical work.
Impact Draft papers to be published 2016.
Start Year 2014