Effective management of induced seismicity for the Net Zero energy transition

Summary:

During this PhD, you will undertake rock deformation and fluid injection experiments at laboratory scale to (a) understand the controls on and micro-mechanisms involved in failure and fault reactivation, and (b) optimise operational controls to minimise micro-seismicity.

Project background

Progress towards a net zero carbon economy involves subsurface activities such as geothermal energy production and geological storage of carbon dioxide (long-term) and hydrogen (seasonal). These activities involve injection and extraction of fluids, which actively disturb tectonic stresses in the Earth's crust. Subsurface ruptures, and associated seismicity, induced by such stress perturbations carry a risk of damage from ground motion, of fluid leakage to the surface due to increased flow pathways, and of potential loss of public confidence. Safe operation of these activities therefore requires effective management to minimise induced seismicity.

Currently, induced seismicity is managed using a 'traffic light' system based on the maximum magnitude of recorded seismic events. In a traffic light system, operations may continue as planned (green), be modified (amber), or suspended (red) depending on the pre-set magnitude threshold. However, such systems can be unreliable, with magnitudes continuing to increase even after cessation of operations due to reactive controls being evoked too late in the process, with potentially catastrophic economic and societal effects. However, recent studies [1,2] have shown that maximum magnitudes can be limited if you vary the injection protocol continuously instead of waiting for the thresholds, when it may be too late.

Recent laboratory work [3] has shown that loading of a porous rock with constant micro-seismic event rate suppresses the number of events of all magnitudes, increases the seismic b-value (the exponent of the frequency-magnitude distribution) and limits the maximum magnitude. Adding event rate control to that of maximum recorded magnitude may therefore be more effective than the current traffic light system for managing the risk of induced seismicity.

In this project you will conduct laboratory experiments to understand how micro-seismicity and rock microstructure evolve during deformation, and during fault reactivation under fluid injection. You will test the hypothesis that fault reactivation due to fluid injection can be controlled effectively by limiting the fluid injection rate continuously to maintain a constant micro-seismic event rate.

Methodology

You will complete a literature review and analyse existing synchrotron data, developing codes to be used for later data analysis. You will then conduct laboratory rock deformation and fluid injection experiments [4,5] to test the hypothesis and optimise operational controls to minimise induced seismicity. This will involve combining direct imaging of the microstructure with indirect monitoring of micro-seismic events using a new experimental apparatus [5] under a range of subsurface pressure conditions and control protocols.

Timetable - Months 1-12: Literature review, analysis of existing synchrotron data, journal publication on these, training on the experimental apparatus; Months 13-24: In-house experiments, synchrotron campaign, data analysis and hypothesis testing; Months 25-36: completion of data analysis, synchrotron database publication; Months 37-42: hypothesis-testing publication, completion of thesis.

References

1. Kwiatek et al. (2019). Controlling fluid-induced seismicity during a 6.1-km-deep geothermal stimulation in Finland. Sci. Adv. 5, eaav7224. https://doi.org/10.1126/sciadv.aav7224
2. Zang et al. (2019). How to Reduce Fluid-Injection-Induced Seismicity. Rock Mech Rock Eng 52, 475-493. https://doi.org/10.1007/s00603-018-1467-4
3. Mangriotis, M.-D. et al., (in review). Loading of a porous rock with constant micro-seismic event rate suppresses seismicity and promotes subcritical failure. Preprint available: https://doi.org/10.21203/rs.3.rs-3054375/v1
4. Charalampidou, E.-M., et al. (2015). Brittle failure and fracture reactivation in sandstone by fluid injection. Eur. J. Environ. Civ. Eng. 19, 564-579. https://doi.org/10.1080/19648189.2014.896752
5. Cartwright-Taylor, A., et al. (2022). Seismic events miss important kinematically governed grain scale mechanisms during shear failure of porous rock. Nat. Commun. 13, 6169. https://doi.org/10.1038/s41467-022-33855-z

Supervisors

You will be based in the Lyell Centre Geoenergy Group at Heriot-Watt University under the supervision of Dr. Alexis Cartwright-Taylor, Dr. Elma Charalampidou and Dr. Nathaniel Forbes-Inskip and will collaborate with external supervisors Prof. Ian Main and Dr. Ian Butler at the University of Edinburgh and Dr. Maria-Daphne Mangriotis at the National Oceanography Centre.

Please contact Dr. Alexis Cartwright-Taylor (a.cartwright-taylor@hw.ac.uk) for informal information.

Training

A comprehensive training programme will provide specialist scientific training and generic transferable and professional skills through both hands-on learning and relevant University-level and School courses. Key project-specific training will be given in experimental techniques and analysing and interpreting integrated micro-seismic and X-ray CT datasets.

Funding

The scholarship will cover tuition fees and provide an annual stipend (£18,622 in 2023/24), for the 42 months duration of the project, as well as research support and travel costs. Thereafter, students will be expected to pay a continuing affiliation fee (currently £130) to cover their continued registration whilst writing up their thesis.

Requirements and eligibility

This studentship is available to UK and international students. We are looking for a highly motivated candidate with a strong interest in deformation processes and the energy transition.

To be eligible, applicants should have a BSc/MSci 2:1 in geoscience, physics or engineering and/or a Masters (MSc) degree at Merit/Distinction level (>60%) and/or evidence of equivalent relevant professional experience. Applicants should further have excellent communication, presentation, and scientific writing skills, and very good to excellent English language skills (verbal and written). Competence in computer programming, and experience of laboratory rock deformation and/or analysis of x-ray image or seismic data would be a significant advantage.

Applications are particularly welcome from women and Black, Asian and Minority Ethnic (BAME) candidates and those with other characteristics who are under-represented in the University. We also welcome applications from candidates who have had recent career breaks or other non-linear career paths and invite you to describe any such circumstances in your covering letter. Flexibility can be offered if someone has any caring responsibilities.

How to apply

To apply you must complete our online application form.

Please select PhD Geoenergy Engineering as the programme and include the full project title, reference number and supervisor name on your application form. Ensure that all fields marked as 'required' are complete.

Once you have submitted your personal details, you will be asked to upload your supporting documents. You must complete the section marked project proposal; provide a supporting statement (1-2 A4 pages) documenting your reasons for applying to this particular project, outlining your suitability and how you would approach the project. You must also upload your CV, a copy of your degree certificate and relevant transcripts and an academic reference in the relevant section of the application form.

You must also provide proof of your ability in the English language (if English is not your mother tongue or if you have not already studied for a degree that was taught in English within the last 2 years). We require an IELTS certificate showing an overall score of at least 6.5 with no component scoring less than 6.0 or a TOEFL certificate with a minimum score of 90 points.

Timeline

The closing date for applications is 17 September 2023 and applicants must be available to start in January 2024.