Objective: The main objective of this PhD project is to develop an understanding of the depositional and diagenetic heterogeneity in the Mercia Mudstone Group and their implications for fluid flow in fracture networks at depth.
Requirements/eligibility: we seek a highly motivated and numerate geoscience, or related, graduate who is willing to (i) undertake sampling and rock description in core-stores, quarries, road-cuts and outcrops, (ii) utilise subsurface logs and integrate outputs from sedimentology, petrophysics, petrography, geomechanics and geophysics, and (iii) develop conceptual and numerical models. This scholarship is available to UK students only who are eligible for home fee status. Applicants should have, or expect to achieve, at least a 2.1 honours degree (or equivalent). The successful applicant will be expected to start in Sept 2023. Equality, diversity and inclusion is fundamental to the success of the University of Liverpool and the National Nuclear Laboratory and is at the heart of all of our activities and leads to enhanced research creativity, productivity and quality, and societal and economic impact. We actively encourage applicants from diverse career paths and backgrounds and from all sections of the community, regardless of age, disability, ethnicity, gender, gender expression, sexual orientation and transgender status.
Context: The UK has been producing and managing radioactive waste since the 1940s. At present, the UK’s radioactive waste is stored on an interim basis with more waste expected to be produced from new nuclear power stations, decommissioning programmes, and the clean-up of existing facilities for many decades. There is international consensus that the safest and most permanent solution for high & intermediate level waste is for it to be emplaced in a Geological Disposal Facility (GDF), deep underground and permanently isolated from people and the environment.
Geological disposal is based on a multi-barrier concept where waste is contained in an engineered barrier system and stored in extremely low-permeability Lower Strength Sedimentary Rocks (LSSR), for example the Mercia Mudstone Group, the focus of this PhD. Geoscientific understanding is essential for growing confidence in the long-term safety of the GDF and for quantifying and managing uncertainties associated with geological disposal.
Key questions: Hosted at Liverpool, and jointly supervised by staff from Liverpool (Worden and Faulkner), the National Nuclear Laboratory (Griffiths, Smith and Tsitsopoulos) and the University of Manchester (Taylor and Ma), the following key questions will be addressed, focussing on Mercia Mudstone Group sediments:
(1) What is the dominant cause of heterogeneity in LSSRs: depositional and diagenetic controls?
(2) What are the dominant effects of various types of heterogeneity on the key rock properties of an LSSR?
(3) How does the combination of depositional and diagenetic processes influence fracture networks and subsurface flow at repository depths?
(4) How can the dominant types of heterogeneity be upscaled?
Method, samples, and data: The PhD project will be split into several tasks:
· Task 1 – Sedimentology and structural geology. Core, outcrop, wireline-log and seismic description to better understand sedimentological and structural (i.e. fracture) variability throughout the Mercia Mudstone Group.
· Task 2 – Petrophysical properties and diagenesis. Petrophysical, mineralogical and textural analysis of representative subsamples, with focus on fractures, will be undertaken using a suite of analytical techniques (e.g., micro-CT, X-ray diffraction, petrography) to determine representative paragenetic histories.
· Task 3- Geomechanics. The lithological characteristics of the various samples, cores and outcrops will be assessed and compared to their geomechanical attributes determined using uniaxial stress and tensile failure approaches. Elastic properties will be determined using log data linked to borehole samples
· Task 4 – Upscaling. Based on outputs from tasks 1 to 3, upscaling will be undertaken as a series of qualitative conceptual models based on an inductive (using depositional models) and deductive approach (based on new and existing data).
· Task 5 – Modelling and NNL placement. Output from tasks 1 to 4 will be used to form the basis of fluid reactive transport models, probably during a short placement at NNL to gain training in modelling.
The PhD will involve a combination of (1) offshore well subsurface data and samples with data from the North Sea Transition Authority’s National Data Repository and core from the BGS core store and onshore well data and samples also archived by the BGS and (2) outcrops, quarries, mines and excavations (e.g., road cuts or tunnels). Offshore data and samples will include wireline log data (abundant), core (less abundant) and possibly cuttings. Samples and wells will be selected that are comparable to the potential GDF site in West Cumbria.
Impact: The UK’s disposal programme is ramping up rapidly and this PhD project has the potential to be an integral part of the delivery. Outputs from this project will help support: site descriptive model (SDM), concept development, underpinning for engineering, underpinning for safety assessments, borehole design/locations, and initial site evaluations (ISE).
Training: will be delivered by the School of Environmental Sciences (SOES) and by the NNL. Our training involves a strong component of impact, with a chapter of the student’s thesis based around an impact theme. Training involves Research training in the first year, centred around background and context, specialist techniques, and academic skills. Specific to this proposed PhD, NNL will offer at least three months of training in modelling, possibly at their Warrington offices, or remotely while the student is at Liverpool. Professional training is a focus of the second and third year, involving data analytics, entrepreneurship, and practical environmental challenges.
Careers: successful completion of the PhD should provide a route to a number of careers, e.g., in nuclear waste disposal, engineering geoscience, geomodelling, etc.
Applying: You should apply via the University Application Portal here: https://app.askadmissions.co.uk/AYApplicantLogin/fl_ApplicantLogin.asp?id=liv
You MUST make contact with the lead project supervisor before submitting an application. When completing the application include the name of the lead project supervisor as the potential supervisor. Enquiries about this project can be sent to Professor Richard Worden – [Email Address Removed] as the lead project supervisor.
Supervisors:
1) Professor Richard Worden ([Email Address Removed])
2) Professor Dan Faulkner ([Email Address Removed])
3) Dr Joshua Griffiths ([Email Address Removed])
4) Professor Nick Smith ([Email Address Removed])
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