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Depositional and diagenetic controls on fluid flow in fractures in a potential Geological Disposal Facility in the Mercia Mudstone Group, UK

   Department of Earth, Ocean and Ecological Sciences

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  Prof R Worden, Prof D Faulkner, Dr Joshua Griffiths, Prof Nick Smith  No more applications being accepted  Funded PhD Project (UK Students Only)

About the Project

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 geo-engineering graduate who is willing to (i) undertake fieldwork for detailed logging and description (sedimentary, diagenetic and structural features, including fracture type and distribution) and sampling of Mercia Mudstone at outcrops, core-stores, quarries and road-cuts, (ii) use subsurface logs to help build a regional picture of the Mercia Mudstone, (iii) undertake lab testing and petrography of selected samples, and (iv) develop conceptual and numerical models of the Mercia Mudstone. 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. This scholarship is available to UK students only who are eligible for home fees status. Applicants should have at least a 2.1 honours geoscience degree. The successful applicant will be expected to start in Sept 2023.

Context: There is international consensus that the safest and most permanent solution for high & intermediate level nuclear waste, which the UK has been creating since the 1940s, 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 low-permeability sedimentary rocks, for example the Upper Triassic rocks of the Mercia Mudstone Group. This PhD is driven by the need for a high level of geoscience understanding to grow confidence in the long-term safety of the GDF and to quantify and manage 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 are the dominant causes and effects of heterogeneity: primary (depositional) or secondary (diagenetic)?

(2)     How does fracture distribution and type relate to various types of heterogeneities?

(3)     How can the dominant types of heterogeneity be upscaled to be helpful for GDF design?

Method, samples, and data: The work on 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 fracture variability throughout the Mercia Mudstone Group.

·      Task 2Petrophysical properties and diagenesis. Mineralogical, textural and petrophysical analysis of representative subsamples, with focus on fractures, undertaken using a range of analytical techniques (e.g., high resolution micro-CT, X-ray diffraction, SEM-petrography) to determine representative paragenetic histories.

·      Task 3- Geomechanics. The geomechanical characteristics of the various samples, cores and outcrops, determined using uniaxial stress and tensile failure approaches, will be assessed and compared to sedimentary, diagenetic and petrophysical attributes.

·      Task 4 – Upscaling. Based on outputs from tasks 1 to 3, upscaling will be undertaken as a series of qualitative conceptual models based on depositional and diagenetic models.

·      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 use offshore and onshore well subsurface data and samples and outcrops, quarries, mines and excavations (e.g., road cuts or tunnels). Samples and wells will be selected that are relevant 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: Technical (field and lab) and skills-based (e.g., data analytics, entrepreneurship) training will be delivered by the School of Environmental Sciences (SOES) and by NNL. Our training involves a strong component of impact, with a chapter of the student’s thesis based around an impact theme. Specific to this proposed PhD, NNL (Warrington) will provide three months of training in modelling.

Careers: Successful completion of the PhD will provide a route to a range of technical careers, e.g., in engineering geoscience, nuclear waste disposal, geomodelling, etc. The PhD will also equip the student with good networking and communication skills, resilience, knowledge of the roles of policy and impact, etc. The geological interval being considered (Upper Triassic Mudstones) is also likely to be vitally important to the growing CCS and hydrogen storage industries in the UK and NW Europe so the PhD could lead to a career in one of these industries.

For more information or to submit an application, visit the University of Liverpool studentship page.

Funding Notes

This PhD position has agreed funding from The National Nuclear Lab and the University of Liverpool. The studentship, only open to those eligible for UK (home) students, is granted on current UKRI levels of support, which include home rate tuition fees and an annual stipend granted for 3.5 to 4 years for full-time study. Awards increase each year; the annual stipend for 2023-2024 is £18,021. Funding also includes a generous Research Training Support Grant over the duration of the project.


Armitage, P.J., Worden, R.H., Faulkner, D.R., Butcher, A.R., Espie, A.A. (2016) Permeability of the Mercia Mudstone: suitability as caprock to carbon capture and storage sites. Geofluids, 16, 26-42.
Armitage, P.J., Worden, R.H., Faulkner, D.R., Aplin, A.C., Butcher, A.R., Espie, A.A. (2013) Mercia Mudstone caprock to carbon capture and storage sites: petrology and petrophysical characteristics. Journal of the Geological Society of London, 170, 119-132.
Wang, K, Ma, L. and Taylor, K.G.. (2023). Microstructure changes as a response to CO2 storage in sedimentary rocks: Recent developments and future challenges, Fuel, 333, 126403
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