Understanding the physico-chemical evolution at the steel-cement interfaces in geological CO2 storage environments

Carbon Capture and Storage (CCS) refers to a number of technologies which involve capturing CO2 from large point sources (e.g. power generation plants, hydrogen production facilities, cement plants and steel production plants), followed by compressing and transporting the CO2 to appropriate subsurface reservoirs for sequestration or enhanced oil recovery. The implementation of such technologies necessitates long-term wellbore integrity to prevent CO2 leakage back into the atmosphere.<br /> <br /> Studies have highlighted that a potential critical point of &ldquo;failure&rdquo; is related to the carbonation reactions associated with casing cement as well as the external integrity of the casing itself . CO2 leakage through the annulus is reported to occur much more rapidly than geological leakage through the formation rock, leading to economic loss, reduction of storage efficiency and compromise of the storage location . The potential for such leaks raises considerable concern regarding long-term wellbore isolation, and the durability of hydrated cement. <br /> <br /> Research by SLB has reviewed the potential for geopolymer cements to afford better CO2 resistance in comparison to ordinary Portland cement through a series of long term exposure experiment. This project is directed towards understanding and quantifying the CO2 resistance of geopolymer cements in contrast to Portland cement with particular focus on (i) assessment of the bulk physico-chemical evolution of alkali-activated cement and the associated pore structure, under super-critical CO2 conditions, and (ii) the reactions mechanisms of casing material in contact with such cements. The successful completion of this project will enable to understand the evolution of both processes simultaneously in a system which experimentally simulates the steel-cement interface, thus enabling the local growth/dissolution at the steel-cement interface to be understood and related to the propensity for de-bonding and CO2 leakage.

<p style="text-align:justify">The project will comprise both destructive and non-destructive examination of cement cores and the steel-cement interface. This will include mass loss, microstructural analysis and phase assemblage pre- and post-exposure via a combination of FIB/SEM/EDX, XRD and thermal analysis. SEM analysis will be performed as a function of radial distance of core samples to assess width of the carbonation front, the nature of reactions taking place and time resolved changes to the integrity of the material. Bulk porosity will be determined using helium pycnometry, with the change in permeability being quantified under wellbore temperatures and pressures using the steady-state (for permeabilities &gt; 10-15 m2) or pulse-decay permeametry (for permeabilities &lt; 10-15 m2) and pore-throat size distribution will be estimated using mercury injection porosimetry (MIP). Dilatometry will enable quantification of carbonation shrinkage, whilst mechanical testing will be used to determine the change in strength and stiffness, with mechanical properties being spatially resolved using micro/nanoindentation. X-ray micro-tomography (&mu;CT) analysis pre- and post-exposure will be used to provide information in relation to changes in pore structure (e.g. tortuosity and pore size distribution) as an indication of any self-healing characteristics reported in the literature, progression of the carbonation front and porosity (for cross-correlation with other methods such as MIP). CT will also be used to analyse the local porosity and local permeability as a function of radial distance through the core and towards the steel-cement interface to achieve an understanding of how the progression of the carbonation front and corrosion at the steel interface influences the local physical properties of the samples. Such observations will be cross-correlated with corrosion measurement from electrical resistance probes, used to measure the general corrosion behaviour occurring at the interface in order to understand the casing material integrity in each environment.</p> <p style="text-align:justify">Achieving the mechanistic understanding of bulk cement and casing degradation, and coupling this together to understand the evolution of the steel-cement interface will not only provide effective understanding/quantification of cement resistant in CO2 environment, but will help pave the way for the future development of new cements with greater resilience.</p>

<p>Formal applications for research degree study should be made online through the&nbsp;<a href="https://www.leeds.ac.uk/research-applying/doc/applying-research-degrees">University&#39;s website</a>. Please state clearly in the Planned Course of Study Section that you are applying for <strong>PhD Mechanical Engineering</strong> and in the research information section&nbsp;that the research degree you wish to be considered for is <em><strong>Understanding the physico-chemical evolution at the steel-cement interfaces in geological CO2 storage environments </strong></em>as well as <a href="https://eps.leeds.ac.uk/mechanical-engineering/staff/501/professor-richard-barker">Professor Richard Barker</a> as your proposed supervisor.</p> <p>If English is not your first language, you must provide evidence that you meet the University&#39;s minimum English language requirements (below).</p> <p><em>As an international research-intensive university, we welcome students from all walks of life and from across the world. We foster an inclusive environment where all can flourish and prosper, and we are proud of our strong commitment to student education. Across all Faculties we are dedicated to diversifying our community and we welcome the unique contributions that individuals can bring, and particularly encourage applications from, but not limited to Black, Asian, people who belong to a minority ethnic community, people who identify as LGBT+ and people with disabilities. Applicants will always be selected based on merit and ability.</em></p> <p class="MsoNoSpacing">Applications will be considered on an ongoing basis. &nbsp;Potential applicants are strongly encouraged to contact the supervisors for an informal discussion before making a formal application. &nbsp;We also advise that you apply at the earliest opportunity as the application and selection process may close early, should we receive a sufficient number of applications or that a suitable candidate is appointed.</p> <p>Please note that you must provide the following documents in support of your application by the closing date of 31 August 2023:</p> <ul> <li>Full Transcripts of all degree study or if in final year of study, full transcripts to date</li> <li>Personal Statement outlining your interest in the project</li> <li>CV</li> <li>Funding information:&nbsp; EPSRC CASE Competition Studentship</li> </ul>

Applicants to research degree programmes should normally have at least a first class or an upper second class British Bachelors Honours degree (or equivalent) in an appropriate discipline. The criteria for entry for some research degrees may be higher, for example, several faculties, also require a Masters degree. Applicants are advised to check with the relevant School prior to making an application. Applicants who are uncertain about the requirements for a particular research degree are advised to contact the School or Graduate School prior to making an application.

The minimum English language entry requirement for research postgraduate research study is an IELTS of 6.0 overall with at least 5.5 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid. Some schools and faculties have a higher requirement.

<p>A highly competitive EPSRC CASE Competition Studentship in partnership with SLB, consisting of the award of fees with a maintenance grant of &pound;18,622 for session 2023/24 for 3.5 years.</p> <p>This opportunity is open to UK applicants only. All candidates will be placed into the EPSRC CASE Competition Studentship Award Competition and selection is based on academic merit.</p> <p>Please refer to the <a href="https://www.ukcisa.org.uk/">UKCISA</a> website for information regarding Fee Status for Non-UK Nationals.</p>

<p>For further information about this project, please contact Dr Richard Barker<br /> e:&nbsp;<a href="mailto:R.J.Barker@leeds.ac.uk">R.J.Barker@leeds.ac.uk</a></p> <p>For further information about your application, please contact Doctoral College Admissions<br /> e:&nbsp;<a href="mailto:phd@engineering.leeds.ac.uk">phd@engineering.leeds.ac.uk</a></p>