Geochemical impact of CO2 and H2 injection on geomechanical and petrophysical properties of caprock to ensure safe containment: an experimental and analytical approach


The overall aim for the PhD is to develop a comprehensive understanding of geochemical effects on the geomechanics and petrophysics of a wide range of caprocks which can be utilised by bp to understand the potential risks of CO2/H2 leakage in future storage reservoirs.

CO2 and H2 storage developers have a moral, social, and legal responsibility to ensure safe containment over geological time scales. Critical to safe and predictable long-term storage of CO2 and H2 within geological media, is the need to understand caprock behaviour in the presence of potentially reactive fluids. Injection of CO2 and H2 for storage into saline aquifers and/or depleted hydrocarbon reservoirs will alter the in-situ geochemical environment (Worden and Smith, 2004), potentially leading to reactions with the caprock that holds the injected gas in place. This, in turn, may alter the geomechanical and petrophysical properties of the caprock, possibly increasing the risk of migration out of the host reservoir (Baines and Worden, 2004). The coupled geochemical and geomechanical effects on caprocks in the presence CO2 or H2 are poorly understood and under-researched despite being key controls on rock strength and sealing capacity. By investigating the interplay between these two disciplines, a new understanding on controllers of rock strength and subsequent leakage pathways can be constrained, helping bp to de-risk future CCUS and potential H2 storage projects.

In this project you will undertake a pioneering experimental study, founded on previous bp-funded work (Armitage et al., 2010, 2011, 2013), that will directly reveal the geochemical effects on key geomechanical properties of caprocks under representative reservoir conditions. You will measure how the strength, permeability, elastic and acoustic properties, and reactive surface area of caprocks are affected by the presence of injected fluids, providing fundamental constraints on caprock integrity for CO2 and H2 injection sites.

This work will enable identification of the unique geochemical and geomechanical differences between CO2 and H2 injection upon key caprock properties, the first comparison study of its kind, aiding bp in future site selection by providing criteria to differentiate and rank sites by the long-term stability of the caprock. This innovative approach represents a major development of previous investment and work sponsored by bp at the University of Liverpool, between 2004 and 2014 (Armitage et al., 2010, 2011, 2013) building upon our expertise in understanding caprock integrity at the In Salah JIP CCUS project. This research leverages unique experimental apparatus and a successful research relationship with the University of Liverpool to answer these key questions.

Caprock samples from storage reservoirs of interest (Southern North Sea and East Irish Sea Basins) will be selected to undergo CO2 and H2 reactive fluid experiments. Comprehensive geomechanical, petrophysical and petrological analyses will be performed, before and after these experiments, with the student invited to use bp’s imaging labs, possibly during your ICASE placement in bp. Once completed, we anticipate that this work can be upscaled and used by bp’s CCUS + H2 geoscientists to identify any potential risk of leakage prior to injection and will compliment to in-house work being undertaken by bp technical teams.

In year 1, you will undertake a comprehensive literature review to understand the key geochemical reactions between individual caprock minerals and CO2/H2, and the subsequent effects upon caprock integrity, resulting in a presentation to bp technical team on key findings and knowledge gaps to be experimentally researched. Design and development of project methodology along with identification and selection of key strategic rock samples from the BGS core store. The aim for end of Year 1 is to identify the knowledge gaps, create a plan to address ones of key concern to bp, develop the methodology, give a technical presentation to bp technical team and select/sample caprocks.

In years 2+3, you will petrologically characterise caprock samples (SEM, XRD, FTIR, XRF, possibly digital rocks) prior to geochemical experiments to highlight any potential reactions identified in the literature review that may be relevant to the samples used. You will commence the ICASE placement in bp’s Sunbury labs. You will give a presentation to bp technical team on caprock geochemistry, possible reaction pathways, and experimental programme prior to returning to the University of Liverpool for geochemical and geomechanical work. You will analyse geomechanical and petrophysical properties of caprock samples (strength, elastic properties, permeability, acoustic properties, reactive surface area, etc.) before, during, and after saturation with (and flow of) fluids (CO2, H2, saturated waters) over varying timescales. Petrological analyses of samples after reactive fluid flow experiments will visualise and quantify any geomechanical and petrophysical changes (student invited to return to Sunbury lab to use geochemical equipment – if required). The aims for end of Year 2+3: petrological, geomechanical, and petrophysical characterisation of caprock samples showing the effects of geochemical reactive fluid experiments at The University of Liverpool and ICBT Sunbury, identify key rock/fluid geochemical reaction processes and their effects on key geomechanical and petrophysical rock properties, undertake the ICASE placement, and give at least two technical presentations to bp.

In year 4 you will complete all analyses and tests and write up your thesis and give final technical presentation to bp staff of key findings and transferable knowledge.


Submit your application online via the Apply Yourself website.



Open to UK applicants

Funding information

Funded studentship

This PhD position has agreed funding as an iCASE studentship from EPSRC in conjunction with bp.  The studentship is granted on current UKRI levels of support, which include home rate tuition fees and an annual stipend granted for 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., Faulkner, D.R., and Worden, R.H. 2013. Caprock corrosion. Nature Geoscience 6 2, pp. 79-80.

Armitage, P. J., D. R. Faulkner, R. H. Worden, A. C. Aplin, A. R. Butcher, and Iliffe, J. 2011. Experimental measurement of, and controls on, permeability and permeability anisotropy of caprocks from the CO2 storage project at the Krechba Field, Algeria. Journal of Geophysical Research - Solid Earth 116, B12208, doi:10.1029/2011JB008385.

Armitage, P. J., R. H. Worden, D. R. Faulkner, A. C. Aplin, A. R. Butcher, and Iliffe, J. 2010. Diagenetic and sedimentary controls on porosity in Lower Carboniferous fine-grained lithologies, Krechba field, Algeria: A petrological study of a caprock to a carbon capture site. Mar. Pet. Geol., 277, 1395–1410, doi:10.1016/j.marpetgeo.2010.03.018.

Baines S. and Worden R.H. (2004) Geological Storage of Carbon Dioxide:  Reducing Greenhouse Gas Emissions. In Geological Storage of Carbon Dioxide. (eds: Baines, S. and Worden, R.H.), Geological Society Special Publication, 233, 1-6.

Worden R.H. and Smith L.K. (2004) CO2 injection into oil fields for enhanced oil recovery (EOR): lessons for the geological sequestration of CO2 in the subsurface. In Geological Storage of Carbon Dioxide. (eds: Baines, S. and Worden, R.H.), Geological Society Special Publication, 233, 211-224.