Laboratory investigation, surface complexation and molecular dynamics modelling of silica-brine-CO2 interfacial properties

CO₂ injection into deep aquifers aquifers or depleted oil reservoirs is a promising method for safe carbon geological storage (CGS). Four primary mechanisms of CGS have been identified as structural, residual, dissolution and mineralisation trapping. The combined contribution of structural and residual trapping mechanisms accounts for more than 75% of the total amount of trapped CO₂ over the first century after injection¹, and both mechanisms are controlled by the rock-brine-CO₂ wetting state. However, the underlying physics of the wettability response to CO₂ injection is still poorly understood. It is generally agreed that wettability alteration associated with CGS is caused by changes in electrostatic interactions at mineral-brine and brine-CO₂ interfaces. These interactions are characterised by an interfacial petrophysical property termed the zeta potential, but polarity and magnitude of the zeta potential in sandstone systems containing both brine and immiscible CO₂ is still debatable. Under supercritical CO₂ conditions, typical for CGS, pH and chemical composition of formation water change leading to rock dissolution and shift in electrochemical equilibrium of the system, all of which impact the zeta potential and therefore wettability.

The aim of this project is to acquire laboratory data on the zeta potential in sandstone-brine-CO₂ systems, and based on these data to model chemical and specific adsorption reactions that take place at the silica-brine and brine-CO₂ interfaces. Laboratory experiments will be carried out using readily available equipment at the School of Engineering. The interpretation of the measured zeta potentials will be carried out using surface complexation modelling software² (PhreeqC) combined with a bespoke molecular dynamics model. The project will improve our understanding of the mechanisms responsible for wettability alteration during CO₂ injection into sandstone formations.

The project will be carried out in collaboration with BRGM and Karlsruhe Institute of Technology (KIT), with the corresponding contribution from Dr Philippe Leroy and Dr Johannes Lützenkirchen. The project is suitable for students with any engineering, physics, chemistry or geoscience background.

The project will require Additional Research Costs (ARC) to cover expenses associated with BRGM and KIT visits and consumables required for laboratory experiments.

Selection will be made on the basis of academic merit. The successful candidate should have, or expect to obtain, a UK Honours degree at 2.1 or above (or equivalent) in geoscience, engineering or other relevant backgrounds.

APPLICATION PROCEDURE:

Formal applications can be completed online: https://www.abdn.ac.uk/pgap/login.php

• Apply for Degree of Doctor of Philosophy in Engineering

• State name of the lead supervisor as the Name of Proposed Supervisor

• State ‘Self-funded’ as Intended Source of Funding

• State the exact project title on the application form

When applying please ensure all required documents are attached:

• All degree certificates and transcripts (Undergraduate AND Postgraduate MSc-officially translated into English where necessary)

• Detailed CV, Personal Statement/Motivation Letter and Intended source of funding

Informal inquiries can be made to Dr J Vinogradov ([Email Address Removed]) with a copy of your curriculum vitae and cover letter. All general enquiries should be directed to the Postgraduate Research School ([Email Address Removed])