Research

The primary purpose of this research is to better understand the role of both capillary forces and chemical reactivity in the process of carbon sequestration in deep saline aquifers, especially those containing carbonate minerals. The group is equipped with two view cells for the measurement of interfacial tension (IFT) between partially miscible fluids at pressures up to 50 MPa and temperatures up to 473 K. This equipment has been used to measure the IFT between CO₂ and water and brines over wide ranges of pressure, temperature and molality that encompass typical CO₂-storage conditions. Current efforts are directed towards understanding the effects on the IFT of impurities that might be present in the CO₂ stream and on measuring the angles between CO₂, brine and carbonate mineral surfaces.

 To study the chemical interactions that occur between CO₂-acidified reservoir fluids and carbonate minerals at reservoir conditions, we employ a batch reactor system. This equipment has been used to measure the kinetics of carbonate-mineral dissolution in both water and brines saturated with CO₂ at reservoir conditions. The effects of surface-bound impurities on the reactivity of calcite has also been studied.

Phase behaviour is of fundamental importance in many areas of science and technology and the group is therefore very active in the measurement and modelling of phase-equilibrium phenomena. We are equipped with a range of facilities, including both analytical and synthetic apparatus, that allow measurements to be made over very wide ranges of pressure (from 0.005 MPa to 50 MPa) and temperature (from 183 K to 474 K) and for a diversity of chemical systems including hydrocarbons and aqueous systems. Current research is directed mainly to mixtures of CO₂ with: hydrocarbons; inorganic gases; brines; and aqueous amine solutions. The results are being modelled using both engineering equations of state and molecular-thermodynamic models such as SAFT. 

In this field, the motivation of our work is to understand the thermodynamic and transport properties of homogeneous fluid mixtures. Two key areas of application are: (a) the behaviour of hydrocarbon reservoir fluids, aquifer fluids and CO₂ at various temperature and pressure conditions that represent hydrocarbon fields and CO₂ storage conditions; and (b) the performance of various solvents in CO₂ capture processes, especially in relation to mass transfer and hydrodynamic calculations. Experiments are designed and performed with state-of-the-art apparatus to determine thermophysical properties of pure and mixed fluids. The measured thermodynamic properties include density, sound speed, and isobaric heat capacity in liquids and gases over wide ranges of temperature and pressure, leading to full thermodynamic characterisation of the fluids under investigation. In the area of transport properties, we measure viscosity and diffusion coefficients at high pressures. Viscosity measurements are made mainly with vibrating-wire instruments developed in our laboratory for application at pressures up to 400 MPa. We have also developed a dual-capillary viscometer for measurements at temperatures up to 600 K, and a Taylor-Dispersion apparatus for measuring diffusion coefficients of dilute solutes.