Viscosity and Density of Aqueous Fluids with Dissolved CO2 Mark McBride-Wright A thesis submitted for the degree of Doctor of Philosophy. Supervisors Professor J.P. Martin Trusler Professor Geoffrey Maitland Sponsors Qatar Petroleum, Shell and Qatar Science and Technology Park Qatar Carbonates and Carbon Storage Research Centre (QCCSRC) Department of Chemical Engineering Imperial College London Declaration of Originality I certify that all material in this thesis which is not my own work has been properly acknowledged. Mark McBride-Wright Copyright Declaration The copyright of this thesis rests with the author and is made available under a Creative Commons Attribution Non-Commercial No Derivatives licence. Researchers are free to copy, distribute or transmit the thesis on the condition that they attribute it, that they do not use it for commercial purposes and that they do not alter, transform or build upon it. For any reuse or redistribution, researchers must make clear to others the licence terms of this work. ii Acknowledgements Firstly I would like to thank my supervisors Prof. Martin Trusler and Prof. Geoffrey Maitland for giving me the opportunity to carry out this exciting piece of research. I am very appreciative of the guidance, support and encouragement I have received throughout. I have really enjoyed my time working at the QCCSRC and I gratefully acknowledge the funding provided by Qatar Petroleum, Shell and Qatar Science and Technology Park. I would also like to thank my colleagues at the Centre for their helpful input when discussing problems and issues which had to be overcome. The installation designed would not have become a reality had it not been for the expert technicians in the chemical engineering workshop and so I would like to say a special thank you to Tony, Sam, Gavin and Richard for all their help and valuable input. Thank you to all my family and friends who have joined me on this journey and who have put up with listening to me for the past four years. Their help and encouragement allowed me to succeed and progress forward. I am very appreciative to my Mum for all the help and support she has provided me. I am particularly grateful for the close friendships which I have made during my time at Imperial, from my MEng through to my PhD. My 11:45am lunch time catch-ups with Paul, Nina, Roochi, Andrew and Charles got me through the day-to-day and have provided me with memories I will never forget. I would to say a special thank you to my very close friend Cat Ball. She has been there for me through it all, providing me with reassurance and reminding me that “nothing endures” and things move on. Lastly, I would like to thank my husband, Dr. Sam McBride-Wright. This journey would not have been completed had it not been for you. I am very grateful for all your love and support and for being my inspiration to succeed. iii Abstract Carbon Capture and Storage (CCS) is considered a technology which can help ease the emissions associated with the use of fossil fuels for energy and industrial processes. In Qatar, rapid industrial expansion has established a need for CCS. Here, saline aquifers represent a potential sink for geologically storing the associated CO2 emissions. CCS is an important component of meeting carbon emission targets; CO2 storage in the carbonate reservoirs of the Middle East and elsewhere will become increasingly important. CO2 can also be used for enhanced oil recovery (EOR), which consequently brings an economic benefit. However, we know little about how CO2 behaves when it is mixed with reservoir fluids (hydrocarbons, water, brines) or with carbonate rocks; so we need more research in this area. In particular, the injection of CO2 into these reservoirs/aquifers depends crucially on the viscosity of the fluids involved. Hence the focus of this research has been on determining experimentally the viscosity and density of aqueous fluids with dissolved CO2. This thesis details the design, construction, testing and utilisation of a new experimental apparatus for performing measurements at high pressure and high temperature (HPHT). Measurements were made at temperatures between (274.15 and 448.15) K, and at pressures up to 100 MPa in the single-phase compressed liquid region. The vibrating-wire technique was used for viscosity determination, with simultaneous measurements of density by means of a vibrating-tube densimeter. Wetted parts were made from Hastelloy- C276 and Pt-Ir alloy, chosen to resist corrosion. Measurements were first performed on the system (water + CO2). Following this, mixtures of salt solutions with dissolved CO2 were measured and the results correlated in useful models which allowed for comparison with literature data where this was possible. Salts investigated include NaCl(aq), CaCl2(aq), each at two different concentrations, and lastly, a synthetic Qatari reservoir brine. A correlation based on the Vogel-Fulcher-Tammann (VFT) equation for viscosity is presented which represents all the data to within ±3%, including the pure Qatari brine and its modification by dissolved CO2. Density is correlated using the partial molar volume of CO2 and gives the densities of the mixtures to within ±0.1 %. iv The results presented in this thesis extend our knowledge of the viscosity of CO2-water- brine systems to significantly higher temperatures and pressures than are currently available in the literature. The effect of temperature on density and viscosity is significant whereas pressure effects are relatively small. Since rigorous theories for gas-saline mixtures are not yet available, semi-empirical correlations with some underlying physicochemical basis have been used to represent the new results. These are capable of estimating the density and viscosity of the fluid mixtures involved to an accuracy that is more than adequate for the design and control of CCS and EOR subsurface processes. v Contents 1. Introduction ....................................................................................................................... 1 1.1 Energy Demand and Climate Change .............................................................................. 1 1.2 Carbon Capture and Storage (CCS) .................................................................................. 2 1.3 Qatar and Its Industrial Development ............................................................................. 3 1.4 Qatar Carbonates and Carbon Storage Research Centre (QCCSRC) ................................ 6 1.5 Sub-surface Processing .................................................................................................... 7 1.6 Thermophysical Properties ............................................................................................ 11 1.6.1 Oil and Gas Industry ................................................................................................ 11 1.6.2 CCS Industry ............................................................................................................ 12 1.6.3 Definition of Transport Properties .......................................................................... 14 1.6.4 Industrial Application of Thermophysical Properties ............................................. 15 2. Viscosity ........................................................................................................................... 17 2.1 Importance of Viscosity Measurements ........................................................................ 17 2.2 Methods for Measuring Viscosity .................................................................................. 19 2.2.1 Capillary Viscometers .............................................................................................. 20 2.2.2 Falling-Body Viscometers ................................................................................... 21 2.2.3 Rotational Viscometers ...................................................................................... 23 2.2.4 Oscillating-Body Viscometers ............................................................................ 24 2.2.5 Vibrating Viscometers ........................................................................................ 26 2.3 Viscosity Modelling ........................................................................................................ 27 2.3.1 Kinetic Theory .................................................................................................... 27 2.3.2 Dilute Gas ........................................................................................................... 28 2.3.3 Dense Fluids and Density Dependence of Viscosity .......................................... 29 2.3.4 Dense Fluid Mixtures ......................................................................................... 30 2.3.5 Hard Sphere Theory ........................................................................................... 31 vi 2.3.6 Corresponding-States Theory ............................................................................ 33 2.3.7 Absolute Reaction Rate Theory .............................................................................. 34 2.3.8 Vesovic-Wakeham (VW) Model ......................................................................... 34 2.3.9 Mixed Solvent Electrolyte Model............................................................................ 35 2.3.10 Empirical Equations .............................................................................................. 37 3. Density ............................................................................................................................