My research interests focus on the thermophysical properties of fluids and fluid mixtures and incorporates applied thermodynamics, apparatus/sensor development, and molecular theory. Experimental, theoretical and computational work is carried out as a part of a fundamental research programme with numerous applications including oilfield processes and carbon dioxide capture and storage. Current projects in these areas include:
- Carbonate reservoir pore/fracture-scale physics and chemistry. This research is being undertaken as a part of the 10-year, $70M Qatar Carbonates and Carbon Storage Research Centre (QCCSRC) programme started in 2008. The project is developing an integrated suite of experimental measurements combined with pore-scale and thermodynamic models of CO2-brine-oil fluid systems in carbonate reservoir formations at a level of detail and with a predictive capability unmatched in the industry. My research is focused on experimental measurements and modelling of phase behaviour, interfacial properties, viscosity, diffusion, pH and mineral dissolution kinetics in complex mixtures at reservoir conditions. A special emphasis has been placed on the study of complex brines, representative of carbonate formation waters, and their mixtures with carbon dioxide. The programme also includes a wide-ranging study of the phase behaviour of mixtures containing CO2, light gases and complex hydrocarbon liquids. The scope has recently been expanded to account for some of the impurities that will typically be present in the CO2 stream, including both diluents (N2, H2, O2) and other acid gases (SO2, H2S). A suite of novel experimental apparatus has been developed to permit the experimental measurements on corrosive fluids (e.g. brines and acid gases) under conditions of elevated temperature (up to 473 K) and elevated pressure (up to 50 MPa). Based largely on the large body of data gathered in this project, a consistent and accurate modelling platform is emerging for the thermophysical properties of CO2 and its mixtures with reservoir fluids in the subsurface environment.
- Thermodynamic properties and flow in micro- and nano-porous rocks. This key research theme in the Shell-funded Digital Rocks programme is aimed at understanding the effects of confinement in micro- and nano-porous materials on the phase behaviour and other properties of mixtures. A key potential application relates to the production of oil and gas from shales and other tight rocks, where the hydrocarbon fluids are confined in a reservoir formation with pore sizes in the nanometre range. A combination of sorption and exclusion phenomena are thought to strongly influence the phase behaviour, and a fundamental understanding of these phenomena could greatly assist in the design of effective, economic and environmentally-sound extraction processes. An experimental study involving synthetic porous media and simple hydrocarbon mixtures has been initiated. Raman spectroscopy is being used together with PVT measurements to infer the composition of hydrocarbon mixtures coexisting in the porous medium and the bulk fluid under conditions of high temperature and high pressure. The experimental studies are closely linked to molecular simulations of hydrocarbon fluids in nanopores. The objective is to develop and validate equation of state models that can ultimately be applied in the field.
- New solvents for post-combustion CO2 capture. This work is a part of the Gas Future Advanced Capture Technology Options (Gas-FACTs) project involving five UK universities (Cranfield, Edinburgh, Leeds, Imperial, Sheffield). New amine-solvent blends with properties suitable for CCS on gas-fired power plant are being investigated. The focus is on the phase-equilibrium properties that determine the cyclic loading capacity of the solvent and on various other thermodynamic and transport properties that affect mass transfer in absorber and stripper columns. The properties of some ionic-liquid solvents are also being studied.
- Pre-Combustion CO2 Capture by Low-Temperature Separation. This project is related to the production of clean hydrogen fuel gas from fossil fuel feedstocks, and focuses on fundamental understanding of the separation of CO2 from a H2- and CO2-rich synthesis gas by means of high-pressure, low-temperature flash processes. The study involves experimental measurements of the low-temperature, high-pressure vapour-liquid and vapour-liquid-solid equilibria of mixtures containing H2, CO2 and other substances that will be present as impurities. A state-of-the-art computer-controlled VLE apparatus has been developed that can operate at pressures up to 20 MPa and at temperatures down to 183 K. We are also investigating the efficacy of alternative hybrid process configurations involving low-temperature flash units in combination with a secondary method such as a pressure-swing sorption of membrane separation.
- The viscosity of crude oils and hydrocarbon mixtures. This project is focused on measurement and modelling of crude-oil viscosity under the conditions of temperature and pressure encountered both in the reservoir and in production tubules. Both synthetic hydrocarbon mixtures and crude-oil systems are being studied, as well as their mixtures with various viscosity reducers such as solvents and supercritical fluids. The work involves two main experimental approaches. First, a bespoke vibrating-wire viscometer developed in our laboratory is sued for low-shear-rate viscosity measurements at pressures up to 200 MPa and temperatures up to 473 K with simultaneous density measurements. Second, a controlled-stress rheometer fitted with a high-pressure measurement cell is sued to study the rheology of crude oils, crude oil emulsions and their mixtures with carbon dioxide at reservoir conditions.
Other active areas of research involve the following key areas of measurement:
- the thermophysical properties of liquid fuels under high-pressure conditions; and
- the speed of sound and derived thermodynamic properties of industrial gases and liquids; and
Generally, the aim of these experiments is to provide accurate data on key systems over wide ranges of temperature, pressure and composition so that they may be used in the validation and improvement of thermodynamic and molecular-theory-based models, some developed in my group and others in collaboration with colleagues.
The experimental studies of model reservoir fluids started in 1996, was subsequently developed with funding from EPSRC, DTI, Shell and Schlumberger, and now forms a part of our research programme under QCCSRC funded by Shell, Qatar Petroleum and the Qatar Science and Technology Park. The background to the work is twofold: first, current efforts within the industry to improve petroleum reservoir management through better modelling; and, second, the objective of CO2 capture and storage. The physical properties of the fluids (gases, oils and reservoir waters) play an important role here and there is a need for validated property models based on experimental results for well-characterised fluid systems. The experimental programme includes measurements with a suite of VLE and PVT apparatus, from which phase behaviour and density may be obtained, and a set of vibrating-wire instruments from which viscosity may be obtained. Measurements have been made on model systems comprising both light and heavy alkanes, inorganic gases and waxes at temperatures up to 473 K and at pressures up to 200 MPa. Additionally, under QCCSRC, aqueous systems have received special attention, brines with dissolved carbon dioxide. The results are used to optimise engineering physical-property models and in the development and testing of new theory. For example, there is presently no well-founded way to predict the viscosity of a fluid mixture over all fluid states and the experimental programme is coupled with theoretical efforts aimed at rectifying this situation. Similarly, usual engineering thermodynamic models fail badly for many complex mixtures and the results of our experiments are being used to test newly-developed molecular-theory models, especially the Statistical Associating Fluid Theory (SAFT) for potentials of the Mie form, which offer superior predictive power.
Acoustical measurements have been and remain a major interest. World-class experimental facilities have been developed under my direction for sound speed measurements on compressed gases and liquids. In the gas phase, results have been obtained for numerous systems from which precise and useful intermolecular-potential models have been derived. New techniques have been developed by means of which all observable thermodynamic properties of the gas may be obtained from sound-speed data. Bespoke equipment has been designed and built for studying compressed liquids and, together with other instruments, this amounts to a measurement system from which thermodynamic properties of liquids may be obtained at pressures up to 400 MPa. All of the sound speed experiments are characterised by very high precision with typical estimated uncertainties ranging from 0.001 to 0.05 percent.
Research Student Supervision
Jones,C, Quantification and monitoring of fluid phase behaviour and trapping in geological carbon sequestration sites
Ansari,H, CO2 enhanced shale gas recovery