Qatar Thermophysical Laboratory
The Qatar Thermophysics Laboratory is dedicated to the study of fundamental physics and chemistry to improve our understanding of carbon sequestration and CO2-driven enhanced oil recovery. There are presently significant gaps in our knowledge concerning the thermophysical properties that are basic input parameters for reservoir simulators and the building blocks of quality predictive simulations of CO2 storage.
The laboratory houses customised high pressure, high temperature (HPHT) equipment to provide high accuracy experimental data for brine/CO2/hydrocarbon systems under reservoir conditions. The properties studied include phase equilibria, density, interfacial tension, contact angle, viscosity and diffusion coefficients. The HPHT equipment for use with brines and high pressure gases, much of which is built in house, requires specialist designs, materials and operating procedures.
In the first phase of QCCSRC, the laboratory considered mainly the thermophysical properties of mixtures of pure CO2 with brines. The solubility of supercritical CO2 in various brines has been measured, as well as density, viscosity and mutual diffusion coefficients for the resulting solutions, over extensive ranges of temperature and pressure. Interfacial tension between coexisting CO2-rich and brine-rich phases was also studied extensively. A number of these properties were also measured for mixtures of supercritical CO2 with hydrocarbon systems.
A key feature of the current phase of our research is the role of the impurities that are inevitably present in the CO2 stream, including diluents, other acid gases and light hydrocarbons. Such impurities can have a strong influence on phase behaviour and interfacial properties when injected CO2 contacts reservoir fluids and minerals. The experimental techniques developed in Phase I are now being deployed to address these issues.
The pH of CO2-saturated brines and their reactions with carbonate minerals at reservoir conditions is also being studied in a bespoke set of batch reactors. Here the emphasis is on measuring surface chemical reaction rates, free of mass transfer effects, and on elucidating the effect of organic surface contaminants on these rates. A variety of surface-science techniques are also being employed to study on a microscopic scale both the process of mineral dissolution in CO2-acidified brines and the properties of adsorbed organic films that may inhibit surface chemical reactions.
Thermophysical and chemical data are generated in the laboratory for a limited number of chemical systems over wide ranges of temperature and pressure. These data are then used to calibrate and validate molecular-based equation-of-state and transport models, which are in turn used to predict the thermophysical properties and chemical reactions for all the different chemical systems and conditions of interest in the pore-scale and reservoir models.
Looking forward: areas under investigation
1. Quantifying carbonate reaction rates with CO2-saturated brines
2. Accurate pH measurements in HPHT CO2-brine systems
3. Phase behaviour through analytical and synthetic analysis
4. Interfacial properties of CO2-brine-mineral systems
5. Density, viscosity and diffusion of reservoir fluids
6. The specific role of impurities in all of the above