A new environmentally friendly treatment for liquid carbon dioxide could improve the efficiency of using it to extract oil from the ground.
Scientists at the University of Bristol have developed the soap-like hydrocarbon additive as a way of thickening liquid CO2 so that it can be used to increase oil production by effectively flushing oil out from the pores of rocks.
The chemical additive, known as TC14, is the first known substance that turns liquid CO2 into a viable solvent for enhanced oil recovery (EOR) but doesn’t contain environmentally damaging fluorine.
Liquid CO2 requires less processing than other petrochemical solvents, can be easily recycled and provides a way of removing carbon from the atmosphere, so finding a way of making it more easily controlled and removing environmental hazards is an important challenge for the energy industry.
TC14 is a surfactant, meaning it lowers the surface tension of the CO2 and allows it to spread more easily. It also has potential to improve processes in other areas where liquid CO2 is used, such as food processing and electronics manufacturing.
The research involved using the STFC’s ISIS Neutron Source facility to study the process of CO2 thickening at the molecular level. The work was funded by the EPSRC and the US Department of Energy, which is now trialling the substance.
‘The problem was that nothing dissolved in liquid CO2 except some fluorocarbons, which are environmentally hazardous,’ project leader Prof Julian Eastoe told The Engineer.
‘The challenge was to reduce the amount of fluorine in those chemicals while maintaining their solubility and that was difficult to achieve, because the chemistry is a whole different game.’
By testing an array of substances over a period of 15 years, the Bristol team settled on a triple-branched molecule that can be easily derived and scaled up from alcohols and organic acids.
‘We nibbled away at the structure to create the perfect balance of solubility,’ said Eastoe.
TC14 works by enabling small pockets to form in the liquid CO2 called reverse micelles that cause the liquid to thicken. Neutron scattering, carried out at ISIS at the Rutherford Appleton Laboratory near Oxford, allowed scientists to study the structure of the reverse micelles as they formed under high pressure.
‘Beams of neutrons are able to penetrate deep inside samples, giving unique information about the location and arrangement of the micelles at a molecular level,’ said ISIS scientist Dr Sarah Rogers, who worked on the project.
‘It would be difficult to look at this system using any other technique as the CO2 needs to be kept under high pressure. Only under the scrutiny of neutron beams can you fully reveal its actions and properties.’