Digital tools to make geological storage of CO2 more affordable
We know it, it is being highlighted as the greatest risk for the world and mankind: everyday human activity pours tons of CO2 into the atmosphere, and their cumulative effect means that, slowly but steadily, the world's average temperature increases and climate changes. One response to this is obviously finding ways to reduce the emissions so that the natural mechanisms to fix CO2 are sufficient. The other one consists in stocking CO2 back into the depths of the earth, from where it was extracted in the form of fossil fuels and gas. Simple to say, but not as easy nor cheap to accomplish, as this implies pumping back liquid CO2 through deep walls through the earth's crust, so that it gets then diluted in deep underground waters. Victor Vilarasa, a young Spanish researcher and innovator, has worked to make this task easier.
Vilarrasa is Postdoctoral Fellow of the prestigious Lawrence Berkeley National Laboratory and has specifically worked on liquid CO2 injection for geological storage in deep saline aquifers. For that, he also received a Special Doctoral Award of the Technical University of Catalonia (UPC), where he obtained his PhD in 2012. As he explains it, ''a lot of research has been carried out on the final phase of the process - how the diluted CO2 behaves once it is deep under ground - and not as much research has addressed the conditions for optimal injection''. That is why, he continues, the process is still very expensive: the CO2 is typically injected into the ground in its supercritical state, that is at high temperature and pressure conditions, at which the fluid has certain characteristics of liquids - such as dissolving materials - and other typical of gases – for instance, they can effuse through solids.
By developing an elaborate simulation software, Vilarrasa has shown that the liquid state may be more suitable for CO2 injection, not only for its much lower costs (operating at non-critical temperature and pressure) but also in terms of efficiency: the lower temperature, for instance, generates mico-shocks that help the fracturation of the rock and the descent of the CO2 by simple gravity.
To establish the ideal temperature and pressure, however, more information is needed. That is where Vilarrasa's software, composed of two modules helps engineers who need to accomplish the injection task: given a number of parameters of the geological environment where the operation takes place, he can simulate the changes in temperature and pressure all along the route, through the well first and through the underlying rock substrate secondly. Existing tools assume a ''much simpler model'' with a fixed temperature and pressure along the entire route, and cannot model how the rock reacts to the injected liquid.
The software is to be tested in a real-case scenario, to send the CO2 generated by a thermoelectric plant in Compostilla (Spain). Once his intuitions are verified in a practical scenario, CO2 may find a shorter path to where it is less harmful to the Earth.