Engineers from Imperial College London say they have dispelled a century-old scientific law used to describe how fluid flows through rocks.

Their work could lead to a range of improvements including advances in carbon capture and storage (CCS) in which industrial emissions are captured before reaching the atmosphere and stored in rock underground.

Scientists are rethinking how fluids flow through rocks.Scientists from the College used the Diamond Light Source facility in the UK to make 3D videos that show how fluids move through rock.

For over 100 years, engineers have been modeling how multiple fluids flow through rocks for a range of reasons. For example, modeling fluid flow enables engineers to determine how to extract oil and gas.

Understanding how seawater flows through rocks provides insights into the volatility of Earth’s crust, and predicting how fresh water flows through rocks enables engineers to manage water resources. More recently, engineers have been modeling how carbon dioxide (CO₂ ) flows through rock as part of CCS.

Scientists have relied on Darcy’s Extended Law, whose premise is that gases move through rock via their own separate, stable and complex microscopic pathways. This has been the underpinning approach used by engineers to model fluid flow for the last 100 years.

However, the Imperial scientists say that rather than flowing in a relatively stable pattern through rocks, the flows are in fact unstable. The pathways that fluids flow through last for a short period of time, tens of seconds at most, before re-arranging and forming into different ones. The team have called this process "dynamic connectivity."

To create the 3D images the researchers used the synchrotron particle accelerator at the Diamond Light Source. The synchrotron enables the researchers to take 3D image at speeds faster than a conventional laboratory X-ray instrument – around 45 seconds compared to hours for a laboratory-based instrument. This enabled them to see the dynamics, which had not been previously observed before.

However, an even higher time resolution would enhance the observations. These fluid pathways re-arrange themselves quickly, so ideally the team would like the observations to capture every 100th of a second. This time resolution is possible using optical light from microscopes combined with high-speed cameras. However, they are limited in their ability to observe fluids moving through real rocks.

The next steps will see the team attempting to overcome this technological obstacle using a combination of novel optical and X-ray imaging techniques. This could enable them to model fluid flow on a large scale, which would be of use for modeling CO₂ storage, the production of oil and gas, and the migration of fluids deep in the Earth’s crust.

The research is published in the journal Proceedings of the National Academy of Sciences and funded by Engineering and Physical Science Research Council’s Doctoral Training Scholarship Scheme and supported by the Qatar Carbonates and Carbon Storage Research Centre, funded jointly by Qatar Petroleum, Shell and the Qatar Science and Technology Park.