10 cubic millimetre cube in the rock, where only the nitrogen fluid blobs are being shown. They are coloured in accordance with how connected they are to other fluid blobs. For example, pink and red blobs are fully connected throughout. Purple are blobs connected only across a handful of pores, and blue nitrogen blobs only inhabit one pore.
The discovery could lead to a range of improvements including advances in Carbon Capture and Storage (CCS). This is where industrial emissions will be captured by CCS technology, before reaching the atmosphere, and safely stored in rock deep underground. Miles below the surface of Earth different types of fluids are flowing through the microscopic spaces between the grains inside rocks. Scientists from the College have used the Diamond Light Source facility in the UK to make 3D videos that show in more detail than ever before how fluids move through rock.
For over 100 years, engineers have been modelling how multiple fluids flow through rocks for a range of reasons. For example, modelling 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 modelling how CO2 flows through rock as part of CCS.
Previously, scientists have used a formula for modelling how fluids move through rocks. It’s called Darcy’s Extended Law and the premise of it is that gases move through rock via their own separate, stable, 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 have discovered that rather than flowing in a relatively stable pattern through rocks, the flows are in fact very unstable. The pathways that fluids flow through actually only 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 they used the synchrotron particle accelerator at the Diamond Light Source. The synchrotron enables the researchers to take 3D image at speeds much 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 significantly 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 only possible right now 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 modelling CO2 storage, the production of oil and gas, and the migration of fluids deep in Earth’s crust.
http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/newssummary/news_17-7-2017-15-19-11
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