Natural geological structures called salt domes in Abu Dhabi could play a leading role in the UAE’s energy transition, new research suggests.
These structures of sedimentary rocks, formed where a large mass of salt has been forced upwards, often forming traps for oil or natural gas, are of interest to engineers who are concerned with the storage of hydrogen generated by renewable energy.
In a new study, to be presented at a conference in Vienna at the end of April, scientists said that UAE authorities are “actively exploring the use” of salt domes for large-scale hydrogen and hydrocarbon storage. This, they said, is being carried out in line with the country’s aim of a “clean energy transition and decarbonisation”.
The scientists from Khalifa University of Science and Technology in Abu Dhabi and oil company Adnoc, said that the Jebel Al Dhanna salt dome stretches up to 2.8 kilometres east to west and 4.2km north to south.
It was analysed using three-dimensional seismic techniques and four boreholes to assess its capacity for salt caverns, which are created within the domes by using liquid to dissolve the salt to leave a cavity that can be used for storage.
Saving energy for times of need
“You engineer the salt caverns by pumping water underground and gradually dissolving over a year or three years,” said Stuart Haszeldine, a geologist and professor of carbon capture and storage at the University of Edinburgh in Scotland.
While the size of salt caverns depends on the size of the structure in which they are being created, Prof Haszeldine said they typically stretch 20 to 30 metres vertically or 30 to 50 metres horizontally, although they can be much larger.
The demand for hydrogen is growing and an advantage is that it can be stored underground until needed. At times of greater energy demand, the hydrogen can be extracted and used to power fuel cells that generate energy, or burned to produce heat.
Hydrogen is ideally stored underground, said Kevin Taylor, a professor in energy geoscience at the University of Manchester in England, because the gas’s low density means that it is not economical to build large-scale storage above the ground.
The use of salt caverns to store hydrogen is still at an experimental stage. However, the European Union is currently supporting a project called HyPSTER (Hydrogen Pilot Storage for large Ecosystem Replication) which is a large-scale salt cavern in Etrez in eastern France for hydrogen storage. The project team announced in late 2024 that the first hydrogen molecules had been injected into a salt cavern.
Other uses for salt caverns
Prof Haszeldine said that in the Gulf states, salt caverns could be used to store hydrogen for either export or domestic use. They are already, he said, “well proven” for the storage of methane.
In separate research published last year, Chinese scientists looked at the potential for salt caverns to be used for the storage of carbon dioxide. With carbon capture and storage, where CO2 released by industrial plants is collected, and direct air capture, where CO2 is sucked out of the air, the carbon dioxide is typically stored deep underground.
Ideally, it is dissolved and mineralised, creating a permanent storage so that the carbon no longer contributes to global warming. However, producing salt caverns to store CO2 permanently in this way may not be realistic, given the costs of creating the cavern, while another drawback is that the gas will not become mineralised.
“You could use salt caverns for CO2 storage, but you would probably make more money injecting hydrogen or methane in and out,” Prof Haszeldine said. “ … If you’re going to mine a cavern as a business, you will probably mine a cavern for the storage of hydrogen.”
While salt caverns may not be ideal for permanent CO2 storage, the researchers from China indicated in the journal Engineering they could be used for non-permanent CO2 storage and so could help to “promote the important transformation of carbon as a waste to [an] industrial resource”.
