Clean energy storage potential (hydrogen, CAES) in salt formations of Western Canada: geological review

The underground H 2 gas storage (UHS) and compressed air energy storage (CAES) are two novel applications of salt caverns essential for net zero carbon economy. This review assesses rock salt units available for UHS and CAES in the subsurface of Western Canada Sedimentary Basin (WCSB). In the industrially developed WCSB south of 60°N, thick halite formations for gas storage occur in the Devonian Elk Point Group. Three salt units suitable for cavern emplacement are the Upper Lotsberg halite (≤ 183 m thick), the Cold Lake halite (mostly ≤ 40 m, locally > 100 m), and halite-dominated occurrences of the Prairie Evaporite Formation (≤ 210 m). To the north of 60°N, the thickest salt units of the broadest geographic expanse occur in the Saline River Formation of Cambrian age. The Saline River salts stretch across frontier areas and require more subsurface exploration for cavern emplacement potential. Whereas the Elk Point Group salts are entirely undeformed and bedded, the Saline River halites extend into the Laramide Cordillera where they form salt walls and diapirs. The salt caverns of WCSB are used for LPG, LNG storage and waste disposal. The depth range of cavern emplacement is between the groundwater protection depth (∼100-600 m) and 2000 m ( S v ≤ 37 MPa, T ≤ 90°C). There are 196 salt caverns in public records, of them 133 currently in UGS or waste disposal use. The vast majority are conventional caverns washed by direct single-well leaching, and 23% of WCSB caverns are operated with dual or triple entry. Most caverns (∼90%) are < 300,000 m 3 in volume, and several larger (up to 756,000 m 3 ) caverns are used for permanent waste fill. As of 2025, the first UHS-CAES cavern operation is under construction. The Upper Lotsberg is chemically the cleanest and most homogeneous halite in WCSB entitled for UHS, although occurrence of this salt is most geographically restricted. The Prairie Evaporite salt occurs over the broadest geographic expanse in three provinces, but cavern-purposed halites there tend to be less pure. In Saskatchewan, the upper Prairie Evaporite is not suitable for gas storage caverns due to high content of carnallite and sylvite. In UHS application, high reactivity of H 2 and production of H 2 S through microbial sulfate reduction will narrow the choice to cleanest halite beds with negligible sulfate mineral content, such as the Upper Lotsberg and the cleanest halite occurrences of the Prairie Evaporite.