Hydrodynamics’ subsurface exploration geology experience is directly applicable to evaluate the CAES potential of both salt domes & bedded salts.
Natural gas and air have been stored successfully in solution-mined salt cavities because of the impermeability of the salt. Salt is an attractive medium because it functions as a self-healing material. The process of solution mining causes the salt to re-crystallize along the cavity walls creating an essentially impermeable surface. The crystallized salt membrane, the exceptionally low matrix permeability, and the plastic nature of salt enable it to seal secondary fractures in the rock to create a nearly ideal gas storage vessel. In salt, natural gas and air storage pressure ranges can exceed hydrostatic pressure for extended periods without impairing the integrity of the storage cavity.
The solution mining of salt typically forms an elongated irregular shaped cavity within the salt bed or salt diaper structure. The solution mining of salt involves the injection of water through a well into the salt bed or dome structure. The dissolved salt in the water solution is then extracted through the annulus of the water injection well for disposal at the surface. Factors that impact the development and use of solution mined salt cavities are:
• Limit on the physical size the cavity,
• Removal of non-soluble impurities in the salt formation,
• Disposal of the solution mined salt, and
• Potential collapse of the cavity because of plasticity of salt.
Of these factors, the presence of non-soluble impurities in the salt formation and the disposal of the solution-mined salt are the most important.
Hydrodynamics has evaluated the potential of developing bedded salts for CAES services in Arizona, Utah, Nebraska, West Texas, Michigan, the Texas Panhandle, Alberta Canada and Larne, Northern Ireland. Our studies show that:
1. Bedded salts are prominent throughout the Western U.S. and in Alberta, Canada.
2. The depth of these bedded salts is adequate for CAES development.
3. The thickness of bedded salts is typically adequate to create a CAES storage cavern.
4. Bedded salts may contain impurities like minor beds of shale Anhydrites, and mud stones. These impurities mean the effective volume of a solution mine cavity could be reduced as much as 50%.