Use of solution-mined caverns in salt for oil and gas storage and toxic waste disposal in Germany

Abstract

The need for storage caverns for oil and gas, and repositories for toxic chemical waste is increasing world-wide. Rock salt formations are particularly suitable for the construction of cavities for such purposes. Owing to its favourable geomechanical properties, rock salt remains stable over long periods of time without support, and it can be shown that the geological barrier of the host rock remains intact for a remarkably long time. Safety analysis must be made for each proposed site based on site-specific data. The methods of doing this are well known and related technical recommendations exist in Germany. These recommendations apply to the planning, construction, operation and post-operational management of salt caverns used for the underground disposal of hazardous wastes. In particular, geotechnical site-specific safety verification, as required by the government's technical regulations on wastes (TA-Abfall) under the section “Underground Disposal”, is required. This safety verification must cover the entire system comprising the waste, the cavern and the surrounding rocks. For this purpose geomechanical models have to be developed. The steps which must be taken when carrying out geological engineering site explorations and when determining geotechnical parameters are discussed. In addition, recommendations are made for the design and construction of underground repositories. For liquid-filled caverns, long-term sealing from the biosphere is of particular interest. In this instance it must be shown that the natural increase in pressure in the closed cavity due to long-term convergence does not exceed the fracture pressure. A special filled test (scale 1:1) has been performed to study this.