Gas tightness of unlined hard rock caverns

摘要

The storage of natural gas in depleted oil and gas fields, aquifers and salt caverns is by far the most important field of underground gas storage today. In many areas, including most of the Scandinavian mainland, these storages are excluded due to geological conditions. For such areas, mined caverns in the hard, crystalline bedrock may provide an alternative. Oil and liquefied petroleum gases (LPG) at low pressure (<1.0 megapascal (MPa)) are routinely stored in excavated hard rock caverns. The major challenge in hard rock storages at present is the development of safe and economical high pressure storages for natural gas and CAES (Compressed Air Energy Storage). For the investigation of the performance of unlined hard rock storages, so-called air cushion surge chambers are found to provide the most relevant and extensive experience. These storages which have the function of damping transients in the head race tunnel at Norwegian hydro power plants, have pressures up to 8 MPa and volumes up to 110,000 m(sup 3). Operational experience and results from specific water curtain tests at these sites, and other relevant experience are found to be in good agreement with theoretical results. Water curtains are installed at three of the ten air cushion surge chambers and at more than ten LPG-storages. The overall experience from these installations is encouraging; gas leakage has not been reported at any of these sites during ordinary operation. 91 refs., 77 figs., 14 tabs.