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Abstract The property of pore structure is the key issue for the tightness of storage caverns. Mercury injection porosimetry tests and scanning electron microscopy(SEM) tests are conducted for different lithological rocks in bedded salt rock. The relationship between porosity and permeability，pore structure，distribution characteristics，as well as the corresponding tightness properties，are analyzed. The mercury injection porosimetry tests indicate that the porosity of the measured salt rock，mudstone and mudstone glauberite is 2.7%，6.0% and 2.5%，respectively. Compared to common rock types，the porosity of the bedded salt rock is extremely low. There exists obvious relationship between porosity and permeability；low porosity is the sufficient but not necessary condition of low permeability，whereas，high permeability is the sufficient but not necessary condition of high porosity. Sometimes，low permeability phenomenon occurs when it is under high porosity. The most influence on permeable property is the connected pores. Once there are connected pores，the permeability will increase rapidly.
The scanning electron microscopy(SEM) tests present that the salt rock is a kind of typical crystalized rocks；and the inner structure is extremely closed with no obvious pores and cracks. In respect to the mudstone，the particle size difference between clay and organic matters influences obviously the pore properties，which exhibits that the mineral particles with different sizes，and bulk or pebble shape tend to cause pore development. But in the region of particles with mean bulk distribution，the structure is much closed and with almost no pores and cracks. The interface of salt rock and mudstone is not the region with developed pores. By contraries，the mudstone and salt rock particles connect and insert with each other；and the fine mudstone particles fill the pores and cracks，which results in further decreased porosity. The pores of salt rock with mudstone(or mudstone with salt rock) are well-developed and of relatively high connectivity，which may cause the region be of high permeability. Therefore，it is recommended that it should avoid the key position in regions with well-developed pores when the storage caverns is designed and constructed. The presented research can serve as important reference for the construction and tightness evaluation of the storage caverns.
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Received: 28 May 2013
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2013, Vol. 32 
