层状盐岩细观孔隙特性试验研究

孔隙特性是决定盐岩储库密闭性的关键因素。对层状盐岩中不同岩性的试样开展压汞法测试和电镜扫描试验，分析层状盐岩孔隙率与渗透率的关系，并对层状盐岩的孔隙结构、分布特性及其密封性能进行研究。压汞测试表明：盐岩、泥岩和泥质钙芒硝的孔隙率平均值分别为2.7%，6.0%和2.5%，与常规岩石对比发现层状盐岩的孔隙率处在非常低的水平。孔隙率与渗透率之间存在明显的关系：低孔隙率是低渗透率的充分非必要条件，而高渗透率是高孔隙率的充分非必要条件，高孔隙率的试样有时也会出现低渗透率的情况。对岩体渗透率影响最大的是相互连通的部分孔隙，一旦存在连通的孔隙，渗透率就会显著增加。电镜扫描结果显示，盐岩是典型的晶体构造，内部结构密实，无明显的孔隙存在。泥岩中黏土和有机质颗粒的差异会显著影响其孔隙性质，颗粒粒径大小不一且呈块状或卵石状的区域孔隙大量发育，颗粒均质、呈块状的区域结构密实，孔隙较不发育。泥岩和盐岩的交界面处并不是孔隙发育的区域，泥岩和盐岩相互咬合、嵌入及泥岩细小颗粒的填充使孔隙率降低。含泥盐岩(含盐泥岩)中局部孔隙较为发育，并且连通度较高，是渗流可能发生的区域，建议储气库设计建造时避免将关键部位设置在孔隙发育区域，以保障密闭性。本文的研究成果可为储气库的建造及密闭性分析提供指导。

EXPERIMENTAL INVESTIGATION ON MESO-PORE STRUCTURE PROPERTIES OF BEDDED SALT ROCK

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.