Research on gas leakage and collapse in the cavern roof of underground natural gas storage in thinly bedded salt rocks
Research on gas leakage and collapse in the cavern roof of underground natural gas storage in thinly bedded salt rocks
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薄层盐岩地下天然气库洞顶瓦斯泄漏与塌陷研究
DOI：
10.1016/j.est.2020.101669
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发表时间：
2020-10-01
影响因子：
9.4
通讯作者：
Chen, Jie
中科院分区：
文献类型：
--
作者：
Liu, Wei;Zhang, Zhixin;Chen, Jie
在薄层盐岩中，盐穴储气库的洞顶岩性各异，有的洞顶可能发生破坏和失密。因此，研究层状盐岩储气库洞顶气体泄漏特性具有重要意义。为了实现这一目标，在本研究中，通过一个洞穴顶板的气体泄漏和诱导塌陷进行了研究。首先选择淮安盐矿ZJ区块盐溶洞作为储气库的选址，其顶板为盐岩、薄石膏层和厚泥质粉砂岩。在此基础上，对采场顶板岩层岩样进行了孔隙度和渗透率的实验室测定。第三，根据ZJ区块的地质条件，建立了数值模拟模型。模拟分析了三种不同顶板条件下的瓦斯渗流和硐室密闭性。结果表明，在洞顶完整的情况下，夹层是储气库的主要渗流通道，夹层渗透率在10 ~（-17）m2或更低时，储气库的密闭性是令人满意的。顶板的盐岩层破坏后，露出部分石膏层，瓦斯漏失量可增加一个数量级左右。而顶板渗流速率和孔隙水压力变化缓慢。因此，操作人员有足够的时间调查事故和转移气体。但薄石膏层破坏后，泥质粉砂岩暴露，气体渗流急剧增加。包括渗漏量、渗漏范围、孔隙水压力等都比上述两种情况下有较大幅度的增加。由于储存安全的严重后果，这种情况应绝对避免。为保证储气库顶板安全和严密性，建议合理的洞顶构造是前提，运行期间应定期进行内压监测和声纳测量。
In the thinly bedded salt rocks, the roofs of salt cavern gas storage may have different lithology, some cavern roofs of these caverns may be damaged and lose tightness. Thus it is significant to study the characteristic of the gas leakage through the cavern roof of the gas storage cavern in bedded salt rocks. To approach such a goal, the gas leakage through a cavern roof and the induced collapse are investigated in this study. At first, the salt cavern of ZJ-block of Huai'an salt mine is selected as the potential gas storage site, which has a roof consisting of salt rock, a thin gypsum layer, and thick argillaceous siltstone. And then, the porosity and permeability of rock samples of the roof strata are measured in the laboratory. Thirdly, a numerical simulation model is established based on the geo-conditions of the ZJ-block. The gas seepage and cavern tightness under three different cavern roof conditions are simulated and analyzed. The results show that, if the cavern roof is integral, the main gas seepage channels of the cavern are the interlayers, and the tightness of gas storage salt cavern is satisfactory once the permeability of interlayers is around 10(-17) m(2) or lower. After the salt rock layer of the roof is damaged and a partial gypsum layer is exposed, the gas leakage amount can increase about one order of magnitude. But the seepage rate and pore pressure both change slowly in the roof. Thus the operators have sufficient time to survey the accidents and transfer the gas away. However, after the thin gypsum layer is damaged and results in the exposure of argillaceous siltstone, the gas seepage sharply increases. Including the leakage amount, the seepage range, and the pore pressure are all increased much than that of the above two conditions. Due to the serious consequence of storage safety, this condition should be absolutely avoided. To ensure the roof safety and tightness of gas storage, it is suggested that the reasonable construction of a cavern roof is the prerequisite, and the internal pressure monitoring, as well as sonar measuring, should be engaged regularly during the operation period.