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国内盐岩矿床的典型特征是夹层多,其中云应、平顶山地区多为石膏夹层。盐岩储库在建造和运行过程中,夹层会浸泡在卤水和石油中。为了研究石膏夹层在腐蚀条件下的断裂韧度和弱化损伤机制,采用国际岩石力学学会建议的V形切槽巴西圆盘试验(CCNBD)试件,分别将其浸泡在淡水、半饱和卤水、饱和卤水和酸性石油中,温度分别为20℃、50℃、80℃,浸泡时间为1个月,并与干试件进行对比。研究结果表明:同一种液体浸泡后,石膏的断裂韧度随着温度的升高而急剧下降,而同一温度下,石膏的断裂韧度随着卤水的浓度增大基本不变。水和卤水浸泡后的石膏断裂韧度变化程度要大于酸性石油。石膏在水和卤水浸泡后的弱化机制是由于水-温度-氯离子的作用,其中水-温度的作用占主导,氯离子的侵蚀作用较小;酸性石油浸泡后的弱化机制是因为温度破坏了氢键及受热膨胀,同时另一原因是石膏和酸性石油(环烷酸)发生弱反应。环烷酸和石膏发生环烷酸钙,而环烷酸钙溶于油相有利于反应正向进行。上述研究对评估盐岩储库的稳定性及其密闭性具有重要意义。
The typical characteristics of the domestic salt rock deposits are mezzanine, where the cloud should be, mostly Pingdingshan gypsum interlayer. Salt rock reservoirs in the construction and operation of the process, the sandwich will be soaked in brine and oil. In order to study the fracture toughness and weakening damage mechanism of gypsum interlayer under corrosion conditions, the CCNBD specimens recommended by the International Society for Rock Mechanics were soaked in freshwater, semi-saturated brine, saturated Brine and acid oil, the temperature was 20 ℃, 50 ℃, 80 ℃, soaking time of 1 month, and compared with the dry specimens. The results show that the fracture toughness of gypsum decreases steeply with the increase of temperature after the same liquid immersion, while the fracture toughness of gypsum remains unchanged with the increase of brine concentration at the same temperature. The degree of fracture toughness change of gypsum after immersing in water and brine is greater than that of acid oil. The weakening mechanism of gypsum after soaking in water and brine is due to the action of water-temperature-chloride ion, of which the effect of water-temperature is dominant and the corrosion of chloride ion is small. The weakened mechanism of acid oil immersion is because the temperature is destroyed Hydrogen bonding and thermal expansion, the other reason is that gypsum and acid oil (naphthenic acid) weak reaction occurs. Naphthenic acid and gypsum calcium naphthenate occurred, and naphthenate dissolved in the oil phase is conducive to the reaction forward. The above research is of great significance to evaluate the stability of rock salt reservoir and its airtightness.