黏土矿物水化膨胀及无机盐溶液对其抑制作用

为揭示富有机质页岩水化膨胀机理，借助于X射线衍射仪对富有机质页岩中主要黏土矿物水化膨胀规律及无机盐溶液对其抑制效果进行了物理实验研究。结果表明：随着去离子水浸泡时间的增加，蒙脱石、伊利石和绿泥石都可以发生一定的膨胀，表明三种黏土矿物都可以发生水化反应，但蒙脱石晶层间距的膨胀程度远高于伊利石和绿泥石。无机盐溶液可以抑制蒙脱石和伊利石的水化膨胀，且对伊利石水化膨胀抑制性更好。不同类型无机盐的抑制效果受到无机盐溶液浓度的影响，在无机盐溶液浓度小于1.2 mol/L时，随着浓度的增加，同种类型无机盐溶液的抑制作用逐渐增强。加入无机盐溶液后随着时间的推移，黏土矿物水化作用始终在进行，晶层间距仍在增大，即无机盐溶液不能完全杜绝黏土矿物水化反应的发生。该研究成果可为页岩气水平井井壁稳定、水力压裂设计及现场工程应用提供技术参考。

Hydration Expansion of Clay Minerals and Its Inhibitory by Inorganic Salt Solution

In order to reveal hydration expansion mechanism of organic-rich shale, the physical experiment about hydration expansion rule of the main clay minerals in organic-rich shale and the inhibitory effect of inorganic salt solutions on hydration expansion of the main clay minerals have been carried out by means of an X-ray diffractometer. The physical experiment results indicate that montmorillonite, illite and chlorite all can expand to a certain extent with the increase of soaking time in deionized water, show that three kinds of clay minerals can occur a content of hydration reaction, but the expansion degree of montmorillonite crystal layer spacing is far higher than that of illite or chlorite. Inorganic salt solution can inhibit the crystal layer hydration expansion of montmorillonite and illite, and inhibitory effect of inorganic salt solution on the hydration expansion of illite is better than montmorillonite. Inhibition effect of different kinds of inorganic salt solution is affected by the concentration of inorganic salt solution. When the concentration of inorganic salt solution is less than 1.2 mol/L, the inhibitory effect of the same type of inorganic salt solution increases gradually with the increase of concentration. With the passage of time, the hydration expansion of clay mineral is always going on after the addition of inorganic salt solution, crystal layer spacing is still increasing, that is, the inorganic salt solution can''t completely put an end to hydration reaction of clay minerals. The research results can provide technical reference for the design and field engineering application of borehole stability and hydraulic fracturing in shale gas horizontal wells.