蒙脱石与不同浓度KOH溶液作用反应产物的矿物学特征分析

Mineralogical characteristics of the products from montmorillonite treated by different concentrations of KOH solution

蒙脱石具有强烈亲水性,遇水体积可膨胀至原体积的数倍甚至数十倍,从而造成油气储层的水敏损害,但在强碱条件下蒙脱石可发生结构变化与物相转变,从而使其亲水性降低。本文具体探讨了天然钠基蒙脱石在80℃,0.1 M KOH、0.5 M KOH、1 M KOH溶液中所发生的碱溶反应;并通过XRD、SEM、EDAX等测试手段分析发现,碱溶相变的发生与碱溶液浓度及反应温度密切相关;碱溶相变最终产物主要是微米级纤维状、柱状、颗粒状的菱沸石和麦钾沸石,均为不具膨胀性的架状硅酸盐矿物;最后通过自由膨胀实验证实蒙脱石碱溶产物膨胀性较原矿物显著降低。

Montmorillonite is a widely distributed clay mineral in the oil and gas basin.When it is encountered with water,its volume can expand by several or tens of times,which can be ascribed to the strong hydrophilic character.Consequently,oil and gas reservoirs might be damaged by its water-sensitive property.In this study,the phase transformation and hydrophilic behaviors of natural Na-smectite were investigated in alkaline solution.The natural smectite was put in solution of 0.1 M KOH,0.5 M KOH and 1 M KOH at 80℃ for 30 days.The pH values of KOH solution after reaction were measured,and solid products were analyzed by X-ray Diffraction（XRD）,Scanning Electron Microscope（SEM）,and electron dispersive analysis of X-rays（EDAX）.The XRD results indicated that part of montmorillonite was transformed into chabazite and merlinoite after 30 days.The results showed that phase change of montmorillonite was related to the concentration of KOH and reaction temperature.Concomitantly,new crystals in plate-like,fibrous and granular forms were observed by SEM.Accom-panied by the phase transformation,the hydrophilicity and the free swelling volume of minerals were reduced.