石英溶解特征及机理的水热实验研究

Hydrothermal Experiment Research on Characteristics and Mechanisms of Quartz Dissolution

对石英在不同温度、p H值条件下与流体相互作用进行了水热实验研究,根据石英溶解的扫描电镜形貌特征、样品质量损失及反应液中Si O2浓度的变化,并结合大牛地气田的石英溶解现象,总结了石英的溶解特征及溶解条件,并在前人研究基础上探讨了石英的溶解机理。研究结果表明,石英溶解具有"雨痕状"溶坑、"蜂窝状"溶孔及"层状"溶蚀的典型电镜形貌特征;随温度及p H值的升高,石英的溶解程度逐渐增强且在碱性条件下更易溶,由此推断大牛地气田上古生界致密砂岩储集层中的石英溶解发生于碱性环境中;在石英晶体的边角、晶面条纹、断口、裂纹或晶体发育缺陷部位更多地存在K面而使得晶体结构单元更易脱落,因而,在这些部位溶解最易发生。

On the basis of morphology features of quartz dissolution observed under scanning electronic microscope,the mass loss of quartz and Si O2 concentration in the reaction liquid,and combining the quartz dissolving phenomenon in the Daniudi gas field,this paper summarized dissolving characteristics and conditions of quartz through hydrothermal experiments under different temperature and p H conditions. This paper also discussed the dissolving mechanism of quartz based on predecessor＇s researches. Our experiment results provided some indications. First,quartz dissolution showed morphology features,such as ＂raindrop imprint＂pits,＂honeycomb＂holes and ＂stratiform＂dissolution,under scanning electronic microscope. Second,quartz dissolution enhanced gradually with increasing of temperature and p H,especially in alkaline solutions. We concluded that the quartz dissolution in the tight sandstone reservoir of the Upper Paleozoic Daniudi gas field occurred in an alkaline environment. A great number of K faces,from where crystal structural units can easily fall off,present at places of crystal edge,corner,striae,fracture,crack and defect lead to that dissolution of quartz usually occurs in these places.