微观结构差异对碳酸盐岩酸蚀损伤的影响

为明确碳酸盐岩矿物成分、微观结构、分布形态等对酸岩反应速率、微观结构以及力学强度的影响,开展了酸岩反应速率实验、表面静态溶蚀实验以及点荷载力学强度实验。结果表明,在盐酸质量分数保持不变的条件下,灰岩与盐酸的反应速率与碳酸盐含量直接相关,碳酸盐含量越高,酸岩反应速率越快,反应越剧烈;由于灰岩裂隙区域基质与裂隙填充物矿物成分存在差异,基质与裂隙孔隙率相差较大,酸液会沿着裂隙方向侵蚀,形成沟槽,并且继续向裂隙深处扩展;灰岩基质破坏形态是裂缝在基质中开始发育,扩展至天然裂隙延伸,最后造成局部破坏;随着滴酸次数的增加,灰岩基质力学损伤系数大于裂隙区域力学损伤系数,灰岩基质由脆性向延性转化。

Influences of Microstructural Differences on Acid Corrosive Damage to Carbonate Rocks

Experiments on acid-rock reaction rate, surface static corrosion and point-load mechanical strength were carried out to investigate the influences of mineral composition, microstructure and distribution of carbonate rock on acid-rock reaction rate, microstructure and mechanical strength. The results show that, at a constant mass fraction of HCL, the reaction rate between limestone and HCL is directly related to the carbonate content. The higher the carbonate content is, the faster the acid-rock reaction rate and the more intense the reaction will be. Since there are differences in the mineral compositions between the matrix in the fracture zone and the fillings in the fractures, the porosity of the matrix is quite different from that of the fractures, so that acid would erode the mineral compositions along the fractures, resulting in grooves. The damages to the matrix of limestone by acid can induce fractures and extend to natural fractures, and consequently local damage occurs. With the increase of the times of acid dropping, the mechanical damage coefficient of the matrix in limestone would be greater than that of the fracture zone, and the limestone matrix transforms from brittle to ductile.