灰质白云岩可溶性影响研究

Study on solubility effect of gray dolomite

目的常温常压条件下方解石与白云石含量组成相近的碳酸盐岩溶蚀研究较少,为揭示此类岩石溶蚀特性,方法选取灰质白云岩作为试验对象,开展常温常压下不同酸性与流态条件下的溶蚀模拟试验,通过分析酸液pH、试样质量与孔隙变化、钙镁离子释放量等碳酸盐岩溶蚀参量,探讨影响灰质白云岩溶蚀速率的因素。结果结果表明:(1)pH≤3时,H+消耗量大于钙镁离子生成量,电导率值呈快速降低趋势;pH>3时,H+消耗量略大于钙镁离子生成量,电导率呈缓慢降低趋势,pH=3是电导率值由大变小转折的关键点,突出体现了H+消耗量与钙镁离子生成量的关系。(2)灰质白云岩方解石溶解速度与溶蚀量均远大于白云石的,初始酸液摩尔浓度较高条件下溶蚀效果更明显。(3)孔隙数量增加会加大岩石与酸溶液接触面积,进而加快岩石溶蚀速度。(4)杂质充填岩石孔隙减小了酸液对岩石的破坏。(5)高摩尔浓度酸液(pH≤3)与较强流态环境下溶蚀速率更大,岩石表面可溶物质溶出能力更强,酸液摩尔浓度较低时(pH≥4),流态变化对溶蚀速率影响较小。结论研究结果可为碳酸盐岩溶蚀研究、溶蚀程度评价与工程建设提供参考。

Objectives Since there are fewer studies on the dissolution of carbonate rocks with similar composition of calcite and dolomite content under normal temperature and pressure,in order to reveal the dissolution characteristics of this kind of rocks,Methods it selected gray dolomite as the test object to carry out dissolution simulation tests under different acidic and flow conditions at normal temperature and pressure to explore the factors influencing the dissolution rate of gray dolomite by analyzing the dissolution parameters of carbonate rockssuch as pH of the acid solution,the quality of the specimen and the change of the pore space,and the amount of calcium and magnesium ions release.Results Results show that:(1)When acid pH≤3,H+consumption is larger than calcium and magnesium ion generation,and the conductivity value shows a rapid decreasing trend,when acid pH>3,H+consumption is slightly larger than calcium and magnesium ion generation,and the conductivity shows a slow decreasing trend,and acid pH=3 is the key point of the turn of the conductivity value from large to small,which highlights the relationship between the consumption of H+and the generation of calcium and magnesium ions(.2)The dissolution rate and amount of calcite in gray dolomite is much higher than that of dolomite,and the dissolution effect is more obvious under the condition of higher initial acid molar concentration.(3)An increase in the number of pores increases the contact area between the rock and the acid solution,which in turn accelerates the rate of rock dissolution.(4)Filling of rock pores with impurities reduces acid damage to the rock.(5)High molar concentration of acid(pH≤3)has a higher dissolution ratein the stronger flow state environment,and has a stronger ability to dissolve soluble substances on the rock surface.When the molar concentration of acid is lower(pH≥4),the change of flow state has less effect on the dissolution rate.Conclusions The results of the study can provide reference for carbonate rock dissolution research,dissolution degree evaluation and engineering construction.