Experimental simulation of the carbonate dissolution process under different occurrence conditions

Abstract

At present, the researches on the dissolution process of carbonate rocks are mostly concentrated on a single environmental equilibrium state, and the researches in different occurrence environments and at a micro scale are relatively weak. In order to explore the dissolution process and the micro change characteristics of carbonate rocks in different occurrence environments, with the help of the developed simulation device of water-rock interaction in different occurrence environments of karst groundwater systems, the indoor dissolution simulation test of the representative rock samples of karst groundwater systems is carried out in the typical open environment, semi-closed environment and closed environment. CO2 solution is used as the acid fluid medium. The changes and control factors of characteristic components in karst groundwater are examined, and the characteristics of the dissolution of representative minerals in different occurrence environments of karst groundwater systems are explored from the macro and micro perspectives. The results show that the spatial variation characteristics of the contents of Ca2+ and \begin{document}${\rm{HCO}}_3^- $\end{document}, saturation index and pH value are different in different occurrence environments, and each characteristic component presents an increasing trend with the runoff direction and dissolution time. Under the influence of the CO2 in the aqueous solution, the carbonate rock has the strongest dissolution in the open environment of the supply area, forming the solution pores and openings with high connectivity. The average value of the total dissolution rate of the carbonate rock is 1.43 times that of the total dissolution rate in the semi-open environment, 2.70 times that of the total dissolution rate in the closed environment. The microstructure in the semi closed environment is between the two forms of the isolated micropores and the completely connected gaps. In addition, with the change of depth, the amount of dissolution decreases gradually, and the change of shallow part is more obvious. The dissolution of carbonate rocks is also controlled by lithology and increases with the increasing CaO/MgO ratio.

Keywords

• occurrence environment
• carbonate rock
• corrosion characteristics
• microstructure