Study of corrosion mechanism of dawsonite led by CO2 partial pressure

Abstract

The stability of dawsonite is an important factor affecting the feasibility evaluation of CO2 geological storage. In this paper, a series of experiments on the interaction of CO2-water-dawsonite-bearing sandstone were carried out under different CO2 pressures. Considering the dissolution morphology and element composition of dawsonite after the experiment and the fluid evolution in equilibrium with dawsonite, the corrosion mechanism of dawsonite led by CO2 partial pressure was discussed. The CO2 fugacity of the vapor phase in the system was calculated using the Peng-Robinson equation of state combined with the van der Waals 1-fluid mixing rule. The experimental results indicated that the thermodynamic stability of dawsonite increased with the increase of CO2 partial pressure and decreased with the increase of temperature. The temperature at which dawsonite dissolution occurred was higher at higher fCO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${f_{{\\rm{C}}{{\\rm{O}}_2}}}$$\\end{document}. There were two different ways to reduce dawsonite’s stability: the transformation of constituent elements and crystal structure damage. Dawsonite undergoes component element transformation and crystal structure damage under different CO2 pressures with certain temperature limits. Based on the comparison of the corrosion temperature of dawsonite, three corrosion evolution models of dawsonite under low, medium, and high CO2 pressures were summarized. Under conditions of medium and low CO2 pressure, as the temperature continued to increase and exceeded its stability limit, the dawsonite crystal structure was corroded first. Then the constituent elements of dawsonite dissolved, and the transformation of dawsonite to gibbsite began. At high CO2 pressure, the constituent elements of dawsonite dissolved first with the increase of temperature, forming gibbsite, followed by the corrosion of crystalline structure.