Carbonated Brine Effect on Wellbore Cement Degradation in Contact Zone with Formation Rock

Abstract

The objective of the work is to examine the cement-formation rock interface, under sequestration conditions. During the laboratory experiments the composed cement-rock samples were exposed in three cycles, to carbonated brine, under simulated underground conditions in order to determine rock and wellbore cement alteration. The rocks which were taken into account are sandstones and shale. The performed examination indicates that both cement and formation rock react in CO2 saturated brine under the experiment conditions. Most of the examined samples provide evidence for dissolution and corrosion processes. With progressing run time the corrosion and dissolution intensify. The alteration of the cement-rock interface is strongly dependent on the rock lithology, which includes rock structure (mainly porosity) and mineral composition. It was found that in consequence of some rocks’ components dissolution the cement-rock interface may be a pathway, where there is a possibility of flowing pore waters rich in CO2 to come into contact with the wellbore cement.