Effect of CO2 solution on Portland cement paste under flowing, migration, and static conditions

Abstract

In this study, a dynamic corrosion device for cement paste was developed according to the underground conditions of oil and natural gas wells, which possess a largely dynamic and constantly migrating corrosive medium. Using CO2 as the corrosion medium, the effects of the three corrosion conditions, namely static non-migration, dynamic non-migration, and dynamic migration of the corrosion solution, on the corrosion process of cement paste were studied. The results revealed that under static non-migration conditions, the corrosion products aggregated on the surface of the cement paste samples and filled the pores of the samples, thereby slowing the corrosion rate. Conversely, the ability of the corrosion products to fill the pores weakened and the leaching effect was enhanced in samples under dynamic non-migration conditions because of the flowing corrosion medium, which further accelerated the corrosion process. The migration of the corrosion medium strengthened the leaching effect of CO2 in the samples. The cracks on the surface of the samples were wider and longer than those of the non-migrated samples. This was more conducive to the invasion of corrosive media and for the acceleration of the corrosion process. These results not only enhance the understanding of cement corrosion, but also provide a new perspective and reference for corrosion research of oil-well cement paste.