Study of corrosion stability of a cement stone in magnesia aggressive environment

Abstract

One of the main tasks in the construction of oil and gas wells is to ensure the high quality of well casing. It is especially difficult to get it in wells, in sections of which there are salt-bearing strata. From the salts, the most dangerous are magnesia salts, which can lead to the destruction of the stone based on portland cement within a few months. The report presents the results of experimental studies on the corrosion of cement stone in aggressive magnesia media.The quantitative indicators reflecting the degree of damage to the stone are taken as the thickness of the damaged layer and the coefficient of stone resistance, characterized by the ratio of the ultimate strength of stone samples for compression or bending stored in an aggressive environment to the strength of control samples at the same time of hardening. In the course of the research, the corrosion resistance of the cement stone to the magnesian corrosive environment was assessed, after 8 weeks in a medium with a constant concentration of MgCl2. In addition, the effect of MgCl2 concentration on the cement stone corrosion mechanism was investigated. The use of the palygorskit additive and the reduction of water cement ratio to reduce the porosity of the cement stone and reduce the rate of corrosion damage are proposed. The kinetics and the main factors affecting the corrosion process are considered, and the x-ray structural analysis of corrosion products and unaffected cement stone is carried out.