RESEARCH OF DYNAMICS OF HYDROGEN SULPHIC CORROSION OF METAL OF CASING UNDER THE LAYER OF MODIFIED CONCRETE

Abstract

The issue of protection of problem areas of oil well casings, which are operated in aggressive environments of formation fluids of Iraq, containing hydrogen sulfide, carbon dioxide and chlorides, is considered. It is pro-posed to reduce the influence of aggressive factors by using modified cement compositions. The chemical composi-tion of Portland cements and modified compositions based on them was studied, experimental samples of cement stone were obtained and tested in a simulated aggressive environment (80% CO2 and 20% H2S) at a temperature of 105˚ C for 1200 hours. The dynamics of corrosion development in steel 45 under the cement layer is analyzed. It is shown that the rate of crevice corrosion of casing metal (steel 45), protected by modified concrete, obtained on the basis of Port-land cement grade G is much lower (5-6 times) relative to protection by unmodified concrete, and the protective effect of modified cement stone increases over time. It is concluded that the modification has a positive effect on the protective properties of cement stone. In the process of researching new grouting materials having improved anticorrosion properties, optimal for-mulations of the developed compositions were selected, the dependence of the strength characteristics, adhesion and gas permeability of the stone, as well as its anticorrosion properties on the ratio of components in grouting mixtures were studied. The use of new grouting materials with improved inhibitory properties will help to reduce the risks of prema-ture deformation of the deep sections of the casing string as a result of the corrosion destruction of its external surface, as well as improve the quality of formation demarcation in oil and gas wells with aggressive fluids con-taining hydrogen sulfide, carbon dioxide and a significant amount of dissolved in formation water of chloride ions, has practical value. The results of the work have the prospect of practical application for fastening deep wells, including direc-tional ones, in difficult mining and geological conditions on exploration areas and industrial oil fields of Iraq. Keywords: casing string, formation fluids, hydrogen sulfide, carbon dioxide, chlorides, corrosion, Portland cement, grouting materials, protective properties