Successful brining the well into production and its durability primarily depend on the quality of annulus cementing operations. The diversity of the chemical composition of formation waters and the high temperatures at which the cement stone hardens does not allow one to unambiguously choose the composition of the cement slurry. Formation waters, which are the most widespread and frequently encountered during well drilling contain magnesium ions, chlorides and sulphate ions in their composition, and are very aggressive towards cement stone. Magnesia salts are among the most dangerous and can lead to the destruction of cement stone based on Portland cement within a few months.
This paper presents the results of experimental studies on the corrosion resistance of stones from a mixture of Portland cement and building caustic magnesite. This magnesite is the basis for magnesia cement, which has proven to be effective in magnesia salts.
The amount of magnesite in the mixture was 5, 10, 15 and 20 percent respectively in order to find out the optimal concentration of the additive. Rheological parameters were measured for each variant of the slurry. The samples were placed in a 10% MgCl2
solution in order to simulate a magnesian layer. The depth of penetration of magnesium ions and compressive strength were taken as an indicator for assessing the degree of cement stone damage. The duration of the experiment was 14 months. Every 2 months the samples were removed and tested. The solution was also simultaneously updated with a new one to eliminate the effect of concentration changes.
The kinetics of magnesia corrosion was considered and several zones of damage to the stone are identified. As a result of the research, it was determined that a mixture of building caustic magnesite and portland cement has less aggressiveness to the casing than magnesia cement.
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F.A. Agzamov, Dr.Sc., Professor, Oil and Gas Well Drilling Chair, Federal State Budgetary Educational Institution of Higher Education Ufa State Petroleum Technological University
1, Kosmonavtov st., Ufa, 450064, Russian Federation
A.N.Makhmutov, PhD Student, of the Department «Oil and Gas Wells Drilling» Ufa State Petroleum Technological University
1, Kosmonavtov st., Ufa, 450064, Russian Federation
I.N. Karimov, Candidate of Engineering Sciences, director of research and development LLC «Cement technologies»
2, October ave., Sterlitamak, 453100, Russian Federation
F.A. Agzamov, A.N. Makhmutov, I.N. Karimov Sovershenstvovaniye retseptur tamponazhnykh rastvorov dlya krepleniya skvazhin pri magnezial'noy agressii [Improvement of oil-well cement formulations for well casing in magnesium aggressive environment]. Neftyanaya Provintsiya, No. 1(33), 2023. pp. 32-45. DOI https://doi.org/10.25689/NP.2023.1.32-45. EDN TBOEJB (in Russian)