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Relevance of this study is concluded in the fact that high quality cementing requires regulation of the cement grouts’ properties using various chemicals. The objective of the work is based on the study of polyelectrolytes’ application efficiency used for regulation of cement slurries’ properties. In order to conduct the research the authors used the devices meeting the API requirements. Properties of cement slurry and cement were evaluated according to GOST 1581-96. In order to study the gas show emergence mechanism during the procedure of WOC (waiting on cement), the authors used a special experimental plant. It has been found that high efficiency during the research was shown by water soluble cationic polyelectrolyte (WSC-402), belonging to the class of cationic polymers. Also the paper considers its analog – cationic polyelectrolyte (PAK) released under the trade mark Praestol. Studying the mechanism of polyelectrolyte additives’ effect on cement showed that the chemicals can slow down the hydrating reaction of С3А in cement-water suspension, and prevent from the growth of gel strength of the grout, which causes drop in hydrostatic pressure of the cement grout column, provoking gas shows.

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To control water production, it is necessary to seal the channels of 20-25 mm thickness in the cement sheath at a depth of hundreds and thousands of meters. The most promising solution is the use of self-healing cements.The concept of self-healing materials has been known since the 1980s due to the studies of Donald Jud. The most fundamental works are who substantiated the concept, suggested technologies and additives to restore the integrity of polymer and cement materials.Despite active research in this area, Schlumberger is the only service company which elaborated and successfully applied the «self-healing» well cement called Futur.The authors of the article set the task of well cement modification that enables autonomous «healing» of water-conducting channels through which formation water migrates.The following materials were used in the study: polyacrylamide (PAA), water-swellable polymer (VNP V-615), sodium polyacrylate (SP), cross-linked PAA copolymers, active waterproofing mineral additives and swelling elastomers. Most of the additives have a degree of swelling of more than 150%, they effectively reduce a permeability of the cement stone, however multi-layer coating is required to control the speed of their swelling. A significant drawback of the analyzed materials was the complexity of the coating.A cross-linked AA copolymer based on anionic polycrylamide was the most effective reagent, which was easy to cover with a water-soluble shell. The cement stone with integrated agent of AA copolymer demonstrated a permeability of 0.0018 μm 2 with the strength of the samples for bending at the age of 2 days equal to 8.0 MPa.

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.