Complications associated with the corrosive environment, according to JSC Orenburgneft, NK Rosneft for the period 01.01.2021, are among the prevailing ones at oil and gas production facilities and share the 1st place with the scaling factor - 26% of the complicated mechanized well stock. Downhole equipment failures due to corrosion account for 20% of the total number of fixed failures in 2020. By the type of exposure to a corrosive environment at the fields operated within the perimeter of Rosneft, JSC Orenburgneft, hydrogen sulfide and mixed corrosion (caused by simultaneous action of CO2 and H2S) are predominant. The article presents the calculated data on the physicochemical characteristics of aqueous solutions of H2S. The existing approaches for description of the mechanisms of hydrogen sulfide corrosion of oilfield equipment with examples of corrosive destruction at producing string are described A dynamic matrix of the various protection technologies and their applicability in hydrogen sulfide-containing environments is presented, which is used in the fields operated by PJSC NK Rosneft and filled according to the results of laboratory and pilot field tests. The criterions of attribution of equipment to abnormal fund on basis of classification of factors complicated exploitation and following determination of equipment category being used in loc alized norms of NK Rosneft are described

The article is devoted to the analysis of corrosion behavior and assessment of the resistance of Hastelloy G 35. Nickel-based alloys (steels) containing chromium, molybdenum, tungsten, possibly iron are widely used as materials for the manufacture of equipment in high-temperature technological processes using solutions of highly hygroscopic halides (chlorides) in molten halides (chlorides) of alkali metals. During the operation of the equipment, the instability of the surface of apparatus and pipelines to corrosion is determined. In this test, 4 samples of 80×20×3 mm were used, of which 2 samples were subjected to provoking heating, and 2 samples were examined in their normal state. Our tests were carried out in a boiling aqueous solution of iron sulfate and sulfuric acid for 48 ± 0.25 h. Further, the bent samples were examined using an MBS-9 microscope with a magnification of х8. The results of corrosion tests are also presented. As a result of the study, the rate of penetration of corrosion of the alloy was calculated. Hastelloy microstructure is presented. The average depth of destruction was determined from the six maximum values detected in six fields of view. According to the research results, the corresponding conclusions were made.

The necessity of the complex approach is defined for increase of reliability of the oil and gas equipment operated under pressure of hydrogen sulfide-containing medium, including:
- control at the stages of design, manufacturing, commissioning , operation, repair and reconstruction;
- organization of corrosion service;
- rational choice of materials for equipment manufacturing and its repair;
- use of different methods to protect equipment against corrosi on:
- diagnostics of equipment and evaluation of corrosion protecti on efficiency;
- conducting corrosion tests of materials and corrosion control .
The trend of increasing corrosive activity of the products of a number of hydrogen sulfide-bearing oil and gas fields is described. This is associated with their watering and contamination by sulfate-reducing bacteria. All types of corrosion-mechanical damage of steels in accordance with GOST R 53679-2009 (ISO 15156- 1:2001) are considered. Comments are given on each of these types of damage and the types of steels that are prone to these defects are shown.
The recommendations of GOST R 53679-2009 (ISO 15156-1:2001) are given for the selection of steel equipment operated under pressure of hydrogen sulfide-containing media depending on the type of their corrosionmechanical failure, with comments.
Requirements for the use of steels modified with rare-earth metals (REM) and alkaline-earth elements (ALE) intended for operation in hydrogen sulfide-containing media are given