The article presents the results of work on identification of the causes of through metal fracture of casing pipe and well completion elements during mechanized oil production at the Vankorskoe oil field. According to the results of scanning electron microscopy and X-ray phase analysis of metal samples and corrosion products from the surface of casing pipe it is established that the corrosion process is of carbon dioxide nature, the through fractures initially occurred due to corrosion of the inner surface of the pipe. Behavior of mechanical impurities carried by well products (transport, accumulation along the well profile) at different flow rates was evaluated in a dynamic multiphase flow simulator. For this purpose, a model of the wellbore section in the interval «intake of ESP system - upper part of the liner – bottomhole» was built and a parametric study of the well operation with the change of flow rate was carried out. Hydrodynamic modeling of multiphase flow with transport of mechanical impurities showed that at flow velocities less than 0.2 m/s there is an accumulation and transport of sand along the lower component of the pipe in horizontal and directional wells, which increases the probability of corrosion-erosion wear by the mechanism of rill and subsurface corrosion. Comparison of sand transport modeling data with the data of intra-pipe flaw detection (magnetic introscopy) showed that the nature and localization of casing pipe damage directly depend on the amount of accumulated sand at the site. Solution of the problem of rill and subsurface carbon dioxide corrosion of casing by increasing the flow rate requires a balanced approach. Increasing the flow rate implies the use of a high-capacity submersible electrical motor, which in its turn leads to acceleration of electrochemical erosion-corrosion due to the growth of vibration loads, the influence of stray currents, high flow rate with mechanical impurities between the submersible electrical motor and the wall of casing pipe. The results of the conducted research allow to reasonably approach the definition of a set of measures aimed at the selection of technologies and materials for protection of casing pipe from corrosion-erosion wear.
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