The performed analysis established that the causes of abnormal heating during operation of electric submersible pumps (ESPs) in wells and pumping out wateroil-gas mixtures are associated with abnormal non-stationary operating modes – pump capacity breakdowns due to the negative effect of free gas on pump characteristics and difference in oil and water densities in heavily flooded wells. Various methods are given for preventing supply failures due to the effect of free gas and a large difference in oil and water densities. The failure of the ESP feed is caused by a decrease in the inflow from the formation, clogging of the intake screen, pump stages and tubing with mechanical impurities and solid phase deposits. Once ESP is used as part of pump-ejector systems, the failure of the feed occurs when the ejector nozzle is blocked by junk. During short-term periodic operation of low-flow wells by ESP units, another cause may occur, associated with additional heating of the well product flow from the stopped pump. Intensification of the processes of oil and water separation in wells during short-term periodic operation by ESP units contributes to an increased risk of failure of the feed and abnormal heating. The expediency of further designed experimental studies of temperature distribution along the length of a multistage ESP during pumping of gas-liquid mixtures with varying degrees of bubble coalescence suppression is shown, which shall serve as a basis for developing methods of calculation for heating the flow by a pump in stationary and non-stationary modes. © 2025, Neftyanoe Khozyaistvo. All rights reserved.