During periodic operation of oil wells using electric submersible pump (ESP) systems there were revealed cases when the temperature sensors installed on the motor casing fix higher temperature than the temperature sensors inside it. This fact indicates the presence of a heat source outside the motor. This source can only be the pump. During the pumping phase, the ESP heats up by drawing fluid from the annulus above and below the pump. In the accumulation phase, new fluid from the reservoir enters the annulus above the pump, where it is heated by heat exchange with the ESP casing and tubing. In the next cycle, during the pumping phase, more heated fluid enters the pump. With each new cycle, the fluid temperature increases, but at the same time the heat transfer to the formation surrounding the casing increases. The temperature rise ends when thermal equilibrium is reached. A mathematical model of this phenomenon is proposed, calculations are made showing that heating will be higher, the higher the pumping rate, the shorter the pumping time and the higher the concentration of undissolved gas. Hot liquid from the pump will get on the motor housing if the check valve does not close completely when the pump is switched off. Calculations showed that the gas-liquid mixture can be heated to temperatures exceeding the critical temperature (200-250 °C) for elastomers used in ESPs. The obtained results can be used in the selection of ESP and periodic operation mode of the selected system in the well.
References
1. Ageev Sh.R., Grigoryan E.E., Makienko G.P., Rossiyskie ustanovki lopastnykh nasosov dlya dobychi nefti i ikh primenenie (Russian vane pumping systems for oil recovery and their use), In “Entsiklopedicheskiy spravochnik” (Encyclopedic reference book), Perm’: Press-master Publ., 2007, 645 p.
2. Kuz’michev N.P., Short-term well operation [STWO] is unique approach to reduction of effects of complicating factors [in petroleum production] (In Russ.), Ekspozitsiya Neft’ Gaz, 2014, no. 4, pp. 56–59.
3. Yudin E.V., Piotrovskiy G.A., Smirnov N.A. et al., Methods and algorithms for modeling and optimizing periodic operation modes of wells equipped with electric submersible pumps (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2023, no. 5, pp. 116–122, DOI: http://doi.org/10.24887/0028-2448-2023-5-116-122
4. Pashali A.A., Khalfin R.S., Sil’nov D.V. et al., On the optimization of the periodic mode of well production, which is operated by submergible electric pumps in Rosneft Oil Company (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2021, no. 4, pp. 92-96, DOI: http://doi.org/10.24887/0028-2448-2021-4-92-96
5. Erka B.A., Osobennosti tekhnologii ekspluatatsii elektrotsentrobezhnymi nasosami skvazhin s neustanovivshimisya rezhimami raboty (Features of the technology of operation of electric centrifugal pumps of wells with unsteady operating modes): thesis of candidate of technical science, Tyumen, 2006.
6. Mikheev M.A., Mikheeva I.M., Osnovy teploperedachi (Fundamentals of heat transfer), Moscow: Energiya Publ., 1977, 344 p.
