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To the problem of scaling in electric centrifugal pumps

UDK: 622.276.72
DOI: 10.24887/0028-2448-2018-9-116-120
Key words: oil production by electric centrifugal pumps, salt deposition, low-yield wells operation
Authors: R.F. Sharafutdinov (Bashkir State University, RF, Ufa), R.A. Valiullin (Bashkir State University, RF, Ufa), A.A. Gareev (Oil and Gas Production Department Nizhnesortymsckheft, Surgutneftegas PJSC, RF, Nizhnesortymscky)

During operation of the electric centrifugal pump, a gas-oil mixture accumulates above its suction eyes. As the temperature rises, the pressure decreases to saturation pressure, and the pump is surrounded by gas bubbles that are in dynamic equilibrium with the layers of oil upflow and downflow. The centrifugal pump efficiency depends mainly on the content of free gas bubbles in the mixture. On model liquids it is shown that with an air-to-oil content of 5%, the pump efficiency can be reduced by 25 - 30%. Pump starvation happens at higher gas content in the mixture. Excessive temperature rise in the pump results in the boiling of the formation water inside it. At lowВ  pump intakeВ  pressure the boiling point of water can be 120-150°C, as the pressure atВ  the pump intakeВ  increases, the water boiling temperatureВ В  also increases. Changes in pressure and the corresponding water boiling temperature are the reason for the beginning of the process of deposition of salts - scale in the internal cavity of the pump.

During electric centrifugal pump well operation the pressure at the pump intake decreases, which leads to an increase in the content of free gas in the gas-liquid mixture. The increase in gas content causes a pump efficiency decrease, which in turn causes an increase in its temperature. If, at the same time, the boiling temperature of the produced water is equal to or less than the temperature of the pump, then the process of its boiling will begin in the cavity of the pump. By adjusting the pressure at the electric centrifugal pump intake, it is possible to avoid boiling of the formation water and, consequently, salt deposits in the cavity of the pump.

References

1. Gareev A.A., On the significance of thermal practices in electrical centrifugal pumps units (In Russ.), Oborudovanie i tekhnologii dlya neftepromyslovogo kompleksa, 2009, no. 1, pp. 23–29.

2. Gareev A.A., About maximum gas content on the electrical centrifugal pump (ECN) suction (In Russ.), Oborudovanie i tekhnologii dlya neftepromyslovogo kompleksa, 2009, no. 2, pp. 21–25.

3. Gareev A.A., Temperature regime of electric submersible pump (In Russ.), Oborudovanie i tekhnologii dlya neftepromyslovogo kompleksa, 2010, no. 6, pp. 35–41.

4. Kashchavtsev V.E., Mishchenko I.T., Soleobrazovanie pri dobyche nefti (Salt formation in oil production), Moscow: Orbita-M Publ., 2004, 432 p.

5. Labuntsov D.A., Fizicheskie osnovy energetiki: Izbrannye trudy po teploobmenu, gidrodinamike, termodinamike (Physical principles of energy: Selecta on heat transfer, hydrodynamics, thermodynamics), Moscow: Publ. of MPEI, 2000.

6. Otte W., Mitt D., Verein der Gross Kesselpesitzer, 1929, V. 17, рр. 34–45.

7. Bulatov M.A., Kompleksnaya pererabotka mnogokomponentnykh zhidkikh sistem (Complex processing of multicomponent liquid systems), Moscow: MIR Publ., 2004.

8. Isaev S.I., Kozhinov I.A., Kofanov V.I. et al., Teoriya teplomassoobmena (The theory of heat and mass transfer): edited by Leont'ev A.I., Moscow: Publ. of Bauman Moscow State Technical University, 1997, 683 p.

9. Tsvetkov F.F., Grigor'ev B.A., Teplomassoobmen (Heat and mass transfer), Moscow: Publ. of MPEI, 2001, 550 p.

During operation of the electric centrifugal pump, a gas-oil mixture accumulates above its suction eyes. As the temperature rises, the pressure decreases to saturation pressure, and the pump is surrounded by gas bubbles that are in dynamic equilibrium with the layers of oil upflow and downflow. The centrifugal pump efficiency depends mainly on the content of free gas bubbles in the mixture. On model liquids it is shown that with an air-to-oil content of 5%, the pump efficiency can be reduced by 25 - 30%. Pump starvation happens at higher gas content in the mixture. Excessive temperature rise in the pump results in the boiling of the formation water inside it. At lowВ  pump intakeВ  pressure the boiling point of water can be 120-150°C, as the pressure atВ  the pump intakeВ  increases, the water boiling temperatureВ В  also increases. Changes in pressure and the corresponding water boiling temperature are the reason for the beginning of the process of deposition of salts - scale in the internal cavity of the pump.

During electric centrifugal pump well operation the pressure at the pump intake decreases, which leads to an increase in the content of free gas in the gas-liquid mixture. The increase in gas content causes a pump efficiency decrease, which in turn causes an increase in its temperature. If, at the same time, the boiling temperature of the produced water is equal to or less than the temperature of the pump, then the process of its boiling will begin in the cavity of the pump. By adjusting the pressure at the electric centrifugal pump intake, it is possible to avoid boiling of the formation water and, consequently, salt deposits in the cavity of the pump.

References

1. Gareev A.A., On the significance of thermal practices in electrical centrifugal pumps units (In Russ.), Oborudovanie i tekhnologii dlya neftepromyslovogo kompleksa, 2009, no. 1, pp. 23–29.

2. Gareev A.A., About maximum gas content on the electrical centrifugal pump (ECN) suction (In Russ.), Oborudovanie i tekhnologii dlya neftepromyslovogo kompleksa, 2009, no. 2, pp. 21–25.

3. Gareev A.A., Temperature regime of electric submersible pump (In Russ.), Oborudovanie i tekhnologii dlya neftepromyslovogo kompleksa, 2010, no. 6, pp. 35–41.

4. Kashchavtsev V.E., Mishchenko I.T., Soleobrazovanie pri dobyche nefti (Salt formation in oil production), Moscow: Orbita-M Publ., 2004, 432 p.

5. Labuntsov D.A., Fizicheskie osnovy energetiki: Izbrannye trudy po teploobmenu, gidrodinamike, termodinamike (Physical principles of energy: Selecta on heat transfer, hydrodynamics, thermodynamics), Moscow: Publ. of MPEI, 2000.

6. Otte W., Mitt D., Verein der Gross Kesselpesitzer, 1929, V. 17, рр. 34–45.

7. Bulatov M.A., Kompleksnaya pererabotka mnogokomponentnykh zhidkikh sistem (Complex processing of multicomponent liquid systems), Moscow: MIR Publ., 2004.

8. Isaev S.I., Kozhinov I.A., Kofanov V.I. et al., Teoriya teplomassoobmena (The theory of heat and mass transfer): edited by Leont'ev A.I., Moscow: Publ. of Bauman Moscow State Technical University, 1997, 683 p.

9. Tsvetkov F.F., Grigor'ev B.A., Teplomassoobmen (Heat and mass transfer), Moscow: Publ. of MPEI, 2001, 550 p.


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