Electric submersible pumping system and method for dewatering gas wells

1. A method of unloading water from a natural gas reservoir, comprising:

deploying a downhole assembly of a pumping system into a wellbore and within a tubular string disposed in the wellbore to a location proximate the reservoir using a cable having coaxial conductors and a strength sufficient to support a weight of the downhole assembly and the cable, wherein:

the downhole assembly comprises a motor, an isolation device, and a multi-stage pump,

the isolation device has an expandable seal and an anchor, and

a maximum outer diameter of the downhole assembly and the cable is less than or equal to two inches;

setting the isolation device, thereby rotationally fixing the downhole assembly to the tubular string and isolating an inlet of the multi-stage pump from an outlet of the multi-stage pump;

supplying a direct current (DC) power signal from the surface to the downhole assembly via the cable extending through a bore of the tubular string, thereby:

operating the motor and multi-stage pump at a speed greater than or equal to ten thousand revolutions per minute (RPM),

pumping the water to the surface through the bore of the tubular string, and

lowering a water level in the tubular string bore to a level proximate the reservoir; and

once the water level has been lowered and while the water level is lowered in the tubular string bore:

unsetting the isolation device; and

removing the downhole assembly from the wellbore using the cable.

2. The method of claim 1 , wherein the downhole assembly further comprises a power conversion module (PCM), and the PCM sequentially switches the DC signal and supplies an output power signal to the motor.

3. The method of claim 2 , wherein the DC power signal is substantially greater than one kilovolt and the output signal is substantially greater than one kilovolt.

4. The method of claim 2 , wherein:

the DC power signal is substantially greater than one kilovolt, and

the PCM includes a power supply operable to reduce the DC power signal voltage, and

the output power signal is less than or equal to one kilovolt.

5. The method of claim 2 , wherein the output power signal is three phase.

6. The method of claim 5 , wherein the motor is switched reluctance.

7. The method of claim 1 , wherein:

the tubular string is a production tubing string hung from the wellhead and isolated from a casing string by a packer, and

the casing string is cemented to the wellbore.

8. The method of claim 1 , wherein the speed is greater than or equal to twenty-five thousand RPM.

9. The method of claim 8 , wherein the speed is greater than or equal to fifty thousand RPM.

10. The method of claim 1 , wherein the isolation device is unset by sending a signal via the cable.

11. The method of claim 1 , wherein the isolation device is unset by exerting tension on the cable.

12. The method of claim 1 , further comprising controlling a speed of the motor.

13. The method of claim 1 , wherein the downhole assembly comprises a sensor, and the method further comprises transmitting a measurement by the sensor to the surface via the cable.

14. The method of claim 1 , wherein the isolation device is set by sending a signal via the cable.

15. The method of claim 1 , wherein the isolation device longitudinally fixes the downhole assembly to the tubular string, thereby supporting the weight of the downhole assembly.

16. The method of claim 1 , wherein the pump is centrifugal and has a housing including a nozzle operable to create a jet effect.

17. The method of claim 1 , wherein the motor is started and operated after setting the isolation device.