SUBMERSIBLE PROGRESSIVE CAVITY PUMP

Abstract

An electric submersible progressive cavity pump assembly is disclosed, which includes an electric motor, a progressive cavity pump, a transmission rotatable by the motor, and a torque isolator coupled between the transmission and the progressive cavity pump, where the torque isolator includes resilient members which accommodate sudden changes in torque.

Claims

1. An electric submersible progressive cavity pump assembly comprising: an electric motor; a progressive cavity pump; a transmission rotatable by the motor; and a torque isolator coupled between the transmission and the progressive cavity pump; the torque isolator including resilient members which accommodate sudden changes in torque.

2. An electric submersible progressive cavity pump assembly according to claim 1, wherein the torque isolator accommodates vertical movement between the progressive cavity pump and the motor.

3. An electric submersible progressive cavity pump assembly according to claim 1, wherein the resilient members are compressible and their compression is proportional to applied torque.

4. An electric submersible progressive cavity pump assembly according to claim 3, wherein the resilient members are Belleville washers.

5. An electric submersible progressive cavity pump assembly according to claim 1, wherein the transmission includes a roller screw or ball screw.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] By way of example the following figures will be used to describe embodiments of the invention.

[0033] FIG. 1 is a section side view of the umbilical deployed electric powered PCP with a decoupled drive between the transmission and PCP.

[0034] FIG. 2 is section side view of the tool assembly shown in FIG. 1 shown adjacent to the downhole position it would be in the well.

[0035] FIG. 3 is a section side view of a well with a surface driven PCP via rods installed down the centre of the production tubing, with the torque isolator tool installed at the lower end of the rods and above the PCP.

[0036] FIG. 4 is a section side view of the torque isolator tool in more detail.

DETAILED DESCRIPTION

[0037] Referring to FIGS. 1 and 4, there is shown an electric pumping assembly consisting of the following sub-assemblies, a progressive cavity pump (PCP) 1, a torque isolator 2, a transmission 3, a permanent magnet motor 4, a telescopic joint 5.

[0038] The PCP 1 is a standard type assembly, and consists of an outer housing 10, which connects to a lower housing 11 which stings into a polished bore receptacle 12 and seal 13 isolate the pump inlet 14 from the pump discharge 15. The upper end of the housing is attached to lower housing of the torque isolator tool 2 via a connection assembly 16 The output shaft from the torque isolator 80 connectors to a flexible shaft 17, which in turn rotates the eccentric rotating PCP pump shaft 18.

[0039] The torque isolator or soft drive tool 2 has an output spline coupling 18 which engages with the internal spline of the flexible shaft 17. The output shaft 80 has a rotating seal 81 which seals against the bore 82 of the outer housing 83. The output shaft 80 is retained axially by circlips 84 and 85 which act against needle roller bearings 86, 87, and radially by ball bearings 100, 101. A slot 88 is cut into the internal end of the output shaft 80. The output shaft from the lead screw 90 locates in the slot 88 and provides the drive from the lead screw to the output shaft. Needle roller bearings 91, 92 are mounted in the flat section of the lead screw output shaft 90 and reduce the friction between these two running surfaces. The output shaft 90 from the lead screw is supported in the bore 82 by two sets of roller bearings 93, 94, and connects to the lead screw nut 95, by counter sunk screws 96. The lead screw nut reacts against a stack of Bellville washers 97. The lead screw thread 98 is the output shaft of the transmission 3. In normal operation, the motor will be driving the load and the reactive torque will cause the lead screw to compress the Bellville washers until they equal the force generated by the reactive torque. If there are any sudden torque spikes, the Bellville washers will compress some more and then relax again once the spike has passed. The motor and transmission will continue to turn at a constant speed and not “see” any of these detrimental effects.

[0040] The transmission 3 employs balls instead of geared teeth. The device consists of an input shaft 21 on which are splines 22 Engaged in these spines are two rings 23, and 24 which have a 45 degree chamfered face 25 which makes a point contact with the balls 26. The rings 23 and 24 are pre-loaded by Bellville washers 27 and 28, which force the balls to contact the inner surface 29 of the outer housing 30. The balls are retained in slots 31 of the planet carrier 32. So in effect, the rings 23 and 24 act as the sun gear, the balls 26 as the planet, and the inner surface 29 of the outer housing as the outer ring. As the input shaft 21 is turned, the balls 26 rotate and drive the output shaft/ball carrier 32. Special transmission oil is used to transmit torque called a traction fluid, which both protect the balls and the running surfaces from wear and also transmit torque as a result of its special properties. More detailed information about these types of traction fluids can be found by referring to one of the following patents U.S. Pat. No. 7,645,395: Variable transmission traction fluid composition, U.S. Pat. No. 6,828,283: Traction fluid with alkane bridged dimer, U.S. Pat. No. 6,623,399: Traction fluids. Many other examples also exist, especially for high temperature applications. This oil is contained in the chamber 33 which also has a pressure compensation piston 34 to equalise the pressure in the chamber with the pressure outside the housing 30 via a communication port 35.

[0041] The transmission connects to the output shaft of the permanent magnet motor, this is very conventional in design. It consists of a rotor shaft 40 on which are mounted permanent magnets 41 adjacent to the stator section 42 the shaft is supported both axially and radially at both ends by bearings 43, 44. The stator is retained in the housing 45, and motor windings 46 pass through the stator. The motor is controlled from surface and receives it power through a cable 47 which is also used to lower the assembly into the well. It will also be appreciated, that the assembly could also be run conventionally on the end of tubing with the power cable strapped to the outside of the tubing.