TECHNICAL FIELD

This document relates to progressing cavity pumps and methods of operation.

BACKGROUND

Progressing cavity pumps are known whose lifespan can be extended by initially using a first rotor to engage a first part of the stator, then pulling and replacing the first rotor with a second rotor that engages a second part of the stator.

SUMMARY

A method is disclosed for operating a progressing cavity pump in a borehole, the progressing cavity pump having a rotor within a stator, the method comprising: axially translating the rotor, relative to the stator, from a first operating position within the stator to a second operating position within the stator; in which, when the rotor is in the first operating position a first axial part of the rotor aligns with a first axial part of the stator to form an active pump section adapted to generate a pumping force on rotation of the rotor in the stator; and in which, when the rotor is in the second operating position the first axial part of the rotor aligns with a second axial part of the stator to form an active pump section adapted to generate a pumping force on rotation of the rotor in the stator.

A progressing cavity pump is disclosed comprising: a stator; a rotor; the rotor having a first axial operating position within the stator in which a first axial part of the rotor aligns with a first axial part of the stator to form an active pump section adapted to generate a pumping force on rotation of the rotor in the stator; the rotor having a second axial operating position within the stator in which the first axial part of the rotor aligns with a second axial part of the stator to form an active pump section adapted to generate a pumping force on rotation of the rotor in the stator.

A progressing cavity pump in an oil or gas well comprises a stator and a rotor, the stator designed to have more than the required stages for the expected pressure resulting in extra length (for example double the stages of a conventional pump), the stator designed to have a constant diameter and eccentricity across its length, the first rotor designed to have active sections which the minor diameter is relatively large and has an interference fit with the stator and creates a seal, the first rotor also having inactive sections which the minor diameter is relatively small has a clearance fit and does not seal with the stator, the active and inactive sections of the first rotor may have equal or unequal lengths along the first rotor, the number of active and inactive sections along the first rotor may vary.

The stator may be connected to the lower end of a tubing string and inserted into a well bore. The first rotor may be connected to the lower end of a rod string and lowered into the tubing string, the rotor is positioned in the stator. Once the pump operates and wears out, the rotor may be lifted via a flush-by unit (or another means) the required distance to move the active sections of the rotor to the previously inactive sections of the stator, thereby restoring the pump. Alternatively, the first rotor may be retrieved from the well if the rotor has experienced significant wear, and a new rotor may be inserted into the stator to restore the pump. The new rotor may have active and inactive sections (sections with interference and clearance fit similar to first rotor) or the new rotor may have a uniform minor diameter that has an interference fit with the stator throughout.

A progressing cavity pump apparatus is disclosed for use in an oil well, comprising the following. A stator, connected to a tubing string, sized with extra stages (or lift). A first rotor connected to a rod string, the first rotor having a varying minor diameter such that multiple sections of the rotor have an interference fit with the stator and multiple sections have a clearance fit. The interference fit sections produce a pumping force and generate wear on the stator in these sections. The clearance fit sections only serve to transmit torque and do not have any interaction with the stator nor do they provide pumping work. The interference fit sections of the first rotor may vary in number and length across the rotor. The first rotor extends through the entire length of the stator. A first active position, that is activated upon the installation of the first rotor and is based on the interference fit of the rotor and stator. A second active position, that is activated once a flush-by unit pulls and sets the rod string upwards or downwards a predetermined distance to place the first rotor in the second active position. The distance will depend on the design of the rotor and stator. A third active position, that is activated once a by a flush-by unit pulls and sets the rod string upwards or downwards a predetermined distance to place the first rotor in the third active position. The distance will depend on the design of the rotor and stator. A second rotor, which is installed upon mechanical failure of the first rotor (wear). The second rotor may have varying minor diameter. The second rotor may have a constant minor diameter. The second rotor extends through the entire length of the stator

A method is disclosed for operating a progressing cavity pump in an oil and gas well bore, comprising the following. Installing a stator on a tubing string, and placing tubing string in a well bore. Installing a first rotor on a rod string, and placing rod string in the tubing string, the rotor being positioned within the stator. The first rotor having multiple sections of interference fit with the stator (relatively large diameter) and multiple sections of clearance fit (relatively small diameter). The first rotor extending completely though the length of the stator. Locating the first rotor in a first active position with the stator. Rotating/operating the first rotor its first position such that a pumping force is generated. Lifting or lowering the rotor via a flush-by unit (or another means) a set distance so that the first rotor now activates sections of the stator that were previously inactive/operating as clearance fit. In one case a user locates the rotor initially in a higher position, followed by lowering the rotor to a lower position. The rotor is sized to extend across an axial length of the stator in the first operating position and the second operating position. Rotating/operating the first rotor in its second position such that a pumping force is generated. If it is found that the second position of the first rotor has poor pumping characteristics due to rotor wear, the first rotor may be removed from the well and replaced with a new rotor that has a constant minor diameter along its length (or replaced with a new rotor that has a varying diameter similar to the first rotor).

In various embodiments, there may be included any one or more of the following features: When the rotor is in the first operating position, a second axial part of the rotor aligns with the second axial part of the stator to form an inactive pump section. The first axial part of the rotor defines a first minor rotor diameter, the second axial part of the rotor defines a second minor rotor diameter, and the first minor rotor diameter is larger than the second minor rotor diameter. When the rotor is in the first operating position: the first axial part of the rotor forms an interference fit with the first axial part of the stator; and the second axial part of the rotor forms a clearance fit with the second axial part of the stator. When the rotor is in the second operating position: the first axial part of the rotor forms an interference fit with the second axial part of the stator. The first axial part of the rotor comprises a plurality of first axial parts of the rotor. The second axial part of the rotor comprises a plurality of second axial parts of the rotor. The first axial part of the stator comprises a plurality of first axial parts of the stator. The second axial part of the stator comprises a plurality of second axial parts of the stator. First axial parts of the rotor and second axial parts of the rotor are arranged in alternating pairs along an axis of the rotor. First axial parts of the stator and second axial parts of the stator are arranged in alternating pairs along an axis of the stator. The first axial part of the stator defines a first minor stator diameter, the second axial part of the stator defines a second minor stator diameter, and the first minor stator diameter is equal to the second minor stator diameter. The first active section is a function of the first rotor position. The stator defines a uniform minor stator diameter across an axial length of the stator. Axially translating the rotor, relative to the stator, from the second operating position within the stator to a third operating position within the stator. When the rotor is in the third operating position a first axial part of the rotor, or another axial part of the rotor, aligns with a third axial part of the stator to form an active pump section adapted to generate a pumping force on rotation of the rotor in the stator. When the rotor is in the first and second operating positions the third axial part of the stator aligns with the rotor to form an inactive pump section. Axially translating the rotor from the first operating position to the second operating position further comprises axially translating the rotor in an uphole or downhole direction. The rotor is axially translated from the first operating position to the second operation position using a flush-by unit. While the rotor is in the first operating position, rotating the rotor relative the stator such that the first axial part of the rotor and the first axial part of the stator generate a pumping force. While the rotor is in the second operating position, rotating the rotor relative the stator such that the first axial part of the rotor and the second axial part of the stator generate a pumping force. The rotor is replaced with a second rotor. The second rotor defines a uniform minor diameter across an axial length of the second rotor. The second rotor has a varying minor diameter across an axial length of the second rotor. The progressing cavity pump assembly mounted to a tubing string in a borehole. Mounting the stator to a tubing string and inserting the stator into the borehole. Mounting the rotor to a rod string and inserting the rotor into the tubing string. The rotor has a helical body configuration, the helical body configuration having a number of helical lobes equal to n, and in which the stator has a helical cavity configuration, the helical cavity configuration having a number of helical lobes equal to n+1.

These and other aspects of the device and method are set out in the claims, which are incorporated here by reference.

