Progressive cavity pump/motor

Abstract

A progressive cavity pump or motor, particularly suitable for hydrocarbon recovery operations, includes a rotor 20 and a stator 10. Fluid pressure in cavities between the stator and the rotor create torque which rotates the bit. An interior surface of the stator is rigidly secured to the outer housing of the pump stator and defines an interior profile. A substantially uniform thickness elastomeric layer 62 is supported on the outer housing. The pump rotor has an exterior profile which corresponds with the interior profile of the elastomeric layer.

Description

FIELD OF THE INVENTION [0001] This invention relates to the design and manufacture of pumps and motors utilizing progressive cavity power sections. More specifically, this invention relates to the design and manufacture of the female stator component of the progressive cavity pump or motor. BACKGROUND OF THE INVENTION [0002] U.S. Pat. No. 1,892,217 discloses a gear mechanism of a progressive cavity pump or motor. This progressive cavity technology is commonly used in a pump to convert mechanical to power fluid energy, and in a motor to convert fluid energy to mechanical power. As a downhole motor, the moving energy of a drilling fluid may be converted to rotary motion to rotate a bit to drill a subterranean well. Other publications of interest including U.S. Pat. Nos. 3,084,631; 4,104,009; 4,676,725; 5,171,138; 5,759,019; 6,183,226; 6,309,195; and 6,336,796; and WO 01 / 44615. [0003] Operation of a progressive cavity pump or motor utilizes an interference between the external profile ...

AI Technical Summary

Problems solved by technology

The resilient material used for the stator introduces weaknesses into the operation and life of the pump / motor.

Mechanical resistance of the elastomer is also of concern since high pressures are generated in the cavities of the pump / motor.

These high fluid pressures and the necessary reactive forces result in significant deflection and stress in the elastomer, particularly along the rotor / stator interferences.

These forces create friction which generates a large amount of heat during operation, and this heat may be very deleterious to the desired characteristics of the elastomer, and thus deleterious to the performance and life of the pump / motor.

If the heat resulting from the previously mentioned sources becomes excessive, the properties of the elastomer will more generally degrade.

Additionally, the high pressure experienced during operation may deflect the thicker sections of elastomer to the extent that the interference is overcome and contact with the rotor is lost.

This loss of contact results in decreasing speeds for the motor and decreasing flows for the pump, resulting in poor efficiency.

In addition, heat from the pump / motor operation, in some cases in conjunction with the environment in which pump / motor operates, distorts the shape of the elastomer molded to the interior of the metal tube.

As a result of the varying thicknesses and the relatively high thermal expansion of the elastomer, the radially thick sections distort more than the thinner sections of the stator, which results in a geometrical profile drastically different than intended, thereby hindering the proper operation of the pump / motor.

This distorted profile may generate additional heat and further distort the stator profile, creating a system which rapidly contributes to its own degradation and ultimate failure.

During operation, a conventional downhole progressive cavity drill motor develops a great deal of heat due to the friction between the rotor and the stator.

The center of the stator profile lobes is subjected to heat from a large percentage of its surrounding area and is the most limited in transferring this heat to the metal tube due to the thickness of the elastomeric material.

With extended operation, the center of the stator profile lobes may become hard and brittle as a result of the excessive heat in this area, and the mechanical properties of the rubber or elastomer in this area are accordingly severely degraded.

As a result, the stator lobe may break or “chunk out” of the stator profile.

In addition, the pressure acting in the chambers between the stator and the rotor may exceed the strength of the elastomeric material, and the stator lobe may deflect from its original shape or may break or “chunk off” the stator lobe.

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