Variable diameter stator and rotor for progressing cavity motor

Patent metadata

Field	Value
Publication number	US-9869126-B2
Application number	US-201514821181-A
Country	US
Kind code	B2
Filing date	Aug 7, 2015
Priority date	Aug 11, 2014
Publication date	Jan 16, 2018
Grant date	Jan 16, 2018

Abstract

A mud motor for use in a wellbore may include a stator and rotor. The tolerance between the stator and rotor may be varied along the length of the mud motor to, for example, reduce wear of the stator at predetermined locations. The tolerance may range from an interference fit to a clearance fit. The tolerance may vary multiple times across the length of the mud motor.

First claim

The invention claimed is:

1. A mud motor for use in a wellbore, the mud motor comprising:
a rotor, the rotor including at least one helical rotor lobe extending therefrom;
a stator, the stator being tubular in shape and including at least two helical stator lobes extending inward from an inner surface thereof, the at least two helical stator lobes interfacing with the at least one helical rotor lobe to create at least one cavity between the stator and the rotor such that the cavity traverses the length of the stator as the rotor eccentrically rotates within the stator;
wherein the distance between the stator and the rotor at an interface between the at least two helical stator lobes and the at least one helical rotor lobe at a given point along the mud motor defines a tolerance; and
wherein the rotor and the stator are formed such that the tolerance at a first point along the mud motor is wider than the tolerance at a second point along the mud motor, wherein the first point along the mud motor is positioned nearer the upper end of the mud motor than the second point along the mud motor.

2. The mud motor of claim 1 , wherein the rotor comprises a first major rotor diameter and a first minor rotor diameter at a first point along the rotor corresponding with the first point along the mud motor and a second major rotor diameter and a second minor rotor diameter at a second point along the rotor corresponding with the second point along the mud motor, and at least one of the first major rotor diameter and the first minor rotor diameter is smaller than the second major rotor diameter and the second minor rotor diameter respectively.

3. The mud motor of claim 1 , wherein the stator comprises a first major stator diameter and a first minor stator diameter at a first point along the stator corresponding with the first point along the mud motor and a second major stator diameter and a second minor stator diameter at a second point along the stator corresponding with the second point along the mud motor, and at least one of the first major stator diameter and the first minor stator diameter is larger than the second major stator diameter and the second minor stator diameter respectively.

4. The mud motor of claim 1 , wherein the stator comprises an outer cover and a stator insert, the outer cover being tubular, and the stator insert being formed within the outer cover and including the at least two helical stator lobes.

5. A mud motor for use in a wellbore, the mud motor comprising:
a rotor, the rotor including at least one helical rotor lobe extending therefrom;
a stator, the stator being tubular in shape and including at least two helical stator lobes extending inward from an inner surface thereof, the at least two helical stator lobes interfacing with the at least one helical rotor lobe to create at least one cavity between the stator and the rotor such that the cavity traverses the length of the stator as the rotor eccentrically rotates within the stator;
wherein the distance between the stator and the rotor at an interface between the at least two helical stator lobes and the at least one helical rotor lobe at a given point along the mud motor defines a tolerance; and
wherein the rotor and the stator are formed such that:
the tolerance at a first point along the mud motor is wider than the tolerance at a second point along the mud motor; and
the tolerance at a third point along the mud motor is wider than the tolerance at the second point along the mud motor;
wherein the second point along the mud motor is positioned between the first point along the mud motor and the third point along the mud motor.

6. The mud motor of claim 5 , wherein the rotor comprises a first major rotor diameter and a first minor rotor diameter at a first point along the rotor corresponding with the first point along the mud motor and a second major rotor diameter and a second minor rotor diameter at a second point along the rotor corresponding with the second point along the mud motor, and at least one of the first major rotor diameter and the first minor rotor diameter is smaller than the second major rotor diameter and the second minor rotor diameter respectively.

7. The mud motor of claim 5 , wherein the stator comprises a first major stator diameter and a first minor stator diameter at a first point along the stator corresponding with the first point along the mud motor and a second major stator diameter and a second minor stator diameter at a second point along the stator corresponding with the second point along the mud motor, and at least one of the first major stator diameter and the first minor stator diameter is larger than the second major stator diameter and the second minor stator diameter respectively.

8. The mud motor of claim 5 , wherein the stator comprises an outer cover and a stator insert, the outer cover being tubular, and the stator insert being formed within the outer cover and including the at least two helical stator lobes.

9. A mud motor for use in a wellbore, the mud motor comprising:
a rotor, the rotor including at least one helical rotor lobe extending therefrom;
a stator, the stator being tubular in shape and including at least two helical stator lobes extending inward from an inner surface thereof, the at least two helical stator lobes interfacing with the at least one helical rotor lobe to create at least one cavity between the stator and the rotor such that the cavity traverses the length of the stator as the rotor eccentrically rotates within the stator;
wherein the distance between the stator and the rotor at an interface between the at least two helical stator lobes and the at least one helical rotor lobe at a given point along the mud motor defines a tolerance; and
wherein the rotor and the stator are formed such that:
the tolerance at a first point along the mud motor is wider than the tolerance at a second point along the mud motor; and
the tolerance at a third point along the mud motor is tighter than the tolerance at the first point along the mud motor;
wherein the first point along the mud motor is positioned between the second point along the mud motor and the third point along the mud motor.

10. The mud motor of claim 9 , wherein the rotor comprises a first major rotor diameter and a first minor rotor diameter at a first point along the rotor corresponding with the first point along the mud motor and a second major rotor diameter and a second minor rotor diameter at a second point along the rotor corresponding with the second point along the mud motor, and at least one of the first major rotor diameter and the first minor rotor diameter is smaller than the second major rotor diameter and the second minor rotor diameter respectively.

11. The mud motor of claim 9 , wherein the stator comprises a first major stator diameter and a first minor stator diameter at a first point along the stator corresponding with the first point along the mud motor and a second major stator diameter and a second minor stator diameter at a second point along the stator corresponding with the second point along the mud motor, and at least one of the first major stator diameter and the first minor stator diameter is larger than the second major stator diameter and the second minor stator diameter respectively.

12. The mud motor of claim 9 , wherein the stator comprises an outer cover and a stator insert, the outer cover being tubular, and the stator insert being formed within the outer cover and including the at least two helical stator lobes.

Assignees

• Nabors Drilling Tech Usa Inc

Inventors

• Evans Nigel

Classifications

• E21B3/00

  Rotary drilling · CPC title

• F04C2250/20

  of the rotor · CPC title

• B29L2031/34

  Electrical apparatus, e.g. sparking plugs or parts thereof · CPC title

• B29C45/14491

  Injecting material between coaxial articles, e.g. between a core and an outside sleeve for making a roll · CPC title

• F04C2/1071 Primary

  the inner and outer member having a different number of threads and one of the two being made of elastic materials, e.g. Moineau type · CPC title