Full tubing inner-diameter spin-through rod centralizers

Abstract

A spin-through drive rod centralizer consisting of a stator constructed of plastic, or other appropriate material, which is mounted on a rotor attached to the body of the drive rod, which provides the bearing surface for rotation of the rotor within the stator. The stator is equipped with multiple vanes which extend to the full internal diameter of the production tubing. In one configuration, the radially oriented vanes have cut-outs which allow the tip of the vane to compress inward, allowing passage through tight spots in the tubing, then rebounding to the full ID of the tubing. In another configuration, the vanes are tangentially attached to the stator body, such that they bend in a circumferential direction to allow passage through tubing tight spots, then rebound to full tubing ID.

Claims

1. A drive rod centralizer to position drive rods at a centerline of production tubing, comprising: a cylindrical rotor, said cylindrical rotor being attached to the body of said drive rod, the centerline of said cylindrical rotor being collinear with the centerline of said drive rod; a stator, said stator being comprised of a cylindrical body, said cylindrical body having an external diameter less than the internal diameter of said production tubing, and having a smooth central bore, said bore having an internal diameter larger than the external diameter of said cylindrical rotor; wherein said stator is installed on said drive rod such that said rotor is within said central bore of said stator; wherein said stator has several, equal length vanes projection radially outward from said cylindrical body, with the major axis of said vanes being oriented along the centerline of said stator body, the axial length of said vanes being approximately equal to the axial length of said stator body; wherein the radially inner surface of each of said vanes is attached to the outer surface of said stator body and the radially outer surface of each of said vanes is longitudinally arc-shaped with the crest of the arc in contact with the inner surface of said production tubing, wherein some material of the body of some of said vanes is removed, forming a cavity oriented along the centerline of said stator body in some of said vanes, wherein vane material between said cavity and the outer surface of the vane flexes inward into the cavity in said vanes, so that the centralizer outer diameter is reduced to pass through one or more tight spots in the production tubing, and wherein the vanes spring back and remain in contact with the inner wall of the tubing once the one or more tight spots have been passed.

2. The drive rod centralizer of claim 1, wherein the cavity is formed completely through said vanes in the circumferential direction, wherein the dimensions of said cavity are sufficient to allow said vane material between said cavity and the outer surface of the vane to deform inward enough so an effective outer diameter of the centralizer is equal to an effective reduced inner diameter of the one or more tight spots in the tubing.

3. The drive rod centralizer of claim 1, wherein the one or more tight spots are portions of the production tubing that have an effective internal diameter reduced by as much as 4% of the specified internal diameter.

4. The drive rod centralizer of claim 1, wherein the vanes are made of a material that has natural elasticity.

5. The rod centralizer of claim 1, wherein the vanes are deformed in the radial direction.

6. The drive rod centralizer of claim 1, wherein the production tubing has a reduced effective internal diameter.

7. The drive rod centralizer of claim 1, wherein the drive rod centralizer allows for sufficient flexibility in the stator blades to allow the passage of said stator past areas of the production tubing where the effective internal diameter is as much as 4% less than the specified internal diameter of the tubing without damaging the centralizer components, and without interfering with the installation of the rod string into the production tubing.

8. The drive rod centralizer of claim 1, wherein the stator blades rebound back to full original outer diameter after multiple flexing to allow passage through areas of the tubing with reduced effective internal diameter, returning the drive rod to the centerline of the production tubing.

9. The drive rod centralizer of claim 1, wherein said cylindrical rotor and said inner bore of said stator comprise a plain bearing, said rotor comprising a journal, and said stator bore comprising a bearing, to provide the rotational axial alignment and support of said drive rod.

10. One or more drive rod centralizers of claim 1, wherein the one or more drive rod centralizers are situated along said drive rod string to prevent rotational instability during rotational operation of said drive rod string.

11. A drive rod centralizer to position drive rods at or near a centerline of the production tubing, comprising: a cylindrical rotor, said cylindrical rotor being attached to the body of said drive rod, the centerline of said cylindrical rotor being collinear with the centerline of said drive rod; a stator, said stator being comprised of a cylindrical body, said cylindrical body having an external diameter less than the internal diameter of said production tubing, and having a smooth central bore, said bore having an internal diameter larger than the external diameter of said cylindrical rotor; wherein said stator is installed on said drive rod such that said rotor is within said central bore of said stator; wherein said stator has several, equal length vanes attached to the outer surface of said cylindrical body of said stator; wherein said vanes being attached to said stator body such that the outer circumferential surface of said vanes is tangential with the cylindrical surface of said stator; wherein the radially outer surface of said vanes is in contact with the inner surface of said production tubing, wherein said vanes are configured to flex in a circumferential direction.

12. The drive rod centralizer of claim 11, wherein the vanes are configured to flex from a first position to a second position in a circumferential direction.

13. The drive rod centralizer of claim 11, wherein the vanes are configured to rebound back to the first position in the circumferential direction.

14. The drive rod centralizer of claim 11, wherein said cylindrical rotor and said inner bore of said stator comprise a plain bearing, said rotor comprising a journal, and said stator bore comprising a bearing, to provide the rotational axial alignment and support of said drive rod.

15. One or more drive rod centralizer of claim 11, wherein the one or more drive rod centralizers are situated along said drive rod string to prevent whirling or other rotational instability during rotational operation of said drive rod string.

16. A drive rod centralizer to position drive rods at a centerline of production tubing, comprising: a cylindrical rotor, said cylindrical rotor being attached to the body of said drive rod, the centerline of said cylindrical rotor being collinear with the centerline of said drive rod; a stator, said stator being comprised of a cylindrical body, said cylindrical body having an external diameter less than the internal diameter of said production tubing, and having a smooth central bore, said bore having an internal diameter larger than the external diameter of said cylindrical rotor; wherein said stator is installed on said drive rod such that said rotor is within said central bore of said stator; wherein said stator has several, equal length vanes projection radially outward from said cylindrical body, with the major axis of said vanes being oriented along the centerline of said stator body, the axial length of said vanes being approximately equal to the axial length of said stator body; wherein the radially inner surface of each of said vanes is attached to the outer surface of said stator body and the radially outer surface of each of said vanes is in contact with the inner surface of said production tubing, wherein some material of the body of some of said vanes is removed, forming a cavity in some of said vanes, wherein vane material between said cavity and the outer surface of the vane flexes inward into the cavity in said vanes, so that the centralizer outer diameter is reduced to pass through a tight spot, wherein an effective internal diameter of the centralizer is as much as 4% less than the specified internal diameter of the tubing.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a prior art drive rod string within production tubing with cut-outs showing spin-through centralizers attached to the drive rod.

(2) FIG. 2 shows a side view of a typical prior art spin-through centralizer rotor molded onto the production tubing.

(3) FIG. 3 shows the components of a prior art commercially available spin-through centralizer.

(4) FIG. 4 shows the end view of a prior art stator of a commercially available spin-through centralizer.

(5) FIG. 5 shows a cross sectional view of prior art commercially available spin-through centralizer within the production tubing.

(6) FIG. 6 shows a cross sectional view of a prior art commercially available spin-through centralizer within production tubing with reduced effective inner diameter.

(7) FIG. 7. shows a spin-through centralizer incorporating the radially flexible stator vane feature of the present invention.

(8) FIG. 8 shows the FIG. 7 centralizer with the stator vanes radially deformed by a reduced diameter tight spot in the production tubing.

(9) FIG. 9 shows a cross section through the FIG. 7 centralizer within the production tubing.

(10) FIG. 10 shows a cross sectional view of the FIG. 7 spin-through centralizer within production tubing with reduced effective inner diameter.

(11) FIG. 11 shows a side view of an alternative configuration of a spin-through centralizer incorporating the radially flexible stator vane feature of the present invention.

(12) FIG. 12 shows a side view of a spin-through centralizer with a stator configuration that provides radial flexibility via circumferential bending of the stator vanes.

(13) FIG. 13 shows a cross section of the FIG. 12 configuration.

(14) FIG. 14 shows the FIG. 8 configuration passing through a tubing tight spot.

DETAILED DESCRIPTION OF THE INVENTION

(15) The present invention is directed at the so-called spin-through rod centralizers as employed in devices which drive a downhole pump via a rotating rod string. FIG. 1 shows a side view of a section of production tubing 10, with cut-out revealing the drive rod string 12, with installed spin-through centralizers 14. The principal components of a spin-through centralizer are the rotor affixed to the rod, which forms the bearing journal (plain bearing) of the device, and the stator, which performs the dual function of centralizing the rod string inside the production tubing, and providing a bearing surface or bushing for the rotor. FIG. 2. shows a typical rotor 16, consisting of a journal portion 18, and end stops 20, molded on to the drive rod body, 22. FIG. 3 shows a side view an assembled spin-through centralizer inside production tubing 10. The stator 26 mounted onto the rotor 16, consisting of several vanes 28 affixed to the stator body 30. Note the gap 32 between the outer edge of the vanes and the inside diameter of the production tubing. FIG. 4 is an end view of an unmounted stator 26, showing vanes 28 and stator body 30, and bearing surface 31. Another type of spin-through centralizer utilizes a modified coupling between rods that provides a steel journal onto which a stator, similar to that described above, is mounted.

(16) In any of these existing spin-through centralizers, the effective OD of the stator is somewhat less than the manufacturer's specified ID of the production tubing forming a gap 32 as shown in FIG. 3, to allow the passage of the centralizer through areas of the tubing that are less than the specified ID. This gap is shown clearly in FIG. 5, a cross-section through the production tubing and centralizer. This gap is necessary in the current designs because the vanes have very little flexibility in the radial direction, and hence, to pass the common ‘tight’ spots in normal production tubing, must have an effective OD equal to or less than the smallest expected ID of the tubing—the so called ‘drift’ diameter. This tight spot situation is shown in FIG. 6, a cross-section similar to FIG. 5, but with the tubing 24 deformed, ovalized in this case, such that the minimum diameter of the tubing is reduced to the drift diameter. The centralizer stator just fits within this reduced diameter. Were the vanes' radial extent any greater, the centralizer would jam in the tubing, preventing further vertical movement.

(17) The present invention is a modification of the vane configuration that allows enough flexibility for the centralizer to pass the ‘tight’ spots, yet rebound back to full inside diameter of the tubing after passing these spots of reduced diameter. This flexibility can be accomplished in two principal ways: deformation of the vanes in the radial direction, and bending of the vanes in a roughly circumferential direction.

(18) FIG. 7 shows a centralizer stator configuration that allows diametrical variation via radial deformation of the vanes. The vanes 36, which extend radially to the full extent of the tubing ID as shown, have a cutout 38 that allows the vane tips to deform inward toward the center of the tubing when a tight spot is encountered. FIG. 8 shows that situation, where the tubing 24 has a reduced effective inside diameter. Full tubing outer diameter is shown by the dashed lines 39. The vanes 36 deform, with the vane tips flexing inward by compressing cutout 38, to squeeze past the tight spot. After passing the tight spot, the natural elasticity of the vane material allows the vane tips to rebound to their normal, full tubing OD extent.

(19) This full tubing inside diameter fit of the FIG. 7 centralizer, as well as the cutouts 38 in the vanes 36 are shown clearly in FIG. 9, a cross-section through the production tubing and centralizer. FIG. 10. in a similar fashion as FIG. 6. above, shows a cross section through the tubing and centralizer in a tubing ‘tight spot’. Note how the vane tips opposite the ‘tight spot’ are compressed, reducing the size of the cutout to 40, and allowing the centralizer to squeeze past the tubing diameter reduction.

(20) Other vane configurations can be devised by those skilled in the art to allow the needed radial flexibility to pass undamaged through the tight spots then return to full size after passing. One such alternative is shown in FIG. 11.

(21) FIGS. 12 and 13 show a configuration that utilizes circumferential bending of the vanes to provide diametrical variation. Note that the four vanes 42 are offset from the purely radial location of the vanes of the centralizers shown in FIGS. 7 and 11, for instance. This offset allows the vanes to flex in a circumferential direction 44 if a tight spot is encountered, as shown in FIG. 14, then rebound back to the original position after the tight spot is passed.