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 the drive rods at the 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 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 body of said vanes are of roughly rectangular solid shape, the radially inner surface of said vane being attached to the outer surface of said stator body, the radially outer surface of said vane being 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.

2. The drive rod centralizer of claim 1, wherein the cavity is formed completely through said vane in the circumferential direction.

3. The drive rod centralizer of claim 1, wherein the cavity allows tips of vanes to deform inward toward the center of the tubing when the vanes are flexed.

4. The drive rod centralizer of claim 3, wherein the vanes are flexed when a tight spot is encountered in the production tubing.

5. The drive rod centralizer of claim 4, wherein the vanes are made of a material that has natural elasticity, such that the vanes rebound to their full tubing outer diameter.

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

7. The rod centralizer of claim 1, wherein the vanes are bent in a roughly circumferential direction.

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

9. The drive rod centralizer of claim 1, wherein the vanes are configured to be compressible due to the cavity in said vanes.

10. The drive rod centralizer of claim 1, wherein the cavity is fully enclosed, such that cavity is not exposed to an outer surface of each of the vanes.

11. The drive rod centralizer of claim 1, wherein the cavity has a bore, such that the bore exposes the cavity to an outer surface of each of the vanes.

12. The drive rod centralizer of claim 1, 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 12, wherein the vanes are configured to rebound back to the first position in the circumferential direction.

14. The drive rod centralizer of claim 1, wherein the effective outside diameter of the stator is equal or very nearly equal to the manufacturer's specified inside diameter of the production tubing, and holds the rod string at the centerline of the production tubing.

15. 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 inside diameter is 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.

16. The drive rod centralizer of claim 1, wherein the stator blades rebound back to full original OD after multiple flexing to allow passage through drift diameter areas of the tubing, returning the drive rod to the centerline of the production tubing.

17. The drive rod centralizer of claim 1, wherein each of said vanes includes a cavity.

18. A drive rod centralizer to position the drive rods at or near the 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 are of roughly rectangular solid shape, 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.

19. A stator for a drive rod centralizer, comprising: a cylindrical body, said cylindrical body and having a smooth central bore, one or more vanes attached to the outer surface of said cylindrical body of said stator, wherein some material of the body of said one or more vanes is removed, forming a cavity within the body of said one or more vanes.

20. The stator of claim 19, wherein the body of said one or more vanes are of roughly rectangular solid shape, the radially inner surface of said one or more vanes is attached to the outer surface of said stator body, the radially outer surface of said one or more vanes being in contact with the inner surface of a production tubing of drive rods.

Description

DESCRIPTION OF DRAWINGS

[0035] FIG. 1 shows a prior art drive rod string within production tubing with cut-outs showing spin-through centralizers attached to the drive rod.

[0036] FIG. 2 shows a side view of a typical prior art spin-through centralizer rotor molded onto the production tubing.

[0037] FIG. 3 shows the components of a prior art commercially available spin-through centralizer.

[0038] FIG. 4 shows the end view of a prior art stator of a commercially available spin-through centralizer.

[0039] FIG. 5 shows a cross sectional view of prior art commercially available spin-through centralizer within the production tubing.

[0040] FIG. 6 shows a cross sectional view of a prior art commercially available spin-through centralizer within production tubing with reduced effective inner diameter.

[0041] FIG. 7. shows a spin-through centralizer incorporating the radially flexible stator vane feature of the present invention.

[0042] FIG. 8 shows the FIG. 7 centralizer with the stator vanes radially deformed by a reduced diameter tight spot in the production tubing.

[0043] FIG. 9 shows a cross section through the FIG. 7 centralizer within the production tubing.

[0044] FIG. 10 shows a cross sectional view of the FIG. 7 spin-through centralizer within production tubing with reduced effective inner diameter.

[0045] 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.

[0046] 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.

[0047] FIG. 13 shows a cross section of the FIG. 12 configuration.

[0048] FIG. 14 shows the FIG. 8 configuration passing through a tubing tight spot.

DETAILED DESCRIPTION OF THE INVENTION

[0049] 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 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.

[0050] 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 tubingthe 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.