SMOOTH BORE COLLAR
A friction-reducing device for use in a well bore, the friction-reducing device being cylindrically shaped with a tapered and partially threaded upper section, cylindrical middle section, and tapered and partially threaded lower section. The middle section comprises a cylindrical outer surface, cylindrical inner surface, solid portion between the cylindrical outer surface and the cylindrical inner surface, and first plurality of friction-reducing units. The friction-reducing units are installed at equally-spaced angular intervals into ports within the solid portion of the middle section in a circular array that lies in a first plane that is perpendicular to a longitudinal axis of the cylindrical bore in the friction-reducing device. Each friction-reducing unit comprises a rear bearing seat, an array of miniature ball hearings, and a main ball bearing with a protruding portion that extends through the inner surface of the middle section into the cylindrical bore.
1. Field of the Invention
The present invention relates to the field of oil well devices that reduce friction between a string of production tubing and a string of sucker rod positioned within the production tubing. More particularly, the present invention relates to those devices that are threadably installed in-line within a string of production tubing and that comprise ball bearings as a friction-reducing mechanism.
2. Description of the Related Art
Although there are a number of issued U.S. patents and patent applications that describe friction-reducing devices for use with oil well drill strings and production, strings, none of these prior art inventions includes the novel features of the present invention. Those features include threaded in-line couplings and friction-reducing ball bearings that make direct contact with a sucker rod positioned within the bore of the invention and that are freely rotatable around any axis of rotation.
U.S. Pat. No. 1,888,216(Bull, 1932) discloses a device for reducing rotational friction between a drill pipe and the sides of a borehole. The invention comprises a cylindrical collar that fits around a section of drill pipe, and the collar comprises a plurality of ball bearing assemblies that allow the drill pipe to rotate within the collar. The invention incorporates gripping plugs with teeth to secure the collar at a fixed position around the outside surface of the drill pipe.
U.S. Pat. Nos. 1,890,529 and 1,890,530 (Santiago, 1952 ) disclose a drill stem bearing device that fits around drill pipe, pump rods, or similar well equipment (referred to generally as “stems”). The invention is attached to a stem via a pair of clamping rings that secure the device against longitudinal movement with respect to the stem. The device provides a rotatable collar comprising an annular ring of sleeves or rollers to reduce rotational friction between the collar and the stem to which it is attached. The sleeves are in the form of non-rotatable ribs, and the rollers are shown as being cylindrical in shape, with each roller comprising an axial pin and each axial pin oriented parallel to the axis of the stem. The sleeves or rollers are enclosed within a segmented carrier.
U.S. Pat. No. 1,911,365 (Bailey, 1933 ) discloses an anti-friction bearing that fits around a drill stem to reduce friction between the drill stem and the surrounding well casing. The invention is generally in the shape of a hollow cylinder or collar. The invention comprises a plurality of annular rollers, with at least one set of rollers oriented so as to reduce axial (longitudinal) friction and at least one other set of rollers oriented so as to reduce rotational friction. The rollers are shown in the drawings as being cylindrical in shape, but are described [page 2, lines 54-55] as being “any suitable shape, either cylindrical or spherical”. Each roller rotates around a rigidly positioned axial pin so that the axis of rotation is fixed for each roller.
The rollers that are oriented so as to reduce rotational friction (the “rotational rollers”) are positioned so that a portion of each rotational roller extends into the hollow interior of the device, thereby causing each of these rotational rollers to contact the drill stem. The rollers that are oriented so as to reduce axial friction (the “axial rollers”) are positioned so that a portion of each of these axial rollers extends beyond the outside perimeter of the collar of the device, thereby allowing some of the axial rollers to contact well casing when the drill stem comes into close proximity with one side of the well casing. This arrangement of the two sets of rollers allows the drill stem to rotate within the device using the rotational rollers as bearings and also allows the drill stem to move up and down within the well casing using the axial rollers as bearings.
U.S. Pat. No. 2,127,796 (Willis, 1938) discloses two embodiments of a bearing structure for use in oil wells. Both embodiments of the invention are designed to allow free passage of oil and gas through the invention while reducing friction between certain moving parts within the well. The first embodiment of the invention is designed to centralize a well tubing within a well casing and reduce friction between the tubing and casing. The first embodiment is designed to be installed around the outside of a tubing string. This embodiment comprises a plurality of hail bearings that are positioned between a sleeve and a collar of the invention. Installation of the first embodiment around a section of well tubing requires molten metal to be poured around the well tubing to form a liner for the first embodiment.
The second embodiment of the invention is designed to centralize a specially-shaped sucker rod within a curved tubing string and reduce friction between the sucker rod and tubing string. The second embodiment is slidably attached around the sucker rod and is held in place against the inner surface of the tubing string by friction. See p. 2 , lines 32-33 (“collar is secured in frictional engagement to the inner periphery of the tube 6 due to inflection of the tube and thereby serves to maintain the sucker rod in spaced relation from said tube”). The second embodiment comprises a plurality of ball bearings that are positioned between a collar in the body of the device and longitudinal grooves that are manufactured into the outer surface of the specially shaped sucker rod. Unlike the present invention, the second embodiment of the Willis invention is not designed to be used in combination with standard (non-grooved) sucker rod, nor is the ball bearing mechanism constructed so as to allow the sucker rod to rotate within the tubing string.
U.S. Pat. No. 2,499,252 (Michael, 1950) discloses an earth-boring tool designed to be lowered into well casing and to drill into soil or rock below the open-ended bottom of the casing. The invention comprises a rotatable drive shall that is attached to a rotatable cutting head. The drive shaft is centered within the casing by a bearing member that is installed around the drive shaft and that fits between the inside surface of the casing and the outside surface of the drive shaft. The bearing member comprises a friction-reducing ball bearing assembly or conventional design—i.e., the bearing assembly is generally ring-shaped and comprises ball bearings or rollers positioned between a circular outer race and a circular inner race.
U.S. Pat. No. 2,758,891 (Klammerer, 1956) discloses a stabilizing device used to center a drill string within a well bore and reduce axial friction of the drill pipe that comes into contact with the walls of the well bore. The device is installed around a drill collar that is located between the bottom piece of drill pipe and the drill bit. The device comprises an inner sleeve and an outer collar. When the drill pipe is rotated, the inner sleeve rotates with the drill pipe, but the outer collar does not rotate. The device comprises two conventional ball bearing assemblies that are positioned between the sleeve and collar.
U.S. Pat. No. 6,585,043 (Murray, 2003) discloses a friction-reducing centralizer used to reduce axial and rotational drag between an oil well tubular and the wall of a well. The invention is designed to fit around the tubular and may be secured in position with stock collars optionally provided at each end of the invention. This invention comprises a plurality of rollers, with a first group of rollers designed to reduce friction between the centralizer and the tubular and a second group of rollers designed to reduce friction between the centralizer and the wall of the well. All of the rollers rotate around axles that are fixed within the body of the centralizer. The first group of rollers has an axis of rotation generally parallel to the axis of the tubular, and the second group of rollers has an axis of rotation that is generally transverse to the axis of the tubular. The first group of rollers is positioned so that a portion of each of the rollers projects through an opening in the inside surface of the invention, so as to contact the outside surface of the tubular member within the centralizer. The second group of rollers is positioned so that a portion of each roller projects through an opening in the outside surface of the invention, so as to contact the wall of the well when the tubular comes into close proximity to the wall of the well. All of the rollers are preferably cylindrical in shape with tapered ends.
U.S. Patent Application Pub. No. 2002/0020526 (Male et al.) discloses a well casing centralizer device that is designed reduce friction between the outside surface of the casing and the wall of the well when the casing is being installed into the well bore. The invention is described [paragraph 0009, lines 4-5] as being attachable to the casing: “may be disposed about a casing joint or indeed connected into the casing string through a threaded coupling . . . . ”The descriptions of the invention, however, only describe an embodiment that is slipped over the casing. See paragraph 0025, describing FIG. 1: “In order to assemble the centralizer on the casing joint CJ, the body of the centralizer is slipped over the pin end of the joint prior to make up of the pin with a box end on an adjacent casing joint.”
The invention is generally tubular in shape with longitudinal fins manufactured into the outer surface. Each of the fins contains a plurality of individual friction-reducing elements, and each of the friction-reducing elements comprises a rotatable ball bearing. The plurality of friction-reducing units is positioned along the outer surface of each fin. In the embodiment described in reference to FIG. 2a, each friction-reducing unit comprises a threaded front bearing seat, an unthreaded rear bearing seat, and a plurality of “micro balls” between the rear bearing seat and the rotatable ball bearing. A portion of each ball bearing protrudes beyond the outer surface of the fin so that the ball bearing contacts the wall of the well when the fin comes into close proximity to a wall of the well thereby reducing frictional drag between the fin and the wall of the well when the casing is rotated or moved longitudinally.
Unlike the present invention, this invention does not provide a low-friction bearing surface between the bore of the device and a tubular member installed within the bore of the device but instead reduces friction between the outside surface of the device and well casing that surrounds the device. The friction-reducing units (i.e., the ball bearing mechanisms) of the Male invention are dissimilar to those of the present invention in that each of the Male units comprises a front bearing seal that is threadably attachable into blind bores incorporated within the body of the device. By contrast, in the present invention, the front bearing seal of each friction-reducing unit is manufactured into the body of the device rather than being a separate part.
In summary, none of the prior art examples cited above incorporates the novel features of the present invention, which most notably include a plurality of ball bearings that partially protrude into the bore of the invention, wherein each ball bearing is capable of free rotation around any three-dimensional axis, and wherein the invention is installable in-line between two lengths of production tubing with threaded connections.
BRIEF SUMMARY OF THE INVENTIONThe present invention is a friction-reducing device for use in a well bore, the friction-reducing device being cylindrically shaped with a tapered and partially threaded upper section, a cylindrical middle section, and a tapered and partially threaded lower section; wherein the middle section comprises a cylindrical outer surface, a cylindrical inner surface, a solid portion between the cylindrical outer surface and the cylindrical inner surface, and a first plurality of friction-reducing units; wherein the inner surface of the middle section forms a cylindrical bore in the center of the friction-reducing device, the cylindrical bore having a constant diameter from top to bottom; wherein the friction-reducing units are installed at equally-spaced angular intervals into ports within the solid portion of the middle section in a circular array that lies in a first plane that is perpendicular to a longitudinal axis of the cylindrical bore; wherein each friction-reducing unit comprises a rear bearing seat, an array of miniature ball bearings, and a main ball bearing with a protruding portion that extends through the inner surface of the middle section into the cylindrical bore of the friction-reducing device; wherein each port extends through the solid portion and penetrates both the outer surface and the inner surface of the middle section; wherein each port comprises a three-dimensional concave portion that penetrates the inner surface of the middle section; wherein the rear bearing seat of each tried friction-reducing unit comprises male threads around an outside circumference of the rear bearing seat that mate with female threads on an inside surface of the port; wherein the rear bearing seat further comprises a hex socket on an outside end of the rear bearing seat and a three-dimensional concave indentation on an inside end of the rear bearing seat; wherein the main ball bearing is positioned against the three-dimensional concave portion of the port, the three-dimensional concave portion of the port forming a front bearing seat for the main ball bearing; wherein the plurality of miniature ball bearings is situated between the three-dimensional concave indentation of the rear bearing seat and a portion of the main ball bearing that faces toward the outer surface of the middle section, and wherein the plurality of miniature ball bearings provides a low-friction rolling surface between the rear bearing seat and the main ball bearing; wherein the main ball bearing is free to rotate in any direction about any three-dimensional axis; and wherein the friction-reducing device is threadably inserted in-line between two adjacent lengths of production tubing, wherein a sucker rod is inserted through the cylindrical bore of the friction-reducing device, and wherein the friction-reducing device maintains a gap between an inside wall of the production tubing and the sucker rod.
In a preferred embodiment, the upper section, the middle section, and the lower section are manufactured as a single unit from a single piece of machined steel. In an alternate embodiment, the invention further comprises a second array of friction-reducing units identical to the first array of friction-reducing units except that the second array of friction-reducing units is installed in a circular array that lies in a second plane that is perpendicular to the longitudinal axis of the cylindrical bore, wherein the first and second arrays of friction-reducing units each has an angular orientation, and wherein the angular orientation of the second array of friction-reducing units is shifted by a certain angle in relation to the angular orientation of the first array of friction-reducing units.
In a preferred embodiment, the middle section further comprises a plurality of threaded holes that extend from the outer surface into the solid portion of the middle section but do not extend to the inner surface of the middle section, and wherein the threaded holes are configured to receive attachment screws for a stabilizer; the friction-reducing device further comprising a stabilizer that is secured to the middle section of the friction-reducing device via the attachment screws, wherein the production tubing has an outside diameter and a magnitude of pulsation movement within a well casing, the stabilizer being configured to increase the outside diameter of the production tubing, thereby reducing the magnitude of pulsation movement of the production tubing inside the well casing.
1 First embodiment of the present invention
2 Upper section
3 Middle section, first embodiment
4 Lower section
5 Rear bearing seat
6 Outer surface of middle section
7 Solid portion of middle section
8 Inner surface of middle section
9 Friction-reducing unit
10 Port
11 Bore
12 Main ball bearing
13 Protruding portion, of a main ball bearing
14 Void space within a port
15 Cup-shaped portion of port
16 Female threads of port
17 Miniature ball bearing
18 Male threads of tear bearing seat
19 Hex socket of rear bearing seat
20 Cup-shaped indentation of rear bearing seat
21 Well casing
22 Subsurface formation
23 First piece of production tubing
24 Second piece of production tubing
25 Sucker rod
26 Second embodiment of the present invention
27 Middle section of the second embodiment
28 First array of friction-reducing units of the second embodiment
29 Array of threaded holes
30 Threaded hole
31 Second array of friction-reducing units of the second embodiment
32 Third embodiment of the present invention
33 Middle section of the third embodiment
34 First array of friction-reducing units of the third embodiment
35 Second array of friction-reducing units of the third embodiment
36 Stabilizer
37 Cap screw
38 Screw hole in centralizes
39 First cap screw
40 First screw hole
41 Second cap screw
42 Bore of stabilizer
DETAILED DESCRIPTION OF INVENTIONThe present invention is a friction-reducing device designed to reduce friction between oil well production tubing and a sucker rod that is installed into and moving within the bore of the production tubing and is particularly suited for use in wells having significant curvature. The present invention is threadably inserted in-line between two adjacent lengths of production tubing and serves as a low-friction centralizer to maintain a gap between the inside wall of the production tubing and the sucker rod. The present invention comprises a plurality of individual ball bearings that protrude into the bore of the invention and provide low-friction bearing surfaces between the invention and the sucker rod. For typical applications, multiple units of the invention are installed at various locations along the length of the production tubing. The present invention comprises three similar embodiments, which differ primarily in overall length and the total number of ball bearing elements utilized per unit.
As shown, in
The main ball bearing 12 is positioned against the cup-shaped portion 15 of the port 10. The dimensions of the cup-shaped portion 15 are selected so as to provide a close but non-binding fit with the spherical surface of main ball bearing 12, so that the cup-shaped portion 15 forms a front bearing seat for the main ball bearing 12. The plurality of miniature ball bearings 17 are disposed in a three-dimensional, cup-shaped array between the cup-shaped indentation 20 of the rear bearing seat 5 and that portion of the main ball bearing 12 that generally faces toward the outer surface 6.
The dimensions of the cup-shaped indentation 20 are selected so that the cup-shaped array of miniature ball bearings 17 forms a close fit around that portion of the spherical source of the main ball bearing 12 that contacts the array of miniature ball bearings 17. This configuration of the rear bearing seat 5, the miniature ball bearings 17, and the main ball bearing 12 provides a low-friction rolling surface between the rear bearing seat 5 and the main ball bearing 12. Note that the main ball bearing 12 is free to rotate in any direction about any three-dimensional axis. Also note that the shape of the inner surface 8 through which a portion of the main ball bearing 12 penetrates is convex in transverse cross section, as viewed looking from the outer surface 6 toward the inner surface as shown in
Although a single unit of the first embodiment 1 is shown installed within the production tubing string in
The first array 28 and second array 31 each comprises six friction-reducing units 9 that are installed in a circular pattern around the middle section 27 in a configuration that is similar to the configuration described in reference to
Although the first, second and third embodiments of the present invention are described as having a particular set of dimensions for the bore diameter, maximum outside diameter, and length, these dimensions may be varied so as to make any of the three embodiments compatible with a variety of sizes of sucker rod and production tubing. Similarly, the outside diameter of the stabilizer may be selected so as to make the present invention compatible with a variety of casing sizes.
Although the preferred embodiment of the present invention has been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader aspects. The appended claims are therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.
Claims
1. A friction-reducing device for use in a well bore, the friction-reducing device being cylindrically shaped with a tapered and partially threaded upper section, a cylindrical middle section, and a tapered and partially threaded lower section;
- wherein the middle section comprises a cylindrical outer surface, a cylindrical inner surface, a solid portion between the cylindrical outer surface and the cylindrical inner surface, and a first plurality of friction-reducing units;
- wherein the inner surface of the middle section forms a cylindrical bore in the center of the friction-reducing device, the cylindrical bore having a constant diameter from top to bottom;
- wherein the friction-reducing units are installed at equally-spaced angular intervals into ports within the solid portion of the middle section in a circular array that lies in a first plane that is perpendicular to a longitudinal axis of the cylindrical bore;
- wherein each friction-reducing unit comprises a rear bearing seat, an array of miniature ball bearings, and a main ball bearing with a protruding portion that extends through the inner surface of the middle section into the cylindrical bore of the friction-reducing device;
- wherein each port extends through the solid portion and penetrates both the outer surface and the inner surface of the middle section;
- wherein each port comprises a three-dimensional concave portion that penetrates the inner surface of the middle section;
- wherein the rear bearing seat of each friction-reducing unit comprises male threads around an outside circumference of the rear bearing seat that mate with female threads on an inside surface of the port;
- wherein the rear bearing sear further comprises a hex socket on an outside end of the rear bearing seat and a three-dimensional concave indentation on an inside end of the rear bearing seat;
- wherein the main ball bearing is positioned against the three-dimensional concave portion of the port, the three-dimensional concave portion of the port forming a front bearing seat for the main ball bearing;
- wherein the plurality of miniature ball bearings is situated between the three-dimensional concave indentation of the rear bearing seat and a portion of the main ball bearing that faces toward the outer surface of the middle section, and wherein the plurality of miniature ball bearings provides a low-friction rolling surface between the rear bearing seat and the main hall bearing;
- wherein the main ball bearing is free to rotate in any direction about any three-dimensional axis; and
- wherein the friction-reducing device is threadably inserted in-line between two adjacent lengths of production tubing, wherein a sucker rod is inserted through, the cylindrical bore of the friction-reducing device, and wherein the friction-reducing device maintains a gap between an inside wall of the production tubing and the sucker rod.
2. The friction-reducing device of claim 1, wherein the upper section, the middle section, and the lower section are manufactured as a single unit from a single piece of machined steel.
3. The friction-reducing device of claim 1, further comprising a second array of friction-reducing units identical to the first array of friction-reducing units except that the second array of friction-reducing units is installed in a circular array that lies in a second plane that is perpendicular to the longitudinal axis of the cylindrical bore, wherein the first and second arrays of friction-reducing units each has an angular orientation, and wherein the angular orientation of the second array of friction-reducing units is shifted by a certain angle in relation to the angular orientation of the first array of friction-reducing units.
4. The friction-reducing device of claim 1, wherein the middle section further comprises a plurality of threaded holes that extend from the outer surface into the solid portion of the middle section but do not extend to the inner surface of the middle section, and wherein the threaded holes are configured to receive attachment screws for a stabilizer;
- the friction-reducing device further comprising a stabilizer that is secured to the middle section of the friction-reducing device via the attachment screws, wherein the production tubing has an outside diameter and a magnitude of pulsation movement within a well casing, the stabilizer being configured to increase the outside diameter of the production tubing, thereby reducing the magnitude of pulsation movement of the production tubing inside the well casing.
Type: Application
Filed: Jun 15, 2015
Publication Date: Dec 15, 2016
Inventor: Walter Calvin Harvey (Bridgeport, TX)
Application Number: 14/739,218