Dual diameter and rotating centralizer/sub and method
A dual diameter centralizing sub for maintaining stand-off and/or centralizing a tubular member inside a larger diameter tubular member, for instance, in a wellbore. The centralizer is provided with bow springs that compress into grooves between radially outwardly-extending vanes that are spaced around the outer diameter of the sub when compressive force is applied to the bow springs. The vanes extend radially outwardly far enough that the effective diameter of the sub in the area of the vanes is greater than the diameter of the sub and/or the tubing to which it is mounted to provide stand-off even under conditions in which the bow springs are fully compressed while still maintaining fluid flow.
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The present application is a continuation-in-part of application Ser. No. 09/655,795, filed Sep. 6, 2000, and having the same title, now issued as U.S. Pat. No. 6,484,803.
BACKGROUND OF THE INVENTIONThe present invention relates to a centralizer for use in wellbore operations. More specifically, the present invention relates to a centralizer with movable bow springs, particularly a stabilizer that is used in relatively small annular spaces and which also expands for use in a larger annular space. In another aspect, the present invention relates to a centralizer that provides a minimum standoff and/or centralization in portions of a wellbore in which known bow spring centralizers cannot provide adequate standoff because the bow springs lack sufficient restoring force.
Bow spring centralizers are used to center one tubular member inside a borehole or other tubular member, e.g., to center a first smaller tubular member in a second larger diameter tubular member (for instance, a tubing string inside a casing in a borehole). Typically, centralizers are run into the borehole on the exterior of an inner tubular member or tubing string and the bow springs project radially outwardly from the outside diameter (O.D.), or surface, of the smaller tubular member into contact with the inside diameter (I.D.), or surface, of the larger diameter tubular. However, there are at least two disadvantages of such centralizers in that they tend to restrict fluid flow in the annular space and, in the event the smaller diameter tubular member needs to be rotated inside the larger diameter tubular member (if, for instance, it becomes stuck during running), rotating tends to damage the bow springs of such centralizers.
Another disadvantage of many known centralizers is illustrated by reference to the many wells that include a portion that is cased and a portion that is not cased, wells in which the diameter of the bore changes, or wells that include one or more lateral bores. Downhole operations are conducted in cased, uncased, different diameter, and/or lateral bores. In such wellbores, the centralizer must pass through a portion of the bore that is relatively small and then down through a portion that is smaller, with the centralizing function needed in the larger diameter, deeper portion of the wellbore. So far as is known, no centralizer is available that is capable of both being run into such bores and then also providing effective centralizing in a larger diameter portion of the wellbore. Similarly, no centralizer is known that provides effective centralizing in bores of both diameters.
Another limitation of known centralizers occurs in the curved portion of a wellbore. In such wellbores, the weight of the tubing or pipe to which the centralizer is mounted exceeds the restoring force of the bow springs such that the tubing or pipe bears against the side of the wellbore. This same problem of the weight of the tubing affects lateral bores, restricting fluid flow and preventing the rotation of the tubing string. There is, therefore, a need for, and it is an object of the present invention to provide, a centralizer that positions the tubing or pipe string off the side of the wellbore in the curved or the horizontal portion of a wellbore and a centralizer that allows rotation of the tubing string in the wellbore.
It is also an object of the present invention to provide positive centralization in areas of the wellbore where a bow spring is not strong enough to position the pipe or tubing string off the side of the well bore but also provide standoff in less severe portions of the borehole.
Another object of the present invention is to provide a centralizer that functions in both a large and/or small diameter annulus and/or wellbore.
Another object of the present invention is to provide a centralizer that maintains both standoff from the wall of the borehole and fluid flow through the borehole.
Yet another object of the present invention is to provide a centralizer that can be run into a borehole through a borehole of small diameter, e.g., a cased portion of the borehole, that also functions to center the tubing in a portion of the borehole having a diameter larger than the small diameter portion such as an uncased portion of the borehole.
Other objects, and the advantages, of the present invention will be made clear to those skilled in the art by the following description of a presently preferred embodiment thereof.
SUMMARY OF THE INVENTIONThese objects are achieved by providing a centralizer sub, connectable in a tubing string, comprising a sub having at each end thereof thread means for threadably connecting the sub in a tubing string, a pair of collars rotatably mounted on the sub, a plurality of bow springs, having a relaxed and a compressed state, fixed to each of the pair of collars, and which in their compressed state, hold the collars at their furthest distance apart along the sub, a pair of shoulders, spaced apart and extending essentially around the exterior circumference of the sub, and each of the shoulders abutting a collar, restricting the axial movement of the collars when the bow springs are in their relaxed state.
In another aspect, the present invention provides a centralizer comprising a sub, a plurality of radially outwardly extending vanes on the sub, and a collar mounted on the sub. A plurality of bow springs are mounted to notches formed in the collar, the bow springs being maintained in spaced relation to the vanes whereby one or more of the bow springs moves between a first, bowed position standing off from the sub to a second compressed position between the vanes and closer to the sub. When the bow springs are compressed into the spaces between vanes, the vanes, which are not compressible under normal operating conditions, provide standoff from the wall of the hole and maintain fluid flow past the centralizer. In a particularly preferred embodiment, the vanes extend radially outwardly from the surface of the sub of the centralizer far enough that the effective diameter of the sub at the location of the varies is larger than the diameter of the sub, thereby providing the standoff from the wall of the borehole.
Referring to
As shown in
As shown in
Referring now to
Referring now to
It will also be recognized by those skilled in the art that the second embodiment 52 shown in
Those skilled in the art will also be aware of the utility of a centralizer that allows the tubing string to rotate relative to the bow springs at any desired time, regardless of whether the bow springs are in the first, uncompressed position or the second, compressed position. Referring now to
The embodiment 58 shown in
The embodiment 64 shown in
Those skilled in the art who have the benefit of this disclosure will recognize that certain changes can be made to the component parts of the apparatus of the present invention without changing the manner in which those parts function to achieve their intended result. For instance, although the vanes 36 are described herein as being welded to the outside surface 16 of sub 12 of the centralizer of the present invention such that it is clear that in the presently preferred embodiment, the vanes 36 are comprised of relativley incompressible metal, those skilled in the art who have the benefit of this disclosure will recognize that vanes 36 may also be comprised of materials other than metal. Further, in certain applications, it may be advantageous to make the vanes 36 of a material that is slightly compressible or even elastically deformable when compressive forces are exerted against the vanes. A variety of polymeric materials are available, for instance, that are high temperature tolerant, or acid resistant, or have other desirable physical properties that will enable them to serve this function. Those skilled in the art who have the benefit of this disclosure will also recognize that, although the preferred embodiment of the centralizer of the present invention has been described herein as being used in a wellbore, the use of the centralizer of the present invention is not so limited. A centralizer constructed in accordance with the teachings of the present invention may be used in any application in which it is desirable to maintain minimum standoff between two concentric tubular members and/or center one tubular member inside another.
Similarly, U.S. Pat. No. 5,575,333 discloses several embodiments of a bow spring centralizer that vary, inter alia, in the configuration of the bow springs and their attachment to the sub of the centralizer. To illustrate how the structure disclosed in that patent can be incorporated into the centralizer of the present invention, one embodiment of the centralizer disclosed in that patent lacks collars altogether, the bow springs being attached directly to the outside surface of the sub of the centralizer and the ends of the bow springs moving in grooves when the bow springs are compressed. Similar grooves can be provided in the surface 16 of the sub 12 of the centralizer of the present invention for receiving the bow springs 20 described herein. Those skilled in the art will recognize that the other structural variations shown in that patent can also be utilized in connection with the centralizer of the present invention. For that reason, U.S. Pat. No. 5,575,333 is incorporated into this specification in its entirety by this reference thereto. Similarly, those skilled in the art will recognize that, as also described in that same U.S. Pat. No. 5,575,333, the centralizer of the present invention will function for its intended purpose with but one of the two collars 24, 26. Likewise, U.S. Pat. No. 3,556,042 discloses a bow spring centralizer in which the collar/bow spring assembly is provided with slightly-bowed so-called inner strips that connect the collars under the bow springs so that compression of the bow springs is resisted. That same patent also discloses a centralizer having a bow spring with a double arc that is used to advantage in connection with the centralizer of the present invention. Because of this disclosure, U.S. Pat. No. 3,556,042 is also incorporated into this specification in its entirety by this specific reference thereto. The alternative embodiments resulting from the incorporation of the structural features of these two patents that are incorporated herein by reference, and other changes that will be made clear to those skilled in the art by this description of the preferred embodiments of the invention, are intended to fall within the scope of the following, non-limiting claims.
Claims
1. A centralizer, connectable in a tubing string, comprising:
- a sub, having a first end and a second end opposite the first end,
- the sub having at each end thereof thread means for threadably connecting the sub in a tubing string;
- a pair of collars, spaced apart from each other, and rotatably mounted on the sub;
- the pair of collars comprising a first collar and a second collar;
- the first collar and the second collar being capable of axial movement along a length of the sub;
- the first collar being located closer to the first end of the sub than the second collar;
- the second collar being located closer to the second end of the sub than the first collar;
- a plurality of bow springs, having a relaxed and a compressed state, fixed to each of the pair of collars, and which in their fully compressed state, hold the collars at their furthest distance apart along the sub;
- a pair of shoulders, fixed to the sub and spaced apart from each other, and extending essentially around the exterior circumference of the sub;
- the pair of shoulders comprising a first shoulder and a second shoulder;
- the first shoulder being located closer to the first end of the sub than the second shoulder;
- the second shoulder being located closer to the second end of the sub than the first shoulder;
- the pair of shoulders being positioned between the pair of collars;
- the length of axial movement of the first collar when moving in the direction toward the first end of the sub being limited solely by the abutment of the second collar with the second shoulder and the compressed state of the bow springs;
- the length of axial movement of the first collar when moving in the direction toward the second end of the sub being limited solely by the abutment of the first collar with the first shoulder;
- the length of axial movement of the second collar when moving in the direction toward the second end of the sub being limited solely by the abutment of the first collar with the first shoulder and the compressed state of the bow springs;
- the length of axial movement of the second collar when moving in the direction toward the first end of the sub being limited solely by the abutment of the second collar with the second shoulder.
2. The centralizer sub of claim 1 wherein the shoulders are formed by milling the body assembly.
3. A centralizer sub as claimed in claim 1 additionally comprising a plurality of vanes, mounted on the sub proximate at least one end of the sub, longitudinally spaced between said end of the sub and the collar closest to said end of the sub so that when the bow springs are in their fully compressed state, the collar will not touch the vanes that are on the collar's end of the sub.
4. A centralizer sub as claimed in claim 3 further characterized by having a plurality of vanes fixed on each end of the sub, disposed around the circumference thereof, the vanes on each respective end of the sub being longitudinally spaced between the respective end of the sub and the respective collar closest to the respective end of the sub so that when the bow springs are in their fully compressed state, the collars will not touch the vanes.
5. A centralizer sub as claimed in claim 3 further characterized by at least one set of the vanes being oriented at an angle to the longitudinal axis of the body from about 15 to about 45 degrees.
6. The centralizer of claim 1, wherein the bow springs and collars are rotatable around the sub, and the respective collars, opposite the direction of movement, are moveable longitudinally along the axis of the sub in response to compression of the bow springs.
7. The centralizer of claim 1, wherein the shoulder, positioned foremost in the direction of movement of the sub, restrains movement of the collar in contact with the shoulder, allowing the collars and bow springs to be pulled into the reduced diameter space.
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- Ray Oil Tool Company—The Centralization Specialists—rayoiltool.com—one page product brochure regarding Bi-Centered Float Shoes, Collars & Inline Type Centralizers printed from this website on Sep. 13, 2004, but same material was printed previously from website on Feb. 25, 2003. Date of origin of this material and website is not known.
- Patent Litigatin: Weatherford International, Inc.and Weatherford / Lamb, Inc., Plantiffs, v. Casetech International, Inc., Defendant. Civil Action No. H-03-CV-05383, In the United States District Court For the Southern District of Texas, Houston Division.
Type: Grant
Filed: Nov 23, 2002
Date of Patent: Nov 22, 2005
Patent Publication Number: 20030070803
Assignee: CaseTech International, Inc. (Houston, TX)
Inventor: Maximillian S. Gremillion (Missouri City, TX)
Primary Examiner: George Suchfield
Attorney: Gordon G. Waggett, P.C.
Application Number: 10/302,641