Reduced Drag Centralizer
An apparatus according to one or more aspects of the present disclosure comprises at least two centralizers, each centralizer having a circumferential stand-off portion and a second circumferential portion defining 360 degrees, at least two bows extending between opposing collars within the stand-off circumferential portion; wherein the at least two centralizers are spaced axially apart and fixedly attached to the tubular with the respective circumferential stand-off portions angularly offset from one another to provide 360 degrees of standoff. According to one or more aspects of the present disclosure, one or both of the collars of each centralizer may be rotationally stationary relative to the tubular and axially moveable relative to the tubular.
This application claims the benefit of U.S. Provisional Patent Application Ser. Nos. 61/167,482 filed on Apr. 7, 2009, 61/221,716 filed on Jun. 30, 2009, 61/237,202 filed on Aug. 26, 2009, 61/263,218 filed on Nov. 20, 2009, and 61/287,665 filed on Dec. 17, 2008, all of which are hereby incorporated by reference herein.
BACKGROUNDThis section provides background information to facilitate a better understanding of the various aspects of the present invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
Oilfield tubulars are disposed in wellbores to perform various tasks. In some applications, a centralizer may be disposed with (e.g., on) a tubular string to position the tubular string within the wellbore (e.g., wall of the borehole, inner wall of an outer tubular such as the casing, liner, etc.). The centralizer is commonly utilized to maintain separation between the tubular string and the wellbore. Centralizers commonly comprise a pair of collars that are interconnected with bows. The centralizers are positioned on the tubular string with the tubular extending through the respective bores of the collars and the bows extending outward from the tubular string. Centralizers may be fastened to the tubular in various manners. Commonly, centralizers are attached to a tubular such that centralizer is axially moveable along a length of the tubular, for example between stop collars, or one end (e.g., collar) is fixedly attached at an axial position and the other collar being free to move axially. In many configurations the centralizer is rotationally moveable relative to the tubular. At least one of the ends (e.g., centralizer collars) is axially moveable to allow substantial collapse of a bow to facilitate running the tubular string and centralizer through tight spots (e.g., restrictions) in a wellbore.
In
In order to move through restriction 14, the running force must be sufficient to overcome the collapse load (e.g., stand-off force) of the centralizer and the frictional forces of running the tubular string. Typically, this requires that the running forces (e.g., collapse and friction) must be less than the weight of the tubular string. Thus, in some applications it is necessary to provide centralizers that have a low collapse force to reduce the tubular running and starting forces to pass through the restriction. However a low collapse force (e.g., low restore force, low stand-off force) utilized for bows 6 of centralizer 3 may not have a sufficient restoring or stand-off force to position the tubular string in the wellbore (e.g., centralize) after passing through the restriction. The lack of sufficient stand-off force may be amplified in high-angle and horizontal wellbore sections.
SUMMARYAccording to one or more aspects of the present disclosure, an apparatus comprises opposing collars spaced apart from one another along a longitudinal axis, each of the opposing collars adapted to be fixedly secured to a tubular with a holding force; and a bow extending between the opposing collars, the bow having an apex and a stand-off force. The centralizer may comprise one or more bows. The centralizer may include a circumferential portion of at least 180 degrees in which bows are not disposed.
According to one or more aspects, an apparatus of the present disclosure comprises opposing collars spaced apart from one another along a longitudinal axis, each of the opposing collars adapted to be fixedly secured to a tubular with a holding force; and two or more bows extending between the opposing collars, each of the two or more bows spaced apart from one another within a circumferential arc no greater than about 180 degrees.
An apparatus according to one or more aspects of the present disclosure comprises at least two centralizers, each centralizer having a circumferential stand-off portion and a second circumferential portion defining 360 degrees, at least two bows extending between opposing collars within the stand-off circumferential portion; wherein the at least two centralizers are spaced axially apart and fixedly attached to the tubular with the respective circumferential stand-off portions angularly offset from one another.
The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.
It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact.
As used herein, the terms “up” and “down”; “upper” and “lower”; “top” and “bottom”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth of the well being the lowest point, wherein the well (e.g., wellbore, borehole) is vertical, horizontal or slanted relative to the surface. The terms “pipe,” “tubular,” “tubular member,” “casing,” “liner,” “tubing,” “drill pipe,” “drill string” and other like terms can be used interchangeably. The terms may be used in combination with “joint” to mean a single unitary length; a “stand” to mean one or more, and typically two or three, interconnected joints; or a “string” meaning two or more interconnected joints.
According to one or more aspects of the present disclosure a centralizer has collars adapted to be fixedly attached (e.g., at least rotationally stationary) to a tubular and a bow extending between the opposing collars is provided. According to one or more aspects of the present disclosure, a centralizer is adapted to pass through a restriction (e.g., reduced diameter) without requiring collapse of the bow according to one or more aspects of the present disclosure. It is recognized that bow(s) may deflect toward the tubular when running tubular operations; however, this limited deflection is permitted and is not an example of collapse.
Collars 21, 22 are adapted to fixedly attach (e.g., fasten, secure) centralizer 20 to a tubular. In the depicted embodiment, collars 21, 22 fixedly secure centralizer 20 so as to be axially and rotationally fixed relative to the tubular. In one embodiment, collars 21, 22 are only rotationally fixed relative to the tubular. Opposing collars 21, 22 are depicted in
Although
Corresponding to the limitation of bows 24 being disposed within the circumferential stand-off portion 40 (e.g., arc) is a second circumferential portion 42 (e.g., arc) in which bows 24 are not disposed. Circumferential stand-off portion 40 and second circumferential portion 42 without bows total the 360 degree circumference of centralizer 20.
A combination of two centralizers 20 of
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure. The scope of the invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. The terms “a,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded.
Claims
1. An apparatus comprising:
- opposing collars spaced apart from one another along a longitudinal axis, each of the opposing collars adapted to be fixedly secured to a tubular with a holding force; and
- a bow extending between the opposing collars, the bow having an at least one apex and a stand-off force.
2. The apparatus of claim 1, comprising a single bow.
3. The apparatus of claim 1, comprising two or more bows.
4. The apparatus of claim 1, wherein fixedly secured comprises rotationally stationary and axially moveable relative to the tubular.
5. An apparatus comprising:
- opposing collars spaced apart from one another along a longitudinal axis, each of the opposing collars adapted to be fixedly secured to a tubular with a holding force; and
- two or more bows extending between the opposing collars, each of the two or more bows spaced apart from one another within a circumferential arc no greater than 180 degrees.
6. The apparatus of claim 5, wherein fixedly secured comprises rotationally stationary and axially moveable relative to the tubular.
7. An apparatus comprising:
- at least two centralizers, each centralizer having a first circumferential stand-off portion and a second circumferential portion together defining 360 degrees, at least two bows extending between opposing collars within the stand-off circumferential portion, wherein the at least two centralizers are spaced axially apart and fixedly attached to the tubular with the respective circumferential stand-off portions angularly offset from one another to provide 360 degrees of standoff.
8. The apparatus of claim 7, wherein the second circumferential portion is at least about 180 degrees.
9. The apparatus of claim 7, wherein fixedly secured comprises rotationally stationary and axially moveable relative to the tubular.
10. An apparatus comprising:
- at least three centralizers, each centralizer having a first circumferential stand-off portion and a second circumferential portion together defining 360 degrees, at least one bow extending between opposing collars within the stand-off circumferential portion, wherein the at least three centralizers are spaced axially apart and fixedly attached to the tubular with the respective circumferential stand-off portions angularly offset from one another to provide 360 degrees of standoff.
11. The apparatus of claim 10, wherein fixedly secured comprises rotationally stationary and axially moveable relative to the tubular.
12. A method comprising:
- providing a centralizer having opposing collars spaced apart from one another along a longitudinal axis, each of the opposing collars adapted to be fixedly secured to a tubular with a holding force; and
- a bow extending between the opposing collars, the bow having an at least one apex and a stand-off force.
13. The method of claim 12, wherein fixedly secured comprises securing the collar to the tubular in a manner to be rotationally stationary relative to the tubular.
14. A method comprising connecting at least two centralizers to a tubular, each centralizer having a first circumferential stand-off portion and a second circumferential portion together defining 360 degrees, at least two bows extending between opposing collars within the stand-off circumferential portion, wherein the at least two centralizers are spaced axially apart and attached to the tubular with the respective circumferential stand-off portions angularly offset from one another to provide 360 degrees of standoff.
Type: Application
Filed: Apr 7, 2010
Publication Date: Oct 7, 2010
Applicant: Frank's International, Inc. (Houston, TX)
Inventors: Jean P. Buytaert (Mineral Wells, TX), Eugene Miller (Weatherford, TX), Ira Hining (Mineral Wells, TX)
Application Number: 12/755,876
International Classification: E21B 17/10 (20060101); E21B 23/01 (20060101);