The present invention relates to centralizers attached to pipe placed in boreholes. The invention discloses a method of hydroforming centralizers and means of their attachment to pipe.
The processes of drilling and completing well bores in earth materials using tubular strings are frequently benefited if the tubular string is prevented from fully eccentering and generally contacting or laying against the borehole wall. Devices, typically referred to as centralizers, are employed to provide this function of reducing eccentricity, or centralizing, the tubular string within the borehole. These devices are configured to economically meet a variety of drilling and completion applications.
As disclosed in Canadian patent application 2350681, filed Jun. 15, 2001 in the name of TESCO Corporation, the demands of drilling with casing lead to the need for inexpensive casing centralizers which are rugged, for example resistant to rib failure, comparatively easy to attach to the casing and able to withstand drilling rotation sufficient to complete at least one well.
Such centralizers are also useful for applications beyond casing drilling.
A hydroformed centralizer and method of manufacture has been invented. The centralizer is suitable for installation on pipe, such as would be useful in well bore drilling and casing operations. The present invention provides a metal centralizer having a cylindrical body carrying outwardly projecting ribs, hydroformed into its sidewall, which when coaxially placed over a pipe may be retained by various means.
The means employed for attachment may be varied according to the needs of the application. For example, in applications such as drilling with casing, typically requiring sufficient structural capacity to substantially prevent significant relative movement of the centralizer on the pipe, the centralizer body is provided with at least one cylindrical interval suitable for attachment by the method of crimping as taught in the aforementioned Canadian Application 2350681.
For applications where centralizer rotation about the pipe on which it is attached, is allowable or preferred, but its axial position is sought to be fixed, the hydroformed centralizer can be installed between stop rings affixed to the pipe, as commonly implemented for casing running. The stop rings may be fixed to the pipe by the method of crimping or by other means generally known to the industry such as set screws threadably mounted in the side wall of the stop rings.
Thus, in accordance with a broad aspect of the present invention, there is provided a centralizer comprising: a generally tubular body having a central opening sufficiently large to allow insertion therethrough of a selected pipe having an external diameter; a sidewall of substantially uniform thickness including an inner-facing surface directed to the central opening and an outer-facing surface onto which are formed a plurality of outwardly protruding ribs by means of hydroforming the sidewall.
In accordance with another broad aspect, the is provided a method for producing a centralizer, the method comprising the steps of: placing a length of metal tubular work piece, the work piece having a sidewall and an central opening, inside a confining surface comprised of mold elements, the mold elements including cavities spaced and shaped in the configuration of desired side wall centralizer ribs, the mold elements being supported substantially against expansion radially outward from their position about the tubular work piece; applying sufficient pressure to the side wall through the inner bore to force the tubular sidewall radially outward against the confining surface and into the mold cavities and thus plastically deform the side wall to form centralizer ribs on the side wall; and removing the tubular work piece from the confining surface.
In accordance with another broad aspect, there is provided a method for producing a centralizer for a pipe comprising: providing a tubular work piece selected to be formed into the centralizer having a central opening defining an inner diameter and a sidewall having an inner-facing surface directed toward the central opening and an outer-facing surface; providing a mold including a plurality of elements together forming a inner-surface defining a substantially cylindrical confining space and cavities formed in the inner surface positioned and configured so as to correspond to the position and configuration of ribs to be formed on the centralizer; positioning the tubular work piece and the mold elements such that the tubular work piece is within the substantially cylindrical confining space formed by the mold elements; securing the mold elements about the tubular work piece; applying sufficient fluid pressure against the sidewall to force the sidewall out against the mold elements and into the cavities of the mold elements to form a centralizer having ribs protruding outwardly
A further, detailed, description of the invention, briefly described above, will follow by reference to the following drawings of specific embodiments of the invention. These drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. In the drawings:
According to the present invention, a hydroformed centralizer is provided as shown in
Referring to
Ribs 7 can be evenly spaced around the main body interval and, in this illustrated embodiment, each rib extends along at least a portion of the length of the centralizer helically as commonly known to the industry. The ribs can be suitably shaped to accommodate the structural and flow requirements encountered in well bores and to stand the main cylindrical surface and ends 3, 4 from the borehole wall. As such the ribs provide a bearing surface 8 at their upper limits. The number, length and pitch of the rib helixes can be arranged so that the starting circumferential position of each rib overlaps the ending circumferential position of at least one adjacent rib.
In applications where the centralizer is rotated with the pipe, such as required for drilling with casing, the bearing surfaces 8 may be provided with a wear resistance coating such as hardfacing to protect the ribs 7 from wear against the borehole wall.
In applications where rotation of the centralizer on the casing is permitted, the internal bore 2 can wear against the pipe. In such applications, therefore, the surface defining the internal bore may be provided over all or a portion thereof with a suitable friction reducing coating 2a such as for example of polyurethane.
The placement of ribs 7 in the tubular wall is supported through provision of a hydroforming process. As shown in cross-section A-A of
The inner surface of the side wall is also deformed and includes indentations 5 that substantially follow the configuration of the outer ribs. The ribs can be formed with smooth, gradual, rather than sharp, surface transitions at the base and throughout the ribs.
In one embodiment, the hydroforming process includes placing a length of metal tubular work piece having a sidewall. The material of the tubular work piece is selected to accommodate plastic deformation and substantially retain the effects hydroforming, while being useful in downhole environments. In one embodiment, the centralizer is formed of ductile metals such as, for example, steel. To hydroform a centralizer, wall thickness combined with the material strength must provide sufficient strength to react the eccentering and perhaps lateral drilling forces encountered by the tubular. These forces vary significantly depending on tubular size, hole geometry, location in the hole, drilling or running, etc. Generally, for example, if using steel, the wall thickness of the material for forming the centralizer is greater than about 1/16″. On a cost benefit analysis, an upper limit for steel wall thickness is about ½″ for petroleum or even geothermal applications. In one embodiment, the material is steel having a wall thickness of ¼″.
The tubular work piece is positioned inside a confining surface comprised of mold elements having cavities spaced and shaped in the configuration of the desired side wall protruding ribs. The confining surface can be generally cylindrical and positioned to generally align with the mid-section of the tubular work piece. The confining surface can be configured to support by cylindrical confinement opposite the end sections of the tubular work piece. The confining surface is contained within a support that holds the mold elements in position. The support can be a confining tube that holds the mold elements against movement radially outwardly away from the tubular work piece. Once the tubular elements are positioned about the tubular work piece, sufficient internal pressure can be applied against the inner surface of the side wall to force, as by inflating, the tubular sidewall radially outward against the confining surface and into the mold cavities and thus plastically form protrusions or ribs projecting outwardly from the side wall of the tubular work piece. The pressure is generated as fluid pressure, as by use of liquids contained to act at high pressures against the side wall. The ribs are formed, while substantially preserving the original tubular length. After formation of the ribs, the formed centralizer can be removed from the forming apparatus including the confining surface and its support. Removal of the mold elements from their support may require some force due to them becoming tightly jammed therein during hydroforming. Removal may be facilitated by providing a close fitting tapered collet between the support and the mold elements and means to axially displace the collet in the direction allowing radial expansion. If desired, the centralizer can then be treated, if required, by various means such as cropping, machining or applying coatings to improve wear resistance or to reduce friction.
Referring now to
For hydroforming, a tubular work piece 102, from which a centralizer is to be formed, is positioned between mandrel 101 and mold assembly 103.
Referring now to
Removal of the mold elements from the formed centralizer after hydroforming can be facilitated by the slits 113 that act to introduce hoop compliance. Additionally, each mold element can form a portion of a cavity so that the elements are not engaged on the centralizer by the protrusion of a rib into a cavity.
Referring now to
Pressures required to hydroform depend, for example, on the strength of the material to be formed and the radius of the curvature to which the wall is formed. In one embodiment, pressures are from 100 to 200 Mpa (15,000 to 30,000 psi). Seals 110, etc. must be capable of containing such pressures.
Referring now to
A hydroformed centralizer can be installed using various means onto a pipe for use in a wellbore. For example, means of mounting the centralizer body on a metal pipe can allow free rotation of the hydroformed centralizer on the metal pipe. If desired, the means of mounting can limit the centralizer's range of axial travel. In such an embodiment, mounting can include placement of the centralizer on the metal pipe between two surfaces upset sufficiently with respect to the metal pipe external diameter to abut the ends of the centralizer body. The abutting surfaces typically provided by the shoulders of stop rings placed coaxially on the pipe on either side of the centralizer, the stop rings being fixed to the metal pipe by means of set screws, bonding or crimping. The means of crimping the stop rings can follow the teachings provided in Cdn. App. 2350681. The selected metal pipe can be, for example, casing for drilling or lining a borehole or drill pipe.
As another example, the hydroformed centralizer can be installed to provide axial load and torque transfer by securing the centralizer to move both rotationally and axially with the pipe on which it is attached.
Referring to
For applications requiring structural attachment of the centralizer 1 to the casing 9 enabling torque transfer, the centralizer can be fixed to the casing by crimping one or both of the end intervals 3a, 4a onto the casing as described in Cdn. App. 2350681. For such applications the material of the centralizer body 1 in one or both of the end intervals 3a, 4a can be selected to preferably have its elastic limit less than that of the casing joint 9.
As an alternate method of attachment providing axial load and torque transfer, one or both of the centralizer end intervals may be provided with set screws (not shown). Once positioned on the pipe, the set screws are tightened to fix the centralizer in place, which method of attachment is well known to the industry. Similarly, the centralizer may be secured by use of welding or by injecting grout or other adhesive into the interface between the centralizer bore and casing, which method of affixing centralizers is also known in the art.
In a further embodiment, for applications requiring axial position control of the centralizer on the pipe but allowing rotation without significant torque transfer,
It will be apparent that these and many other changes may be made to the illustrative embodiments, while falling within the scope of the invention, and it is intended that all such changes be covered by the claims appended hereto.
Number | Date | Country | Kind |
---|---|---|---|
2404577 | Sep 2002 | CA | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/CA03/01392 | 9/23/2003 | WO | 00 | 6/1/2006 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2004/027207 | 4/4/2004 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
349718 | Hollerith et al. | Sep 1886 | A |
4319471 | Benteler et al. | Mar 1982 | A |
4763503 | Hughes et al. | Aug 1988 | A |
6092593 | Williamson et al. | Jul 2000 | A |
6305204 | Tauzer | Oct 2001 | B1 |
6409226 | Slack et al. | Jun 2002 | B1 |
6435275 | Kirk et al. | Aug 2002 | B1 |
6497030 | Marando | Dec 2002 | B1 |
6820317 | Okada | Nov 2004 | B2 |
20010006109 | Kaiser et al. | Jul 2001 | A1 |
20030010540 | Kirk et al. | Jan 2003 | A1 |
Number | Date | Country |
---|---|---|
1002 423 | Feb 1957 | DE |
2 197 008 | May 1988 | GB |
WO 9837302 | Aug 1998 | WO |
WO 9846382 | Oct 1998 | WO |
WO 0153652 | Jul 2001 | WO |
WO 0166904 | Sep 2001 | WO |
WO 0198622 | Dec 2001 | WO |
WO 0231312 | Apr 2002 | WO |
WO 0232596 | Apr 2002 | WO |
Number | Date | Country | |
---|---|---|---|
20060231250 A1 | Oct 2006 | US |