US2849071A

US2849071A - Casing centralizers

Info

Publication number: US2849071A
Application number: US600913A
Authority: US
Inventors: Robert O Park
Original assignee: Baker Oil Tools Inc
Current assignee: Baker Hughes Oilfield Operations LLC
Priority date: 1956-07-30
Filing date: 1956-07-30
Publication date: 1958-08-26
Anticipated expiration: 1975-08-26

Description

RQ o. PARK cAsING CENTRALIZERS Aug. 26, 1958 2 Sheets-Sheet 1 Filed July 30, 1956 INVENTOR. 05597 0. .P4/ex:

A gsm as 20.' 2 I al n( 2 f.,

Aug. 26, 1958 R. o. PARK cAsING cENTRALIzERs 2 Sheets-Sheet 2 Filed July 50, 1956 IEH A '55567 0. Paez IN VEN TOR.

United States Patent 'Oliice 2,849,071 Patented Aug. 26, 1958 parte CASDIG CEN TRALIZERS Robert 0.. Park, Lakewood, Calif., assignor to Baker Oil Tools, Inc., Los Angeles, Calif., a corporation of California Application July 30, 1956, Serial No. 600,913 6 Claims. (Cl. 166-241) The present invention relates to apparatus for centering casing and similar conduits in well bores.

This application is a continuation-impart of my application for Casing Centralizer, Serial No. 528,576, tiled August i6, 1955, now abandoned.

An object of the invention is to provide centralizers to be mounted on conduit strings positionable in well bores, embodying outwardly bowed springs welded to and arranged on collars in such manner as to minimize the chance of spring failure at their welded locations, and to reduce the diameter of the centralizers when the springs are in their fully collapsed position against the conduit string, thereby enabling the centralizers to be run through close clearance surface casing.

Another object of the invention is to provide casing centralizers that are economical to manufacture, of strong and sturdy construct-ion, and of a reduced overall diameter when the outwardly bowed springs of the centralizers are collapsed substantially fully against the casing on which. the centralizers are mounted.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several forms in which it may be embodied. Such forms are shown in the drawings accompanying and forming part of the present speciiication. These forms will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a side elevation of a centralizer mounted on casing disposed in a well bore;

Fig. 2 is a cross-section taken along the line 2--2 on Fig. l;

Fig. 3 is an enlarged side elevational and sectional view of the upper portion of the centralizer;

Fig. 4 is a cross-section taken along the line 4 4 on Fig. 3;

Fig. 5 is a side elevation corresponding to Fig. l of a modified form of centralizer;

Fig. 6 is an enlarged side elevational and sectional View of the upper portion of the centralizer shown in Fig. 5.

As disclosed in Figs. l to 4 of the drawings, a string of well casing A, or similar conduit string, is to be maintained in a substantially centered location within a well bore B. To achieve this purpose, a casing centralizer apparatus C is mounted on the casing string. This centralizer device includes longitudinally spaced upper and

lower collars

10, 11, or generally cylindrical members, that are preferably slidably mounted on the casing. Circumferentially spaced, outwardly bowed springs 12 extend between and are secured to these collars, the medial portions 13 of the springs engaging the wall of the well bore B. Because of the force that the springs 12 exert against the Wall of the well bore, they tend to 'position and maintain the casing string A in a substantially central location within the well bore.

The upper and lower portions of the centralizer are eS- sentially the same, although oppositely disposed. The upper collar 10 is in the form of a generally cylindrical member, which may be made of sheet metal for purposes of economy in production. A relatively light gauge of sheet metal may be provided. The inner portion 14 of the collar is of a diameter that is slightly greater than the outside diameter of the casing A, in order that the collar will slidably lit the casing section on which it is mounted. The collar also has an `outer inturned flange 15 of an internal diameter substantially the same as the internal diameter of the inner portion 14 `of the collar. Such llange also will slide along the casing A and serve to maintain the collar 10 in proper relation on the casing.

Between the inner, generally cylindrical portion 14 and outer inturned flange 15 of the collar, the latter is formed with an intermediate collar port-ion 16 which has lan internal diameter that is greater than the internal diameter of the inner collar portion 14 by an amount that is substantially Vequal to twice the thickness of an outwardly bowed spring 12. Actually, the outermost end of the intermediate collar portion 16 isintegral with and merges into the outer inturned ange 15, whereas the inner end of the intermediate collar portion 16 is connected to the inner part 14 of the collar by an inturned ange 17, this latter flange being integral with bot-l1 the intermediate portion and the inner portion of the collar. In effect, the intermediate `portion 16. of the collar may be considered as constituting the web portion of a relatively long and shallow channel section that is integral with upper and lower inturned flanges V15, .17. inasmuch as the collar 10 is made from sheet metal, .the thicknesses of the inturned

flanges

15, 17, intermediate web portion 16fand inner portion 14 are substantially the same and uniform.

The outwardly bowed springs 12 are arranged circumferentially around the

collars

10, 11 and are spaced from each other Vpreferably by equal amounts. The upper portion 18 of each spring extends through an elongate slot 19 in the intermediate collar portion 16, this slot being of slightly greater width than the Width of the spring. It may extend from the lower inturned flange `1'7 to the upper region 20 of the intermediate portion of the collar 16, this upper region being continuous in an arcuate direction. The terminal portion 21 of each spring is relatively flat and substantially parallel to the axis of the centralizer. rlhis terminal portion extends along the inner wall of the continuous section 20 of the intermediate collar portion, its -outermost end being closely adjacent the outer inturned flange 15. As a matter of fact, the end of the spring may actually abut the outer inturned flange 15. The terminal 21 of the spring is secured to the lcollar by the use 'of welding material 22. Thus, the terminal portion of the spring may be spot welded to the continuous section 20 of the collar, with the spring lying flat against the inner wall of the collar section 20. However, to more securely integrate each spring yto the collar, the latter may be provided with a hole 23 overlying the end 21 of the spring, the latter being secured to 'the continuous collar section 20 by means of a plug weld 22 run around the circumferential portion of the hole 23 and integrating the spring to the continuous section of the collar itself.

As was stated above, the upper and lower portions of the centralizer are alike although oppositely disposed. The lower ends 18 of the springs extend through the collar slots 19, the lower portions being plug welded or spot welded to the continuous section 20 of the collar 3 11, the springs lying flat against the inner wall of this lower continuous section 20.

The centralizer C is mounted upon a casing section A, there being a suitable annular stop member 25 secured to the casing section between the inner portions 14 of the

collars

10, 11. This stop member 25 is adapted to engage with the innermost edges 26 of the collars. Originally, the distance across the intermediate portions 13 of the centralizer springs is substantially greater than the diameter of the well bore B, so that the insertion of the casing in the well bore will cause the springs to be collapsed inwardly to a partial extent, pushing against the wall of the formation and tending to locate the casing A in a substantially centered position within the bore B. During the lowering of the string of well casing in the well bore, the annular stop member 25 will engage the inner edge 26 of the inner collar portion 14 of the lower collar 11, and exert a pulling action on the centralizer, forcing it downwardly in the well bore with the casing on which the centralizer is mounted, the intermediate portions 13 of the springs sliding along the wall of the hole. If a restriction in the well bore is encountered, the annular stop ring 25 will still engage and exert a downward force on the lower collar 11, causing the latter to pull the springs past the obstruction, the springs merely being forced inwardly to a greater extent until the centralizer has moved beyond the obstruction. The downward force is transmitted from the collar 11, through the welds 22, to the springs 12, the welds having more than adequate strength to safely carry the loads imposed upon them.

As the springs 12 are urged inwardly by the wall of the formation or by a restriction encountered therein, their upper and lower portions 18 will be forced against the exterior of the casing A on which the centralizer is mounted, inasmuch as the slots 19 through which the outer portions of the springs extend into the collars are of an elongated extent. As the outer portions 18 of the springs bear upon the casing A, when the intermediate parts 13 of the springs are urged inwardly by the wall of the hole or the formation, they tend to shift the terminal portions 21 of the springs in an outward direction. The force accompanying such outward shifting tendency is not imposed upon the welds 22, but is transferred from terminal portions in an outward direction directly to the continuous section of each collar. Accordingly, it is evident that substantially the only loads that the welds are required to carry is a pulling load, necessary to move the centralizer springs 12 longitudinally along the wall of the well bore.

The above action occurs upon movement of the casing string in both directions. Thus, if the casing string A were to be elevated instead of being lowered, as described above, the stop ring 25 would engage the innermost edge 26 of the upper collar 10, shifting the latter in an upward direction and moving the springs 12 in an upward direction through the agency of the upper plug welds 22, which secure the springs to the upper collar. Inward collapsing of the springs will cause their upper and lower portions 18 to merely liatten against the exterior of the casing, with the outward expanding tendency of the terminal portions 21 of the springs being prevented and resisted by the continuous collar sections 20, the force exerted by the terminal portions not being imposed on the plug welds 22.

Inasmuch as the welds need not resist the outward movement of the terminal portions 21 of the spring 12, a very good and strong weld is not esesntial to the proper fabrication and operation of the apparatus. In view of the fact that the welds are not critical, a less expensive spring steel can be used for the outwardly bowed spring member 12, but despite the use of a more economical spring steel, the springs themselves will still possess the proper desirable spring characteristics. The springs need not be of the finest quality as long as they have good weldability characteristics to insure the appropriate attachment of the springs to the collar. Because of the construction described, the

collars

10, 11 can be made of lighter gauge material and still be of strong and rugged construction. The outer and inner inturned llanges 1S, 17 at opposite ends of the larger diameter portion 16 of the collar aid materially in stiffening each collar and contributing to its strength. The lack of necessity for providing welds capable of withstanding great forces makes it possible to use a less expensive steel for the collars, and, in addition, the steel from which the collars are made can be of lighter gauge.

In addition to the economy of manufacturing the centralizer for the reasons pointed out above, it is capable kof passing through close clearance surface casing. The intermediate portions 13 of the outwardly bowed springs can be flattened substantially completely against the casing A, the inward movement of the end portions 18 of the springs being permitted by the slotted collar construction. The extension of the inner portions of the slots 19 through the inner franges 17 permits the springs to collapse inwardly until they will lie upon the outer periphery of the inner portions 14 of the collar. Inasmuch as the external radius of the intermediate collar portion 16 is greater than the external radius of the inner collar portion 14 by an amount equal to the thickness of a spring 12, the flattening of the spring against the periphery of the inner collar portion 14 will result in a collapsed spring diameter that is no greater than the outside diameter of the intermediate collar portion 16 itself. Thus, the external diameter -of the intermediate collar portion 16 will determine the minimum size hole or surface casing through which the centralizer C can be moved. Such minimum outside diameter is reduced to a substantial extent, since it need only be the outside diameter of the casing plus twice the thickness of the collar and spring, the collar as stated above, being made of relatively light gauge material.

Accordingly, it is evident that a casing centralizer with outwardly bowed springs has been provided, in which relatively inexpensive materials can be used, and in which the welds need not be capable of withstanding much of the forces to which the centralizer is subjected. In addition, the diameter of an encompassing enclosure through which the centralizer can be moved is substantially less than in prior devices of a similar nature.

For vthe purpose of facilitating assembly of the centralizer on the casing string, it is preferred to make the upper and

lower easing collars

10, 11 in sections that are hinged to one another, which will allow the collar sections to be spread apart for transverse disposition around the casing string. As disclosed, each collar is made of tWo like

halves

28, 28 having hinged knuckles 29 at their circumferential ends which are substantially diametrically opposite one another. The hinge knuckles on one collar section will interleave with the hinged knuckles on the other collar section, after which a suitable hinge pin 30 can be inserted through all of the hinge knuckles of each hinge portion to secure the sections together. In effect, each centralizer collar is made of two

main parts

28, 28 that have the springs 12 welded thereto. The two parts are placed around the casing section A, the hinge knuckles 29 being interleaved, and the hinge pins 30 on diametrically opposite sides of each collar section inserted through all of the knuckles. The knuckles 29 do not extend along the whole length of the collar sections, terminating inwardly of the innermost ends 26 of each collar, in order that the insertion of the hinge pin therethrough will not cause it to extend inwardly beyond the inner ends 26 of the collars. In effect, the hinge knuckles are only formed on the intermediate collar section 16 of greater diameter than the inner collar section, which will insure that the knuckles 29 are disposed outwardly of the periphery of the casing and esaaofri will not interfere with the ability of each collar to slide relative to the well casing.

With the hinged arrangement disclosed, a stop ring 25 need not necessarily be placed on the casing section by 4a welding operation, or the like, or in some other manner. Instead, the upper and

lower collars

10, 11

can be placed on opposite .sides of a casing coupling 25,.

which secures adjacent casing sections A, A1 together. The casing coupling 25 then a-cts not only to perform the primary function of securing the casing sections together, but also as an annular stop member engageable with either the lower collar 11 or the upper collar 10, to pull the centralizer in either a downward lor an ward direction within the well bore, depending upon direction of which the casing string is moved.`

The form of invention disclosed in Figs. 5 and 6 is similar to the embodiment illustrated in Figs. 1 to 4, inclusive. However, the inner portion 14 of each collar Illa, 11a is eliminated and the inner portion of the collar terminates at an inner internal flange 17a that extends inwardly to substantially the same extent as the outer internal flange 15a. The intermediate or web portion 16a of each collar is unslotted immediately adjacent its inner internal flange 17a, the inner ends of the slots 19a, however, terminating fairly close to the inner flange, in order to permit the springs 12a to deflect inwardly to a maximum extent before a spring would engage the inner unslotted portion 20a of the web.

The upper and lower collars a, 11a are alike, being oppositely disposed with respect to one another, the upper and lower ends 21a of the outwardly bowed springs 12a extending through the respective slots 19a and engaging the outer internal flanges a. Such ends Zia lie flush against the inner surface of the web portions loa of the collars, to which they are plug welded, or otherwise suitably secured. The terminal portions 21a of the springs may be curved to conform generally to the curvature of the casing A, or other conduit string, on which the centralizer is mounted. Actually, the centralizer may slide along the casing by virtue of the bearing of such terminal portions 21a thereon, although the sliding and guiding of the centralizer may also be effected by the inner portions of the inner Iand outer

internal flanges

17a, 15a.

The centralizer disclosed in Figs. 5 and 6 may be of the hinge type, and may be mounted on the casing string A with the upper and lower collars 10a, 11a on opposite sides of the annular stop ring 2S, in the same manner as the other form of invention. When the casing is moving downwardly in the well bore, the stop ring 25 engages the inner frange 17:1 of the lower collar 11a, to pull the springs 12u down along the wall of the hole B and past any restrictions or obstructions encountered therein. On the other hand, upward movement of the casing will cause the stop ring 25 to engage the inner llange 17a of the upper collar 10a to exert a pulling action on the springs 12a, sliding them along the wall of the well bore and past any restrictions or obstructions encountered therein.

The inventor claims:

1. An apparatus adapted to be mounted on a well conduit: longitudinally spaced supporting members, each supporting member having an inner generally cylindrical portion to iit on the well conduit and an outer circumferential channel-shaped portion comprising longitudinally spaced flanges separated by a web integral therewith which is substantially parallel to and spaced outwardly of said cylindrical portion, one of said flanges extending inwardly of one end of said web and being integral with said cylindrical portion and the other of said flanges extending inwardly of the other end of said web, said web having circumferentially spaced longitudinally elongated slots therein; circumferentially spaced outwardly bowed spring members disposed around said supporting members and overlying the exteriors of said the cylindrical portions, the end portions of said spring members extending through said slots and engaging the inner walls of said webs longitudinally outwardly of said slots; and means for securing said end portions of said springs to said channel-shaped portions longitudinally outwardly of said slots.

2. In apparatus ad-apted to be mounted on a well conduit: longitudinally spaced supporting members, each supporting member having an inner generally cylindrica'l portion of a diameter to slidably `tit on the well conduit and an outer circumferential channel-shaped portion comprising longitudinally spaced inner and outer iianges separated yby a web integral therewith which is substantially parallel to `and spaced outwardly of said cylindrical portion, said inner iiange extending inwardly of said web and being integral with the outer end of said cylindrical portion, and said outer ange extending inwardly of said web; the web lof each supporting member having circumferentially spaced longitudinally elongated slots therein extending longitudinally outwardly from said inner flange and terminating short of said outer flange, the portion of said web `between said slots and said outer flange being circumferentially continuous; circumferenti- -ally spaced outwardly bowed spring members disposed around said supporting members and overlying the exteriors -of said cylindrical portion, the end portions of said spring members extending through said slots and engaging the inner walls of said circumferenti-ally continuous web portions; and means for securing said end portions to said web portions.

3. In apparatus adapted to be mounted on a well conduit: longitudinally spaced supporting members, each supporting member having an inner generally cylindrical portion of a diameter to slidably iit on the well conduit 'and an vouter circumferential channel-shaped portion comprising longitudinally spaced inner land outer anges separated by a web integral therewith which is substantially parallel to and spaced outwardly of said cylindrical portion, said inner flange extending inwardly of said web iand being integral with the outer end of said cylind-rical portion, :and said outer flange extending inwardly of said web and having an inside diameter substantially equal to the inside diameter of said cylindrical portion; said web having circumferentially spaced longitudinally elongated slots therein extending longitudinally outwardly from said inner flanges Iand terminating short of said outer flanges, said slots extending through said inner flanges, the portion of each web between said slots and said outer ange being circumferentially continuous; circumferentially spaced outwardly bowed spring members disposed around said supporting members and overlying the exteriors of said cylindrical portions, the end portions of said spring members extending through said slots and engaging the inner walls of said circumferentially continuous web portions, the termini of said spring members being disposed adjacent said outer flanges; and means for securing said end portions to said web portions.

4. In yapparatus adapted to -be mounted on a well conduit: longitudinally spaced supporting members, each supporting member .having an inner generally cylindrical portion of a diameter to slidably t on the well conduit and an outer circumferential channel-shaped portion comprising longitudinally spaced inner and outer flanges separated by `a web integral therewith which is substantially parallel to and spaced outwardly of said cylindrical portion, said in ner ange extending inwardly 4of said web and being integral with the outer end of said cylindrical portion, and said outer ilange extending inwardly of said web and having `an inside diameter substantially equal to the inside diameter of said cylindrical portion; said web having circumferentially spaced longitudinally elongated slots therein extending longitudinally outwardly from said inner flanges and terminating -short of said outer flange, said slots extending through said inner flange, the portion 'of each web -between said slots land said outer ange being circumferentially continuous; circumferentially spaced outwardly bowed spring members disposed around said lsupporting members and overlying the exterior of `said cylindrical portions, the end portions of said spring members extending through said slots and adapted to bear upon the conduit string and engaging the inner walls of said circumferentially continuous web portions, the termini of said spring members being disposed adjacent said outer flanges; and means for securing said end portions to said web portions; the outside diameter of said webs being equal to the outside diameter of said cylindrical portions plus twice the thickness of a spring member.

5. In :apparatus `adapted to 4be mounted on a well conduit: longitudinally spaced supporting members, each supporting member having a circumferential channelshaped portion comprising longitudinally spaced inner and outer flanges separated by a web integral therewith, said ilanges extending inwardly of said web, said web having circumferentially ,spaced longitudinally elongated slots therein extending from a point adjacent said inner ilange `and terminating short of said outer ange, the portion of said web between said slots and said outer flange being circumferentially continuous; circumferentially spaced outwardly bowed spring members disposed around said supporting members and overlying the exterior of said inner flanges, said spring members having end portions extending through said slots and engaging the inner walls of said circumferentially continuous web portions, the terminals of said end portions being adjacent said outer 8 anges; and means for securing said end portions to said web portions.

6. In -apparatus adapted to be mounted on a well conduit: longitudinally spaced supporting members, each supporting member having a circumferential channel-shaped portion comprising longitudinally spaced inner and outer terminal ilanges separated by `a web integral therewith, said anges extending inwardly of said web, said web having circumferentially spaced longitudinally elongated slots therein extending from =a point adjacent said inner flange and terminating short of said outer flange, the portion of said web between said slots `and said outer ange being circumferentially continuous; circumferentially spaced -outwardly bowed spring members disposed around said supporting members and overlying the exterior of said inner flanges, said spring members having end portions extending through said slots and engaging the inner wall of said circumferentially continuous web portions, the terminals of said end portions being adjacent said outer flanges; and means for securing said end portions to said web portions.

References Cited in the le of this patent UNITED STATES PATENTS