US2735495A

US2735495A - Well bore scratcher

Info

Publication number: US2735495A
Authority: US
Publication date: 1956-02-21
Anticipated expiration: 1973-02-21

Description

Feb. 21. 1956 J. E. HALL, SR

WELL BORE SCRATCHER 2 SheetsSheet 1 Filed June 18, 1953 n 5 R WM m5 ATTORNEK Feb. 21, 1956 Filed June 18, 1953 J. E. HALL, SR 2,735,495

WELL BORE SCRATCHER 2 Sheets-Sheet 2 Ely. 11.

0 Z I 1% I INVENTOR;

ATTORNEW WELL BORE SCRATCHER Jesse E. Hall, Sn, Weatherford, Tex. Application June 18, 1953, Serial No. 362,475 8 Claims. (Cl. 166-173) This invention relates to improvements in well bore scratchers and refers more particularly to scratchers of the circular band or collar type utilizing angularly disposed bristles or wire abrading elements and adapted to be mounted on the exterior of a tubular casing or pipe and reciprocated with the casing in a Well bore. The salient features of novelty reside in the arrangement for fastening the wire abrading elements to the collar, the type of coil springs wound into the wire abrading elements and the manner of mounting the coil springs within the collar or upon its outer surface to minimize the wall thickness of the scratcher and provide improved reversibility.

One of the major problems in well conditioning preparatory to cementing where scratchers are used is the reduction of the thickness of the scratcher collar thereby minimizing the obstruction and hindrance presented to the passage of mud or circulated well fluid. In tight holes where the annulus between the casing and well bore is narrow, a condition often referred to as close tolerance, exists and the thickness of the scratcher collar is of vital importance to the success of the operation. Another factor critical to reversibility is the capability of the scratcher collar to move through the plane of engagement of the wire ends with the well bore upon reversal of direction of movement of the casing during reciprocation without causing hanging or fouling of the wires in the coil springs of adjacent wires.

An object of the invention therefore is to reduce to a minimum the thickness of the scratcher by providing a coil spring structure which will give the abrading wires the desired flexibility and at the same time restrict within narrow limits the height of the coils and their projection above the periphery of the collar.

Another object is to simplify the attachment arrangement necessary to hold the abrading wires rigidly to the collar, and make the construction easy to assemble whether mounted on the inside or the outside of the collar band.

Other and further objects will appear from the description which follows. In the drawings which form a part of the instant specification, and wherein are shown several embodiments of the invention, like reference numerals have been used to indicate like parts in the various views.

Fig. 1 is a vertical elevational view of a scratcher with parts broken away to reveal the internal wire anchoring structure;

Fig. 2 is a end-on, axial view of the scratcher shown in Fig. 1;

Fig. 3 is a vertical elevational view of a modified construction with the abrading wires mounted upon the exterior of the collar band;

Fig. 4 is a end-on, axial view of the scratcher shown in Fig. 3;

Fig. 5 is an enlarged perspective detail of a scratcher wire unit adapted to be mounted upon the inside of the collar;

States Patent 0 7 Patented Feb. 21, 1956 Fig. 6 is an enlarged perspective detail of a scratcher wire adapted for outside collar mounting;

Fig. 7 is an enlarged detail showing a modified form of inside collar mounting employing but a single tongue or lance;

Fig. 8 is a sectional view taken along the line 8-8 in Fig. 7 in the direction of the arrows;

Fig. 9 is a sectional view taken along the line 9-9 in Fig. 7 in the direction of the arrows;

Fig. 10 is an enlarged detail showing a modified form of outside collar mounting; and

Fig. 11 is a sectional view taken along the line 11-11 side collar band attachment, coil springs for out side collar attachment and cross-over portions 11d by means of which the wire units are affixed to the collar, whether the units are mounted within the collar or outside the collar. In Figs. 5 and 6, the structure of the units for inside and outside mounting is shown in somewhat greater detail. Fig. 5 shows the structure of a unit that is attached within the collar, with the coil springs 11b located in apertures 10a punched in the collar shown best in Figs. 7 and 8. The coil spring construction as shown in Fig. -5 comprises a single convolution of relatively large diameter at the bottom of the coil, and surmounting this large loop are three loops.

of wire of substantially the same diameter but of smaller diameter than the large convolution. From the upper convolution of each of the coil springs extend the free ends 11a, which are preferably inclined slightly with respect to a plane normal to the axis of their respective coils.

Returning to the mounting of the unit 11 such as is shown in Fig. 5, lances or gripping tongues 12 are first cut or pierced from the collar, band, the base portions of the tongues are unsevered leaving the lances attached to the collar band. Also, the collar bands are perforated in two circumferential rows, the holes being spaced apart to receive the wire abrading units in the manner shown in Figs. 1, 7 and 8. The diameter of the apertures 10a is somewhat smaller than the diameter of the large convolutions of coil springs 11b but larger than the diameter of the smaller convolutions. Consequently, when the Wire units are mounted within the collar with the gripping tongues or lances 12 pressed tightly down upon the cross-over portions 11d of the units, there will be provided a rigid attachment for each of the wire units with the smaller convolutions of the coil springs extending through the apertures Ida and the larger convolutions of the coil springs abutting against the inside of the collar.

It should be noted that the crossover portions 11d of the units are straight sections of wire located between the coils substantially at a diametric position so extensions of the cross-over would pass through the axes of the respective coils. This unique positioning of the cross-over relative to the coil springs is for the purposes of easy assembly and preventing movement or displacement of the wire units after they have been mounted within the collar.

The collar 10, it will be noted, is formed with its midsection domed and the marginal rims 10b of somewhat smaller diameter. This doming of the central portion of the collar provides a protected enclosure of sufficient height toaccommodate the two thicknesses of metal pro-- ver portion 11d. In other words, the marginal rims ofv the collar have a diameter only slightly greater than the outside diameter of the casing or pipe upon which the scratchers are mounted. The central portions offthe scratcher collars are enlarged or domed sufficiently to accommodate but two thicknesses of metal required for any attachment arrangement. Thus, it will be seen that the obstruction to the annular space between the casing and the bore of the well has been reduced to a minimum including but three narrow metal sections, the section of the lances or tongues 12, the wire cross-over portion 11d and the outer wall of the collar itself.

The collar mounting shown in Figs. 1 and 2 employs two lances or gripping tongues 12 to hold the wire units in position within the collar. In the modification shown in Figs. 7 and 8 but a single lance is used to hold the cross-over portion of the wire units rigidly Within the collar assisted by dimples 13 which are formed in the wall of the collar adjacent the cross-over portion shown best in Figs. 7 and 8. Another variation in the structure of the scratcher collar is the manner of welding the two ends together to form a circular band. In the embodiment shown in Figs. 1 and 2, a plain straight butt weld is used running axially of the collar band. In the modification shown in Figs. 7 to 11, inclusive, the joining of the collar ends by welding is supplemented by a backing strip 14 located beneath the abutting ends and serving as a reinforcement within the collar between the marginal inturned rims. The marginal edges of the collar ends are the only portions which are butt welded, the central portion being reinforced by the backing strip as indicated.

The seratcher construction shown in Figs. 3 and 4 and 10 and 11 utilize a wire unit as shown in Fig. 6. The coil springs in this wire unit have two lower convolutions or loops of large diameter and two convolutions or loops of smaller diameter located within the larger loops with the free ends extending from the top convolutions of the coils and projecting from the collar substantially parallel to each other. These wire units, instead. of being attached to the inside of the collar with the coils projecting through the apertures 10a, are mounted on the periphery of the collar. The scratcher shown in Figs. 3 and 4 employs two lances 12 for the attachment of each wire unit, and, as before, the cross-over portions 11d of these units extend between the coils substantially at a diametric position. This attachment of the cross-overs against the outer surface of the collar, with the flat bottoms of the lower convolutions resting against the collar surface, and the cross-overs located on a medial line between the coils assures rigid attachment of the units to the collar surface. Circumferentially spaced between the wire units and extending across the width of the collar bands are ridges or prominences 15. These ridges have a height corresponding substantially to the height of the coils and prevent hanging or fouling of the free ends of the wires upon adjacent coil springs as the collar passes between the wires during reciprocation of the casing, as illustrated in Fig. 12.

It should be appreciated that these scratchers are mounted at intervals along the length of the pipe or casing and are located to clean the bore of the well of accumulated mud where the cement column is to be placed. The annulus between the casing and the well bore being relatively narrow causes the free ends or abrading wires 11a to drag against the well wall and bend upwardly as the casing is run into the hole or during the downstroke when reciprocated. On the upward movement of the casing, since the scratchers are mounted upon the casing between stops, the movement of the free ends of the wires are F reversed, at which time the scratcher collars must pass through the wires as they are closely wrapped about the collar due to the narrow space, within which they operate. utsminences 0r projections o any o t. such as t e top of the coil springs, ext n eyond the outer urface of the scratchers and are not protected, the free ends of the wires are apt to hang upon these projections fouling the wires upon the springs and in some instances tearing them from their attachment to the collar. When this occurs, the effectiveness of the abrading wires and scratchers is materially reduced. it is for this reason that in the construction shown in Figs. 1 and 2 and in the modified structure shown in Figs. 7 and 8, the wire units are attached to the collar by an inside mounting and the height of the coil springsreduced to a minimum. Where the attachment of the wire units is made to the outside of the collar as in Figs. 3 and 4 and the modified structure shown in Figs. 10 and 11, guard members, such as the marginal ridges 16 and circumferentially spaced transverse ridges 15 are provided to permit the abrading ends of the wires to pass freely over the surface of the collar and prevent hanging or fouling of the wires with the coils.

Where but a single lance 12 is used as the principal holding element as in the structure shown in Figs. 10 and ll, displacement of the wire units is prevented by positioning prominences or dimples 17 adjacent the crossovers lid on either side of the gripping tongues or lances 12. These prominences may be small rivet heads or the metal wall of the collar may be deformed in the shape of hemispherical prominences or dimples located to fit against the side of the cross-over and with the lances 12 hold the wire units rigidly in place. Also, in this modification, the marginal ridges 16 and the axial ridges 15 serve to prevent hanging of the wires during reciprocation. it has been found that at least four convolutions are essential in the coil springs to provide the required resiliency and reversibility of the free ends of the wires during reciprocation. If the wire units are mounted within the collar, the thickness of the scratcher can be held to a minimum by having a large convolution within the collar and the three smaller convolutions protruding through the collar apertures. Where the wire units are mounted on the outer surface of the collar, there is a slight sacrifice in scratcher thickness and the coil springs are necessarily subjected to greater abrasive wear, but a relatively thin structure may still be maintained by depressing the smaller'convolutions within the larger convolutions as shown in Fig. 11 and protecting the coil springs by the circumferential and axial ridges.

It will be seen that the invention is well adapted to attain all of the ends and objects hereinbefore set forth together with the other advantages which are obvious and which are inherent to the structure. There has been provided a scratcher construction wherein the wire units have rigid attachment to the collar, either by an inside mounting or by mounting upon the outer surface of the scratcher. The thickness of the scratcher has been reduced to a minimum providing the least possible obstruction to the passage of well fluids. There havebeen provided wire units which due to the construction of the coil springs have a maximum of resiliency. The attachment arrangement by which the wire units are fastened to the collars automatically locate the units upon the collar, greatly reducing time and labor necessary for the manufacture of the scratchers.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may be employed with out reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that a ma ter hereto. set for h r shown n he acc mp nying drawings is to be nterpret d ll trative and not in a limiting sense. a

Having thus described my invention, I claim:

1. in a well bore scratcher, the combination with a circular collar band support adapted to be fitted over a casing, of a plurality of wire abrading units attached to the collar, said units each comprising a central straight cross-over portion disposed against the collar, a pair of coil springs wound into the wire at the extremities of the cross-over portion each having one coil thereof disposed flat against the collar, said cross-over portion extending between the coil springs substantially at a diametric position intermediate the coils, and a free end portion projecting from each of the respective coil springs outwardly away from the collar, said wire units being attached to said collar by at least one tongue overlapping and confining said cross-over portion.

2. A scratcher as in claim 1 wherein a pair of pro tuberances are provided on said collar, one on each side of said tongue, each protuberance being located adjacent said cross-over portion and the said one coil on the corresponding side of said tongue.

3. A scratcher as in claim 1 wherein two laterally spaced tongues are provided for attaching said cross-over portion to said collar, each tongue being located adjacent the said one coil of the respective coil spring.

4. A scratcher adapted to be mounted on an oil well casing comprising an annular collar, circumferentially spaced coil springs secured to said collar and projecting beyond the periphery thereof, each spring terminating in a free wire projecting outwardly from said springs and disposed nonradially with respect to the collar, all said Wires being at substantially the same angularity with respect to the collar, and circumferentially spaced axial ridges on said collar interposed between adjacent ones of said springs and of substantially equal height therewith to prevent interengagement of the free wires with the coil springs.

5. A scratcher as in claim 4 wherein said collar is also provided with circumferential ridges adjacent its marginal edges.

6. A scratcher as in claim 4 wherein said springs are arranged in two spaced circumferential rows each having an equal number of springs, each spring in one row being connected with a corresponding spring in the other row and each connected pair of springs together with their extending wire ends being a single Wire abrading unit, said ridges being interposed between adjacent ones of said wire abrading units.

7. In a well bore scratcher, the combination with a circular collar band support adapted to be rotatably mounted on a pipe or casing, of a plurality of circumferentially spaced wire abrading units attached to the exterior of said collar each comprising a central crossover portion anchored to the collar, a pair of coil springs wound into the wire at the extremities of the cross-over portion, and a free wire end extending from each spring, each coil spring having a plurality of convolutions of large diameter and a plurality of convolutions of lesser diameter and so formed that the latter convolutions telescope within the larger convolutions to reduce the over-all height of the spring.

8. A well bore scratcher as in claim 7 wherein an axially directed ridge is provided on the exterior of said collar between each two circumferentially adjacent abradin g units to prevent interengagement of the wire ends with the coils of the springs.

References Cited in the file of this patent UNITED STATES PATENTS 2,412,876 Edwards Dec. 17, 1946 2,506,405 Wright May 2, 1950 FOREIGN PATENTS 809,063 Germany July 23, 1951 667,707 Great Britain Mar. 5, 1952 OTHER REFERENCES The Oil Weekly, vol. 102, No. 5, July 7, 1941, page 37.