US2228649A

US2228649A - Casing centralizer

Info

Publication number: US2228649A
Application number: US340949A
Authority: US
Inventors: Julien A Welles
Original assignee: Baker Oil Tools Inc
Current assignee: Baker Hughes Oilfield Operations LLC
Priority date: 1940-06-17
Filing date: 1940-06-17
Publication date: 1941-01-14
Anticipated expiration: 1958-01-14

Description

Jan. 14, 1941. J. A. WELLES 2,228,649

CASING CENTRALIZER Filed June 17, 1940 '(fUL/EN A. T V-LLES,

6 444 a. mew,

Patented Jan. 14, 1941 UNITED STATES PATENT OFFICE CASING CENTRALIZER Application June 17, 1940, Serial No. 340,949

18 Claims.

This invention relates to casing centralizers, being particularly concerned with centralizers of the spring type, which tend to maintain the casing centered in the bore hole. Such centering is desirable and important to insure that a uniform thickness of cement will be deposited around the casing for the purpose of providing an effective cementitious seal against the passage of encroaching waters on other fluids into the well or casing.

In my application Serial No. 296,099, filed September 22, 1939, for Casing centralizers, a centralizer has been described and claimed embodying leaf springs yieldably engageable with the sides of the casing or hole. These springs are pulled and not pushed through any restrictions or obstructions as the casing is raised or lowered in the hole, to prevent their buckling or collapsing. The leaf springs are shown' in the application as arranged circumferentially around the casing by being welded to axially spaced collars. Such mode of securing the spiings decreases their spring properties in the region of the welds, with attendant limitations on their loading capacity. 25 Moreover, the labor time consumed in welding the springs to the collars is a large item of expense in the cost of production of the centralizers.

Accordingly, it is an object of the present invention to provide a centralizer of the leaf spring 30 type in which the springs can be arranged circumferentially around axially spaced collars and secured thereto. without resort to any additional holding means, as welding material. More specifically, this invention contemplates forming the 35 collars and springs so that they interlock when assembled together and retain such interlocking relationship while in operation within a well bore or casing.

As aforementioned, centralizing of the casing is 40 important to obtain a circumferentially uniform cementitious seal around the casing, and thusprevent migration of waters past this seal. Although casing centralization is important, it has been foimd that in many instances the mud cake on the wall of the bore hole breaks down to form a channel around the cement seal through which migrant waters can flow. Removal of the mud cake in the region at which cement is to be depositedprevents such channeling by allowing the cementitious material to bond firmly with the formation itself, rather than coacting with the fine, low strength, and easily broken down mud cake.

It is another object of the invention to provideing in the hole, but which also embodies mechanical means for scraping the mud cake or sheath from the wall of the bore hole. The scraping members are preferably designed to slide over the mud cake when moved downwardlyin the bore and to remove the mud cake by a scraping action when moved upwardly in the hole.

- The invention has other objects that will become apparent from a consideration of the embodiment shown in the drawing accompanying 10 and forming part of the present specification. This form will now be described in detail, but it is to be understood that such detailed description isnot to be taken in a limited sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawing:

Figure 1 is a side elevational view of a centralizer prior to its assembly on a casing;

Figure 2 is a cross-sectional view takengeneralally along the line 2-2 of Figure 1;

Figure 3 is a view similar to Figure 1, showing the centralizer assembled ona casing within a bore hole; and I Figure 4 is a longitudinal section on an enlarged scale through part of the centralizer and casing shown in Figure 3.

' As shown in the drawing, and as described and claimed in my above-identified application, the centralizer A includes a plurality of outwardly bowed leaf springs l0 secured to and spaced circumferentially around a pair of axially separated collars ll, I2. The ends [3 of each spring extend beyond the collars and terminate in inwardly bent stop portions 14 adapted to cooperate with stop rings l5, I6 attached to the casing B. When assembled on the casing and with the springs under no-load, the rings l5, l6 are spaced outwardly from the collars and abut the stops It on the end of the springs. In moving in either direction within a well bore, the leading stop ring l5 or IE engages the spring stops or abutments I4 to pull the springs I0 through any restrictions in a well bore or casing, the bowed portions ll of the springs moving radially inwardly toward the cas ing and shifting the trailing collar I I or I 2 toward the trailing stop ring. The spaces l8 initially allowed between the collars II, I! and stop rings l5, l6 should preferably be sufiicient to allow the bowed spring portions H to be flattened into contact with the casing 13 without engagement occurring between the collars and rings.

Heretofore, the outwardly bowed leaf springs Ill have been rigidly welded to the collars ll, l2

in order to maintain their assembled relationship.

The welds decrease the resilient propertiesof the springs, limiting their load carrying capacity, and the deflection to which they can be subjected before failure occurs. By means of the present invention, the springs are secured to the collars,

performing their same functions as before without resort to welding or impairing their physical properties.

In furtherance of this end, each spring is formed with an outwardly bowed intermediate section l1 and with an inwardly directed oflset l9 formed adjacent each collar ll, l2. The medial portion l9a of each ofiset is generally straight in longitudinal section so that its inner and outer surfaces are generally parallel to the surface of the casing B on which the centralizer is mounted and to the inner surface of the collar to which the leaf spring is attached. The ends of each offset I9 are constitutedby shoulders l9b extending outwardly from the medial portions I9a. These shoulders are adapted to engage the bottoms 20 of aligned notches 2| formed on opposite ends of each collar H, l2, defined by aligned fingers 22 extending longitudinally in opposite directions from the central body 23 of each collar. These fingers 22 embrace the sides of the springs at their shoulderedportions l9b to hold them circumferentially positioned with respect to one another, while the engagement of the outer faces of the shoulders l9b with the collar at the bottoms 20 of the notches prevents axial displacement of the springs [0 after the parts of the centralizer have been assembled together. For the purpose of greater assurance that the circumferential disposition of the springs will be maintained, the fingers 22 may be bent inwardly so as to embrace the shoulders l9b to a greater extent.

In any event, the ends 220. of the fingers should preferably not extend inwardly to a greater degree than the inner surfaces l9c of the spring offsets.

The inside diameter of the main body portion 23 of each collar is made greater than the outside diameter of the casing B on which the centralizer is to be mounted by an amount which is approximately equal to twice the thickness of the medial offset portions l9a. Similarly, the end portions l3 of each spring should be spaced from the casing by an amount at least equal to the thickness of the stop rings l5, l8, and the stops ll at the end of each spring should extend inwardly no greater than the thickness of these rings l5, l6. If these proportions are employed, the medial offset portions l9a of the springs will have a proper sliding fit over the exterior surface of the casing without any binding occurring, and the stop rings l5, 16 will have adequate'abutting engagement with the inturned stop fingers M at the ends of the springs. i

One mode of assembling the casing centralizer A consists in placing the springs Ill within the collars I I, I2 with their medial offset portions l9a engaging the inner surfaces of the collars, and with their shoulders I91), I91) embraced by the aligned fingers 22 extending in opposite directions from the main body 23 of the collar. After the required number of springs has been thus positioned in both of the collars, the split stop rings l5, it are contracted so that they can be moved through the intumed spring abutments it into proper position between theouter ends of the collars and the abutments. After clearing the spring stops, each ring l5, I6 can be allowed to expand to its initial shape with its outer surface engaging the end portions l3 8 of the springs, preventing the spring shoulders I91) and medial offsets 19a from moving out of assembled relationship with respect to the collar and bowed springs, the entire assembly can be placed on the casing B, with the stop rings l5, l8 moved outwardly into abutting position with the intumed portions ll of the springs. While in this position and in a no-load condition, the ends of the ring defining the slot 24 are welded together, and the rings themselves are rigidly secured to the casing by welding beads 25 around the circularly spaced holes 28 in each ring. 'Upon performance of this welding operation, the casing centralizer A has been completely assembled on the casing B and is in condition for being run into the well bore, the stop rings l5, I8 exerting a pulling rather than a pushing action on the bowed springs l0 regardless of the direction of movement of the casing through the hole, as brought out in my prior filed application. I

It is to be noted that by the device of embracing the bottoms 20 of the collar notches by the spring shoulders I91), and confining these shoulders by the collar fingers 22, the collars l I, I2 and springs III are interlocked and secured to one another without resort to a welding operation. The metal from which the spring is made is not subjected to high temperatures, resulting in each spring retaining its physical properties throughout its entire length. Moreover, a maximum bow can be given to the spring, permitting the centralizer to be mounted on a casing for effective centralizing over a wide range of bore hole diameters in which the casing can be run.

In addition to providing a device for centering the casing in the hole, the present invention also contemplates a centralizer capable of actingas a scraping tool, whose primary purpose is to remove the mud cake or sheath from the walls of the hole. This is accomplished by

weldingwings

21, 28 to opposite sides of the bowed portions ll of each spring. It is to be noted that the wings are axially displaced, with the upper ones 21 extending circumferentially from the same side of each spring, and with the lower wings 28 all extending circumferentially from the other side of each spring so that the wings will not interfere with each other upon radial movement of the spring bows. The upper and

lower wings

21, 28 overlap to insure collective contact of the springs l8 and their wings around the entire circumference of the bore hole. Thus, the springs and wings together can operate to scrape the full circumference of the well bore wall, which action is desired in removing the mud sheath therefrom, in order that the cementitious material can bond firmly with the formation rather than with the mud itself.

While running the casing in the hole with one or more centralizers mounted thereon, it is preferred that the mud not be scraped or removed from the wall of the hole along its entire length. It is only desirable or necessary to remove the mud from the region of the hole at which the cementitious material is to be deposited for the purpose of securing a water or other fluid shut-off. This objective can be accomplished by providing scraping edges 21a, 28a at the upper ends of the wings only, the lower ends 21b, 28b being bevelled so that the wings will slide over the mud sheath be elevated and then lowered by slowly reciprocating it from the surface of the bore. In moving upwardly, the scraping edges 21a, 28a. will dig into the mud sheath or cake and remove it by disintegration. While moving downwardly, the lower bevelled edges 21b, 28b will cause the wings to slide over the wall of the hole. The casing can be reciprocated as many times as is necessary and through a sufiicient length of stroke, until the mud sheath in the region of deposition of the cement slurry has been removed, enabling the cement to contact and bond firmly with the formation itself.

I claim:

1. A centering device, comprising a collar, leaf springs spaced circumferentially around said collar, each of said springs having an ofiset including shoulders engageable with oppositely facing portions of said collar.

2. A centering device, comprising a collar, bowed springs each having an offset including shoulders engageable with oppositely facing portions of said collar, and means extending from said collar to hold said springs in spaced relation circumferentially around said collar.

3. A centering device, comprising a generally cylindrical member, bowed springs spaced circumferentially around said member, each of said springs having an offset including shoulders engageable with oppositely. facing portions of said member, said member having fingers extending therefrom for embracing said shoulders.

4. A centering device, comprising a generally cylindrical member, leaf springs each having an outwardly bowed portion and an inwardly directed ofiset adjacent said bowed portion, said offset including a medial portion engageable with the inner surface of said cylindrical member and shoulders at opposite ends of said medial portion engageable with oppositely facing portions of said member.

5. A centering device, comprising agenerally cylindrical member, leaf springs each having an outwardly bowed portion and an inwardly directed offset adjacent said bowed portion, said ofiset including a medial portion engageable with the inner surface of said cylindrical member'and shoulders at opposite ends of said medial portion engageable with oppositely facing portions of said member, said member having fingers extending longitudinally therefrom for embracing said shoulders.

6. A centering device, comprising. a pair of spaced collars, leaf springs spaced circumferentially around said collars, each spring having a bowed portion between said collars and an offset adjacent each collar, each offset including shoulders engageable with oppositely facing portions of said adjacent collar, to prevent relativelongl tudinal movement between said springs and collars.

7. A centering device, comprising a pair of spaced collars, leaf springs spaced circumferen tially around said collars, each spring having an outwardly bowed portion between said collars and an inwarly directed ofiset adjacent each collar, said offset including a medial portion engageable with the inner surface of an adjacent collar and shoulders at opposite ends of said medial portion engageable with oppositely facing portions of said adjacent collar, to prevent relative longitudinal movement between said springs and. collars.

8. A centering device, comprising a pair of spaced collars, leaf springs each having a bowed portion between said collars and an offset adjacent each collar, each of said offsets including shoulders engageable with oppositely facing portions of an adjacent collar to prevent relative longitudinal movement between said springs and collars, and fingers extending longitudinally from said collars for embracing said shoulders to hold .said springs spaced circumferentially around said collars.

9. A casing centering device, comprising a pair of spaced collars, leaf springs each having an outwardly bowed portion between said collars and an inwardly directed offset adjacent each collar, said offset including a medial portion engageable with the inner surface of an adjacent collar and shoulders at opposite ends of said medial portion engageable with oppositely facing portions of said adjacent collar to prevent relative longitudinal movement between said springs andgcollars, and fingers extending longitudinally from, said collars for embracing said shoulders to hold said springs spaced circumferentially around said collars.

10. A casing centering device, comprising a pair of spaced collars, outwardly bowed springs arranged circumferentially around said collars and extending therebeyond with their terminal portions disposed inwardly to form abutments spaced longitudinally from said collars, each spring having an inwardly directed offset adjacent each collar, each of said offsets including a medial portion engageable with the inner surface of an adjacent collar and shoulders at opposite ends of said medial portion engageable with oppositely facing portions of said adjacent collar to prevent longitudinal movement between said springs and collars, fingers extending longitudinally from said collars toward said abutments for embracing said shoulders to hold said springs circumferentially disposed around said collars, and stop rings between said abutments and fingers, said rings preventing radially inward movement of said spring offsets.

11. A centering device, comprising a pair of spaced collars, leaf springs each having a bowed portion between said collars and an ofiset adjacent each'collar, said springs extending beyond said collars with their terminal portions disposed inwardly to form abutments spaced longitudinally from said collars, each of said offsets including shoulders engageable with oppositely facing portions of an adjacent collar to prevent relatiye longitudinal movement between said springs and collars, fingers extending longitudinally from said collars for embracing said shoulders to hold said springs spaced circumferentiallyi around said collars, and a stop ring between each collar and spring abutments.

12. A centering device; comprising a collar; leaf springs each having a bowed portion on one side of said collar, an offset adjacent each collar, and an inwardly directed abutment spaced longitudinally from said collar on the other side thereof said offset including shoulders engageable with oppositely facing portions of said collar to prevent relative longitudinal movement between said springs and collar; fingers extending longitudinally from said collar for embracing said shoulders to hold said springs spaced circumferentially around said collar; and a stop ring between said collar and abutments.

13. In combination with a casing; a centering device comprising a collar; leaf springs each having an outwardly bowed portion on-one side of said collar, an inwardly directed offset adjacent said collar, and an inwardly directed abutment spaced longitudinally from said collar on the other side thereof; each of said offsets including a medial portion slidable on said casing and engageable with the inner surface of said collar,

and shoulders at opposite ends of said medial portion engageable with oppositely facing pore tions of said collar; fingers extending longitudinally from said collar for embracing said shoulders to hold said springs spaced circumferentially around said collar; and a stop ring fixed to said casing between said collar and abutments.

14. In combination with a casing; a centering device; comprising a pair of spaced collars: leaf springs each having an outwardly bowed portion between said collars, an inwardly directed offset adjacent each collar, and an inwardly directed abutment beyond each collar; each of said offsets including a medial portion slidable on said casing and engageable with the inner surface of an adjacent collar, and shoulders at opposite ends of said'medial portion engageable with oppositely facing portions of an adjacent collar;

fingers extending longitudinally from said col- 16. A casing centering device, comprising a pair of spaced collars, circularly spaced outwardly bowed springs secured to said collars, and scraper wings secured on opposite sides of each spring to extend substantially completely across the circumferential spaces intervening between said springs, whereby said springs and wings are operable to scrape the walls of a bore hole over its full circumference.

17. A casing centering device, comprising a pair of spaced collars, circularly spaced leaf springs secured to said collars and bowed outwardly therebetween, a first scraper wing secured to one side of the bowed portion of each spring, a second scraper wing secured to the other side of the bowed portion of each spring, the wings on each spring being longitudinally separated, and the first scraper wing of each spring overlapping the second scraper wing of an adjoining spring when the bowed spring portions are urged toward the casing.

18. A casing centering device, comprising a pair of spaced collars, circularly spaced outwardly bowed springs secured to said collars, and scraper wings extending from said springs to substantially completely subtend the circumferential spaces intervening between said springs, whereby said springs and wings are operable to scrape the walls of a bore hole over its full circumference, the bottom edges of said wings being bevelled to slide over the wall of the bore hole.

JULIENA.W'E1LES.