US3209836A - Strong bow centralizer - Google Patents

Description

Oct. 5, 1965 J. E. HALL, SR 3,209,336

STRONG BOW CENTRALIZER Filed Feb. 1, 1965 5 4 mm 25 i 6b /3 /6 v /7 a r a I /4 5 /.9 5 F 5. 649 :H 25 23 72 INVEN TOR. Jesse 5 fla/g 5/:

AITTOIQ/VEYfi United States Patent 3,209,836 STRONG BOW CENTRALIZER Jesse E. Hall, Sr., Weatherford, Tex., assiguor to Trojan, Inc., Panama, Panama, a Panamanian corporation Filed Feb. 1, 1963, Ser. No. 255,531 9 Claims. (Cl. 166241) This invention relates to improvements in centralizer construction, referring particularly to the constructional design of centering devices mounted on the exterior surfaces of casings or pipes used to produce liquids and/ or gases from wells, the subject centralizer having relatively great radial compressional rigidity, while yet retaining some flexibility under such radial compression.

In the drilling of wells, particularly oil wells, and in the conditioning of the well bore for cementing, fluids, such as slurries of mud and water, mud and oil, and cement and water, are circulated in the annular passageway between the well bore and the exterior of the casing or pipe. Well tools in some instances are mounted on the exterior of the casing to center the casing in the well bore and to remove mud and cake from the bore when the well is being conditioned for cementing. The mounting of tools on the exterior of the casing inevitably forms an obstruction to the passage of fluids in the annular space surrounding the casing. Centralizers usually are constructed with upper and lower collars or sleeves to which are attached bands or strips of metal extending between the collars and outbowed at their mid-sections to frictionally contact the well bore. By spacing the centralizers at intervals along the pipe or casing, the latter is held in a centered position in the well bore, forming an annulus or passageway of relatively uniform radial depth around the casing for the flow of fluids.

Previously there have been provided a number of types and forms of centralizers which are generally adequate for actually centering a pipe in a well bore against the usual stresses encountered therein, but, which, under certain circumstances fail to adequately resist the extreme radial compressional stresses encountered by the pipe in the well bore. Thus, the leaf spring centralizer, the concave leaf spring centralizer and the wire centralizer, to name some of the most well-known conventional types, are generally adequate and operable, but do not in most cases possess any marked rigidity to application of radial compressional force.

Previously, a number of Well tool organizations have provided band type centralizing devices wherein the bands extend essentially flatly between the collars adjacent their ends and, then, toward the centers thereof, the bands arch more sharply outwardly to an essentially half-circle shape in side view. This type of band has relatively great radial compressional resistance, but is not universal in the sense that centralizing devices utilizing such will fit into a plurality of bore holes of different diameter, particularly including those of lesser diameter than the greatest outer diameter of the centralizer device. Thus, in centralizers lacking universal applicability, as possesssed by the more flexible centralizers, the bands, as formed, are too stiff, thus requiring the pipe carrying the centralizing devices to be forced into the bore hole until the weight of the pipe above them is sutficiently greater than the resistance created by their passage to 3,209,836 Patented Oct. 5, 1965 r ce the well. Additionally, such a rigid, arched band will not easily go through restrictions in the hole.

In some previously known operations and devices, a solid bar centralizer, comprising a plurality of solid metal bars welded right onto the well pipe, may be employed. The bar elements of this type of centralizing device will not compress at all under radial application of force and, thus, meet any requirement or radial compressional resistance. However, some radial compressional resiliency of the centralizer element is desired. Additionally, it is desirable that a centralizer be able to rotate on the pipe and, as well, have fair vertical thrust characteristics, features not shared by the solid metal bar type centralizers.

My Patent 2,727,576, issued December 20, 1955, entitled Centralizers discloses a straight band centralizer which is not sufliciently resistant to radial compressional stress for the purposes of situations with which I am presently concerned. My Patent 2,717,650, issued September 13, 1955, entitled Wire Centraiizers for Well Cementing discloses a wire centralizer which is also deficient in resistance to radial compression in the situations for which the instant centralizer is designed.

There are many well completion situations today where the close tolerance which exists between the exterior of the casing and the well wall imposes stringent operating requirements on the devices used on the casing to center it in the well bore and to aid in effecting a good cement job. This is particularly true in wells of extreme depth. In such wells the annular space between the casing and bore is of small thickness and anything applied to the exterior of the casing must be of correspondingly small thickness in order to insure that the casing can be lowered into the bore with the minimum of interference. On the other hand, because of the depth of the well and the forces which may be imposed, any exterior appliances must concurrently be extremely strong. A third requirement is that they furthermore must provide sutficient open space around the casing as to permit the free circulation past the appliance of mud and cement during the cementing operation.

An object of the invention is to provide a band type centralizer which has great compressional strength and rigidity while still retaining a certain amount of compressional flexibility.

Another object of the invention is to provide a band type centralizer having numerous desirable compressional rigidity characteristics wherein the centralizer is additionally rotatable on the pipe and universal in the sense that if it can be employed in bore holes of varying diameters, from a diameter less than the greatest outer diameter of the centralizer to a diameter markedly greater than the said greatest outer diameter of the centralizer.

Another object of the invention is to provide a band type centralizer which is extremely simple in construction, relatively easy to manufacture, easy to install on the casing and very extremely rugged and resistant to all sorts of radial and compressional stress.

Another object of the invention is to provide a band construction for a well bore centralizer which has all of the advantages and none of the disadvantages of a concave type centralizer band and yet, additionally, has other and further new advantages thereover peculiar to its own configuration.

Another object of the invention is to provide a band for a centralizer structure utilizable in well bores mounted on well bore pipe wherein a maximum strength and resistance to compressional and other stress is achieved in the band yet the width of the band is no greater than flat or concave bands on like centralizing elements, great advantages being present with respect to the stress resistance under these known conventional type bands.

Another object of the invention is to provide a centralizer band having a concave portion therein, said centralizer band having no trace of the failure disadvantage of the concave type centralizer band or spring in that it will not fail or lose resilience under heavy or even reverse compression.

Another object of the invention is to provide a centralizer band or bow which has suflicient resilience to insure maximum functioning of the centralizer, yet will compress to the casing size and return therefrom to maximum workable diameter without any substantial yield loss, a situation generally unsatisfactory in both the straight and convex bands or bows known to the art.

One of the important objects of the present invention is to provide a well casing guide which, due to its manner of construction and assembly, uniquely meets all of the requirements heretofore set forth for close tolerance wells. Not only does the guide according to my invention occupy a minimum of the annulus surrounding the casing, but also it is of exceptional strength and is capable of effectively absorbing end (axial) loads of great magnitude without impairment to the performance of its essential functions.

A further object of the invention is to provide a casing guide of the character described which has a construction such that its ability to hold the casing away from contact with the well bore is greatly improved over conventional guides and centralizers.

Yet another object of the invention is to provide a casing guide having the foregoing characteristics and which is so constructed that its minimum effective diameter can ing guides having the foregoing operational advantages and which are susceptible of manufacture and assembly at relatively low cost.

Other and further objects of the invention will appear in the course of the following description thereof.

In the drawings, which form a part of the instant specification and are to be read in conjunction therewith, an

embodiment of the invention is shown and, in the various views, like numerals are employed to indicate like parts.

FIG. 1 is a side view of a centralizer construction employing a bow or band of improved type.

FIG. 2 is a top plan view of the centralizing construction of FIG. 1.

FIG. 3 is a view taken along the line 3-3 of FIG. 1 in I the direction of the arrows.

The invention comprises a centralizer construction and the bands or bows therefor which is adapted to be mounted on casing or pipe used in wells for the production of fluids, particularly oil, gas or water, comprising upper and lower collars with internal diameters enough larger than the casing or pipe to fit slidably thereon, narrow A bows or bands extending between the collars with their upper ends attached to the upper collar and their lower ends attached to the lower collar, each of said bands so formed in transverse cross section as to achieve certain stress and compressional resistance properties.

Referring to FIGS. 1 and 2, therein is shown an assembled centralizer. Collars 11 and 12 form the upper and lower ends of the centralizer and are of an internal diameter slightly greater than the outer diameter of any pipe or casing on which same would be mounted. A plurality of relatively narrow substantially rectangular bands generally designated 13 are fixed to the upper and lower collars adjacent their upper and lower edge, respectively, preferably by welding as at 25 to the outer surfaces of said collars.

Before mounting on the collars, the basically rectangular bands are first formed in transverse cross section to the shape shown in FIG. 3 and thereafter or simultaneously therewith formed to an outwardly bowed shape best seen to the left and right in FIG. 1 with the upper and lower ends thereof slightly flattened whereby to provide good attachment to the collars 11 and 12.

Referring to FIG. 3, it may be seen that the transverse cross-sectional shape of each of the elongate bands or bows 13 has three parts. Centrally of the bow is a concave crown portion 13a having at the edges thereof rim portions 13b and 130. The outer edges of portrons 13b and 13c, designated 14 and 15, respectively, are preferably substantially parallel planes, the planes extending parallel to the direction of extension of the bow. The upper and lower surfaces of portions 131) and 13c are preferably also parallel with one another, these designated 16 and 17 for the outer (upper in FIG. 3) faces thereof and 18 and 19 for the inner (lower in FIG. 3) faces thereof. It should be noted that the sum of the widths of the portions 13b and from their inner to their outer edges are preferably less than the total width of the section 13a. Yet further, the under side of crown: portion 13a, at its outermost extremity 20, preferably 1s positioned (extends) outwardly of the upper faces 16 and 17. The entire width of portion 13a is preferably of substantially or precisely equal curvature whereby to provide a uniformly curved concave crown for the hat section. The bow or band 13 is preferably of equal thickness along its entire transverse cross-sectional width and its entire length.

Referring again to the collars 11 and 12, the collars may be of solid ring construction, hinged split type or latch-on construction having hinges 21 and 22 of substantially conventional form firmly attached to the opposed free ends of the collar halves (see FIG. 2) with t e loops of the hinges, indicated at 23 and 24, respectively, registrable with one another to provide mated loops which may be engaged by suitable pins of conventional sort (not shown).

The bows themselves (bands 13) are preferably arcuate in their entire longitudinal length as best seen at the right and left in FIG. 1 with a weld attachment or other conventional attachment as seen at 25 between the outer surface of the collars 11 and 12 and the end portions of the bands. The bands themselves may be slightly flattened very closely adjacent the collars to provide a more uniform attachment, but this is not either required or necessary. As the bands flex inwardly and outwardly under great compressional stress and release thereof, the collars would move apart and together on the well bore casing. Preferably, bands are attached immediately next to the lace-on connections to provide the greatest strength in those zones.

The degree of bowing or curvature in the longitudinal aspect of the bows may be varied des re but the lowing typical extension for certain sized holes may be employed:

Centralizer, O.D., Use Where Height of inches Length hole diameter Collar style Type of Bow style, inches each bow, overall, Sizesavailable, exceeds easing installation inches mohes inches diameter,

Maximum Minimum inches over casing size /32x1%,hu1nped 1% 2% 1 23 3% thru 20...- 2% ormore.

O 1% 2% 1 23 ..do D0. 1 a 0. 1% 2% 1 2% or more. 1% 2% 1 Do. 1% 4% 1 4% or more. 1 Do.

Method of installation Initial test-New centralizer 4130 tem ered to Rockwell 440 Over C.C.; S.C.; F.B.between stops; stop and C.C.; p 1

C.Cs. Principal load in pounds on spring No.- Over F.B.between stops; stop and C.C.; C.Cs; Weld gg lugs. l 2 3 4 5 6 Average n so s' sto and CC." Over betwee tp P x 1,047 1,067 977 1,007 987 377 994 C,Cs, 1,057 1,707 1,587 1,087 1,587 1,487 1,619 3 2,347 2,407 2,277 2,377 2,357 2,167 2,332 Over F.B.-hetween stops; stop and C Wild 1 ,187 3247 3,097 3,267 3,287 2,827 3,152

lugs. Over CO; 8.0.; F.B.-between stops; stop and QC; mad Dmded Between sprmgsNo" C.Cs. 40 1-2 2-3 3-4 4-5 5-6 0-1 Over F.B.between stops; stop and CO; COS; weld 1 987 1,027 1, 017 807 900 C so FB b 1 t 1 nd cc '28? 25%? 3 '38? r C. eween so 8" sop a 2, 2, 07 2, 2,359 Ov C p 7 3,207 3,217 3,187 2,917 3,180

s. Over p p and C-CS; Weld Retest-After Springs Flattened lugs.

, 1 2 3 4 r 0 NOTE.--S.C. means Stop Collar. S.Cs. means Stop 0 Collars. RB. means Friction Band. C.C. means Casing 7. 947 917 907 017 927 857 912 Coupling. C.Cs. means Casing Couplings. 1,507 1,547 1,387 1,547 1,547 1,387 1,487 2,227 2,307 2,207 2,287 2,377 2,027 2, 238 As an example of the compress1onal stress resistance 2,987 3, 237 3,067 3,307 3,287 2,817 3,117 th followin inormation resulted from deflection tests 6 g L Load Divided Between Springs No.- upon a (5 /2 6-Spr1ng Slngle Bow Centrahzer Pertinent data: 1 2 2 3 3 4 4 5 5 0 0 1 4130 tern ered to Mammal p 54, 997 997 1,017 977 1,017 937 0 Rockwell 44C. 1,687 1, 047 1,077 1, 647 1,059 L 5 f t 1' 23" 777 215 eng 0 cen raizer ,3 Outer diameter of centralizer 8%".

. B dHe' htofS N Length of spr ng 22". owe 1g pnng 0 Width of spring 1 /2". 1 2 3 4 5 6 Width of collar 4".

1 New 1.52 1.57 1.58 1.58 1.60 1.50 1.573 Thlckness of collar A3 After test. 1.49 1.51 1.55 1.53 1.54 1,54 1,527 hi k f Spring ?y Loss f he1ght.. .03 .06 .03 .05 .00 .05 .046

' 7 o meqs- Ratio of final bowed height to initial bowed height, 97.087.

Centrahzer tested 1ns1de casing havmg the fOllOWlll 7 l l t i l g g fi i 292%. l 1 0 urements: Ratio 0 1m 12 owe eight to annu ar e earance, 96.9.

Outside diameter 9%. In p r i n, when the centralizer has been applied Inside diameter 8% n to the well bore casing by either laclng thereon or s11dn ing thereon, the casing is moved into the well bore, If Welght 107 Poundsthe casin is forced into a well bore of lesser LD, than 0 1 g s a Casing 1ns1de centrahzer measured 5 /2 0D. the CD. of the centrallzer, lmrnedlate compressional stresses are encountered. in other cases, compressional stresses may not be encountered until greater depths in the well or during reciprocation of the casing or the like. In any case, analyzing the behavior of the particular bows under radial compressional stress, such stress would be applied from the left and the right in FIG. 1 against opposed bows, for example, or from the left and right in FIG. 2 against the oppositely opposed bows, or downwardly on the bow of FIG. 3. In any spring deformation, one side of the metal lengthens (the downward side in FIG. 3), while the other side shortens. A curve of deformation may be plotted with, in a flat spring, there being generally a neutral zone of minimum deformation between the side lengthening and the side shortening. The side elongating is usually considered hot metal, that is, expanding, while the shortening side is usually considered cold metal, that is, contracting. The compression and elongation process proceeds unevenly, with elongation happening before compression in a leaf spring of optimum thickness.

If one considers the spring dynamics of a concave type spring, which would be the shape of FIG. 3 with portions 13]) and 13c removed, the action is as follows: If one pushes down on the arch or inwardly against the arch, the spring is quite stiff in starting bending. There is a neutral zone of minimum bending between the crown of the arch and the edges thereof. The edges tend to stretch first before the crown compresses. The great difiiculty with a true concave type leaf spring is that, while the spring is stiff to start and resists well, once it begins to yield, it caves in and yields centrally, often with deformation of a permanent type and damage to the spring, per se.

In considering the dynamics of the instant spring, this spring gives a combination of eflfects (plus certain new results of its own) of the flat leaf spring and the concave leaf spring. This bow has the greater initial resistance to deformation of the concave spring, while retaining the continuous resistance into flattening or resilience of the initially bowed flat leaf spring. At all times, there is retained a greater rigidity than any fiat leaf spring. At all times, on the other hand, there is retained a continuous strong resistance to radial compressional stress which is not the case in the concave leaf spring. These advantages and features are borne out by the data copied above.

Further analysis of the action of the hat-shaped spring here shown can start logically from the analysis of the concave leaf spring. As noted above, in a concave leaf spring, when radial compression is started, the edges tend to stretch before the crown compresses. However, in the instant case, considerable metal and strength has been added to the concave spring edges, which additions reflect the stress back into the crown without excessive stretching of the said edges. Thus the center of the bow, or crown of the hat, is employed more from the beginning in the compression process with the neutral zone displaced away from the edges of the concave portion of the spring, upwardly toward the crown. Finally, as the spring approaches flattening, it is entirely possible for the flat side edges, depending on their percentage of the Width of the hat-shaped spring, to bow themselves slightly upwardly at their free edges. This action requires additional force to achieve and provides additional radial compressional resistance in the centralizer. Thus, in the instant bow,

spring or band, more metal is being stressed and a more efficient continuous action is achieved. A greater resistance and longer life with a greater maximum compression and elongation, with complete return, is possible.

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 without 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 all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. A centralizer construction comprising an upper and a lower collar adapted to fit on a well bore pipe or casing, a plurality of elongate strips having substantially parallel longitudinal edges connecting the upper and lower collars and spacing them apart from one another, said strips outwardly bowed intermediate of their ends and connected to said collars adjacent their ends, said strips arcuately formed outwardly in transverse cross section inwardly of the said substantially parallel longitudinal edges thereof.

2. A centralizer as in claim 1 wherein the strips are relatively flattened in transverse cross section adjacent their collar connection.

3. A centralizer as in claim 1 wherein the strips are fastened to the outer surface of said collars intermediate the upper and lower edges thereof.

4. A centralizer construction as in claim 1 wherein the collars are formed of sections each latched to each other.

5. A centralizer construction as in claim 1 wherein the outwardly arcuately formed portion of the elongate strip section extends outwardly of said collars.

6. A centralizer construction as in claim 1 wherein the outwardly arcuately formed portion of the elongate stri section is of greater width than the width of the strip edge portions positioned laterally thereof.

7. A centralizer construction as in claim 1 wherein said strips are of greater thickness than the said collars.

8. A centralizer construction as in claim 1 wherein the collars are formed of sections each latched to each other and one of said elongate strips is fixed to each collar portion adjacent each section latch connection.

9. A centralizer construction as in claim 1 wherein said strips are of said outwardly formed arcuate transverse cross section along substantially their entire length and are also of arcuate form in side elevation along substantially their entire length.

References Cited by the Examiner UNITED STATES PATENTS 2,718,266 9/55 Berry et al 166241 2,886,111 5/59 Hall 166241 3,000,444 9/ 61 Wright et al 16624l CHARLES E. OCONNELL, Primary Examiner. BENJAMIN BENDETT, Examiner.

Claims (1)

1. A CENTRALIZER CONSTRUCTION COMPRISING AN UPPER AND A LOWER COLLAR ADAPTED TO FIT ON A WELL BORE PIPE OR CASING, A PLURALITY OF ELONGATE STRIPS HAVING SUBSTANTIALLY PARALLEL LONGITUDINAL EDGES CONNECTING THE UPPER AND LOWER COLLARS AND SPACING THEM APART FROM ONE ANOTHER, SAID STRIPS OUTWARDLY BOWED INTERMEDIATE OF THEIR ENDS AND CONNECTED TO SAID COLLARS ADJACENT THEIR ENDS, SAID STRIPS ARCUATELY FORMED OUTWARDLY IN TRANSVERSE CROSS SECTION INWARDLY OF THE SAID SUBSTANTIALLY PARALLEL LONGITUDINAL EDGES THEREOF.

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