US3351136A

US3351136A - Casing centralizer and well bore wiper

Info

Publication number: US3351136A
Application number: US396222A
Authority: US
Inventors: Fred B Nelson
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-09-14
Filing date: 1964-09-14
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07

Description

Nov. 7, 1967 F. B. NELSON CASTING CENTRALIZER AND WELL BORE WIPER 4 SheetS Sheet 1 Filed Sept. 14, 1964 F'IGJ- FIG. 5.

ADHESIVE SLURRY F'IG- 3' INVENTOR FRED B. NELSON. BY: g Z

; CEMENT snos ATTORNEY- Nov. 7, 1967 Y F. B. NELSON CASTING CENTRAIJIZER AND vWELL BORE WIPER Filed Sept. 14, 1964 4 Sheets-Sheet 2 FIG- ll- WIPER FIG.

FIGJ'I.

INVENTOR. FRED B. NELSON, BY; 2

E I I I D o N I A B CEMENT ATTORNEY.

Nov. 7,1967 F. B. NELSON CASTING CENTRALIZER AND WELL BORE WIPER Filed Sept. 14, 1964 Y 4 Sheets-Sheet 5 PIPE RACK CABLE GRIP FIG.

PIPE RACK INVENTOR FRED B. NELSON, W

KM NE QF PULL ATTORNEY.

Nov. 7, 1967 F. B. NELSON CASTING CENTRALIZER AND WELL BORE WIPER Filed Sept. 14, 1964 4 Sheets-Sheet 4 /(LINEOF PULL "vlse PLIERS" CLAMP HERE LINE OF PULL N O m s n mu V W8 D E R F ZMQW ATTORNEY- United States Patent 3,351,136 CASING CENTRALIZER AND WELL BORE WIPER Fred B. Nelson, Lafayette Parish, La., assignor to Norman A. Nelson Filed Sept. 14, 1964, Ser. No. 396,222 2 Claims. (Cl. 166-173) This invention relates to the drilling of oil Wells and their preparation for the production of oil therefrom.

In the drilling of oil and gas wells it is customary to make use of a rotary drilling bit which is attached to the lower end of a tubular drilling string through which drilling mud is circulated downwardly to pass upwardly in the annulus of the bore surrounding the string. Upon completion of the drilling operation a tubular well casing of somewhat smaller diameter than the bore is frequently inserted in the bore and cemented therein by introducing cement into the annulus between the casing and the wall of the bore to isolate the bore from the surrounding formation. At times several casing strings or liners may be required in the same well bore and it is important that these be properly cemented to assure a secure bond between the pipe and the formation. Such a bond is necessary to prevent channeling which may result in fluid communication vertically in the annulus between the pipe and wall of the bore between different vertically spaced zones of the formation and also to provide adequate physical strength. The cementing operation is customarily carried out by pumping a cement slurry downwardly through the pipe and upwardly in the annulus where it displaces the drilling fluid.

In the preparation of wells in this manner, great difficulty is often encountered in properly positioning the casing in the bore due to the fact that it is necessary to maintain the hydrostatic pressure in the bore at a higher value than the pressure in the surrounding formation, which sometimes results in the casing being forced into intimate contact with the wall of the well by the difference in pressure causing the casing to stick to the wall. Such a condition is referred to as wall-sticking or pressure differential sticking,

Another major problem encountered in the cementing of casing in wells is incomplete displacement of the drilling mud by the cement due to channeling of the cement up one side of the pipe, leaving mud on the other side. This problem is especially likely to occur when the pipe is not centered in the well bore.

Still another difliculty encountered in the cementin of casing in wells is that the bore is sometimes enlarged during the drilling operation due to cavitation of the surrounding formation or from other causes, leaving pockets or recesses in which the drilling mud accumulates. Under these conditions the cement is prevented from completely displacing the mud and filling the annulus about the casing, which may result in longitudinal channeling in the annulus between vertically spaced locations in the formation.

Various expedients have been employed heretofore in attempting to overcome the above noted difficulties in the completion of oil wells, such as the application of wall scratchers to the casing and the vertical reciprocation or rotation of the casing to remove excess mud cake from the wall of the bore and clean out contaminated and jelled mud during cementing to prevent channeling. Attempts have also been made to prevent wall-sticking and centralizing the pipe by the use of centralizers or stabilizers on the casing to hold the casing out of contact with the surrounding wall of the bore.

Such expedients have not, however, satisfactory, because of inability to proven completely exactly center the casing in the Well bore and also they do not eliminate channeling due to the presence of mud filled enlargements or cavities in the bore.

The present invention has for an important object the overcoming of the above mentioned difficulties in the cementing of pipe or casing in well bores by the use of wiper means applied to the casing which is capable of removing excess mud cake from the surrounding wall of the well bore and from enlargements or recesses therein and which may also serve as a centralizin means for the casing.

Another object of the invention is to provide wiper means for use with well casing which also serves as a means for preventing differential pressure wall sticking of the casing.

A further object of the invention is the provision of a device for application to the external surface of a Well casing and having a portion extending radially outwardly therefrom for engagement with the surrounding wall of Well bore and which is flexible to permit the device to conform to the shape of the well bore and to extend into cavities or other irregularities in the bore wall to wipe the same and to promote turbulent and spiral flow of the cement around the pipe when cementing the casing in the well.

Another object of the invention is to provide a device in the form of an elongated flexible strip which may be applied to the external surface of a well casing in a number of different ways so that it acts as a centralizer and wiper without interferring With the circulation of fluid in the annulus of a well bore into which the casing is inserted.

A further object of the invention is the provision of a device which may be positioned spirally on a well pipe or casing between the external surface of the casing and the surrounding wall of the bore to cause fluid introduced into the annulus to flow in a spiral path whereby the fluid is moved into intimate contact with the surrounding wall of the bore.

A further object of the invention is the provision of a tool for use in applying the casing centralizer and well bore wiper to the external surface of a well casing whereby the centralizer and wiper is securely held in place at the desired location thereon while being attached to the casing.

The above and other objects and advantages of the invention will be apparent from the following detailed description, constituting a specification of the same, when considered in conjunction with the annexed drawings, Wherein FIGURE 1 is a fragmentary, vertical, cross-sectional view of a well bore, illustrating the casing centralizer and wiper attached to a casing in a well and showing how the invention is used in the cementing of a casing in a well;

FIGURE 2 is a cross-sectional view, taken along the line 2-2 of FIGURE 1, looking in the direction indicated by the arrows;

FIGURE 3 is a view similar to that of FIGURE 2, of a well bore in which a casing has been cemented, showing an undesirable condition therein which the invention is designed to prevent;

FIGURE 4 is a view similar to that of FIGURE 2, showing another undesirable condition sometimes encountered in the cementing of well casing and which the invention is designed to prevent;

FIGURES 5 and 6 are fragmentary perspective views, on a somewhat enlarged scale, showing portions of two different modifications of the centralizer and wiper of the invention;

FIGURE 7 is a fragmentary cross-sectional view, on a somewhat enlarged scale, of a portion of a well casing,

showing a modified form of the centralizer and wiper mounted thereon and the manner in which the device is attached to the casing;

FIGURE 8 is a fragmentary, vertical cross-sectional view of a well bore, with a casing therein, showing a somewhat different form of the centralizer and wiper of the invention applied thereto;

FIGURE 9 is a perspective view of a portion of the well casing of FIGURE 8, illustrating the rnanner in which the centralizer and wiper are attached thereto;

FIGURE 10 is a cross-sectional view, taken along the line 10-10 of FIGURE 8, looking in the direction of the arrows, and showing the manner in which the centralizer and wiper of FIGURES 8 and 9 operates when the well casing is substantially centralized in the well bore but with incomplete displacement of the mud from around the pipe;

FIGURE 11 is a view similar to that of FIGURE 10, showing the operation of the centralizer and wiper so as to remove mud from around the pipe by rotating the casing during the cementing operation;

FIGURE 12 is a fragmentary perspective view of a somewhat enlarged scale, illustrating a modified form of the centralizer and wiper;

FIGURE 13 is a view similar to that of FIGURE 12, illustrating another modification of the centralizer and wiper;

FIGURES 14, 15 and 16 are cross-sectional views similar to those of FIGURES l0 and 11, showing, somewhat schematically, the manner of operation of the forms of the invention ilustrated in FIGURES 12 and 13;

FIGURE 17 is a view similar to that of FIGURE 12 illustrating another modification of the centralizer and wiper of the invention;

FIGURE 18 is a view similar to that of FIGURE 12 illustrating a still further modification of the centralizer and stabilizer;

FIGURE 19 is a plan view of a section of well casing positioned on a pipe rack, showing the centralizer and wiper mounted on casing and .the means by which the device is applied and secured in place;

FIGURE 20 is a plan view, on an enlarged scale of one of the clamping and tightening devices by which the centralizer and wiper is held in place on the casing preparatory to securing the same thereon;

FIGURE 21 is a cross-sectional view, taken along the line 21-21 of FIGURE 20, looking in the direction indicated by the arrows;

FIGURE 22 is a cross-sectional view, taken along the line 2222 of FIGURE 20, looking in the direction indicated by the arrows;

FIGURE 23 is a cross-sectional view, taken along the line 23--23 of FIGURE 20, looking in the direction indicated by the arrows;

FIGURE 24 is a fragmentary perspective view, on a greatly enlarged scale, illustrating a modified form of cable gripping means of the clamping and tightening device of the invention;

FIGURE 25 is a view similar to that of FIGURE 24 showing a further modification of the cable gripping means, and

FIGURE 26 is a fragmentary side elevational view illustrating a modified form of the clamping means by which the tightening mechanism is applied to a well casing.

Referring now to the drawings in greater detail, the invention is illustrated herein in connection with its use in the cementing of oil and gas wells, but it will be understood that the invention may have other uses, such as for the insulating of inner and outer pipes or conduits from each other, for the purpose of reducing the corrosive effects of electrolysis on pipe lines, or the like, and for other purposes.

The centralizer and wiper of the invention comprises an elongated strip, generally designated 10, of resilient material, such as rubber, or the like, with or without a cable or wire 12 embedded therein, which strip is applied to the exterior of a well casing C, located in a well bore B, as by winding the strip in a spiral about the casing, as illustrated in FIGURES l and 19, and attaching the strips in place, as by means of metal bands 14 at suitably spaced intervals.

The strip 10 has a base portion 16, which is widened and which may be formed with a concave face 18 for engagement with the curved external face of the casing C, whereby the strip closely fits the casing when in place thereon. A flexible, wiper or blade portion 20 extends radially outwardly from the base 16 throughout the length of the strip, the outer edge of the wiper portion being disposed for engagement with the surrounding wall of the well bore to wipe the bore and hold the casing substantially centralized therein.

The base 16 may vary in thickness and width, and the wiper portion 20 may vary in thickness and in its radial length as seen at 20 and 20 in FIGURES 5 and 6. The strip may also be formed as illustrated in FIGURE 7, with recess 22 in its inner face whose bottom wall is provided with projections or ribs 24, whereby the strip is adapted for attachment to the exterior of the casing by means of a suitable adhesive, such as an epoxy resin cement, or the like, by which the strip is cemented to the casing.

The wiper portion 20 of the strip may be of a radial length substantially greater than the width of the annulus A between the casing and the surrounding wall of the bore B, so that the wiper portion will be flexed or bent over by engagement with the bore wall to effectively wipe the bore and to extend into cavities and irregularities in the bore, upon rotation of the casing in the bore, to stir up and remove mud which may have been deposited r therein.

In the cementing of casing in well bores a slurry of cement is pumped down through the well casing C into the bore B, which surry moves upwardly about the casing to displace mud from the annulus. When the cementing of casing is carried out without the use of centralizing wiper means, deposits of mud are often left in the bore as the cement flows upwardly in the annulus, such as those illustrated at M in FIGURES 3 and 4, which the cement, indicated at S, has failed to displace. Such deposits of residual mud are especially likely to occur where the casing is not centered in the bore, as illustrated in FIG- URE 4, and often result in the channeling of formation fluid in the bore past the cement when the Well is under production.

As illustrated in FIGURE 2, however, when the centralizer and wiper of the invention is applied to the casing C, the wiper portion of the strip wipes away the mud and agitates the same in the annulus as the casing is moved and holds the casing away from the wall of the bore, and causes cement to flow turbulently and spirally around the pipe, even when the pipe is stationary, so that the mud is displaced upwardly in the annulus which is thus uniformly filled with cement.

A somewhat modified form of the centralizer and wiper of the invention, and the manner of attaching the same to the casing is illustrated in FIGURES 8 and 9, wherein the strip, generally designated 10', is straight and is formed with a base portion 26 having a curved face 28 for engagement with the external surface of the casing C;

The strip 10' has a radially outwardly extending flexible wiper or blade portion 30. The base 26 extends somewhat to one side of the wiper portion 30 and is formed with an upwardly opening groove or longitudinal recess 32 extending throughout the length of the strip, for the reception of a reinforcing rod or wire 34. The strip may also be formed with longitudinally spaced openings or slots 36, such as those shown in FIGURE 12, through which metal straps or hands 14 may be extended to encircle the casing to secure the strip :in place thereon and securely hold the rod 34 in the groove 32, as best illustrated in FIGURE 9. Several lengths of the strip may be secured to the casing at peripherally and longitudinally spaced intervals thereon, as shown in FIGURE 8, to wipe the well bore and agitate the mud in the annulus upon rotation of the casing during the cementing operation.

The strip may also have the modified form illustrated in FIGURE 13, wherein the base 26 and wiper portion are merged to form a structure of increased thickness, having a longitudinal opening 3-8 therethrough into which the rod or wire 34 may be inserted through a longitudinal side slot 40.

A further modification of the centralizer and wiper strip is shown in FIGURE 17, wherein the strip has a central, longitudinal, upwardly opening groove 42 in which the rod or wire 34 is positioned. This form of the strip may be secured to the casing by metal bands passing about the casing and strip over the groove 42 to hold the strip securely on the casing and to hold the rod 34 in the groove.

The strip may also take the modified form illustrated in FIGURE 18, wherein the curved face 28 is formed on one side of the base of the strip for engagement with the casing and a longitudinal groove 42 is provided in the opposite side of the base for the reception of the rod 34.

The form of the invention illustrated in FIGURE 8 functions in substantially the same manner as that shown in FIGURE 1, the strip 10' being attached to the casing C by means of the bands 14 extended through the slots 36, to hold the strip on the casing with the flexible blade portion 30 extending parallel to the axis of the casing and extending radially outwardly for engagement with the surrounding wall of the well bore.

As seen in FIGURES 10 and 11, the strip 30 extends substantially across the width of the annulus A, so that mud in the annulus will be agitated as the cement flows upwardly therein to displace the mud, as the casing is rotated in the bore. Rotation of the casing also serves to stir up the cement, causing the same to completely fill the annulus. In the event that the casing should be positioned somewhat eccentrically in the bore, such as might be the case when the bore is curved or slanted, the blade portion 30 of the strip will be flexed, as shown in FIG- URE 11, as the casing rotates, to wipe the surrounding Wall of the bore about its entire periphery.

Under conditions, such as that illustrated in FIGURES 14, 15 and 16, in which the wall of the bore is irregularly shaped or cavitated, the blade portion of the strip may be of sufficient radial length to extend into the cavities or recesses of the wall to wipe the mud therefrom, the blade being flexed in the portions of the annulus which are narrower to maintain the blade in contact with the wall throughout substantially the entire periphery of the bore.

For the purpose of applying the centralizer and wiper of FIGURE 1 to the casing, the apparatus illustrated in FIGURES 19 to 26 is provided. The clamping and tightening mechanism of the invention comprises a pair of clamps, generally designated 50, each of which has a frame 52 made up of spaced apart, parallel bars 54, which may be of angle or other convenient shape in crosssection. Mediate its ends the frame 52 is provided with a toothed element 56 positioned for engagement with the external surface of the casing C when the clamp is attached to the casing, and the frame has a chain 58, or the like, secured at its opposite ends at spaced locations beyond the ends of the element 56, which chain may be extended about the casing and tightened in engagement therewith to clamp the element 56 into gripping contact with the casing, as seen in FIGURE 21. One end of the chain 58 is secured between the bars 54 of the frame, as by means of a bolt 60, and the other end of the chain is attached to a threaded shaft 62 which may be inserted between the bars 54 and which is provided with a nut 64, cam device 65 or other suitable toggle means, such as that shown in FIGURE 26, which may be tightened to draw the chain into tight engagement with the casing C.

A cable gripping device is attached to the frame 50, by means of a universal coupling 66 attached to the frame, as by means of a bolt68, and extending beyond one end of the frame. A threaded shaft 70 is threadably extended at one end through the universal coupling and carries at its other end a cable clamp 72 attached thereto, as by means of a yoke and

pin connection

74, 76. The cable clamp 72 includes a clamping plate element 78 of generally U-shape in cross-section, between whose opposite arms a toothed clamping cam 80 is rotatably mounted as by means of a pin 82, the cam being provided with an actuating arm 84, whereby an end of the cable 12 may be inserted between the cam and clamping plate and securely clamped in place by the cam.

The shaft 70 of each clamping device has a nut 86 by which the shaft may be moved longitudinally relative to the universal coupling 66 to tighten the cable 12.

In attaching the strip 10 to the casing C by means of the clamping and tightening apparatus of the invention, one of the above described clamps is attached to the casing by extending the chain 58 about the casing and tightening the nut 64 to draw the chain into tight engagement with the casing and clamp the toothed element against the casing. One end of the cable 12 is then clamped in the cable clamp 72 and the strip is wound spirally about the casing. With the strip thus wound on the casing the other end of the cable 12 is clamped in the cable clamp 72 of another of the clamping and tightening devices, which is then clamped on the casing at a suitable distance from the first such device, whereupon the cable may be tightened by the nuts 86 to hold the strip in tight engagement Wilh the casing throughout the entire length of the strip. With the strip thus held on the casing the bands or straps may be secured in place in the usual manner, after which the clamping devices may be removed.

A- somewhat different form of cable clamp for use in the Clamping and tightening apparatus is illustrated in FIGURE 24 wherein a metal block 88 is threadably secured at one end to the end of the shaft 70, which block has a bore 90 at its opposite end which is curved or angled relative to the axis of the block, and through which an end of the cable 12 may be extended. With the cable end thus extended through the bore 96 the cable end may be gripped by suitable means, such as a clamp or pliers of the type which may be releasably locked in gripping engagement with the cable to hold the cable against removal from the bore during tightening of the cable.

A further modified form of cable gripping device for use with the clamping and tightening apparatus is illustrated in FIGURE 25. In this form of the device a claw element 92 is attached to the end of the shaft 70, which claw has a central slot 94 in which the end portion of the cable 12 may be positioned with the cable end thus extended through the claw, the end of the cable may be gripped by a clamp or pliers of the type mentioned, where by the cable will be releasably connected to the shaft 70' during tightening of the cable.

When the wiper strip is formed with a core which takes the form of a rod or wire, the strip may be preformed by shaping the same into a spiral, in which case the strip may be more readily positioned on the casing preliminary to the application of the bands or ties.

It will thus be seen that the invention provides a casing centralizer and well bore wiper and means for applying the same for use in well cementing and for other purposes, which is of simple design and economical manufacture and which is convenient in use.

The invention is disclosed herein in connection with certain specific embodiments of the same, which it will be understood are intended to be illustrative only and which are capable of various modifications within the scope of the appended claims.

Having thus clearly shown and described the invention,

what is claimed as new and desired to secure by Letters Patent is:

1. In combination with a well casing rotatably extended into a well bore a centralizing and bore wiping element comprising a strip of resilient material extending longitudinally of the casing having a base portion positioned in contact with the external surface of the casing and a Wiper portion of reduced thickness extending away from the casing for wiping contact with the surrounding wall of the bore, said element having an external longitudinal groove formed therein, an elongated metallic reinforcing element located in said groove and means surrounding the casing and extending over said element over said groove to secure the element and member to the casing.

2. In combination with a well casing rotatably extended into a wall bore a centralizing and bore wiping element comprising a strip of resilient material extending longitudinally of the casing having a base portion positioned in contact with the external surface of the casing and a Wiper portion of reduced thickness extending away from 20 the casing for wiping contact with the surrounding wall of the bore, said element having an external longitudinal UNITED STATES PATENTS 1,633,843 6/1927 Bostic 308 4 1,891,615 12/1932 Bostic 308-4 1,959,367 5/1934 Kennedye 308-4 1,959,368 5/1934 Kennedye 166-241 X 2,598,280 5/ 1952 McLean 16662 X 2,714,500 8/1955 Snyder 308--4 2,870,845 1/1959 Tripplehorn 166-176 3,064,731 11/1962 Hall 166-173 X 3,176,771 4/1965 Claiborne et al 166173 CHARLES E. OCONNELL, Primary Examiner.

D. Hi BROWN, Assistant Examiner.