CA2309942C - Casing centralizer - Google Patents
Casing centralizer Download PDFInfo
- Publication number
- CA2309942C CA2309942C CA 2309942 CA2309942A CA2309942C CA 2309942 C CA2309942 C CA 2309942C CA 2309942 CA2309942 CA 2309942 CA 2309942 A CA2309942 A CA 2309942A CA 2309942 C CA2309942 C CA 2309942C
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- Canada
- Prior art keywords
- retaining collar
- outer sleeve
- casing
- centralizer
- joint
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- 238000000034 method Methods 0.000 claims abstract description 37
- 239000000463 material Substances 0.000 claims description 12
- 239000011324 bead Substances 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 2
- 230000006835 compression Effects 0.000 claims 2
- 238000007906 compression Methods 0.000 claims 2
- 238000005553 drilling Methods 0.000 abstract description 9
- 238000009434 installation Methods 0.000 description 5
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- 239000004519 grease Substances 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000001010 compromised effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
- E21B17/10—Wear protectors; Centralising devices, e.g. stabilisers
- E21B17/1014—Flexible or expansible centering means, e.g. with pistons pressing against the wall of the well
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Earth Drilling (AREA)
Abstract
A tubing centralizer for borehole drilling disclosed. The centralizer includes a retaining collar and an outer sleeve. In a method for installing the centralizer onto a joint of tubing, the retaining collar is mounted onto the joint of tubing and the outer sleeve is installed thereover.
Description
CASING CENTRALIZER
Field of the invention:
The present invention relates to centralizers for centring pipe strings in wellbores, and, in particular, a casing centralizes.
Background of the invention:
l0 In the drilling of wells, such as those for oil and gas, a string of tubulars is threaded together to form a drillstring having a drill bit mounted on the distal end.
The drill bit is rotated either from the earth's surface by rotating the drillstring of tubulars or by a downhole motor.
To enhance such rotary well drilling operations, numerous tool have been developed for mounting and use at sub-surface locations in the drillstring. One such tool is a centralizes.
A centralizes contacts the borehole wall and effectively serves as a radial bearing or lateral support for the rotating drillstring in the borehole. By holding the drillstring against lateral forces or radial movement, the centralizes acts along the unsupported 2o column length of the drillstring to prevent buckling as well as preventing excessive wear of the drillstring against the borehole wall. The centralizes also reduces the bending stresses induced by movement of the drillstring.
With the development of casing drilling, where the casing is used as the drill string and remains downhole as the wellborn liner, it is important that the integrity of the casing be maintained. To accomplish this, centraslizers are used to prevent the drillpipe from contacting the borehole wall.
In conventional drilling, centralizers are usually formed by a tubular member with a 3o plurality of outwardly extending fixed blades having wall contacting surfaces of hardened material that bear against or contact the sides of the borehole. The outwardly extending S:1C41472\3236116710001-2-app.doc blades are usually mounted vertically or in a helical arrangement. The centralizers have threaded connections and are inserted into the drillstring at regular intervals by threading to the drillpipe threads in a conventional manner.
Casing drilling uses both special tubular sections and special threaded connections that ensure the integrity and gas tightness of the threaded connections.
Centralizers that thread into the casing string are very expensive and are not convenient for use since they must be selected to fit exactly to the connection type being used.
1o Other prior art centralizers include locking collars to secure the centralizes to the drillstring. A locking collar uses set screws that engage into the material of the pipe.
Through the locking collar, the centralizes is prevented from moving axially and from relative rotation on the pipe. However, a centralizes including a locking collar with set screws is relatively weak and sometimes cannot withstand the harsh drilling environment.
In addition, the set screws damage the casing pipe, reducing its strength.
Summary of the invention:
The present invention provides a centralizes and method for securing a centralizes to the 2o drillstring. The centralizes is particularly useful where the drillstring is formed of casing.
By utilising the centralizes of the present invention, the casing string is centred in the borehole to reduce buckling forces and is protected from abrasion against the borehole walls without reducing the strength of the casing to undesirable levels.
Centring the drillstring in the borehole is desirable to ensure that the borehole is drilled straight into the earth without unwanted deviation and to improve cementing. The centralizes also enhances hole cleaning by scraping against the borehole wall and by creating turbulence in the drilling mud passing thereby. A centralizes also acts to maintain the casing string spaced from the borehole wall to, thereby, reduce differential sticking.
3o The centralizes according to the present invention, includes an outer sleeve and a retaining collar. The outer sleeve has a tapering, frustoconical inner surface and an outer S:1C4\472\32361 \6710001-2-app.doc 2 surface including bearing surfaces such as, for example, blades or by application of weld beads. The retaining collar includes an outer frustoconical surface that substantially mates with the inner surface of the sleeve and a substantially cylindrical inner surface.
The retaining collar is formed as a c-ring including a longitudinally extending open slit to allow for adjustment of its diameter and to permit mounting about casings of various diameter. Providing the retaining collar as a c-ring also provides that its inner diameter can be adjusted such that it will have good surface contact with the outer surface of the casing about which it is mounted.
A method is provided according to the present invention. In a broad aspect, a method for installing a centralizer on a joint of tubing comprises: providing a centralizer retaining collar having an outer conical surface, a substantially cylindrical inner surface and a longitudinally extending slit; providing an centralizer outer sleeve, having a tapering, generally conical inner surface substantially mateable with the outer surface of the retaining collar and an outer surface including bearing surfaces; mounting the retaining collar about the joint of tubing with the retaining collar inner surface adjacent the tubing outer surface; sliding the outer sleeve over the retaining collar such that their conical surfaces mate and the outer sleeve compresses the retaining collar into close engagement with the joint of tubing.
The method permits that the centralizer can be mounted over a joint of tubing, such as a casing joint, and can be held in place by frictional engagement between the outer sleeve the retaining collar and the tubing outer surface. Forces are distributed evenly over the interface surface of the tubing and, as is particularly desirable for casing drilling, the casing integrity is not compromised by welding thereon or installation of set screws thereagainst.
In one embodiment, the retaining collar is selected such that it's normal inner diameter is less than the outer diameter than the joint of tubing and the method further comprises 3o expanding the retaining collar at the slit to fit over the joint of tubing.
To enhance S:\C4\472\3236116710001-2-app.doc CA 02309942 2000-OS-29 ' engagement between the parts, preferably, the contacting surfaces of the parts are cleaned prior to assembly to remove grease and/or oil therefrom.
The step of sliding the outer sleeve over the retaining collar such that their conical surfaces mate and the outer sleeve compresses the retaining collar into close engagement with the joint of tubing can be accomplished by heating the outer collar such that it expands prior to sliding the outer sleeve onto the retaining collar until it is wedged thereover. The outer collar, when permitted to cool, will shrink to further compress the retaining collar. In another embodiment, the outer sleeve is forced into wedging 1o engagement over the retaining collar by application of force thereto as by hydraulics or hammering.
Brief description of the drawings:
A further, detailed description of the invention, briefly described above, will follow by reference to the following drawing of a specific embodiment of the invention.
This drawing depicts only a typical embodiment of the invention, and is therefore not to be considered limiting of its scope. In the drawings:
Figure 1 is a cross sectional view of a centralizer according to the present invention 2o installed on a section of casing Figures 2A and 2B are end and vertical sectional views, respectively, of a casing centralizer retaining collar useful in the present invention.
Figures 3A - 3C are end, side and sectional views of a centralizer sleeve useful in the present invention.
Detailed description of the present invention:
3o The drawing figures are not necessarily to scale, and certain features are shown in generalised form in the interests of clarity only.
S ',C4\47213236116710001-2-app.doc Referring to Figure 1, a centralizes 10 according to the present invention is shown installed on a section of casing 12. Although, the centralizes can be used on other tubular members, it is particularly useful for casing where it is important to avoid reducing the integrity of the casing wall to undesirable levels. Centralizes 10 includes an outer sleeve 14 mounted over a retaining collar 16.
Referring also to Figures 2A and 2B, retaining collar 16 is formed as a C-ring having a slit 18 extending along the length thereof. The slit permits the retaining collar to be 1o expanded and compressed to adjust its inner diameter IDs. Since the OD of casing can vary significantly from joint to joint, the retaining collar slit provides that one size of a collar can accommodate variation in casing OD. The inner diameter of retaining collar 16, when the collar is compressed to minimise the width of slit 18, is the less than the outer diameter ODc of the casing tube on which the centralizes is to be installed. In one embodiment, the inner diameter of the collar, when no forces are applied to it, is the same or less than the outer diameter of the casing tube on which it is to be installed.
Inner surface 20 of retaining collar 16 is substantially cylindrical, while outer surface 22 tapers from first end 16a to opposite end 16b forming a frustoconical surface.
The angle 2o a of the taper can be very small such as, for example, between about 0.5 to 2 degrees. In one preferred embodiment, the angle of taper is 1 degree.
Referring also to Figures 3A to 3C, outer sleeve 14 includes an inner surface 30 and an outer surface 32. Inner surface 30 is frustoconical in shape tapering from first end 14a to opposite end 14b. The taper is selected to correspond to the taper on outer surface 22 of retaining collar 16 so that the two parts can fit together closely. As will be appreciated to enhance the fit between the parts, preferably the angle a of taper on outer surface 22 of retaining collar 16 is the same as the angle of taper b on the inner surface of sleeve 14. A
taper b in the range of 0.5 to 2 degrees is preferred. In the illustrated embodiment, the 3o inner surface 30 has a 1 degree taper.
S:',C4\472\32361\6710001-2-app.doc The inner diameter of outer sleeve is selected to be mateable with the outer diameter of retaining collar when it is disposed about the casing tube of interest. In particular, the outer sleeve must be capable of riding along and wedging over the frustoconical outer surface of the retaining sleeve.
Outer surface 32 of outer sleeve 30 has formed or secured thereon a plurality of centralizer blades 34 to act as bearing surfaces. Blades 34 are spaced apart and formed of high strength material that can withstand abrasive contact such as with the borehole walls. The spacing of blades 34 permits the flow of fluids therepast when the centralizer to is located in a wellbore. Blades 34, as illustrated, are formed integral with the material of outer sleeve by building up a raised surface of multiple weld beads. These beads are very strong as they become integral with the sleeve material. The welding rod used for such beads is similar to that used for hardbanding of drill pipe and collars. The bearing surfaces can be formed by laying a plurality of beads of weld onto the outer sleeve in other configurations other than elongate blades. In another embodiment, the bearing surfaces can be cast onto the outer sleeve. In yet another embodiment, blades are formed of steel strips welded onto the outer surface, however, there is a risk of the welds failing and the strips becoming jammed in the annulus. Therefore, this approach is not preferred 2o Retaining collar 16 and outer sleeve 14 are formed of strong materials capable of withstanding borehole conditions such as, for example, carbon steel. If heat expansion is to be used for assembling the outer sleeve over the retaining collar, the outer sleeve must also be formed of a heat expandable material selected to return substantially to its original form upon cooling to at least usual downhole temperatures The centralizer is installed on a tube such as a joint of casing 12. For convenience of installation, the centralizer is mounted close to the pin end (i.e. three to six feet from the pin end) of the casing tube. Preferably, the outer surfaces of the tube, the inner and outer surfaces of the retaining collar and the inner surface of the outer sleeve are cleaned, as by 3o use of a solvent, to remove any grease and/or oil present thereon in order to maximise friction between the parts.
S:\C4\472\32361167\0001-2-app.doc The retaining collar 16 is installed on the casing, preferably for ease of installation, with its tapered end toward the pin end of the casing. Preferably, the retaining collar is formed to fit closely about the tubing. In particular, the retaining collar size is selected such that it must be expanded by pulling apart at the slit in order to position it on the joint of casing. To facilitate installation of such a collar, snap ring tongs can be used to expand the collar to such a degree that it will not be in contact with the tubing as it is positioned thereover.
to Outer sleeve 14 is then installed and wedged over the retaining collar. The outer sleeve is slid over the retaining collar with the tapered surfaces of each coacting. To wedge the outer sleeve over the retaining collar, force can be applied, as by hammering or hydraulics, to the outer sleeve to drive it into close engagement with the retaining collar.
Alternatively or in addition, the outer sleeve 14 can be heated prior to installation to cause the material to expand. When the centralizer is formed of carbon steel, it is preferably heated to approximately 400°F to achieve expansion. Heated sleeve 14 has a maximum inner diameter greater than the minimum outer diameter of retaining collar 16 and can be slid up on the collar 16. Heat expansion provides that the sleeve can be slid over the collar further than it would be able to if it were cold. Once the heated outer sleeve is slid onto collar 16 as far as possible, it is forced further onto the collar, as by tapping with an annular slide hammer. After the outer sleeve cools it shrinks to engage the retaining collar and to compress the retaining collar into increased engagement with the casing.
The outer sleeve can be tack welded to the retaining collar to ensure that the parts will not come apart. Preferably, care should be taken to avoid applying welds to the casing, as this may damage the casing integrity. It is now ready for use.
3o Although the preferred embodiments of the present invention have been described in some detail hereinabove, those skilled in the art will recognise that various substitutions S:.C41472132361',6710001-2-app.doc and modifications may be made to the invention without departing from the scope and spirit of the appended claims.
S:\C41472132361\6710001-2-app.doc
Field of the invention:
The present invention relates to centralizers for centring pipe strings in wellbores, and, in particular, a casing centralizes.
Background of the invention:
l0 In the drilling of wells, such as those for oil and gas, a string of tubulars is threaded together to form a drillstring having a drill bit mounted on the distal end.
The drill bit is rotated either from the earth's surface by rotating the drillstring of tubulars or by a downhole motor.
To enhance such rotary well drilling operations, numerous tool have been developed for mounting and use at sub-surface locations in the drillstring. One such tool is a centralizes.
A centralizes contacts the borehole wall and effectively serves as a radial bearing or lateral support for the rotating drillstring in the borehole. By holding the drillstring against lateral forces or radial movement, the centralizes acts along the unsupported 2o column length of the drillstring to prevent buckling as well as preventing excessive wear of the drillstring against the borehole wall. The centralizes also reduces the bending stresses induced by movement of the drillstring.
With the development of casing drilling, where the casing is used as the drill string and remains downhole as the wellborn liner, it is important that the integrity of the casing be maintained. To accomplish this, centraslizers are used to prevent the drillpipe from contacting the borehole wall.
In conventional drilling, centralizers are usually formed by a tubular member with a 3o plurality of outwardly extending fixed blades having wall contacting surfaces of hardened material that bear against or contact the sides of the borehole. The outwardly extending S:1C41472\3236116710001-2-app.doc blades are usually mounted vertically or in a helical arrangement. The centralizers have threaded connections and are inserted into the drillstring at regular intervals by threading to the drillpipe threads in a conventional manner.
Casing drilling uses both special tubular sections and special threaded connections that ensure the integrity and gas tightness of the threaded connections.
Centralizers that thread into the casing string are very expensive and are not convenient for use since they must be selected to fit exactly to the connection type being used.
1o Other prior art centralizers include locking collars to secure the centralizes to the drillstring. A locking collar uses set screws that engage into the material of the pipe.
Through the locking collar, the centralizes is prevented from moving axially and from relative rotation on the pipe. However, a centralizes including a locking collar with set screws is relatively weak and sometimes cannot withstand the harsh drilling environment.
In addition, the set screws damage the casing pipe, reducing its strength.
Summary of the invention:
The present invention provides a centralizes and method for securing a centralizes to the 2o drillstring. The centralizes is particularly useful where the drillstring is formed of casing.
By utilising the centralizes of the present invention, the casing string is centred in the borehole to reduce buckling forces and is protected from abrasion against the borehole walls without reducing the strength of the casing to undesirable levels.
Centring the drillstring in the borehole is desirable to ensure that the borehole is drilled straight into the earth without unwanted deviation and to improve cementing. The centralizes also enhances hole cleaning by scraping against the borehole wall and by creating turbulence in the drilling mud passing thereby. A centralizes also acts to maintain the casing string spaced from the borehole wall to, thereby, reduce differential sticking.
3o The centralizes according to the present invention, includes an outer sleeve and a retaining collar. The outer sleeve has a tapering, frustoconical inner surface and an outer S:1C4\472\32361 \6710001-2-app.doc 2 surface including bearing surfaces such as, for example, blades or by application of weld beads. The retaining collar includes an outer frustoconical surface that substantially mates with the inner surface of the sleeve and a substantially cylindrical inner surface.
The retaining collar is formed as a c-ring including a longitudinally extending open slit to allow for adjustment of its diameter and to permit mounting about casings of various diameter. Providing the retaining collar as a c-ring also provides that its inner diameter can be adjusted such that it will have good surface contact with the outer surface of the casing about which it is mounted.
A method is provided according to the present invention. In a broad aspect, a method for installing a centralizer on a joint of tubing comprises: providing a centralizer retaining collar having an outer conical surface, a substantially cylindrical inner surface and a longitudinally extending slit; providing an centralizer outer sleeve, having a tapering, generally conical inner surface substantially mateable with the outer surface of the retaining collar and an outer surface including bearing surfaces; mounting the retaining collar about the joint of tubing with the retaining collar inner surface adjacent the tubing outer surface; sliding the outer sleeve over the retaining collar such that their conical surfaces mate and the outer sleeve compresses the retaining collar into close engagement with the joint of tubing.
The method permits that the centralizer can be mounted over a joint of tubing, such as a casing joint, and can be held in place by frictional engagement between the outer sleeve the retaining collar and the tubing outer surface. Forces are distributed evenly over the interface surface of the tubing and, as is particularly desirable for casing drilling, the casing integrity is not compromised by welding thereon or installation of set screws thereagainst.
In one embodiment, the retaining collar is selected such that it's normal inner diameter is less than the outer diameter than the joint of tubing and the method further comprises 3o expanding the retaining collar at the slit to fit over the joint of tubing.
To enhance S:\C4\472\3236116710001-2-app.doc CA 02309942 2000-OS-29 ' engagement between the parts, preferably, the contacting surfaces of the parts are cleaned prior to assembly to remove grease and/or oil therefrom.
The step of sliding the outer sleeve over the retaining collar such that their conical surfaces mate and the outer sleeve compresses the retaining collar into close engagement with the joint of tubing can be accomplished by heating the outer collar such that it expands prior to sliding the outer sleeve onto the retaining collar until it is wedged thereover. The outer collar, when permitted to cool, will shrink to further compress the retaining collar. In another embodiment, the outer sleeve is forced into wedging 1o engagement over the retaining collar by application of force thereto as by hydraulics or hammering.
Brief description of the drawings:
A further, detailed description of the invention, briefly described above, will follow by reference to the following drawing of a specific embodiment of the invention.
This drawing depicts only a typical embodiment of the invention, and is therefore not to be considered limiting of its scope. In the drawings:
Figure 1 is a cross sectional view of a centralizer according to the present invention 2o installed on a section of casing Figures 2A and 2B are end and vertical sectional views, respectively, of a casing centralizer retaining collar useful in the present invention.
Figures 3A - 3C are end, side and sectional views of a centralizer sleeve useful in the present invention.
Detailed description of the present invention:
3o The drawing figures are not necessarily to scale, and certain features are shown in generalised form in the interests of clarity only.
S ',C4\47213236116710001-2-app.doc Referring to Figure 1, a centralizes 10 according to the present invention is shown installed on a section of casing 12. Although, the centralizes can be used on other tubular members, it is particularly useful for casing where it is important to avoid reducing the integrity of the casing wall to undesirable levels. Centralizes 10 includes an outer sleeve 14 mounted over a retaining collar 16.
Referring also to Figures 2A and 2B, retaining collar 16 is formed as a C-ring having a slit 18 extending along the length thereof. The slit permits the retaining collar to be 1o expanded and compressed to adjust its inner diameter IDs. Since the OD of casing can vary significantly from joint to joint, the retaining collar slit provides that one size of a collar can accommodate variation in casing OD. The inner diameter of retaining collar 16, when the collar is compressed to minimise the width of slit 18, is the less than the outer diameter ODc of the casing tube on which the centralizes is to be installed. In one embodiment, the inner diameter of the collar, when no forces are applied to it, is the same or less than the outer diameter of the casing tube on which it is to be installed.
Inner surface 20 of retaining collar 16 is substantially cylindrical, while outer surface 22 tapers from first end 16a to opposite end 16b forming a frustoconical surface.
The angle 2o a of the taper can be very small such as, for example, between about 0.5 to 2 degrees. In one preferred embodiment, the angle of taper is 1 degree.
Referring also to Figures 3A to 3C, outer sleeve 14 includes an inner surface 30 and an outer surface 32. Inner surface 30 is frustoconical in shape tapering from first end 14a to opposite end 14b. The taper is selected to correspond to the taper on outer surface 22 of retaining collar 16 so that the two parts can fit together closely. As will be appreciated to enhance the fit between the parts, preferably the angle a of taper on outer surface 22 of retaining collar 16 is the same as the angle of taper b on the inner surface of sleeve 14. A
taper b in the range of 0.5 to 2 degrees is preferred. In the illustrated embodiment, the 3o inner surface 30 has a 1 degree taper.
S:',C4\472\32361\6710001-2-app.doc The inner diameter of outer sleeve is selected to be mateable with the outer diameter of retaining collar when it is disposed about the casing tube of interest. In particular, the outer sleeve must be capable of riding along and wedging over the frustoconical outer surface of the retaining sleeve.
Outer surface 32 of outer sleeve 30 has formed or secured thereon a plurality of centralizer blades 34 to act as bearing surfaces. Blades 34 are spaced apart and formed of high strength material that can withstand abrasive contact such as with the borehole walls. The spacing of blades 34 permits the flow of fluids therepast when the centralizer to is located in a wellbore. Blades 34, as illustrated, are formed integral with the material of outer sleeve by building up a raised surface of multiple weld beads. These beads are very strong as they become integral with the sleeve material. The welding rod used for such beads is similar to that used for hardbanding of drill pipe and collars. The bearing surfaces can be formed by laying a plurality of beads of weld onto the outer sleeve in other configurations other than elongate blades. In another embodiment, the bearing surfaces can be cast onto the outer sleeve. In yet another embodiment, blades are formed of steel strips welded onto the outer surface, however, there is a risk of the welds failing and the strips becoming jammed in the annulus. Therefore, this approach is not preferred 2o Retaining collar 16 and outer sleeve 14 are formed of strong materials capable of withstanding borehole conditions such as, for example, carbon steel. If heat expansion is to be used for assembling the outer sleeve over the retaining collar, the outer sleeve must also be formed of a heat expandable material selected to return substantially to its original form upon cooling to at least usual downhole temperatures The centralizer is installed on a tube such as a joint of casing 12. For convenience of installation, the centralizer is mounted close to the pin end (i.e. three to six feet from the pin end) of the casing tube. Preferably, the outer surfaces of the tube, the inner and outer surfaces of the retaining collar and the inner surface of the outer sleeve are cleaned, as by 3o use of a solvent, to remove any grease and/or oil present thereon in order to maximise friction between the parts.
S:\C4\472\32361167\0001-2-app.doc The retaining collar 16 is installed on the casing, preferably for ease of installation, with its tapered end toward the pin end of the casing. Preferably, the retaining collar is formed to fit closely about the tubing. In particular, the retaining collar size is selected such that it must be expanded by pulling apart at the slit in order to position it on the joint of casing. To facilitate installation of such a collar, snap ring tongs can be used to expand the collar to such a degree that it will not be in contact with the tubing as it is positioned thereover.
to Outer sleeve 14 is then installed and wedged over the retaining collar. The outer sleeve is slid over the retaining collar with the tapered surfaces of each coacting. To wedge the outer sleeve over the retaining collar, force can be applied, as by hammering or hydraulics, to the outer sleeve to drive it into close engagement with the retaining collar.
Alternatively or in addition, the outer sleeve 14 can be heated prior to installation to cause the material to expand. When the centralizer is formed of carbon steel, it is preferably heated to approximately 400°F to achieve expansion. Heated sleeve 14 has a maximum inner diameter greater than the minimum outer diameter of retaining collar 16 and can be slid up on the collar 16. Heat expansion provides that the sleeve can be slid over the collar further than it would be able to if it were cold. Once the heated outer sleeve is slid onto collar 16 as far as possible, it is forced further onto the collar, as by tapping with an annular slide hammer. After the outer sleeve cools it shrinks to engage the retaining collar and to compress the retaining collar into increased engagement with the casing.
The outer sleeve can be tack welded to the retaining collar to ensure that the parts will not come apart. Preferably, care should be taken to avoid applying welds to the casing, as this may damage the casing integrity. It is now ready for use.
3o Although the preferred embodiments of the present invention have been described in some detail hereinabove, those skilled in the art will recognise that various substitutions S:.C41472132361',6710001-2-app.doc and modifications may be made to the invention without departing from the scope and spirit of the appended claims.
S:\C41472132361\6710001-2-app.doc
Claims (35)
1. A centralizer for installing about a joint of tubing, the centralizer comprising: a retaining collar including an outer tapering, frustoconical outer surface and a substantially cylindrical inner surface, the retaining collar being mountable about the joint of tubing with its inner surface in contact with the tubing outer surface and; an outer sleeve mounted about and in frictional engagement with the retaining collar, the outer sleeve having a tapering, frustoconical inner surface selected to be mateable with the outer surface of the retaining collar and an outer surface including bearing surfaces.
2. The centralizer of claim 1 where the bearing surfaces are spaced apart and formed of built up weld beads.
3. The centralizer of claim 1 wherein the inner diameter of said retaining collar, before being mounted about said joint of tubing, is less than the outer diameter of the joint of tubing, such that the retaining collar may be secured about the joint of tubing through compression and frictional forces.
4. The centralizer of claim 1 wherein the inner diameter of said outer sleeve is such that when the outer sleeve is forced into place over said retaining collar, the outer sleeve is secured about the retaining collar by compression and friction forces.
5. A method for installing a centralizer on a joint of tubing comprising:
providing a centralizer retaining collar having an outer frustoconical surface, a substantially cylindrical inner surface and a longitudinally extending slit; providing an centralizer outer sleeve, having a tapering, frustoconical inner surface mateable with the outer surface of the retaining collar and an outer surface including bearing surfaces; mounting the retaining collar about the joint of tubing with the retaining collar inner surface adjacent the tubing outer surface; sliding the outer sleeve over the retaining collar such that their conical surfaces mate and the outer sleeve compresses the retaining collar into close engagement with the joint of tubing.
providing a centralizer retaining collar having an outer frustoconical surface, a substantially cylindrical inner surface and a longitudinally extending slit; providing an centralizer outer sleeve, having a tapering, frustoconical inner surface mateable with the outer surface of the retaining collar and an outer surface including bearing surfaces; mounting the retaining collar about the joint of tubing with the retaining collar inner surface adjacent the tubing outer surface; sliding the outer sleeve over the retaining collar such that their conical surfaces mate and the outer sleeve compresses the retaining collar into close engagement with the joint of tubing.
6. The method of claim 5 further comprising prior to sliding the outer sleeve over the retaining collar, the outer sleeve is heated to cause material expansion thereof.
7. The method of claim 5 further comprising after sliding the outer sleeve over the retaining collar, they are secured together.
8. The method of claim 5 wherein the retaining collar is expanded by pulling apart at the slit prior to mounting the retaining collar about the tubing outer surface.
9. A method for installing a centralizer collar and outer sleeve on a joint of a drill string casing comprising: providing an adjustable centralizer retaining collar having an outer frustoconical surface, a substantially cylindrical inner surface and a longitudinally extending slit; providing a centralizer outer sleeve, having a tapering, frustoconical inner surface mateable with the outer surface of the retaining collar and an outer surface including bearing surfaces; mounting the retaining collar about the joint of the drill string casing with the retaining collar inner surface adjacent to an outer surface of the casing; heating the outer sleeve to cause material expansion thereof; sliding the outer sleeve over the retaining collar such that their conical surfaces mate and the outer sleeve compresses the retaining collar into close engagement with the joint of the drill string casing.
10. The method of claim 9 further comprising after sliding the outer sleeve over the retaining collar, the outer sleeve and the retaining collar are secured together.
11. The method of claim 9 wherein the retaining collar is expanded by pulling apart at the slit prior to mounting the retaining collar about the casing outer surface.
12. The method of claim 9 wherein the tapering of the outer sleeve is selected to correspond to a tapering of an outer surface of the retaining collar, the tapering being selected in the range of 0.5 to 2 degrees.
13. The method of claim 9 wherein after the heated outer sleeve is slid over the retaining collar, the outer sleeve is allowed to cool to compress the retaining collar into increased engagement with the casing.
14. The method of claim 10 wherein the outer sleeve is welded to the retaining collar.
15. The method of claim 9 wherein the sliding of the outer sleeve over the retaining collar is driven into close engagement by hammering or hydraulics.
16. The method of claim 9 further comprises providing a plurality of centralizer blades on an outer surface of the outer sleeve.
17. The method of claim 9 wherein the retaining collar is expanded or compressed such that an inner diameter of the retaining collar is adjusted to an outer diameter of the joint of the casing.
18. A method for installing a centralizer collar and outer sleeve on a joint of a drill string casing comprising: providing an adjustable centralizer retaining collar having an outer frustoconical surface, a substantially cylindrical inner surface and a longitudinally extending slit; providing a centralizer outer sleeve, having a tapering, frustoconical inner surface mateable with the outer surface of the retaining collar and an outer surface including bearing surfaces; expanding the retaining collar by pulling apart at the slit prior to mounting the retaining collar about an outer surface of the casing; mounting the retaining collar about the joint of the drill string casing with the retaining collar inner surface adjacent to the outer surface of the casing; sliding the outer sleeve over the retaining collar such that their conical surfaces mate and the outer sleeve compresses the retaining collar into close engagement with the joint of the drill string casing.
19. The method of claim 18 further comprising prior to sliding the outer sleeve over the retaining collar, the outer sleeve is heated to cause material expansion thereof.
20. The method of claim 19 wherein after the heated outer sleeve is slid over the retaining collar, the outer sleeve is allowed to cool to compress the retaining collar into increased engagement with the casing.
21. The method of claim 18 further comprising after sliding the outer sleeve over the retaining collar, they are secured together.
22. The method of claim 21 wherein the outer sleeve is welded to the retaining collar.
23. The method of claim 18 wherein the tapering of the outer sleeve is selected to correspond to a tapering on an outer surface of the retaining collar, the tapering being selected in the range of 0.5 to 2 degrees.
24. The method of claim 18 wherein the sliding of the outer sleeve over the retaining collar is driven into close engagement by hammering or hydraulics.
25. The method of claim 18 further comprises providing a plurality of centralizer blades on an outer surface of the outer sleeve.
26. The method of claim 18 wherein the retaining collar is expanded or compressed such that an inner diameter of the retaining collar is adjusted to an outer diameter of the joint of the casing.
27. A method for installing a centralizer collar and outer sleeve on a joint of a drill string casing comprising: providing an adjustable centralizer retaining collar having an outer frustoconical surface, a substantially cylindrical inner surface and a longitudinally extending slit; providing a centralizer outer sleeve, having a tapering, frustoconical inner surface mateable with the outer surface of the retaining collar and an outer surface including bearing surfaces; mounting the retaining collar about the joint of the drill string casing with the retaining collar inner surface adjacent to an outer surface of the casing; sliding the outer sleeve over the retaining collar such that their conical surface mate and the outer sleeve compresses the retaining collar into close engagement with the joint of the drill string casing wherein the sliding of the outer sleeve over the retaining collar is driven into close engagement by hammering or hydraulics.
28. The method of claim 27 further comprising prior to sliding the outer sleeve over the retaining collar, the outer sleeve is heated to cause material expansion thereof.
29. The method of claim 28 wherein after the heated outer sleeve is slid over the retaining collar, the outer sleeve is allowed to cool to compress the retaining collar into increased engagement with the casing.
30. The method of claim 27 further comprising after sliding the outer sleeve over the retaining collar, they are secured together.
31. The method of claim 30 wherein the outer sleeve is welded to the retaining collar.
32. The method of claim 27 wherein the retaining collar is expanded by pulling apart at the slit prior to mounting the retaining collar about the casing outer surface.
33. The method of claim 27 wherein the tapering of the outer sleeve is selected to correspond to a tapering of an on an outer surface of the retaining collar, the tapering being selected in the range of 0.5 to 2 degrees.
34. The method of claim 27 further comprises providing a plurality of centralizer blades on an outer surface of the outer sleeve.
35. The method of claim 27 wherein the retaining collar is expanded or compressed such that an inner diameter of the retaining collar is adjusted to an outer diameter of the joint of the casing.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA 2309942 CA2309942C (en) | 2000-05-29 | 2000-05-29 | Casing centralizer |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA 2309942 CA2309942C (en) | 2000-05-29 | 2000-05-29 | Casing centralizer |
Publications (2)
Publication Number | Publication Date |
---|---|
CA2309942A1 CA2309942A1 (en) | 2001-11-29 |
CA2309942C true CA2309942C (en) | 2007-01-30 |
Family
ID=4166300
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA 2309942 Expired - Lifetime CA2309942C (en) | 2000-05-29 | 2000-05-29 | Casing centralizer |
Country Status (1)
Country | Link |
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CA (1) | CA2309942C (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CA2550801C (en) | 2006-06-22 | 2010-07-20 | Boart Longyear Inc. | Drilling equipment |
CN114991687B (en) * | 2022-06-30 | 2023-08-18 | 江苏赛瑞机器人装备有限公司 | Be applied to oil exploitation's intelligent sucker rod device equipment |
CN115405238B (en) * | 2022-10-14 | 2024-06-11 | 东营华辰石油装备有限公司 | Casing centralizer with adaptive variable diameter function |
-
2000
- 2000-05-29 CA CA 2309942 patent/CA2309942C/en not_active Expired - Lifetime
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Publication number | Publication date |
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CA2309942A1 (en) | 2001-11-29 |
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