CA2041270A1 - Well bore packing apparatus and methods of drilling thereof - Google Patents

Abstract

Abstract Of The Disclosure A well bore packing apparatus and various methods of drilling the apparatus. The packing apparatus may include packers and bridge plugs utilizing engineering grade plastic components substituted for previously known cast iron com-ponents therein. Methods of drilling out the packing apparatus without significant variations in the drilling speed and weight applied to the drill bit may be employed.
Alternative drill bit types, such as polycrystalline diamond compact (PDC) bits may also be used.

Description

J ' ,i WELL BORE PACKING APPARATUS AND METHODS OF DRILLING rL'H'EREOF
Background Of The Invention 1. Field Of The Invention This invention relates to packing apparatus for use in a well bore and methods of drilling such apparatus out of the well bore, and more particularly, to the drilling of packers and bridge plugs having drillable co~ponents therein made of engineering grade plastics.

2. Description Of The Prior Art In the drilling or reworking of oil wells, it is often desirable to seal tubing or other pipe in the casing of the well. For example, when it is desired to pump cement or other slurry down tubing and force the slurry out into a for~ation, it becomes necessary to seal the tubing to the well casing and to prevent the fluid pressure of the slurry from lifting the tubing out of the well. Packer~ and bridge plugs designed for these general purposes are well known in the art.
When it is desired to remove many of these packers and plugs from a well bore, it is ~requently simpler and le8 e~pensive to mill or drill the packer out rat'her t'han to implement a complex retrieving operation~ In milling, a milling cutter i9 used to grind the packer or plug, or at least the outer components thereof, out of the well bore.
'Milling is a relatively slow process, but it can be used on packers or bridge plugs having relatively hard components such as erosion-resistant hard steel. One such packer is disclosed in U. S. Patent No. 4,151,875 to Sullaway, 7 r, ~3 assigned to the assignee of the present invention and sold under the trademark EZ Disposal'n packer.
In drilling, a drlll bit is used to cut and grind up the components of the packer or bridge plug to remove it from the well bore. This is a much faster operation than milling, but requires the packer or bridge plug to be made out of materials which can be accommodated by the drill bit.
Typically, soft and medium hardness cast iron are used on the pressure bearing components, along with some brass and aluminum items. Packers of this type include the Halliburton EZ Drill~ and EZ Drill SV~ squeeze packers.
The EZ Drill SV~ squee~e packer, for example, includes a lock ring housing, upper slip wedge, lower slip wedge, and lower slip support made of soft cast iron. These components are mounted on a mandrel made of medium hardness cast iron.
The EZ DrillO squeeze packer is similarly constructed. The Halliburton EZ Drill~ bridge plug is also similar, except that it does not provide for fluid flow therethrough.
All of the above-mentioned packers are disclo~ed ln Halliburton Service~ Sales and Service Catalog No. 43, pages 2561~2562, and the bridge plug is disclosed in the same catalog on pages 2556-2557.
The EZ Drill~ packer and bridge plug and the EZ Drill SV~ packer are designed for fast removal from the well bore by either rotary or cable tool drilling methods. Many of the components in these drillable packing devices are locked together to prevent their spinning while being drilled~ and the harder slips are grooved so that they will be broken up in small pieces. Typically, standard "tri-cone" rotary drill bits are used which are rotated at speeds of about 75 to about 120 rpm. A load of about 5,000 to about 7,000 pounds of weight is applied to the bit for initial drilling and increased as necessary to drill out the remainder of the packer or bridge plug, depending upon its size. Drill collars may be used as required for weight and bit stabili-~ation.
These drillable packing devices have worked well and provide improved operating performance at relatively high temperatures and pressures. The packers and plug are designed to withstand pressures of about 10,000 psi and tem-peratures of about 425 F. after being set in the well bore.
Such pressures and temperatures require the cast iron com~
ponents previously di~cussed.
However, drilling out iron components requires certain techniques. Ideally, the operator employs variatiorls in rotary speed and bit weight to help break up the metal parts and reestablish bit penetration should bit penetration cease while drilling. A phenomenon known as "bit tracking" can occur, wherein the arill bit stays on one path and no longer cuts into the packer plug. When this happens, it is necessary to pick up the bit above the drilling surface and rapidly recontact the bit with the packer or plug and apply weight while continuing rotation. This aids in breaking up the established bit pattern and helps to reestablish bit ~J 'Y " ~

penetration. If this procedure is used, there a~e rarely problems. However, operators may not apply these -~echniques or even recognize when bit tracking has occurred. The result is that drilling times are greatly increased because the bit merely wears against the surface of the packer or plug rather than cutting into it to break it up.
While cast iron components may be necessary for the high pressures and temperatures for which they are designed, it has been determined that most wells cemented throughout the world experience pressures less than 10,000 psi and tem-peratures less than 425 F. In fact, in the majority of wells, the pressure is less than about 5,000 psi, and the temperature is less than about 250 F. Thus, the heavy duty metal construction of the previous packers and bridge plugs described above is not necessary for many applications, and if cast iron components can be eliminated or minimized, the potential drilling problems resulting Erom bit tracking might be avoided as well.
The packing apparatu~ of the present inventlon ~olves this problem by providing packers and bridge plugs whereln at least some o~ the components, including pressure bearing components, are made of engineering grade plastics rather than metal. Such plastic components are much more easily drilled than cast iron, and new drilling methods may be employed which use alternative drill bits such as polycrystalline diamond compact bits, or the like, rather than standard tri-cone bits.

Summary Of The Invention The well bore packing apparatus of the present invention utilizes the same general geomekric configuration of pre-viously known drillable packers and bridge plugs, but repla-ces at least some of the metal components with engineering grade plastics which can still withstand the pressures and temperatures exposed thereto in many well bore applications.
The plastic components are easier to drill out and allow the use of alternative drilling techniques to those previously known.
In one embodiment, the well bore packing apparatus comprises a center mandrel, slip means disposed on the mandrel for grippingly engaging the well bore when in a set position, the slip means comprising a component thereof made of a plastic material, and packing means disposed on the mandrel for sealingly engaging the well bore when in the set position. The component in the slip means made of plastic may be selected from a group comprising such components as a lock ring housing, a 61ip wedge and a 51ip ~upport. The slips them~elves may also be lncluded in this group of slip means components. The slips may require the addition of hardened inserts for the actual engagement of the well bore.
The slip means may be an upper slip means disposed above the packing means, and the apparatus may further comprise a lower slip means disposed below the packing means, the lower slip means also comprising a component made of a plastic material.

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Most of the components of the slip means are subjected to substantially compressive loading when in a sealed operating position in the well bore, although some tensile loading may also be experienced. The center mandrel typi-cally has tensile loading applied thereto when setting the packer and when the packer is in its operating position. In another embodiment, the mandrel may also be made of a plastic material.
One preferred plastic material for at least some of these components is a glass reinforced phenolic resin having a tensile strength of about 18,000 psi and a compressive strength of about 40,000 psi, although the invention is not intended to be limited to this particular plastic or a plastic having these specific physical properties. The plastic materials are preferably selected such that the packing apparatus can withstand well pressures less than about 10,000 psi and temperatures less than about 425 F.
In one preferred embodiment, but not by way o~ limitation, the plastic materials o~ the packing apparatus are selected ~uch that the apparatus can withstand well pressures up to about 5,000 psi and temperatures up to about 250 F.
One new method of the invention is a well bore process comprising the steps of positioning a well packing device into gripping and sealing engagement with the well bore;
prior to the step of positioning, constructing the device such that a component thereof subject to substantially compressive loading, when the device is engaged, is made of plastic; and then drilling the device out o~ the well bore The device is selected from a group comprising p~ckers a~d bridge plugs, and the plastic component therein is selected from a group comprising such items as lock rings housings, slip wedges and slip supports as previously mentioned. In another embodiment, the process further comprises the step of constructing the device such that a component thereof subject to at least some tensile loading is also made of plastic. This plastic component subject to tensile loading may be selected from a group of such items as the center mandrel of the packing device.
In another embodiment, the step of drilling is carried out using a polycrystalline diamond compact bit. Regardless of the type of drill bit used, the process may further comprise the step of drilling using a drill bit without substantially varying the weight applied to the drill bit.
In another method of the invention, a well bore process comprises the steps o~ positioning and setting a packer or plug in the well bore, a portion o the packer or plug being made o~ engineering grade plastic, contacting the packer or plug with well fluids, and drilling out the packer or plug using a drill bit having no moving parts such as a polycrystalline diamond compact bit. This or a similar drill bit might have been previously used in drilling the well bore itself, so the process may be said to further comprise the step of, prior to the step of positioning and setting the packer, drilling at least a portion of the well s ~ J r bore using a drill bi-t such as a polycrystalline diamond compact bit.
In one preferred embodiment, the step of contacting the packer is at a pressure of less than about 5,000 psi and a temperature of less than about 250 F, although higher pressures and temperatures may also be encountered.
It is an important object of the invention to provide a packing apparatus utilizing components made of engineering grade plastic and methods of drilling thereof.
It is another object of the invention to provide a packing apparatus which may be drilled by alternate methods to those using standard rotary drill bits.
Additional objects and advantages of the invention will ; become apparent as the following detailed description of the preferred embodiment is read in conjunction with the draw-ings which illustrate such preferred embodimentO
' Brief Description Of The Drawin~
FIG. 1 illustrates the packing apparatus oE the pre~ent invention positioned in a well bore with a drill bit dis-posed thereabove.
FIG. 2 illustrates a cross section of a typical drillable packer made in accordance with the invention.
Description Of The Preferred Embodiment Referring now to the drawings, and more particularly to FIG. 1, the well bore packing apparatus of ~he present invention is shown and generally designated by the numeraI

g 10. Apparatus 10 is shown in a sealing, operating position in a well bore 12. Apparatus 10 can be set in ~his position by any manner known in the art such as setting on a tubing string or wire line. A drill bit 14 connected to the end of a tool or tubing string 16 is shown above apparatus 10 in a position to commence the drilling out of apparatus 10 from well bore 12. Methods of drilling out apparatus 10 will be further discussed herein.
Referring now to FIG. 2, the details of a squeeze packer embodiment 20 of packing apparatus 10 will be described.
The size and configuration of packer 20 i5 substantially the same as the previously described prior art EZ Drill SV~
squeeze packer. Packer 20 defines a generally central opening 21 therein.
Packer 20 comprises a center mandrel 22 on which most of the other components are mounted. A lock ring housing 24 is disposed around an upper end o~ mandrel 22 and generally encloses a lock ring 26.
Di~posed below lock ring housing 24 and pivotally con-nected thereto are a pluraliky o upper 91ips 28 initially held in place by a retaining band 30. A generally conical upper slip wedge is disposed around mandrel 22 adjacent to upper slips 30. Upper slip wedge 32 is held in place on mandrel 22 by a wedge retaining ring 34 and a plurality Of screws 36.
Adjacent to the lower end of upper slip wedge 32 is an upper expanding shoe 38 connected to the upper slip wedge by a pin 39. Below upper expanding shoe 38 are a pair o~ end packer elements 40 separated by center packer element 42. A
lower expanding shoe 44 is disposed adjacent to the lower-most end packer element 40.
A generally conical lower slip wedge 46 i5 positioned around mandrel 22 adjacent to lower expanding shoe 44, and a pin 48 connects the lower expanding shoe to the lower slip wedge.
Lower slip wedge 46 is initially attached to mandrel 22 by a plurality of screws 50 and a wedge retaining ring 52 in a manner similar to that for upper slip wedge 32. A plural-ity of lower slips 54 are disposed adjacent to lower slip wedge 46 and are initially held in place by a retaining band 56. Lower slips 54 are pivotally connected to the upper end of a lower slip suppor~ 58. Mandrel 22 is at~ached to lower slip support 58 at threaded connection 60.
Disposed in mandrel 22 at the upper end thereo is a tension sleeve 62 below which is an internal ~eal 64. A
sliding valve 66 is slidably dispo0ed in central openiny 21 at the lower end of mandrel 22 adjacent to f:Luid ports 68 in the mandrel. Fluid ports 68 in mandrel 22 are in com-munication with fluid port~ 70 in lower lip housing 58.
The lower end of lower slip support 58 is closed below ports 70.
Sliding valve 66 defines a plurality of valve ports 72 which can be aligned with fluid ports 68 in mandrel 22 when sliding valve 66 is in an open position. Thus, fluid can i; i 3 flow through central opening 21. As illustrated in FIG. 2, sliding valve 66 is in a closed position wherein fluid ports 68 are sealed by upper and lower valve seals 74 and 76.
Opening and closing of valve 66 is in a manner known in the art.
Setting And Operation Of The Packer Apparatus Packer 20 is positioned in well bore 12 and set into gripping and sealing engagement therewith in a manner substantially identical to similar packers and plugs of the prior art. Full details of this setting operation are disclosed in the above-referenced U. S. Patent No. 4,151,875 to Sullaway, a copy of which is included herein by reference, so only a brief description of the setting opera-tion will be described herein.
By pulling upwardly on mandrel 22 while holding lock ring housing 24, the lock ring housing is moved relatively downwardly along the mandrel which orces upper sl ip5 28 outwardly and shears screws 36 to push upper slip wedge 32 downwardly against packer ele~ents 40 and 42. Screw~ 50 are also ~heared and lower slip wedge 46 is pushed downwardly toward lower slip support-58 to force lower slip6 54 out-wardly. Eventually, upper 81ips 28 and lower slips 54 are placed in gripping engagement with well bore 12 and packer elements 40 and 42 are in sealing engagement with the well bore. The action of upper slips 28 and 54 prevent packer 20 from being unset. As will be seen by those skilled in the art, pressure below packer 20 cannot force the packer out of -12~ .h "i. ,~i ~J '1,~

well bore 12, but instead, causes it to be even more tightly engaged.
In prior art drillable packers and bridge plugs of this type, mandrel 22 is made of a medium hardness cast iron, and lock ring housing 24, upper slip wedge 32, lower slip wedge 46 and lower slip support 58 are made o-f soft cast iron for drillability. Most of the other components are made of aluminum, brass or rubber which, of course, are relatively easy to drill. Prior art upper and lower slips 28 and 54 are made of hard cast iron, but are grooved so that they will easily be broken up in small pieces when contacted by the drill bit during a drilling operation.
As previously described, the soft cast iron construction of lock ring housing 24, upper and lower slip wedges 32 and 46, and lower slip support 58 are adapted for relatively high pressure and temperature conditions, while a majority o well applications do not require a design Eor such conditions. Thu~, the apparatu~ of the present invention, which is generally de~igned for pressures lower than 10,000 psi and temperatures lower than 425 F., utilizes engi-neering grade plastics ~or at least some of the components.
For example, one embodiment of the apparatus is designed for pressures up to about 5,000 psi and temperatures up to about 250 F., although the invention is not intended to be limited to these particular conditions.
In a first preferred embodiment, at least some of the previously soft cast iron components of the slip means, such -13- 2 3 ~

as the lock ring housing 24, upper and lower slip wedges 32 and 46 and lower slip support 58 are made o engineering grade plastics. In particular, upper and lower slip wedges 32 and 46 are subjected to substantially compressive loading. Since engineering grade plastics exhibit good strength in compression, they make excellent choices for use in components subjected to compressive loading. Lower slip support 58 is also subjected to substantially compressive loading and can be made of engineering grade plastic when packer 20 is subjected to relative low pressures and tem-peratures.
Lock ring housing 24 is mostly in compression, but does exhibit some tensile loading. However, in most situations, this tensile loading is minimal, and lock riny housing 24 may also be made of an engineering grade plastic of substan-tially the same type as upper and lower slip wedges 32 and 46 and also lower slip housing 58.
Upper and lower 91ips 28 and 54 may also be o plastic in some applications. Hardened inserts for gripping well bore 12 when packer 20 is set may be required as part of the plastic sl ip9 .
Lock ring housing 24, upper slip wedge 32, lower slip wedge 46, and lower slip housing 58 comprise approximately 75% of the cast iron of the prior art squeeze packers~
Thus, replacing these components with similar components made of engineering grade plastics will enhance the drillability of packer 20 and reduce the time and cost -14- c,~

required therefor.
Mandrel 22 is subjected to tensile loading during setting and operation, and many plastics will not be accep-table materials therefor. However, some engineering plastics exhibit good tensile loading characteristics, so that construction of mandrel 22 from such plastics is possible. Reinforcements may be provided in the plastic resin as necessary.
Example A packer 20 was constructed in which upper slip wedge 32 and lower slip wedge 46 were constructed by molding the parts to size from a phenolic resin plastic with glass rein-forcement. The specific material used was Fiberite 4056J
manufactured by Fiberite Corporation of Winona, Minnesota.
This material is classified by the manufacturer as a two stage phenolic with glass reinforcement. It has a tensile strength of 18,000 psi and a compressive strength of 40,000 psi .
The test packer 20 he:Ld to 8,500 psi without ailure to the wedyes, more than sufficient for most well bore con-ditions.
Drilling Out The Packer Apparatus Drilling out any packer apparatus 10, such as the illustrated packer 20, may be carried out by usi~g a stan-dard drill bit at the end of tubing string 16. Wire line drilling may also be used. With a standard "tri-cone" drill bit, the drilling operation is similar to that of the prior -15- ;~; s~

art except that variations in rotary speed and bit weight are not critical because the plastic materials are con-siderably softer than prior art cast iron, thus Jnaking packer 20 much easier to drill out. This greatly simplifies the drilling operation and reduces the cost and time thereof.
In addition to standard tri-cone drill bits, and par-ticularly if packer 20 is constructed utilizing engineering grade plastics for mandrel 22 as well as for lock ring housing 24, upper slip wedge 32, lower slip wedge 46 and lower slip housing 58, alternate types of drill bits may be used which were impossible for packers constructed substan-tially of cast iron. For example, polycrystalline diamond compact (PDC) bits may be used. Drill bit 14 in FIG. 1 is illustrated as a PDC bit. Such drill bits have the advan-tage of having no moving parts which can jam up. Also, if the well bore itself was drilled with a PDC bit, it is not necessary to replace it with another or dif~erent type bit in order to drill out packer 20.
While a speciEic squeeze packer configuration oE packing apparatus 10 has been described herein, it will be understood by those skilled in the art that other squeeze packers of this general configuration mentioned may also be constructed utilizing components selected of engineering grade plastics. Additionally, bridge plugs of this general configuration may also be manuEactured with plastic com-ponents.

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It will be seen, therefore, that the well bore packing packer apparatus and Tnekhods of drilling thereof o the pre-sent invention are well adapted to carry out the ends and advantages mentioned as well as those inherent therein.
While a presently preferred embodiment of the apparatus and various drilling methods have been discussed for the pur poses of this disclosure, numerous changes in the arrange-ment and construction of parts and the steps of the methods may be made by those skilled in the art. All such changes are encompassed within the scope and spirit of the appended claims.

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Claims (20)

1. A well bore process comprising the steps of:
positioning a well packing device into sealing engagement with the well bore;
prior to said step of positioning, constructing said device such that a component thereof subject to sub-stantially compressive loading is made of plastic; and drilling said device out of said well bore.

2. The process of claim 1 wherein said device is selected from a group comprising packers and bridge plugs.

3. The process of claim 1 wherein said component in said device is selected from a group comprising lock ring housings, slips, slip wedges and slip supports.

4. The process of claim 1 further comprising the step of constructing said device such that a component thereof subject to at least some tensile loading is made of plastic.

5. The process of claim 4 wherein said component sub-ject to tensile loading is a center mandrel of said device.

6. The process of claim 1 wherein said step of drill-ing is carried out with a polycrystalline diamond compact bit.

7. The process of claim 1 wherein said step of drilling is carried out using a drill bit without substan-tially varying weight applied to said drill bit.

8. A well bore process comprising the steps of:
positioning and setting a packer in said well bore, a portion of said packer being made of engineering grade plastic;

contacting said packer with well fluids; and drilling out said packer using a polycrystalline diamond compact bit.

9. The process of claim 8 wherein said step of con-tacting is at a temperature of less than about 250° F.

10. The process of claim 8 wherein said step of con-tacting is at a pressure of less than about 5,000 psi.

11. The process of claim 8 wherein said portion of said packer is one of a lock ring housing, slip, slip wedge, slip support, and mandrel thereof.

12. The process of claim 8 further comprising the step of, prior to said step of positioning and setting said packer, drilling at least a portion of said well bore using a polycrystalline diamond compact bit.

13. The process of claim 8 wherein said step of drilling is carried out without substantially varying weight applied to said bit.

14. A well bore packing apparatus comprising:
a center mandrel;
slip means disposed on said mandrel for grippingly engaging said well bore, said slip means comprising a slip wedge made of a plastic material; and packing means disposed on said mandrel for sealingly engaging said well bore when in a set position.

15. The apparatus of claim 12 wherein said slip means is an upper slip means disposed above said packing means and further comprising a lower slip means disposed below said packing means, said lower slip means comprising another slip wedge made of a plastic material.

16. The apparatus of claim 14 wherein said slip means comprises a lock ring housing made of a plastic material.

17. The apparatus of claim 14 wherein said slip means comprises a lower slip support made of plastic material.

18. The apparatus of claim 14 wherein said slip means comprises slips made of plastic material.

19. The apparatus of claim 14 further wherein said man-drel is made of a plastic material.

20. The apparatus of claim 14 wherein said plastic material is a glass reinforced phenolic resin.