Note: Descriptions are shown in the official language in which they were submitted.
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
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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
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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.
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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
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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
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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
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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
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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
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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.
-16~ r~;~
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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