U.S. patent application number 12/162083 was filed with the patent office on 2009-12-10 for remote plugging device for wells.
Invention is credited to Alexander Jeffrey Burns, Jonathan Paul Edwards.
Application Number | 20090301720 12/162083 |
Document ID | / |
Family ID | 38308779 |
Filed Date | 2009-12-10 |
United States Patent
Application |
20090301720 |
Kind Code |
A1 |
Edwards; Jonathan Paul ; et
al. |
December 10, 2009 |
REMOTE PLUGGING DEVICE FOR WELLS
Abstract
Remote cement plugging device (10) and method of use. The device
has at least one means (60) for perforating at least one hole
through a wall of a first well casing, and means to inject cement
into an annulus between the inner well casing and a second well
casing. The perforating means has at least one punch (65) actuated
by compressed fluid (hydraulic, pneumatic) to form the hole(s), and
thereafter the cement is delivered to the annulus between the inner
and outer/intermediate casings to form the cement plug without the
need to withdraw the device from the well casing.
Inventors: |
Edwards; Jonathan Paul;
(West Perth, AU) ; Burns; Alexander Jeffrey;
(Willetton, AU) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA, 101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Family ID: |
38308779 |
Appl. No.: |
12/162083 |
Filed: |
January 24, 2007 |
PCT Filed: |
January 24, 2007 |
PCT NO: |
PCT/AU07/00065 |
371 Date: |
December 1, 2008 |
Current U.S.
Class: |
166/281 ;
166/120 |
Current CPC
Class: |
E21B 43/112 20130101;
E21B 33/146 20130101 |
Class at
Publication: |
166/281 ;
166/120 |
International
Class: |
E21B 33/13 20060101
E21B033/13; E21B 33/12 20060101 E21B033/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 24, 2006 |
AU |
2006900347 |
Claims
1. A remote plugging device for well operations, including at least
one perforating means for perforating at least one hole through one
or more casings of a well, and sealant injection means to inject
sealant into an annulus between at least one of said one or more
well casings and at least another of said well casings or a further
well casing, wherein the perforating means includes at least one
punch actuated by pressurised fluid to perforate the at least one
hole, and thereafter the sealant is delivered to the annulus to
form a sealant plug without need to withdraw the device from the
one or more well casings.
2. A device as claimed in claim 1, wherein the at least one punch
is actuated by hydraulic or pneumatic pressure.
3. A device as claimed in claim 1, wherein the at least one punch
is extended and retracted by at least one double acting hydraulic
or pneumatic piston.
4. A device as claimed in claim 1, wherein the at least one punch
is extended by hydraulic or pneumatic pressure and retracted by at
least one resilient biasing means.
5. A device as claimed in claim 4, wherein the at least one
resilient biasing means includes at least one return spring.
6. A device as claimed in claim 1, further including an outlet for
sealant flow provided adjacent one of said at least one perforation
means.
7. A device as claimed in claim 1, further including at least one
packer assembly whereby, when the device is inserted into the well,
the at least one packer assembly is expanded to hold the device by
pressure against a bore of the one or more well casings.
8. A device as claimed in claim 7, including a fluid pressure
accumulator provided within or proximate to a leading nose end of
the device, the accumulator providing fluid pressure to the at
least one packer assembly in the event of a failure of the
device.
9. A device as claimed in claim 7, wherein the at least one packer
assembly is actuated by compressed or pressurised fluid.
10. A device as claimed in claim 9, wherein the compressed or
pressurised fluid is a hydraulic or pneumatic supply.
11. A device as claimed in claim 1, wherein said at least one punch
includes a breakaway shaft such that in the event of the punch
being jammed in the hole, the punch can be positively retracted and
a working end of the punch sheared off.
12. A device as claimed in claim 1, wherein the at least one
perforation means includes at least one resilient packer that
absorbs shock induced on the punch when the casing is
perforated.
13. A device as claimed in claim 12, wherein the at least one
resilient packer is formed of silicon rubber, rubber, nitrile,
PEEK, UHMPE, HFPE, Nylon, other ultra high density synthetic
material, or combinations thereof.
14. A device as claimed in claim 1, wherein the perforation means
is arranged to consecutively perforate holes through a multiplicity
of well casings of said one or more well casings, and the sealant
is arranged to be injected between at least one of said
multiplicity of well casings and said further well casing.
15. A method of sealing a well riser, including the steps of: a)
inserting a remote plugging device into a riser; b) supplying
pressurised fluid to the plugging device; c) perforating at least
one hole through at least a first well casing wall using at least
one respective punch actuated by the fluid; and d) pumping a
sealant through said at least one hole into an annulus between the
first casing wall and an outer casing or an intermediate casing to
form a plug seal.
16. A method as claimed in claim 15, wherein the sealant contains
cement or drilling mud.
17. A method as claimed in claim 15, further including the step of
retracting the at least one punch by hydraulic or pneumatic
pressure, or by using at least one resilient biasing means.
18. A method as claimed in claim 15, further including retaining at
least one said at least one punch extended after perforating the
casing.
19. A method as claimed in claim 15, wherein: the step of
perforating said at least one hole includes perforating through a
multiplicity of well casing walls including said first well casing
wall; and the pumping step includes injecting the sealant into the
annulus being between at least one of said multiplicity of well
casing walls and said outer casing or said intermediate casing.
20. A method as claimed in claim 15, further including utilising at
least one packer to provide an initial seal between the device and
the first well casing against hydrocarbon leakage prior to pumping
sealant into the at least one hole.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the plugging of hydrocarbon
wells, particularly subsea hydrocarbon wells, when barriers must be
maintained between the hydrocarbon formation and the surface to
prevent hydrocarbon contamination by leakage from the well.
BACKGROUND OF THE INVENTION
[0002] In the field of subsea oil and gas production there are
regulations that require barriers to be maintained between the oil
and/or gas formation and the surface.
[0003] During abandonment of subsea wells the barrier system must
be maintained to ensure that any residual oil or gas in the
formation does not dissipate from the well leading to a potential
pollution event, with the associated environmental and social
impact.
[0004] Barrier systems for offshore wells consist of active and
passive systems, with the passive systems a physical barrier is
maintained between the formation and the seabed. Active systems are
designed then in the case of an emergency or in unforeseen
circumstance the active system deploys to provide a barrier between
the formation and the seabed.
[0005] When abandoning an offshore well the use of active systems
to maintain the barriers between the seabed and the formation is
not suitable as there will be no ongoing maintenance of the
barrier. Further during removal of the well head of the subsea well
one of the barriers covering the annulus between the inner casing
and the first intermediate casing is removed and needs to be
replaced prior to severing the well head.
[0006] One way of maintaining the barriers during abandonment of a
subsea well is the use of cement. A cement plug is cast into the
central casing and cement is injected into the annulus between the
central casing and the first intermediate casing. To pump the
cement into the annulus it is first necessary to provide a pathway
for the cement to travel from the central casing into to the
annulus. This is usually done by the use of explosives to puncture
holes in the central casing through to the annulus.
[0007] When a subsea well is abandoned the use of a jack up oil
rig, work barge or semi submersible has traditionally been used.
With the use of these types of vessel, the production of holes in
the casing through to the annulus is usually by the use of
explosives. There are several issues with the use of explosives not
least of which is the safety aspects. Further a large stable
platform must be provided so that explosives can be safely
handled.
[0008] The existing methods for subsea intervention and abandonment
of wells have some inherent disadvantages including the use of
large vessels so that explosives can be used, these vessels tend to
be slow moving, take a relatively long time to reach offshore oil
and gas fields and are expensive to operate while on station.
[0009] In order to alleviate problems of the cost and time taken to
get a large work platform on a station, the use of a work boat is
desired. Problems with using a work boat arise when using
explosives, so alternative methods and means of providing holes in
the casing and injecting cement are required.
[0010] The reference to any prior art in this specification is not,
and should not be taken as, an acknowledgement of any form of
admission that the prior art forms part of the common general
knowledge in Australia.
SUMMARY OF THE INVENTION
[0011] With the aforementioned in mind, in one aspect the present
invention provides a device for oil field operations including
means for perforating holes in a wall of a first well casing and
means for injecting sealant into an annulus between the first well
casing and a second well casing,
[0012] including at least one punch assembly, a cutting tool the
cutting tool being designed to produce a hole in the casing and a
sealant delivery means.
[0013] wherein the tool is able to perforate the holes and deliver
sealant to the annulus without the need to withdraw the tool from
the well casing.
[0014] A further aspect of the present invention provides a remote
plugging device for well operations, including at least one
perforating means for perforating at least one hole through one or
more well casings, and sealant injection means to inject sealant
between at least one of said one or more well casings and at least
another of said well casings or a further well casing,
[0015] wherein the perforating means includes at least one punch
actuated by pressurised fluid to perforate the at least one the
hole, and thereafter the sealant is delivered to the annulus to
form the sealant plug without the need to withdraw the device from
the well casing.
[0016] In another preferred embodiment the device and ancillary
equipment is adapted for deployment from a work boat for use in
subsea applications.
[0017] Another aspect of the present invention provides a remote
plugging device for well operations, including at least one
perforating means for perforating at least one hole through a wall
of a first well casing, and injection means to inject a sealant
into an annulus between the first well casing and a second well
casing,
[0018] wherein the perforating means includes at least one punch
actuated by compressed fluid to perforate the at least one the
hole, and thereafter the sealant is delivered to the annulus to
form the sealant plug without the need to withdraw the device from
the well casing.
[0019] Preferably the sealant is cement based, or may be a none
setting medium such as drilling mud.
[0020] Actuation of the punch(s) by compressed fluid advantageously
avoids the need for explosive charges to effect perforation.
[0021] The at least one punch may be actuated by hydraulic or
pneumatic pressure.
[0022] The at least one punch may be extended or retracted by at
least one double acting hydraulic or pneumatic piston, which
provides positive actuation and retraction to assist in ensuring
that the perforator(s) is/are retracted so that the sealant can
flow through the perforation(s). Alternatively, the at least one
punch may be extended by hydraulic or pneumatic pressure and
retracted by at least one resilient biasing means, which simplifies
the means of return actuation, such as by return spring(s).
[0023] Preferably there may be one or more outlet/ports for sealant
flow provided adjacent at least one of said at least one
perforation means. This helps to ensure that sealant flow readily
reaches the perforation(s) and reduces the overall amount of cement
required.
[0024] At least one packer assembly may be provided, whereby, when
the packer assembly or assemblies is/are expanded to hold the
device by pressure inside the well casing e.g. by pressure against
an interior wall of the inner casing of the well. Such packers may
be energized by hydraulic or pneumatic pressure.
[0025] Alternatively or in addition, packers may be provided which
are self energizing. These may expand as a result of initial
pressure from a pressurized fluid supply line (e.g. from the
surface) or from hydrocarbon escaping through at least one hole
made by the device. The applied pressure causes the packers to seal
the device within the bore prior to the sealant being pumped into
the hole(s).
[0026] The device may include at least one fluid pressure
accumulator, preferably hydraulic or pneumatic accumulator(s),
within or proximate to a leading nose end of the device, the
accumulator providing fluid pressure to the at least one packer
assembly in the event of a failure of the device. Fluid pressure
may be supplied from the hydraulic or pneumatic supply used to
actuate the perforation means.
[0027] At least two of the perforation means may be spaced apart
such that the distance between a first punch of a first perforation
means and a first punch of a second perforation means is greater
than a length of coupling members used to couple together lengths
of well casing.
[0028] One or more of the punches may have a breakaway shaft such
that in the event of the punch being jammed in the perforated hole,
the piston and base of the punch can be positively retracted and a
working end of the punch sheared off.
[0029] At least one of the punches may be retained to the piston by
a quick release means, such as by a quick release ring, clip or
other retainer.
[0030] At least one resilient packer may be provided which absorbs
shock induced on the respective punch during perforation of the
casing. Silicon rubber, rubber, nitrile, or the like, or
combinations thereof may be used.
[0031] The perforating means may be adapted to perforate
consecutive holes through multiple casing walls, one after the
other. That is, where the well has multiple casings one within
another, the perforator may, for example, perforate a hole through
more than one casing to set a sealant (e.g. cement) plug between
the first and/or second and third concentric casings.
[0032] A further aspect of the present invention provides a method
of sealing a well riser, including the steps of;
[0033] a) inserting a remote plugging device into a riser;
[0034] b) supplying compressed fluid to the plugging device;
[0035] c) perforating at least one hole through at least a first
well casing using at least one respective punch actuated by the
compressed fluid; and
[0036] d) pumping a sealant through said at least one hole into an
annulus between the at least one first casing and a second or
intermediate casing to form a plug seal.
[0037] The method may further include the steps of perforating one
or more holes with a respective at least one punch, and leaving at
least one said punch extended to act as an anchor for the device.
Thus, one or more punches may remain unretracted to anchor the
device. There can be significant hydrocarbon pressure on the device
when a hole is perforated through the casing, and the unretracted
punch(es) may act as a secondary lock to hold the device in place.
Also, in the event that the device needs to be abandoned within the
well for any reason, this anchoring arrangement can assist in
maintaining the device in place. An accumulator may be employed to
provide sufficient pressure to maintain the at least one punch
extended. A one way or check valve may be employed to prevent
pressure loss once the hydraulic or pneumatic feed is removed from
the device.
[0038] The method may include withdrawing the at least one punch
from at least one respective hole. However, it is envisaged that
the device may pump fluid around, through, or a combination
thereof, the at least one punch; Hydraulic fluid may be used to
actuate the punch(s). Preferably the sealant contains cement.
[0039] Retraction of the at least one punch may be by hydraulic or
pneumatic pressure. Alternatively, extending the at least one punch
may be by hydraulic or pneumatic pressure and retraction by
resilient biasing means.
[0040] Perforating said at least one hole may be through a
multiplicity of well casing walls, and injecting the sealant into
the annulus between at least one of said multiplicity of walls and
a further casing wall.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 shows an overview of an embodiment of the device.
[0042] FIG. 2 shows a section of the entry nose and lower packer
assembly of the embodiment shown in FIG. 1.
[0043] FIG. 3 shows a section of hydraulic punch assembly of the
embodiment shown in FIG. 1.
[0044] FIG. 4 shows the lower perforation tool of FIG. 1 in more
detail.
[0045] FIG. 5 shows an alternative embodiment of the device.
[0046] FIG. 6a shows a sectional view of an alternative embodiment
of the device including spring return hydraulic pistons.
[0047] FIG. 6b shows a perspective view of the complete device of
FIG. 6a.
[0048] FIG. 7a is a perspective view of a perforation assembly of
an embodiment of the present invention.
[0049] FIG. 7b is a sectional view of the embodiment shown in FIG.
7a.
DETAILED DESCRIPTION
[0050] The invention will now be described with reference to the
accompanying figures. Referring first to FIG. 1 that shows an
overview of the remote plugging device herein after referred to as
the "tool". Whilst cement is referred to hereinafter as the
sealant, it will be appreciated that other sealants may be
employed, such as drilling mud.
[0051] The construction of the tool 10 is based on modular
construction methods so that individual components can be replaced
if they are damaged during an offshore campaign. Other possible
arrangement of the components are possible provide that they allow
for the operation of the tool 10 such that the casing is perforated
and cement is injected into the annulus. Only a typical example is
described in the following detailed description.
[0052] The overall layout of the tool 10 includes of an entry nose
20 at a leading end 25, designed to allow the cement injection tool
10 to be inserted into a subsea well. The entry nose 20 is
connected to a lower packer mandrel 30 that has a packer assembly
40 fitted. This packer assembly 40 is designed so that when the
tool 10 is inserted into the inner casing of the subsea well, the
packer assembly 40 can expand and hold the tool 10 in place and
seal the tool 10 in the casing. The lower packer mandrel 30 is
connected to a hydraulic module 50 at the hydraulic module first
end 52.
[0053] The hydraulic module 50 consists of a number of punch
assemblies 60 with punches 65. The punch assemblies 60 are arranged
circumferentially around the hydraulic module 50 and are designed
so that they can punch holes in the inner casing. It will however
be appreciated that at least one said punch may be used to
perforate through more than one casing wall, such that sealant can
be pumped into the annulus or cavity between further casings e.g.,
between the inner and intermediate casing, and between the
intermediate casing and an outer casing.
[0054] At the hydraulic module second end 54, there is a cement
exit port 75. At the hydraulic module second end 54 there is an
upper packer mandrel 80 which includes a packer assembly 90 to seal
the tool 10 into the well inner casing attached to the second end
81 of the upper packer mandrel 80 there is a breakaway barrier 70.
On the upper most portion of the tool 10, there is a hydraulic hose
guide 100 and lifting points 110 connecting the cement injection
tool 10 by a lifting cable and hydraulic and services lines to the
boat.
[0055] As shown in more detail in FIG. 2, the entry nose 20 is
designed with a taper 22 at the leading end thereof to allow for
positioning the tool in a subsea well and to guide the tool 10 in
to the well inner casing during deployment of the tool 10. The
entry nose 20 has also been designed to incorporated a hydraulic
accumulator 25. The hydraulic accumulator 25 is used to provide
hydraulic pressure to the packer assemblies 40, 90 in the event of
a failure in the tool 10 necessitating abandonment of the tool 10
in the well. The hydraulic accumulator 25 allows for the tool 10 to
act as a barrier in the event that the tool 10 needs to be
abandoned. The entry nose 20 may be held by a threaded portion 28
to the first end 31 lower packer mandrel 30.
[0056] The lower packer mandrel 30 is generally hollow but could be
made of a range of materials or densities to provide the desired
buoyancy characteristics of the tool 10. The packer assembly 40
associated with the lower packer mandrel 30 is designed that once
subjected to a hydraulic pressure, the packer assembly 40 can
expand and seal against the inner casing. The pressure that can be
applied to the packer assembly 40 is approximately 5000 psi, but
could be more on some applications. At the second end 32 of the
lower packer mandrel 30 there is packer mandrel threaded portion 33
that connects the lower packer mandrel 30 to the hydraulic module
50 at the hydraulic module first end 52.
[0057] The hydraulic module 50 is the module that contains active
hydraulic components and the tooling required to perforate holes
through the well inner casing. The hydraulic module 50 includes at
least one hydraulic punch assembly 60, though there may be as many
as ten or more hydraulic punch assemblies 60. The spacing and
orientation of the hydraulic punch assemblies 60 is such that holes
can be perforated through the inner casing in different locations
around the circumference of the inner casing and in different
positions vertically along the inner casing.
[0058] In a preferred embodiment, the punch assemblies 60 are
spaced apart such that the distance between a first punch 62 and
second and subsequent punches 65 is greater than the length of the
coupling members not shown normally used to couple lengths of well
casing together. This is so that when the tool 10 is inserted into
an inner casing holes can still be perforated even if one punch
assemblies 60 is behind a coupling member, the remaining punch
assemblies 60 will not coincide with the coupling members and
therefore will able to perforate the inner casing.
[0059] At the second end of the upper punch mandrel 82 there is a
breakaway barrier 70. This breakaway barrier 70 is designed such
that should the device need to be abandoned in the well due to
unforeseen circumstances, the well remains plugged such that the
contents of the well will not leak. The breakaway barrier 70 has
hydraulic lines and coupling check valves connected so that in the
event of a breakaway event, the hydraulic pressure in the packer
assemblies 40 90 remains constant, thus, ensuring that the packer
assemblies 40 90 are held firmly in place against the inner casing.
The breakaway barrier 70 is designed to have locking pins to take a
predetermined load. These locking pins are designed to have
sufficient strength that the tool 10 can be extracted from the
inner casing even with residual cement surrounding the hydraulic
module 50 yet can be broken away in the event that the tool 10 must
be abandoned. A typical breakaway load is 25 tons but this load
could be varied depending on the application of the tool 10.
[0060] The breakaway barrier 70 also includes a check valve on the
sealant line that may be actuated by hydraulic pressure or
automatically actuated (e.g. by spring loaded pressure). This check
valve may be located in the upper packer mandrel 80 the check valve
can be a normally closed check valve that is actuated by hydraulic
pressure, or pneumatic pressure.
[0061] The tool may be provided with a number of lines that
communicate with the vessel (not shown). These lines will include
hydraulic, control, monitoring and bypass lines. These line allow
for the tool 10 to be operated from the vessel and parameters such
as the pressure in the well can be monitored.
[0062] Referring now to FIG. 3, the hydraulic punch cylinder
assemblies 60 include two way hydraulic pistons 61 capable of at
least 5000 psi or more, though the upper pressure limit may vary
depending on the expected loads required to perforate the casing.
The hydraulic pistons are fitted with punches 65 used to perforate
the inner casing. The two-way piston is selected to ensure that the
punch 65 can be retracted once a hole has been perforated in the
inner casing. The two way type of hydraulic punch assembly includes
a hydraulic feed 69 to provide hydraulic pressure to retract the
piston
[0063] The punch 65 is manufactured of a tool steel and is used to
punch holes in the inner casing. The punch 65 is designed with a
breakaway shaft 66 so that in the event of the punch 65 being
jammed in the perforated hole in the inner casing the hydraulic
piston 61 can be positively retracted and the punch 65 sheared. The
punch 65 is held into the punch piston assemblies with a quick
release ring 67. This quick release ring can be removed to allow
for field removal and replacement of the punch 65 in the situation
where multiple wells are being abandoned and a punch 65 requires
replacement. In the case of punches used for anchoring the device,
these would preferably be non-breakaway punches, such that the
punches remain extended to hold the device in place.
[0064] Behind the quick release ring 67 is a resilient packer 68
that acts to absorb the shock induced on the punch 65 when the
holes are produced. The resilient packer 68 may be made out of a
range of materials capable of absorbing a shock load. Preferred
materials are ultra high molecular weight synthetic materials, such
as PEEK, UHMPE, HFPE, or Nylon etc, or other water stable dense
synthetic materials.
[0065] In an alternate embodiment, the hydraulic pistons 61 are not
two way hydraulic pistons but use the pressure of the cement or
formation to retract the hydraulic pistons 61 once the holes have
been punched. In a possible variation the use of spring actuated
hydraulic pistons may be used when the tool 10 is intended to be
abandoned in the well.
[0066] FIG. 4 shows the hydraulic module 50 of the lower
perforation tool of FIG. 1 in more detail. The module that contains
active hydraulic components and the tooling required to perforate
holes through the well inner casing. The hydraulic module includes
at least one hydraulic punch assemblies 60, and one of the cement
feed outlets 75.
[0067] FIG. 5 shows an alternative embodiment of the device
including first 60a and second 60b lower perforation assemblies,
and first 60c and second 60d upper perforation assemblies. These
are connected via a cable link 110 of variable length "D" to suit a
particular application. Upper cup packer 112a and lower cup packer
112b are provided. These act to provide a seal between the device
and the casing wall to prevent cement from flowing beyond the
packer. They also provide a pressure seal if hydrocarbons present
after perforating would otherwise leak out.
[0068] Upper and lower bore supply ports 114 are provided. These
ports supply cement respectively to the upper and lower sections of
the device.
[0069] FIGS. 6a and 6b shows a further embodiment including single
acting spring biased hydraulic punches 65a-65d. The punches are
hydraulically extended to create holes through the inner casing of
the bore, and are biased by spring pressure to the retracted
position shown in the figures.
[0070] FIGS. 7a and 7b show one of the hydraulic perforation
assemblies 60. FIG. 7a is a perspective view of the assembly with a
punch 65. In sectional view FIG. 7b of the assembly 60, with the
hydraulic piston 61b retracted within the body 61a of the assembly.
The punch 65 is retained in place by a screw fit ring 120 analogous
to the quick release ring in FIG. 3. Grub screws 122a and 122b
retain the hydraulic cylinder 61a within the casing 124.
[0071] A hydraulic release shackle 116 is provided (analogous to
the breakaway system previously described), which allows the device
to be completely uncoupled i.e. in the event that the device
becomes unrecoverable from the well. Annulus bore pressure
monitoring and bleed off ports are provided.
[0072] In operation the cement injection tool 10 is lowered from a
vessel 1 and with the assistance of divers or an ROV is positioned
into the inner casing of a subsea well. Once the cement injection
tool 10 is lowered and is positioned, hydraulic pressure is applied
forcing the packer assemblies 40, 90 to lock the cement injection
tool 10 against the inner casing walls. The packers are then tested
to ensure there are no leaks. Hydraulic pressure is then applied to
each of the punch assembly 60 in turn resulting in a series of
holes being perforated in the inner casing. Any pressure from the
annulus is then bled off in a controlled manner either into the sea
or into a tank on the vessel. Ideally the hole punching will result
in multiple holes being punched in the inner casing, the holes
being evenly distributed around the circumference and along a
length of the inner casing.
[0073] Once the holes in the inner casing have been perforated, a
cement inhibitor is injected to inhibit the setting of the cement
in the crevices and joints surrounding the packer assemblies and
the punch assemblies. The inhibitor is injected through the cement
injection port 54, it then travels down past the hydraulics in the
hydraulic module 50.
[0074] After the inhibitor has been injected, cement is injected
through the cement injection port 54 and flows around the hydraulic
module 50 and through the holes punched in the inner casing into
the annulus between the inner casing and the first intermediate
casing. Once the cement is injected into this annulus and pressure
tested, the packer assemblies are released and the cement injection
tool 10 is extracted.
[0075] The punch assembly 60 includes hydraulics specifically
designed for this application, which include a double acting
hydraulic piston 61 (positive displacement and retraction piston).
This is designed so that the punch 65 can be forcibly retracted
from the inner casing in the event of a problem. The punch 65 is
inserted into a hydraulic ring and is held in place by a shock
absorbing ring 66 and a punch retaining member 67.
[0076] Variations and modifying are possible to the tool 10 that
will still fall with the scope of the invention.
* * * * *