U.S. patent application number 13/510307 was filed with the patent office on 2012-09-13 for external casing packer.
Invention is credited to Ian Gray.
Application Number | 20120227969 13/510307 |
Document ID | / |
Family ID | 46794476 |
Filed Date | 2012-09-13 |
United States Patent
Application |
20120227969 |
Kind Code |
A1 |
Gray; Ian |
September 13, 2012 |
External Casing Packer
Abstract
A method and apparatus for cementing a zone of borehole casing
using an external casing packer (ECP). The method involves sealing
the base of the ECP with a ball dropped in a seat, and then
pressurising the casing to inflate an elastomeric packer sleeve
through a one-way valve. When a design differential pressure is
reached across the casing and elastomeric sleeve, a grout valve in
the upper part of the packer opens to limit the sleeve inflation
pressure and to provide a one-way valve through which cement grout
passes to permit grouting of the annulus between the casing and the
borehole.
Inventors: |
Gray; Ian; (Coorparoo,
AU) |
Family ID: |
46794476 |
Appl. No.: |
13/510307 |
Filed: |
November 19, 2010 |
PCT Filed: |
November 19, 2010 |
PCT NO: |
PCT/AU2010/001548 |
371 Date: |
May 17, 2012 |
Current U.S.
Class: |
166/285 ;
166/118 |
Current CPC
Class: |
E21B 21/103 20130101;
E21B 33/14 20130101; E21B 33/1277 20130101; E21B 33/127
20130101 |
Class at
Publication: |
166/285 ;
166/118 |
International
Class: |
E21B 33/13 20060101
E21B033/13 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2009 |
AU |
2009905659 |
Claims
1. A method of cement grouting an annulus between a casing and a
borehole using an inflatable packer system, comprising: placing a
casing with an external casing packer attached thereto at a
location in a borehole for cement grouting a portion of the
borehole annulus that is located above the external casing packer;
inflating an inflatable elastomeric sleeve of the external casing
packer to block the annulus of the borehole by pressurising the
casing with an inflation fluid, which opens a one-way inflation
valve in the external casing packer with the pressurised inflation
fluid and inflates the inflatable sleeve to a preset pressure;
determining the preset pressure by a pressure relief valve located
between the external casing packer and the annulus which opens at
the preset pressure and then becomes a one-way grout valve; pumping
a liquefied cement grout mixture down through the casing via the
open one-way grout valve which is located in the external casing
packer above a portion of the inflated inflatable sleeve; and
biasing the grout valve to a closed position using an elastomeric
member attached to the packer, whereby when the pressure of the
cement grout mixture is reduced in the casing, the elastomeric
member causes the grout valve to close and prevent backflow of the
cement grout mixture from the annulus back into the casing.
2. The method of claim 1, further including rupturing or shearing a
portion of the grout valve at a given pressure to open the grout
valve and permit a pressure drop in the casing.
3. The method of claim 2, further including using the pressure drop
in the casing to maintain closure of the sleeve inflation
valve.
4. The method of claim 1, further including pressurising the casing
to open the one-way inflation valve and inflate the inflatable
sleeve, and using the pressurised casing to shear an element of the
grout valve to allow the grout valve to open when the inflatable
sleeve is inflated.
5. The method of claim 1, further including biasing the grout valve
to a closed condition by the elastomeric member, by using an
elastomeric sleeve member which both encircles the packer and is
attached to a movable part of the grout valve.
6. The method of claim 1, further including fabricating the
elastomeric sleeve of the grout valve as part of the inflatable
elastomeric sleeve, whereby when the grout valve is opened the
elastomeric sleeve member stretches radially outwardly.
7. The method of claim 5, further including bonding a portion of
the elastomeric sleeve of the grout valve to a mandrel of the
packer and bonding the elastomeric sleeve of the grout valve to a
chamfered grout valve member, which is the movable member of the
grout valve.
8. The method of claim 5, further including forming the elastomeric
sleeve member as a unitary part of the inflatable elastomeric
sleeve during one manufacturing process.
9. The method of claim 1, further including using a sleeve of an
elastomeric material as a flap member of the non-return inflation
valve, and bonding one annular edge of the elastomeric flap member
sleeve to the mandrel of the packer, allowing another annular edge
of the sleeve of elastomer material to be free for lifting off of
respective ports in the mandrel to permit one-way fluid flow.
10. A method of setting an external casing packer in an annulus of
a borehole to fix a casing therein, comprising: sealing a base of
the packer; pressurising the packer to inflate an inflatable
elastomeric sleeve surrounding a portion of a packer mandrel by
passing a pressurised fluid through a one-way inflation valve into
the inflatable sleeve; limiting the inflation pressure of the
inflatable sleeve by using a pressure relief valve in the packer
which relieves the pressure in the packer to the outside of the
casing when a design differential pressure is reached; using the
pressure relief valve as a one-way valve to permit a grout material
to flow therethrough to the annulus of the borehole; and closing
the pressure relief valve to prevent a backflow of the grout
material from the annulus back into the packer.
11. A method according to claim 10 whereby the base of the packer
is sealed by dropping a ball into a seat located in the base of the
packer.
12. A method of cement grouting a borehole using an inflatable
packer system, comprising: lowering into a borehole a casing with
the inflatable packer system attached thereto; pressurising the
casing with a fluid so that the pressurised fluid enters one or
more one-way inflation valves in the packer system to inflate a
sleeve and obstruct an annulus of the borehole; increasing the
pressure of the fluid in the casing until one or more one-way
frangible grout valves rupture to allow pressurised fluid to enter
the borehole annulus above the packer system, whereby the pressure
of the casing drops and the one-way inflation valves close and
maintain the inflation of the sleeve in the borehole annulus;
pumping cement grout down through the casing and through the
ruptured one-way grout valves into the portion of the borehole
annulus located above the packer system.
13. The method of claim 12, further including pumping a
predetermined volume of the cement grout down the casing and into
the borehole annulus, and then stopping the pumping of the cement
grout, whereby the one-way grout valves close and prevent a
backflow of the cement grout from the annulus back into the
casing.
14. The method of claim 12, further including sealing the base of
the packer system before pumping the cement grout down the casing
to prevent the cement grout from passing into a perforated portion
of the casing below the packer system.
15. The method of claim 13, further including forcing a plug down
through the casing after the predetermined volume of cement grout
has been pumped down the casing, to clear at least a portion of the
cement gout from the casing and force the same through the one-way
grout valves and into the borehole annulus.
16. The method of claim 15, further including drilling the portion
of the cement grout that has set in the packer system to provide a
flow path of production fluid from the bottom of the borehole to
the top of the casing.
17. The method of claim 12, further including forming an
elastomeric sleeve around a mandrel body of the packer system,
where an annular top portion of the sleeve is anchored and scaled
to the mandrel, and a bottom portion of the sleeve is slideable
along and sealed to the mandrel as the sleeve is inflated.
18. The method of claim 17, further including forming a portion of
the elastomeric sleeve over the one-way grout valves so that
elasticity of the sleeve moves the one-way grout valves into closed
positions in respective ports formed in the mandrel.
19. The method of claim 17, further including anchoring the top
portion of the sleeve to the mandrel using a retaining ring which
clamps the sleeve around the mandrel, and forming the one-way
inflation valves by using an elastomeric flapper which covers
respective ports formed in the mandrel, where the flappers are
anchored at one end thereof to the mandrel under the retaining
ring.
20. An inflatable packer system for grouting a borehole annulus,
said packer system comprising: a mandrel forming a body of the
packer system, said mandrel adapted for attachment to a casing,
said mandrel having formed therein one or more ports for respective
grout valves, and one or more ports for respective inflation
valves; a seat formed in a bottom part of said mandrel, said seat
adapted for being blocked by a ball dropped down the easing; an
elastomeric sleeve formed around the mandrel and around the
inflation valve ports; an anchor seal formed at a top portion of
the elastomeric sleeve around the mandrel above the inflation valve
ports and below the grout valve ports; a sliding seal formed at a
bottom portion of the elastomeric sleeve along said mandrel; one or
more one-way inflation valves, each said one-way inflation valve
located over one said inflation valve port, each said one-way
inflation valve adapted for allowing an inflation fluid to pass
through the inflation valve port and into the elastomeric sleeve,
but not in a reverse direction; one or more one-way grout valves,
each said one-way grout valve located over one said grout valve
port, each said one-way grout valve adapted for allowing a cement
grout to pass through the grout valve port and into the borehole
annulus, but not in a reverse direction; and each said one-way
grout valve formed with a frangible member which breaks in response
to a predetermined inflation fluid pressure, whereby when said
elastomeric sleeve is inflated to the predetermined fluid pressure
the frangible members break to enable operation of the one-way
grout valves, and the one-way inflation valves close to allow the
elastomeric sleeve to maintain the predetermined inflation fluid
pressure.
Description
RELATED PATENT APPLICATION
[0001] This PCT application claims the benefit of two Australian
provisional applications, both filed on 19 Nov. 2009, and accorded
respective application numbers 2009905659 and 2009905660. The
disclosures of the Australian provisional patent applications are
incorporated herein by reference.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates in general to the field of
completing hydrocarbon or water wells, and more particularly to
methods and apparatus for manufacturing inflatable packers, and
sealing the base of a casing by cement grouting the annulus above
the packer, while not damaging the underlying borehole with
grout.
BACKGROUND OF THE INVENTION
[0003] The conventional process to install a casing in a borehole
is to first drill a borehole, install a casing therein, and cement
the casing in place. The borehole can then be extended beyond the
bottom of the casing by drilling a smaller size hole, which usually
occurs in the production zone. The cementing process usually
involves pumping cement through the casing and out of the bottom
thereof, and up into the annulus between the casing and the
borehole. The cement is displaced downwardly and out of the casing
by pumping a drilling fluid or water into the top of the casing. A
cement displacement plug is normally used to separate the water
from the cement in the casing. Sometimes a float shoe (one way
valve) is attached to the bottom of the casing so as to avoid the
need to hold pressure within the casing while the cement in the
annulus sets.
[0004] An alternative process is to drill the borehole to final
gauge and depth, and then run the casing with an external packer
attached in the casing string or to the end thereof into the
borehole. A port at the base of the external casing packer is
closed and the casing is pressurised to set the packer. Cementing
ports are then opened above the packer, cement is pumped through
the casing ports and into the annulus to cement the casing in
place. At the end of the cementing process a displacement plug is
run down the casing and the cement is displaced out of the casing
and into the annulus. The cementing ports are then closed. The
casing is then free of cement and the annulus is cemented within
the borehole. The normal process is then to run a drill string and
drill bit back into the casing to drill out any cement remaining in
the packer, drill out the cement displacement plug and the bottom
port to clean out the borehole below the packer. In existing
external casing packers, the bottom port is usually blocked by a
ball dropped into the casing. The cementing ports are actuated by
either rotating, raising or lowering the casing or by dropping
balls or darts of different sizes into the casing to move sliding
annular seals.
SUMMARY OF THE INVENTION
[0005] The external casing packer according to the various
embodiments described herein is referred to at times as "ECP." The
operation of the ECP is however simpler than existing packer
systems. The manufacture is also simpler and more cost effective
than other packer devices currently available.
[0006] The external casing packer, according to the invention, is
attached to the outer cylindrical surface of the casing, with the
casing extending above and in some cases below the ECP. A
non-return valve is fitted in the base of the ECP, which permits
fluid to enter the casing from the borehole during lowering of the
casing into the borehole, but prevents the reverse flow of liquids
from the casing down into the borehole. In its simplest form, the
non-return valve is a port formed or installed in the base of the
ECP, and is sealed by a ball that is dropped into the casing from
surface. The ball seats in the port in a conventional manner in the
base of the ECP. Such a system enables flow in and out of the
casing until the ball is dropped. Alternative non-return valve
arrangements may be used, such as a wire line retrievable plug, or
a one-way valve such as a float shoe.
[0007] Once the one-way valve in the base of the ECP is actuated,
the casing is pressurised to inflate an elastomeric sleeve of the
ECP. The inflation of the sleeve is achieved by use of a non-return
inflation valve system located between the casing and the ECP
sleeve. As the pressure in the casing is raised, an elastomeric
sleeve of the ECP inflates to expand and engage the annular wall of
the borehole. At a preset pressure in the casing, frangible grout
valves constructed within the mandrel of the ECP are actuated to
open and to subsequently allow a cement grout mixture to be pumped
through the grout valves to the portion of the annulus located
above the ECP. The grout valves are constructed to function as a
combination of a burst or shear disk, and a non-return check valve.
With the failure of the burst or shear disk in the grout valve
during the sleeve inflation process, the pressure inside the casing
drops so that the ECP sleeve no longer inflates through the
non-return inflation valve, as the pressure in the ECP sleeve
exceeds that in the casing. The fracturing and the opening of the
grout valves thus functions as a relief valve to prevent
over-inflation of the elastomeric sleeve. Thus, the preset pressure
to which the casing is pressurised is relative to the point at
which the frangible grout valve discs break, and to the desired
pressure to be maintained in the elastomeric sleeve.
[0008] At this stage of the process, the inflation valve is closed
and the grout valve of the ECP is activated and opened, whereupon a
cement grout mixture is pumped down through the casing. The cement
grout mixture flows down the casing and pushes the grout valves
open. The cement grout then flows through the grout valves and into
the annulus between the casing and the wall of the borehole, in the
annulus area above the ECP. When the required volume of cement
grout has been pumped down the casing, a cement displacement plug
is introduced into the top of the casing. A liquid is then pumped
down the casing to force the displacement plug downwards to the
ECP. This is continued until the displacement plug reaches a
location just beyond the grout valves, whereupon further downward
movement of the displacement plug is halted, because a hydraulic
lock forms between the cement displacement plug and the closed
non-return valve in the base of the ECP. There is generally no
further need to pressurise the casing to support the cement grout,
as the grout valves are one-way check valve devices which prevent
the backflow of cement grout from the annulus back into the casing.
The grout valves also permit breaks or interruptions in the cement
grout pumping process without the backflow of the grout from the
annulus back into the casing. At the completion of the cementing
operation a drill string can be run into the casing to drill out
the cement displacement plug and the bottom non-return valve
arrangement, along with any residual cement grout which has
hardened in the drill path.
[0009] Various features of the invention include the grout valves,
the inflation valves and the manufacture process which can be
incorporated into a single elastomer layer bonding operation.
[0010] The one-way grout valves each comprise a chamfered valve
member which is preferably a seal disc that scats in a chamfered
port formed in the ECP mandrel above the packer sleeve. The valve
or seal members are attached to respective burst or shear discs.
The discs are preferably constructed of a frangible material having
a well defined shear failure stress such as some plastics, metals
or ceramics. The chamfered valve member is attached to an
elastomeric grout valve sleeve which surrounds the mandrel. In the
absence of pressure in the casing, the elastomeric nature of the
grout valve sleeve retains the chamfered valve member and ensures a
seal with the chamfered seat of the mandrel on closure. Preferably,
the elastomeric grout valve sleeve is bonded to the top of the
chamfered valve member and forms part of the inflatable ECP sleeve
situated around the mandrel.
[0011] The inflation valve comprises a flap of an elastomeric
material situated on the inflatable elastomeric sleeve side of the
mandrel. The inflation valves each cover a small port formed in the
mandrel. Fluid can therefore flow through the inflation ports in
one direction and displace the flap outwardly to inflate the
elastomeric sleeve of the ECP. On cessation of the fluid flow to
inflate the ECP sleeve (when the grout valve discs shear and open),
the inflation ports are closed by the respective flaps, which
prevents the packer sleeve from deflating. The inflation flap
preferably comprises part of the ECP sleeve construction to
simplify the manufacturing process.
[0012] The inflation valves and the grout valves are both operated
in a sequence during the process of inflating the elastomeric
sleeve to set the packer and casing in the borehole. The inflated
sleeve provides an obstruction in the borehole annulus so that the
annulus area above the obstructing sleeve can be filled with a
cement grout mixture. To that end, the casing and ECP attached
thereto arc lowered at the desired location in the borehole. The
open one-way valve in the bottom of the ECP allows air and any
liquid in the lower part of the borehole to equilise during
lowering of the casing and ECP therein, as the ball has not been
dropped down the casing. A ball is then dropped down the casing to
seat with the one-way valve in the bottom of the ECP, thereby
plugging said valve. The casing is then pressurised with a liquid
to inflate the elastomeric sleeve via the inflation valves. As the
sleeve is inflated and engages the sidewall of the borehole, the
pressure of the inflation liquid increases, whereupon the shear
point of the grout valves is reached and such valves arc actuated
and opened. When the grout valves burst open, the inflation valves
automatically close due to the reverse differential pressure across
the inflation valves. The closed inflation valves leave the sleeve
pressurised and compressed against the wall of the borehole. The
cement grout mixture can then be pumped down the casing and out of
the opened grout valves into the annulus area above the inflated
sleeve.
[0013] The sealing system between the packer sleeve and mandrel
comprises the packer sleeve being bonded directly to the packer
mandrel at one end of the mandrel. At the other end of the packer
there is a seal which moves axially along the outer surface of the
mandrel and accommodates shortening of the packer sleeve as it
expands radially outwardly during inflation. In most packers this
takes the form of a sliding elastomeric hydraulic seal between the
sleeve and the mandrel. Such a hydraulic seal requires a
substantial housing to contain it. In the preferred embodiment of
the invention, the sliding hydraulic seal is replaced by a sealing
sleeve of elastomer that is bonded at one end to the packer sleeve
at a position below a packer retaining ring, and to the packer
mandrel at the other end. Thus, as the packer sleeve is inflated
and shortens in a longitudinal direction, the sealing sleeve
compresses longitudinally but maintains a seal to the mandrel. The
sealing sleeve is pressed via inflation pressure against the
mandrel and is prevented from being torn from the packer sleeve by
the packer retaining ring which maintains an outer diameter and
confines the seal. In one embodiment, the packer sealing sleeve is
reinforced by an open mesh interlayer which is placed on the bias
to the packer axis to permit longitudinal changes in sealing sleeve
dimension, and to reinforce the elastomeric sleeve against tears by
preventing excessive local strain.
[0014] The bonded sleeve system is used to transfer load between
the packer sleeve reinforcement and the packer retaining ring. In a
packer where the sleeve is reinforced with flexible cords or straps
of low inextensibility, the reinforcing carries tensile load. The
tensile load is retained against expansion by the packer retaining
ring. The loading force on the packer retaining ring comprises the
component perpendicular to the retaining ring which is restrained
by the packer retaining ring operating as hoop reinforcement. There
is also an axial component which tends to slide the packer
retaining ring axially away from the inflated portion of the packer
sleeve. Thus, the retaining ring tends to be pushed over the packer
sleeve reinforcement contained in the elastomeric sleeve. By
bonding a stiff or rigid sleeve, which is in contact with the
packer retaining ring, to the elastomeric sleeve, which is in turn
bonded to the reinforcing, shear is transferred between the packer
retaining ring and the reinforcement via the rigid sleeve and the
elastomer. The rigid sleeve may advantageously be made in a
longitudinally split form to permit the easy assembly and bonding
to the underlying elastomer while relieving the manufacture of
close tolerance issues. The sleeve system is therefore of low cost
to fabricate and rapidly incorporated into the packer
construction.
[0015] The overall design of the packer, can therefore include one
or more features which are easily incorporated into the manufacture
of a packer by layers of elastomer to be cured and bonded, or
specifically not bonded together, according to the design. The
elastomer may be derived from natural or synthetic sources, and is
usually bonded together in a process involving pressure and heat.
This is known for natural rubber systems as the process of
vulcanisation. It is thus possible, to achieve very strong bonding
between layers of elastomer and between the elastomer and the
mandrel (especially to steel) by the use of the correct surface
preparation of the metal.
[0016] According to one embodiment of the invention, disclosed is a
method of cement grouting a borehole using an inflatable packer
system. The method includes placing a casing with an external
casing packer attached thereto at a location in a borehole for
cement grouting a portion of the borehole annulus that is located
above the external casing packer. Also included is the inflation of
an inflatable elastomeric sleeve of the external casing packer to
block the annulus of the borehole by pressurising the casing with
an inflation fluid, which opens a one-way inflation valve in the
external casing packer and inflates the inflatable sleeve to a
preset pressure. The preset pressure is determined by a pressure
relief valve located between the external casing packer and the
annulus which opens at the preset pressure and then becomes a
one-way grout valve. A liquefied cement grout mixture is pumped
down through the casing via the open one-way grout valve which is
located in the external casing packer above a portion of the
inflated inflatable sleeve. The grout valve is biased to a closed
position using an elastomeric member attached to the packer,
whereby when the pressure of the cement grout mixture is reduced in
the casing, the elastomeric member causes the grout valve to close
and prevent backflow of the cement grout mixture from the annulus
back into the casing.
[0017] According to another embodiment of the invention, disclosed
is a method of setting an external casing packer in an annulus of a
borehole to fix a casing therein. The method includes sealing a
base of the packer, and pressurising the packer to inflate an
inflatable elastomeric sleeve surrounding a portion of a packer
mandrel by passing a pressurised fluid through a one-way inflation
valve into the inflatable sleeve. The inflation pressure of the
inflatable sleeve is limited by using a pressure relief valve in
the packer which relieves the pressure in the packer to the outside
of the casing when a design differential pressure is reached. The
pressure relief valve is used as a one-way valve to permit a grout
material to flow therethrough to the annulus of the borehole. The
pressure relief valve is closed to prevent a backflow of the grout
material from the annulus back into the packer.
[0018] According to yet another embodiment of the invention,
disclosed is a method of cement grouting a borehole using an
inflatable packer system. The method includes lowering into a
borehole a casing with the inflatable packer system attached
thereto. The casing is pressurised with a fluid so that the
pressurised fluid enters one or more one-way inflation valves in
the packer system to inflate a sleeve and obstruct an annulus of
the borehole. The pressure of the fluid in the casing is increased
until one or more one-way frangible grout valves rupture to allow
the pressurised fluid to enter the borehole annulus above the
packer system, whereby the pressure of the casing drops and the
one-way inflation valves close and maintain the sleeve inflated in
the borehole annulus. A cement grout is pumped down the casing and
through the ruptured one-way grout valves and into the portion of
the borehole annulus located above the packer system.
[0019] With regard to yet another embodiment of the invention,
disclosed is an inflatable packer system for grouting a borehole
annulus. The packer system includes a mandrel forming a body of the
packer system, where the mandrel is adapted for attachment to a
casing, and the mandrel has formed therein one or more ports for
respective grout valves, and one or more ports for respective
inflation valves. A seat is formed in a bottom part of the mandrel,
where the seat is adapted to be blocked by a ball dropped down
through the casing. An elastomeric sleeve is formed around the
mandrel and around the inflation valve ports. An anchor seal is
formed at a top portion of the elastomeric sleeve around the
mandrel above the inflation valve ports and below the grout valve
ports. A sliding seal is formed at a bottom portion of the
elastomeric sleeve along the mandrel. One or more one-way inflation
valves are provided, where each one-way inflation valve is located
over one of the inflation valve ports, and each one-way inflation
valve is adapted for allowing an inflation fluid to pass through
the inflation valve port and into the elastomeric sleeve, but not
in the reverse direction. One or more one-way grout valves are
provided, where each one-way grout valve is located over one of the
grout valve ports, and each one-way grout valve is adapted for
allowing a cement grout to pass through the grout valve port and
into the borehole annulus, but not in the reverse direction. Each
one-way grout valve is formed with a frangible member which breaks
in response to a predetermined inflation fluid pressure, whereby
when the elastomeric sleeve is inflated to the predetermined fluid
pressure the frangible members break to enable operation of the
one-way grout valves. The one-way inflation valves then close to
allow the elastomeric sleeve to maintain the predetermined
inflation fluid pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Further features and advantages will become apparent from
the following and more particular descriptions of the preferred and
other embodiments of the invention, as illustrated in the
accompanying drawings in which like reference characters generally
refer to the same parts, functions or elements throughout the
views, and in which:
[0021] FIG. 1A-1F schematically illustrate the sequence of steps
for installing the external casing packer in a borehole;
[0022] FIG. 2 is a cross-sectional view illustrating the external
casing packer according to an embodiment of the invention;
[0023] FIG. 3 is a cross-sectional view illustrating the grout
valve according to an embodiment of the invention, in a closed
condition;
[0024] FIG. 4 is a cross-sectional view of the grout valve of FIG.
3, but in an open condition;
[0025] FIG. 5 illustrates in a one-quarter longitudinal section
view the upper end of the packer with the inflation valve,
according to an embodiment of the invention, in an open condition;
and
[0026] FIG. 6 illustrates in a one-quarter longitudinal section
view the lower sliding end of the packer and the construction of
the scaling sleeve according to an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0027] FIG. 1A illustrates the external casing packer, enclosing a
casing 2 which has been lowered into a borehole 1. The portion of
the casing 2 above the ECP extends to the surface, and the casing
portion 3 below the ECP is optionally perforated, as shown. The
body of the packer is constructed using a metal mandrel 5. The ECP
includes an inflatable reinforced elastomeric sleeve 4 which
encircles the mandrel 5. The grout valve at the upper end of the
casing packer is shown as numeral 6. The packer seat 8 of the
non-return valve is located in the lower portion of the mandrel 5,
and is a cone of material, usually concrete. The inflation valve 7
is adapted for use in inflating the elastomeric sleeve 4 to
obstruct or otherwise block the annulus of the borehole 1.
[0028] FIG. 1B illustrates a cementing system attached to the top
end of the casing 2. The cementing system includes a top casing
section 10 which contains a cement displacement plug 15 therein.
Also included are grout and inflation valves 11 and 13 which are
connected to the top casing section 10. Once the casing 2 is
situated at a desired location in the borehole 1, a ball 16 is
dropped down through the casing 2 and into contact with the valve
seat 8 to seal the bottom end of the packer. The elastomeric sleeve
4 of the ECP is then inflated by pumping a fluid into the top
section 10 of the casing 2 via port 14 and valve 13. The
pressurisation of the casing 2 causes the flap of the one-way
inflation valve 7 in the packer mandrel 5 to open and permit the
pressurised fluid to enter the space between the mandrel 5 and the
packer sleeve 4, thereby inflating and expanding the elastomeric
sleeve 4 into contact with the borehole 1.
[0029] FIG. 1C illustrates the elastomeric sleeve 4 of the ECP
fully expanded and in contact with the wall of the borehole 1.
Eventually, the differential of the fluid pressure across the
expanded elastomeric sleeve 4 exceeds a designed threshold,
whereupon the frangible grout valve 6 is activated to open and
initially allow fluid to flow from the casing 2 into the annulus
between casing 2 and borehole 1. As noted above, when the grout
valves 6 open, the pressure in the casing 2 drops and closes the
inflation valves.
[0030] FIG. 1D illustrates the process of pumping the cement grout
17 into the casing top section 10 via port 14 of grout valve 13.
The cement grout 17 passes down through the casing 2 and out of the
opened grout valve 6 to fill that part of the annulus above the
packer and between the casing 2 and the borehole 1. The cement
grout 17 also flows down through the mandrel 5 of the ECP, to the
ball 16 and closed valve seat 8.
[0031] View 1E shows a fluid being pumped into port 12 through
inflation valve 11 while grout valve 13 is closed. This fluid
pushes the cement displacement plug 15 down into the casing 2 and
into the top of the mandrel 5 until the cement displacement plug 15
forms a seal below the grout valve 6. At this point, a hydraulic
lock forms between the cement displacement plug 15 and the ball 16
in the valve seat 8.
[0032] FIG. 1F illustrates the use of a conventional drill bit 19
attached to the end of a drill string 18 to drill out the cement
grout displacement plug 15 (shown already drilled out), as well as
drill out the cement grout 17 within the remainder of the casing 2,
the mandrel 5, and the ball 16 and valve seat 8. When drilled in
the manner noted, the production zone below the packer is coupled
to the casing 2 above the packer.
[0033] FIG. 2 illustrates the structural details of the ECP. As
noted above, in the embodiment shown the ECP comprises a mandrel 5
partially covered or encircled with a reinforced elastomeric sleeve
4. The sleeve 4 is constructed of various layers of material to
carry out the functions described herein. The elastomeric sleeve 4
is multilayered and would normally be constructed of a natural or
synthetic rubber. The sleeve 4 is bonded to the mandrel 5 at the
top of the packer beneath outer rigid sleeve layer 23, but is not
bonded to the mandrel 5 over the remainder of sleeve 4 length.
Between the packer retaining rings 20 and 21 the packer sleeve 4
may expand outwardly in response to internal, pressure to form a
seal in the annulus of the borehole. The packer retaining rings 20
and 21 are manufactured from high tensile steel and are bonded to
the elastomeric sleeve 4, and restrained by upper and lower rigid
outer sleeves 22 and 23 which are also bonded to the sleeve 4. The
rigid outer sleeves 22 and 23 can be constructed of a rigid
material or metal, such as steel. The mandrel 5 is shown with
threaded connections at the top 26 and bottom 27 to permit
attachment to casing sections located above and below the packer.
The absence of bonding between the reinforced elastomeric sleeve 4
and mandrel 5 at the lower end of the packer allows the lower end
of the sleeve 4 to slide up the mandrel 5 as the sleeve 4 becomes
inflated. It is realised that when the reinforced elastomeric
sleeve 4 is inflated, the natural tendency is for the overall
length to become shortened. The other alternative is for the
material of the elastomeric sleeve 4 to stretch during inflation,
but with the reinforced construction of the sleeve 4, stretching of
the sleeve material is not preferred. The seal between the sleeve 4
and the mandrel 5 is described in more detail in below. The lower
end of the mandrel 5 contains a cone-shaped valve seat 8 which
forms a non-return valve when the ball 16 is dropped down the
casing 2 and rests on the conical-shaped seal 8. The cone-shaped
element 8 can be cast in concrete or other suitable materials to
lower manufacture cost. The non-return inflation valve 7 and the
grout valves 6 described above are also illustrated. The grout
valves 6 described in more detail below are covered, by an
elastomeric grout valve sleeve 25.
[0034] FIG. 3 illustrates the details of the grout valve 6 in a
closed position. As noted above, the grout valve 6 is constructed
with a chamfered port 30 formed in the sidewall of the mandrel 5.
Seated in the port 30 is a chamfered valve member 31 which in its
preferred embodiment is made of metal and which is attached to a
frangible shear disc 32. The shear disc 32 is preferably made of a
material having a well-defined shear strength such as a plastic,
metal or ceramic. The force exerted by the pressure of fluid in the
casing during the sleeve inflating process is sufficient to fully
inflate the sleeve, and shortly thereafter shear the shear disc 32.
The shear disc 32 is connected to the valve member 31 via a
fastener 33, shown as a screw. The elastomeric grout valve sleeve
25 encircles the mandrel 5 and is bonded to the outer surface of
the grout valve member 31, but not to that part of the mandrel 5
shown to the right of the grout valve 6 in the drawing. The
elastomeric grout valve sleeve 25 is, however, bonded to the
mandrel 5 at the location to the left of the grout valve 6.
[0035] In operation, when the differential pressure across the
grout valve 6 exceeds a specified design value during inflation of
the elastomeric sleeve, the peripheral rim of the frangible burst
disc 32 undergoes stress and eventually shears, whereupon the
chamfered grout valve member 31 is activated and moves out from its
seated position to thereby allow fluid to flow through the opened
grout valve 6. As will be described below, during inflation of the
large elastomeric sleeve through the open inflation valves, a point
is reached where the elastomeric sleeve is fully inflated in the
annulus and the grout valves 6 then rupture and open. At this time,
the pressure in the casing drops abruptly, whereupon the inflation
valves close. To that end, the opening of the grout valves 6
function as a relief valve for the inflation of the elastomeric
sleeve. When the grout valves 6 are forced open, the elastomeric
grout valve sleeve 25 is forced to expand outwardly, as shown in
FIG. 4. After the casing is set by the inflated sleeve, the cement
grout can be pumped down the casing. The force of the liquefied
cement grout on the grout valves 6 causes them to open and allow
flow in the direction of the arrow. Once a specified volume of the
cement grout mixture is pumped through the grout valves 6 end into
the borehole annulus, the cement grout pumping operation is halted.
The expanded elastomeric grout valve sleeve 25 then contracts,
which action returns the chamfered valve member 31 and the
remaining part of the shear disc 32 back into a seated condition
with the chamfered port 30 of the mandrel 5. Once the grout valve 6
returns to its seated condition due to the contraction of the
elastomeric grout valve sleeve 25 around the mandrel 5, a seal is
provided between the chamfered grout valve member 31 and the
chamfered port 30 of the mandrel 5.
[0036] FIG. 4 illustrates the grout valve 6 in an open position, as
noted above. The frangible shear disc 32 is shown with its
peripheral edge sheared off following its failure at the design
inflation pressure of the ECP. The elastomeric grout valve sleeve
25 positions the chamfered valve member 31 during fluid flow,
including that of cement grout, so that when the fluid flow ceases,
the chamfered valve member 31 returns to the seated condition in
the chamfered valve port 30. The registration of the grout valve
member 31 and the valve port 30 is achieved by bonding the
elastomeric grout valve sleeve 25 to the outer surface of the
chamfered valve member 31 and to the mandrel 5 at location 34. The
elastomeric grout valve sleeve 25 can be manufactured as part of an
extension of the packer sleeve, but this is not a necessity.
[0037] FIG. 5 illustrates the upper zone of the packer sleeve 4,
the inflation valve 7, the retaining ring 21 and the bonded
elastomeric sleeve 4. The reinforced elastomeric sleeve 4 is of
multi-layered construction, including an outer elastomer layer 40,
a reinforcing layer 41, (depicted here as a single layer for
diagrammatic convenience, but could be made of layers of steel cord
or steel strips embedded in the elastomer) and an inner elastomer
layer 42. The layered elastomeric sleeve 4 is bonded over surface
area 43 to the outer cylindrical surface of the mandrel 5. The
outer elastomer layer 40 of the reinforced sleeve 4 is bonded to
the rigid outer sleeve 23 which bears against the packer retaining
ring 21 at location 44. The retaining ring 21 has acting on it the
loads from the sleeve reinforcing layer 41. This would tend to move
the retaining ring 21 axially to the right in the drawing. The
rigid outer sleeve 23 however restrains the retaining ring 21 from
being moved to the right because it is bonded to the elastomer
layer 40 which is in turn bonded to the reinforcing layer 41. The
radial component of the load on the packer retaining ring 21 is
contained by hoop stress within the retaining ring 21. The axial
component of the load on the retaining ring 21 is transferred to
the rigid sleeve 23 via the contact surface at location 44. The
axial load imparted on the retaining ring 21 is transferred through
shear stress in the elastomer layer 40 back to the reinforcing
layer 41. The contact surface 44 is shown as an acute angled
abutment so that the rigid sleeve 23 does not disengage under load
from the packer retaining ring 21.
[0038] The inflation valve system which permits fluid to expand the
packer sleeve 4 is fitted in a concentric recess in the mandrel 5
at location 48. Although one inflation valve 7 is illustrated, it
is to be understood that a number of such valves are formed around
the packer mandrel 5. At the location 48, a port 47 is drilled in
the mandrel 5 to provide an inflation fluid entry point. Movement
of the inflation valve 7 is provided by an elastomeric annular flap
46 which is bonded over the outside surface of the mandrel 5 at
location 45. The bonding of the annular end of the elastomeric
annular flap 46 to the mandrel 5 is under the metal retaining ring
21 to maintain the annular edge of the flap 46 anchored to the
mandrel 5. During inflation of the packer sleeve 4, the inflation
fluid forces the elastomeric annular flap 46 open, as shown in the
drawing. When pumping the packer inflation fluid to a specified
pressure, the grout valves rupture and open, whereupon the pressure
in the casing drops, thereby causing the elastomeric annular flap
46 to close the respective ports 47. The inflation valve 7 is held
in the closed state by fluid pressure contained between the packer
sleeve 4 and the mandrel 5. The force exerted on the inside of the
closed elastomeric annular flap 46 by the inflated packer sleeve 4
is greater than the fluid force exerted on the other side of the
inflation flapper 46 by the cement grout forced down the casing
during the grouting process. Accordingly, the cement grout does not
force the flapper valve 46 open during the grouting process.
Otherwise, the cement grout would enter between the packer sleeve 4
and the mandrel 5.
[0039] The rigid outer sleeve 23 is advantageously made in
longitudinally split form so as to facilitate assembly of the
packer while minimising the need for precise tolerance in diameter
between the rigid outer sleeve 23 and the elastomer layer 40.
During assembly, the rigid, split sleeve 23 is clamped into place
to the underlying elastomer layer 40 to permit the formation of a
bond therebetween. It should be appreciated by those skilled in the
art of elastomer construction that various bond and de-bonded
sections of layers are advantageous to produce the ECP.
[0040] FIG. 6 illustrates the structural details of the lower end
of the packer sleeve 4 as shortened during inflation. The lower end
of the packer sleeve 4 includes the sliding seal 55, the retaining
ring 20 and the outer sleeve layer 40. The arrangement of the
packer sleeve 4 at the lower end thereof includes the inner
elastomer layer 42, the reinforcing layer 41, the outer elastomer
layer 40, the retaining ring 20, and the rigid outer sleeve 22, all
of which are similar in construction to that described above in
connection with the upper end of the packer in FIG. 5. The major
difference is that the inner elastomer layer 42 is manufactured so
that it can slide over the mandrel 5 in an axial direction at
surface area 53 as the packer sleeve 4 shortens during inflation.
Unlike most packers which have a form of sliding hydraulic seal,
the packer disclosed herein utilises an annular sleeve seal 55 made
of an elastomer which is preferably of a similar elastomer
construction as the sleeve 4. The annular sleeve seal 55 is
contained in an annular external groove 54 formed in the mandrel 5.
The annular sleeve seal 55 is bonded to the outside of the mandrel
5 over surface area 58, and to the inside of the packer inner
elastomer layer 42 over surface area 57. The sleeve seal 55 is
otherwise not bonded, but is free to slide axially on the mandrel 5
within the external groove 54. In the drawing the packer sleeve 4
is shown in an inflated state, engaged in contact with the borehole
1. In the inflated state the sleeve seal 55 is longitudinally
compressed from its original position where it occupies the entire
length of the external groove 54. The distance by which the sleeve
seal 55 becomes compressed is shown as the dimension G. The sleeve
seal 55 is shown in the drawing as having been manufactured with a
reinforcing layer 56. This would preferably be an open weave mesh
laid on the bias so that it can compress axially. The reinforcing
mesh 56 would be bonded into the elastomer and prevent uneven
strain of the sleeve seal 55, which could otherwise lead to tears
within the material of the sleeve seal 55. The sleeve seal 55 is
held against the mandrel 5 within groove 54 by fluid pressure in
the expanded sleeve 4 and is prevented from being torn from the
inner elastomer 42 of the sleeve 4 by the tight annular restraint
of the packer retaining ring 20.
[0041] While, the preferred and other embodiments of the invention
have been disclosed with reference to a specific external casing
packer, and associated methods of use and manufacture thereof, it
is to be understood that many changes in detail may be made as a
matter of engineering choices without departing from the spirit and
scope of the invention, as defined by the appended claims.
* * * * *