Method and apparatus for setting an inflatable packer

A setting assembly tool suitable for suspension in a subterranean well by a wireline is provided for activating an inflatable packer. A downhole firing head with a combustion device is utilized for generating downhole a high fluid pressure in a passageway of the setting assembly tool, with the passageway being in fluid communication with the packer for setting the packer. In response to a pressure buildup of a predetermined level, fluid pressure is dumped from the passageway to the well while a check valve closes to retain the packer in the set position. To deactivate the retrievable packer, a conventional fishing tool supported by a wireless may be used to exert an axial force on a housing sufficient to move the housing relative to the packer and open a fluid port for discharging liquid from the packer. The setting assembly tool may be retrieved to the surface via the wireline immediately after the packer is set.

BACKGROUND OF THE INVENTION 
1. Field of the Invention. 
This invention relates to methods and apparatus for activating and 
deactivating pressure responsive downhole equipment and, more 
particularly, to methods and apparatus for setting and unsetting downhole 
retrievable inflation packers. 
2. Description of the Prior Art. 
Packers are widely used in the petroleum recovery industry for sealing 
against the well bore, the casing I.D. surface, or the O.D. surface of a 
tubing string. Packers may generally be categorized as either permanent 
packers or retrievable packers. As its name suggests, a permanent packer 
is intended to be set in the well and left in place for an indefinite 
period of time. A retrievable packer, on the other hand, is returned to 
the surface when its intended function is complete. Retrievable packers 
frequently must be able to be lowered downhole through a small diameter 
production tubing string, effectively seal against a large diameter 
casing, and then be returned to the surface through the tubing string. A 
retrievable packer is cost effective since the packer may be reused. 
Moreover, its retrieval to the surface is often critical in order that the 
packer not interfere with subsequent downhole operations. 
Packers may be set or activated by either mechanical or hydraulic forces; 
the latter type is frequently called an inflation packer. Inflation 
packers, activated by fluid pressure, have certain advantages over packers 
activated by mechanically moving parts, including generally increased 
expansion capability. Thus, an inflation packer is generally preferred 
when the packer must pass from the surface downhole through a small 
diameter restriction, be activated or "set" to seal against a much larger 
diameter casing, and then be deactivated or "unset" and retrieved back to 
the surface through the small diameter restriction. 
Prior art inflation packers are typically set by passing a pressurized 
fluid from the surface through a tubing string downhole to the packer. The 
pressurized fluid fills the expandable bladder or bladders of the packer, 
and pressurizes the bladder with an axially directed force for sealing 
engagement against the casing. For this reason, an inflatable packer is 
commonly referred to as a Production Injection Packer, or PIP. 
With respect to mechanically activated packers, the packers may be set 
either by dropping a weight through the production tubing, or by using an 
explosive pressure setting assembly supported by a wireline. The latter 
device utilizes the products of combustion to move a slidable piston, 
which then operates various mechanical components in the packer to set the 
packer. A significant advantage of a wireline pressure setting device is 
that the expense of a surface rig or coil tubing mechanism is avoided. The 
disadvantages, however, of packers set by the movement of mechanical 
components relate to their generally reduced sealing area compared to 
inflation packers, and to the difficulty or impossibility of retrieving 
mechanically set packers through relatively small diameter restrictions. 
SUMMARY OF THE INVENTION 
The present invention relates to methods and apparatus for setting and 
unsetting a retrievable inflation-type packer. A pressure setting assembly 
tool is provided downhole conveniently supported by a wireline for setting 
one or more selectively positionable inflation packers also supported by 
the wireline. The downhole pressure setting assembly is provided with a 
conventional firing head for burning a power charge. Combustion forces 
move a burning chamber piston, which in turn pressurizes liquid in a 
chamber below the piston. The liquid chamber is in fluid communication 
with a passageway in the packer, and fluid pressure passes through the 
passageway, through a poppet check valve, and to the packer sealing 
elements to set the packer. In response to the buildup of fluid pressure 
in the packer to a predetermined pressure level after the packer is set, a 
first pin is sheared, allowing a pressure relief piston within the packer 
and in fluid communication with the pressurized fluid in the setting 
assembly to move, thereby expelling excess pressure from the packer to the 
well bore. This "dumping" of excess pressure to the well bore ensures that 
fluid pressure within the packer is maintained within a safe range. 
Simultaneous with this dumping of fluid pressure, the check valve in the 
setting assembly closes to trap fluid pressure in the packer and maintain 
the packer in the set position. 
When the pressure relief piston moves in response to the shearing of the 
first pin, collet fingers are released, enabling the setting mandrel and 
burning chamber to be retrieved to the surface by the wireline. When the 
packer is to be deactivated, a conventional fishing tool may be used to 
grasp the downhole outer housing of the packer, and an upward force 
exerted to shear a second pin, thereby axially moving the outer housing 
with respect to a packer sub and opening a port to allow fluid from the 
packer to be discharged. The packer may then be retrieved to the surface 
via the wireline and fishing tool. 
A check valve may be provided for initially passing well fluid into the 
liquid chamber of the downhole setting assembly or, alternatively, the 
liquid chamber may be substantially filled with a desired liquid before 
the setting assembly is lowered into the well. In either event, a 
substantial portion of the liquid chamber in the setting assembly will be 
filled with a substantially incompressible fluid prior to activation of 
the combustion charge, thereby minimizing the travel of the combustion 
chamber piston necessary to transmit sufficient pressurized fluid through 
the setting assembly to set the packer. The amount and type of power 
charge is selected for the particular well conditions, the size of the 
packer, and the number of packers to be activated. The size of the shear 
pin for securing the pressure relief piston is selected so that once the 
packer is set, the increasing fluid pressure will automatically be dumped 
to the well bore before pressure rises to a level which might cause 
rupture of the packer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 depicts a pressure setting assembly 10 according to the present 
invention supported by a conventional wireline for setting an upper packer 
12 into sealing engagement with the interior wall of casing 16. The 
assembly of the present invention may be used to set more than one packer, 
and accordingly FIG. 1 depicts a conventional side pocket mandrel 18 
between the upper packer 12 and a lower packer 14. 
The apparatus shown in FIG. 1 is supported by a conventional wireline 20, 
and may thus be activated and deactivated without the expense of a time 
consuming drilling rig or coil tubing apparatus. Directly connected to 
wireline 20 is a combustion device 22, including a firing head 24 for 
igniting the combustible materials in combustion chamber 26. The products 
of combustion create a pressure increase in chamber 26, which moves piston 
28 downwardly, transferring the pressure increase to liquid chamber 30. 
The top surface 27 of piston 28 is exposed to fluid pressure within 
combustion chamber 26, while the lower surface 29 is exposed to fluid 
pressure in cavity 30. Piston 28 thus translates the pressure increase in 
chamber 26 to liquid chamber 30 by moving piston 28 downward during the 
combustion of the power charge. 
As shown in FIG. 1, the surface area of 27 is equal to the surface area of 
29, so that when piston 28 is stationary the pressure in combustion 
chamber 26 and liquid chamber 30 will be equal. It should be understood, 
however, that a pressure increase or a pressure decrease could easily be 
provided by appropriately sizing the exposed surfaces of piston 28. The 
combustion device 22 described herein, including the firing head 24, is 
similar to combustion devices previously utilized in the prior art to 
transmit forces through mechanical means to a mechanically actuated 
packer. According to the present invention, however, forces for activating 
the packer are not transmitted through mechanical components 
interconnecting the piston 28 and the packer, but instead are transmitted 
through fluid pressure to activate an inflatable packer. Further details 
regarding a suitable combustion device 22 according to the present 
invention are disclosed in a 26 page technical manual distributed by Baker 
Service Tools dated June 1, 1981 for Unit 4115, hereby incorporated by 
reference. 
The other components of the setting assembly 10 simplicitly shown in FIG. 1 
are structurally interconnected to combustion device 22, and form a 
passageway 32 for transmitting fluid pressure from cavity 30 to packer 12. 
Packer 12 is structurally connected at its top end to assembly 10, and at 
its bottom end to side pocket mandrel 18. Both packers 12 and 14 thus 
include a passageway in fluid communication with passageway 32 for 
transmitting fluid pressure to the inflatable member or members in the 
packer and, if desired, for passing pressurized fluid to another packer. 
Mandrel 18 thus separates the upper and lower packers shown in FIG. 1, and 
transmits fluid pressure to the lower packer 14 through passageway 34. 
Packer sub 44 is structurally connected to the lower end of packer 14, and 
includes a passageway 36 also in fluid communication with the passageways 
32, 34 and the inflatable members of the packers. During service, fluid 
may be removed from the passageways by unthreading plug 38. Finally, a 
bottom shoe 40 is shown connected to the packer sub 44 and having an 
opening 42 exposed to fluid within the well or casing 16. 
As explained further below, it is preferable that passageways 32, 34, 36 
and the expandable fluid chambers in the packers in fluid communication 
therewith be filled with a liquid before activating combustion device 22. 
Accordingly, prior to actuation of the device 22, fluid at substantially 
the pressure and temperature of the well fluid exterior to the components 
illustrated in FIG. 1 may enter the bottom shoe 40 through opening 42, and 
be passed upward through a central passageway 46 in a packer sub, through 
a central passageway in packer 14, through central passageway 48 in the 
side pocket mandrel 18, through a passageway in packer 12, through a 
central passageway 50 in setting assembly 10, past check valve 51, and 
into cavity 30, the passageways 32, 34, 36, and the inflatable members of 
the packers 12 and 14. Thus, the chambers to be subsequently subjected to 
increased fluid pressure because of the power charge are at least 
substantially filled with a substantially incompressible fluid, thereby 
reducing the distance piston 28 must travel to effectively set both 
packers. 
It is also within the concept of the present invention to fill fluid cavity 
30, passageways 32, 34, 36, and the expandable or inflatable members in 
the packers with a selected fluid, e.g., oil, prior to lowering the 
assembly shown in FIG. 1 into the well via wireline 20. One advantage of 
this latter technique is that fluid with abrasive and corrosive 
characteristics is not utilized to primarily occupy the passageways within 
the components illustrated in FIG. 1. Check valve 51 need not be employed 
and the passageway 50 permanently sealed from the passageway 32. In this 
event the selected fluid may be input into the passageway 32 and all 
cavities connected therewith at the surface, and opening 42 could be 
plugged. An advantage of this latter technique is that only selected fluid 
is used to fill the cavities and passageways to be subsequently 
pressurized, thereby increasing tool life and reliability. Even though the 
cavities are filled with a selected fluid at the surface, check valve 51 
may still be employed to pass a small amount of well fluid into cavity 32, 
thereby further pressurizing all passageways to the downhole fluid 
pressure prior to activating device 22 to set the packers. In addition to 
the advantage gained by reducing the travel distance at piston 28, another 
advantage of using the check valve 51 is that the pressure within these 
passageways will be substantially equalized with the downhole pressure. 
The inflatable members in packers 12 and 14 will thus not be affected by 
downhole fluid pressure prior to activation of device 22 since the 
pressure in the interior of the packer expandable member will be 
substantially equal to the pressure in the interior 52 of the casing and 
exterior to the packer expandable member. 
FIG. 2 depicts in detail the portion of setting assembly 10 below 
combustion device 22 shown generally in FIG. 1, and the upper portion of 
the packer 12. Top sub 56 having threads 58 may be used to structurally 
interconnect combustion device 22 with setting mandrel 62, with O-ring 
seal 104 maintaining a fluid-tight relationship between these components. 
Mandrel 62 thus forms a portion of the sealed passageway 32 for 
transmitting pressure from liquid chamber 30 to one or more packers. Two 
ports 64 and 66 are provided for passing fluid from the interior to the 
exterior of the cylindrical-shaped mandrel 62. 
When fluid pressure increases in passageway 32 to a preselected extent due 
to the actuation of combustion device 22, fluid pressure acting through 
port 66 presses against seal 106 in poppet valve 68, forcing the slidable 
valve member downward, compressing spring 70 and thereby establishing 
fluid communication between passageway 32 and passageway 72. Spring 70 
thus exerts a preselected axially-directed force on poppet valve 68, so 
that the valve 68 will open only after a pre-selected nominal pressure is 
obtained in the setting assembly 10. Once valve 68 opens, pressurized 
fluid is transmitted from passageway 72 to passageway 74 in the top packer 
sub 75. Passageway 74 is in fluid communication with the expandable 
members of the packer, so that the packer will thus be subjected to 
pressurized fluid and will set in a conventional manner. 
It is a particular feature of the invention to provide pressure relief 
means to prevent rupture of the expandable packer member due to a pressure 
increase in the setting assembly beyond an acceptable range. While the 
packer is being set, pressurized fluid from passageway 32 via port 64 is 
also increasing the fluid pressure in passageway 76 between setting 
mandrel 62 and the inner sleeve 78. The collet 77 is provided with a 
plurality of finger engaging members 102 which structurally interconnect 
collet 77 with inner sleeve 78 as explained subsequently. Fluid passes 
between the fingers, increasing fluid pressure in passageway 80. Upper 
surface 84 of piston member 86 is thus exposed to fluid in passageway 80, 
and as pressurized fluid rapidly increases in passageway 32 once the 
packer is set, the force exerted on the piston 86 will shear the pin 88 
structurally interconnecting piston 86 to inner sleeve 78. Pin 88 is thus 
intended to shear when a preselected axial force is applied to the piston 
due to a pressure increase in passage 32, e.g., 1500 p.s.i., sufficient to 
effectively set the packer. It should be understood that the pressure 
value stated above to set a packer is the increased pressure over downhole 
pressure, and is merely exemplary of the pressure required to effectively 
seal the packer against casing. 
The lower surface 90 of piston 86 is open to downhole pressure, so that pin 
88 will shear when the fluid pressure in passageway 80 exerts a 
preselected force on surface 84 greater than the force exerted on face 90 
of the piston due to downhole pressure. Once pin 88 shears, slidable 
piston 86 moves downward against stop surface 100 (see FIG. 3). This 
downward movement of piston 86 causes the piston to break sealing 
engagement with seal 60, and thus opens chamber 80 to the well bore 
annulus. Once fluid pressure in passageway 32 drops due to movement of 
piston 86, spring 70 closes poppet valve 68, thereby retaining 1500 p.s.i. 
in passageway 74 and retaining pressure to the packer sufficient to 
maintain effective sealing engagement with the casing. Passageway 92 
beneath piston 86 was previously in fluid communication with the exterior 
of the assembly 10 and thus would normally be filled with well fluid. When 
pin 88 shears, movement of piston 86 thus expelled well fluid from the 
assembly 10 through U-shaped passageway 93 and out outport 94 provided in 
housing 96. A plurality of ports 94 thus ensure that well fluid can 
readily exit the assembly 10 as the piston moves downward, although well 
fluid could also be discharged in the space 98 between the sub 97 and 
housing 96. 
As shown in FIG. 2, sub 97 is threadably connected to intermediate sleeve 
82, which is turn serves as a guide for slidable piston 86. Seals 60 in 
sleeve 82 and in the inner sleeve 78 act against piston 86, sealing the 
passageway 32 from the exterior well fluid until pin 88 shears. Once 
piston 86 moves downward against stop surface 100, neither of the seals 60 
remains in sealing engagement between the piston, the intermediate sleeve 
82, and inner sleeve 78. At this stage, the packers 12, 14 are set and 
valve 68 is closed. 
Extension sub 83 is threaded at its upper end for interconnection with 
intermediate sleeve 82, and is threaded at its lower end for 
interconnection with top packer sub 75. Top packer sub 75, in turn, is 
structurally connected to conventional inflatable packer components. 
O-ring seals 104 are provided for fluid-tight engagement between various 
parts described above, as shown in FIG. 2. Most of the components shown in 
FIG. 2 are at least partially contained within housing 109, which 
physically protects the various components while being lowered into the 
well. 
Collet 77 is threadably connected to setting mandrel 62, and inner sleeve 
78 is similarly connected to top packer sub 75. The collet has a plurality 
of conventional collet fingers 102, which engage the groove in the mandrel 
78 and thus prevent axial movement of setting mandrel 62 relative to 
housing 109 until the packers are set and piston 86 moves downward against 
stop 100. Before the packers are set, piston 86 and setting mandrel 62 
thus limit radial movement between the engaging fingers 104 to prevent 
disengagement of the fingers. 
FIG. 3 illustrates a portion of the setting assembly 10 with the piston 86 
against stop surface 100 and collet 77 disengaged from collet 78 by the 
above-described packer setting operation. Once the packers are set, 
fingers 102 of collet 77 are free to move against the interior diameter of 
intermediate sleeve 82. With the packer set, the wireline 20 may be lifted 
upward, retrieving to the surface the combustion device 22 and setting 
mandrel 62, the collet 77 and the check valve 51, while the remaining 
packer components remains downhole. 
When it is desired to unset the packers, a conventional internal fishing 
tool (not shown) may be dropped downhole by wireline for engagement with 
the exposed upper fishing neck portion 108 of housing 109. Once the 
fishing tool has grasped the housing 109, an upward force may be exerted 
by the wireline until pin 112 shears. Pin 112 structurally interconnects 
the extension sub 83 and the sleeve 85 threaded to housing 109, and may, 
for example, be set to shear with an upward force of 1000 pounds applied 
on the wireline while the packers are set. Once pin 112 shears, sleeve 85 
and housing 109 are free to move upward by the continued upward force on 
the wireline until stop surface 87 of sleeve 85 engages stop surface 89 of 
intermediate sleeve 82. At this point, port 114 in extension sub 83 will 
be open since seals 104 no longer engage sleeve 85, and fluid within the 
packer or packers may freely pass from the packer through passageway 74, 
passageway 72, and out port 114, thereby unsetting the packers. With the 
packers unset, the packer and any intermediate subs or apparatus connected 
thereto, may be removed by the wireline. 
Thus the present invention enables inflatable packers to be easily and 
inexpensively set in a subterranean well, then unset and retrieved to the 
surface, by utilizing a wireline rather than coiled tubing or through 
production tubing. The components of a suitable inflatable packer 
according to the present invention which was not depicted in FIGS. 2 and 3 
are disclosed in U.S. Pat. No. 4,349,204, and inflatable packers, side 
pocket mandrels, packer subs, and bottom shoes are well known in the art 
and are commercially available. 
Although the invention has been described in terms of the specified 
embodiments which are set forth in detail, it should be understood that 
this is by illustration only and that the invention is not necessarily 
limited thereto, since alternative embodiments and operating techniques 
will become apparent to those skilled in the art in view of the 
disclosure. Accordingly, modifications are contemplated which can be made 
without departing from the spirit of the described invention.