WO1994021882A1

WO1994021882A1 - Hydrostatic activated ballistic blocker

Info

Publication number: WO1994021882A1
Application number: PCT/US1994/002493
Authority: WO
Inventors: Richard J. Ross
Original assignee: Baker Hughes Inc
Current assignee: Baker Hughes Holdings LLC
Priority date: 1993-03-15
Filing date: 1994-03-09
Publication date: 1994-09-29
Anticipated expiration: 1995-09-15
Also published as: AU6362394A

Abstract

A method and an apparatus for use in a wellbore are provided to prevent an igniter (78) from igniting a power charge (80) within a wellbore pressure setting assembly until after the wellbore pressure setting assembly is positioned downhole within the wellbore. A blocking member (104) is movable between two positions for selectively obstructing an ignition pathway between the igniter and power charge. An actuator (112, 108, 118) is provided which, when exposed to downhole wellbore pressure, urges the blocking member (104) from a position obstructing the ignition pathway to a position for allowing the igniter to ignite the pyrotechnic device.

Description

HYDROSTATIC ACTIVATED BALLISTIC BLOCKER

BACKGROUND OF THE INVENTION

1. Field of the Invention:

This invention relates in general to an apparatus and method for use to provide a downhole well tool which is prevented from actuating until the downhole well tool is positioned downhole within a wellbore, and in particular to a downhole well tool including a wireline pressure setting assembly having a hydrostatic activated ballistic blocker which prevents actuation of the wireline pressure setting assembly until after it is lowered downhole within a wellbore.

2. Background of the Invention:

Prior art downhole well tools have been used for converting chemical components of power charges into forces for performing work downhole within wellbores for setting bridge plugs and packers within wellbores. An example of such a prior art downhole well tool is the cable conveyed bridge plug for setting within a cased wellbore shown in U.S. Patent No. 2,637,402, entitled "Pressure Operated Well Apparatus," invented by R.C. Baker et al., and issued to Baker Oil Tools, Inc. on May 5, 1953. A similar cable conveyed downhole well tool is disclosed in U.S. Patent No. 2,695,064, entitled "Well Packer Apparatus," invented by T.M. Ragan et al., and issued to Baker Oil Tools, Inc. on November 23, 1954. These patents disclose cable conveyed downhole well tools for setting a bridge plug within a wellbore casing. These cable conveyed downhole well tools were actuated by the percussion of a firing pin causing a cartridge to explode and ignite a prior art power cartridge, or combustible charge.

An example of a prior art wireline conveyed well packer apparatus is disclosed in U.S. Patent No. Re. 25,846, entitled "Well Packer Apparatus," invented by D.G. Campbell, and issued to Baker Oil Tools, Inc. on April 31 , 1965. The wireline conveyed well packer apparatus disclosed includes a power charge which is ignited to generate a gas for setting the well packer apparatus within a wellbore. The power charge is ignited by passing an electric current down the wireline and exploding an igniter cartridge, which causes a flame to ignite the power charge.

An example of a prior art power charge for use in downhole well tools to generate a gas to provide a force for use to set packers and bridge plugs is a combustion charge disclosed in U.S. Patent No. 2,640,547, entitled "Gas- Operated Well Apparatus," invented by R.C. Baker et al., and issued to Baker Oil Tools, Inc. on June 2, 1953. The combustion charge is comprised of combustion materials which, when ignited within a downhole well tool disclosed in the patent, will take at least one second for a maximum pressure to be attained within the downhole, well tool. This prior art combustion charge includes both a fuel and a self-contained oxygen source. The combustion charge is ignited to generate a gas having a pressure which provides a force for setting the gas-operated well apparatus. The combustion charge of the gas- operated well apparatus is ignited by exploding an igniter to start the combustion reaction for burning the combustion charge. The combustion charge, once ignited, burns in a self-sustained combustion reaction to generate the gas.

A prior art wireline pressure setting assembly is disclosed in U.S. Patent No. 2,692,023, entitled "Pressure Operated Subsurface Well Apparatus," invented by M.B. Conrad, and issued to Baker Oil Tools, Inc. on October 19, 1954. This wireline conveyed downhole well tool includes a power charge which is burned in a combustion reaction to generate a gas. The power charge is ignited by electrically exploding an igniter cartridge which then emits a flame to start the power charge burning. Combustion of the power charge generates the gas having a pressure which provides force for operation of the wireline setting tool to set a downhole tool such as a packer or bridge plug within the wellbore. Each of the above-referenced patents, U.S. Patent No. 2,640,547, U.S. Patent No. Re. 25,846, U.S. Patent No. 2,695,064, U.S. Patent No. 2,637,402, and U.S. Patent No. 2,692,023, are hereby incorporated by reference as if fully set forth and disclosed herein.

The above prior art downhole well tools for converting the chemical components of a power charge into a mechanical force exerted over a distance typically require a separate igniter cartridge for igniting the power charge. Typically, explosive components are used for prior art igniter materials, such as, for example, gunpowder or lead azide. These types of igniter materials are easily ignited and represent hazards both to operators utilizing these materials in downhole well tools, and to successful completion of wellsite operations. Some of these types of primary ignition or igniter materials are susceptible to ignition from applications of small amounts of electric current, or even discharge of static electricity.

Wellsite operations utilizing prior art downhole well toois which present hazards if operated outside of the wellbore would be safer if prevented from operating until lowered downhole with a wellbore. Such a safety feature would enhance operator safety, as well as promote successful wellsite operations.

SUMMARY OF THE INVENTION

It is one objective of the present invention to provide a method and apparatus for use in a wellbore to prevent an igniter from igniting a propellant within a wellbore pressure setting assembly until after the wellbore pressure setting assembly is lowered downhole within the wellbore.

It is another objective of the present invention to provide a method and apparatus for use in a wellbore to automatically provide an ignition pathway between an igniter and a power charge containing a propellant within a wireline pressure setting assembly once the wireline pressure setting assembly is lowered downhole within the wellbore.

These objectives are achieved as is now described. A method and an apparatus for use in a wellbore are provided to prevent an igniter from igniting a power charge within a wellbore pressure setting assembly until after the wellbore pressure setting assembly is positioned downhole within the wellbore. A blocking member is movable between two positions for selectively obstructing an ignition pathway between the igniter and power charge. An actuator is provided which, when exposed to downhole wellbore pressure, urges the blocking member from a position obstructing the ignition pathway to a position for allowing the igniter to ignite the pyrotechnic device.

In the preferred embodiment of the present invention, a method and apparatus for use in a wellbore are disclosed for automatically providing an ignition pathway for passing thermal energy from an igniter to a power charge within a wireline pressure setting assembly once the wireline pressure setting assembly is lowered downhole within a wellbore. A valve member having a passageway extending laterally therethrough is provided for selectably obstructing a bore extending between a primary and a secondary igniter within a wireline pressure setting assembly. A bias spring retains the valve member in a blocking position obstructing the bore extending between the primary and secondary igniter until the wireline pressure setting assembly is lowered downhole within the wellbore to an activation depth having a wellbore fluid which exerts a predetermined level of hydrostatic fluid pressure. The wellbore fluid at the activation depth presses against the valve member and urges the valve member to an ignition position, aligning the passageway extending laterally through the valve member with the bore extending between the primary and secondary igniters to provide an ignition pathway therebetween.

Additional objects, features and advantages will be apparent in the written description which follows.

BRIEF DESCRIPTION OF THE DRAWING

The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:

Figure 1 is a partial longitudinal section view of a wellbore depicting a wireline tool string which includes the downhole well tool of the preferred embodiment of the present invention;

Figure 2 is a longitudinal section view of the downhole well tool of the preferred embodiment of the present invention, which includes a wireline pressure setting assembly which is shown prior to running downhole within a wellbore and prior to actuation within the wellbore; and

Figure 3 is a longitudinal section view of a portion of a wireline pressure setting assembly of the preferred embodiment of the present invention, which depicts a firing head having a connector housing and an igniter housing, and which is shown prior to lowering to a downhole position within a wellbore; and Figure 4 is a longitudinal section view of the firing head of Figure 3, shown after lowering downhole within a wellbore and activating the hydrostatic activated ballistic blocker of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to Figure 1, a partial longitudinal section view depicts wellbore B having casing C within which wireline tool string T is secured to wireline W. Electrical power supply E is schematically shown for providing power to tool string T. Wireline tool string T includes downhole well tool 2 which, in the preferred embodiment of the present invention, is a wireline pressure setting assembly. Tool string T further includes a packer P which is releasably secured to downhole well tool 2 for positioning and setting within casing C.

With reference to Figure 2, a longitudinal section view shows downhole well tool 2 prior to being lowered downhole within a wellbore and prior to actuation. In the preferred embodiment of the present invention, downhole well tool 2 is, in general, a wellbore pressure setting assembly, and in particular, downhole well tool 2 is a wireline pressure setting assembly having an elongated tubular body, and including firing head 4 and pressure setting tool 6.

Pressure setting tool 6 includes pressure chamber 8. Pressure chamber

8 includes a manual bleeder valve 10 for bleeding pressure from within pressure chamber 8 after operation of downhole well tool 2. An upper end of pressure chamber 8 threadingly engages firing head 4 and fluid flow therebetween is prevented by seal 12.

Upper cylinder 14 is threadingly coupled to a lower end of pressure chamber 8, and seal 16 prevents fluid flow therebetween. Within upper cylinder

14 is floating piston 18, which is a pressure responsive member. Floating piston 18 is movable within upper cylinder 14 and, during operation of downhole well tool 2, is urged to move downward by gas pressure within pressure chamber 8. Seal 20 prevents fluid flow between an outer circumference of floating piston 18 and an interior diameter of upper cylinder 14.

Cylinder connector 22 is threadingly coupled to a lower end of upper cylinder 14. Seal 24 prevents fluid flow between an outer circumference of an upper end of cylinder connector 22 and an interior of the lower end of upper cylinder 14. Cylindrical connector 22 includes flow port 26 having orifice 28 which substantially measures three-sixteenths of an inch in diameter at an upper end of flow port 26.

Lower cylinder 30 has an upper end which is threadingly coupled to a lower portion of cylindrical connector 22. Seal 32 prevents fluid flow between an outer circumference of the lower end of cylindrical connector 22, and an interior of the upper end of lower cylinder 30.

Secondary piston 34 is disposed interiorly of and is movable within lower cylinder 30. Secondary piston 34 is a second pressure responsive member and is movable within lower cylinder 30. Seal 36 seals between an outer circumference of secondary piston 34 and an interior diameter of lower cylinder

30.

Piston rod 38 is secured to secondary piston 34 by lock pin 40, and is also movable within lower cylinder 30.

Cylinder head 42 is threadingly coupled to the lower end of lower cylinder 30. Seal 44 prevents fluid flow between the outer circumference of cylinder head 42 and the interior diameter of lower cylinder 30. Seal 46 prevents fluid flow between an interior surface of cylinder head 42 and an outer circumference of piston rod 38, which is movable with respect to cylinder head 42 and seal 46. Mandrel 48 has an upper end which is threadingly secured within cylinder head 42. Set screw 50 prevents rotation of mandrel 48 within cylindrical head 42 after mandrel 48 is threadingly secured within cylindrical head 42. Mandrel 48 includes longitudinally extending slot 52, and longitudinally extending slot 54 which are two diametrically opposed longitudinally extending slots through an outer tubular wall of mandrel 48.

Cross link 56 inserts through longitudinally extending slot 52 and longitudinally extending slot 54, and is movable longitudinally within slots 52 and 54. Cross link 56 further inserts through piston rod 38 and sleeve 58 to couple sleeve 58 to piston rod 38. Cross link retaining ring 60 retains cross link 56 within sleeve 58 to maintain cross link 56 in engagement within sleeve 58 and piston rod 38. Lock screw 62 (not shown) secures cross link retaining ring 60 to sleeve 58.

Sleeve 58 is a driven member which is driven downward by piston rod 38 and cross link 56 when secondary piston 34 is urged into moving downward during operation of downhole well tool 2.

Pressure equalization ports 64 and manual bleeder valve 10 are provided for releasing fluid pressure from within pressure chamber 8, upper cylinder 14, and lower cylinder 30 after operation of downhole well tool 2. Pressure equalization ports 64 are provided at seal 16, seal 24, and seal 44. During disassembly of downhole well tool 2 after operation within wellbore B, thread pressure equalization ports 64 allow release of pressure from within downhole well tool 2 by passing over seal 16, seal 24, and seal 44, respectively, prior to the threaded connections of these seals being completely uncoupled. Thread pressure equalization ports 64 thus allow pressure to be released from the interior of downhole well tool 2 prior to fuliy uncoupling portions of downhole well tool 2.

Hydraulic fluid 66 is contained between floating piston 18 and secondary piston 34 to provide an intermediate fluidic medium for transferring force between floating piston 18 and secondary piston 34. As shown in Figure 2, prior to actuating pressure setting tool 6, hydraulic fluid 66 is primarily disposed within upper cylinder 16.

Pressure ports 68 extend laterally through the side walls of the upper end of pressure chamber 8. Pressure ports 68 provide a fluid flow pathway for wellbore fluids to exert wellbore fluid pressures on a portion of firing head 4 which, when threadingly connected to pressure chamber 8, is disposed interiorly of pressure chamber 8.

During operation of pressure setting tool 6 to move sleeve 58 with respect to mandrel 48, a gas pressure generated within pressure chamber 8 urges floating piston 18 downward. Downward movement of floating piston 18 presses hydraulic fluid 66 through orifice 28 and flow port 26 to drive secondary piston 34 downward. Movement of secondary piston 34 downward within lower cylinder 30 causes piston rod 38, cross link 56, and sleeve 58 to move downward with respect to lower cylinder 30 and mandrel 48. Firing head 4, pressure chamber 8, upper cylinder 14, cylinder connector 22, lower cylinder 30, cylinder head 42, and mandrel 48 remain stationery as floating piston 18, hydraulic fluid 66, secondary piston 34, piston rod 38, cross link 56, sleeve 58, and cross link retaining ring 60 move within pressure setting tool 6.

Still referring to Figure 2, power charge 70 is shown disposed within pressure chamber 8 prior to actuation for providing pressure to urge floating piston 18 downwards within upper cylinder 14. In the preferred embodiment of the present invention, chemical components within power charge 70 serve as a propellant which burn to generate a gas having a pressure which urges floating piston 18 downwards. Power charge 70 is self-contained since it is packaged within a singular container in the preferred embodiment of the present invention.

Referring now to Figure 3, a longitudinal section view of a portion of the wireline pressure setting assembly of the preferred embodiment of the present invention, downhole well tool 2, depicts firing head 4. Firing head 4 threadingly secures to the upper end of pressure chamber 8, and is sealed by seal 12 as discussed above. Firing head 4 is electrically connected to pov/er supply E (not shown in Figure 3) by, in part, power conductor 72. Firing head 4 includes connector housing 74, and igniter housing 76. Igniter housing 76 houses primary igniter 78, such as a BP3A primary igniter, and further houses secondary igniter 80. BP3A primary igniter 78, secondary igniter 80, and power charge 70, are manufactured by and available from Baker Oil Tools Incorporated, a division of Baker Hughes Incorporated, both of Houston, Texas. In the preferred embodiment of the present invention, primary igniter 78 and secondary igniter 80 include explosive materials for igniting power charge 70.

An upper end of connector housing 74 is threaded for connection to a wireline tool string (not shown in Figure 3). A lower end of connector housing 74 threadingly engages an upper end of pressure chamber 8 (not shown in Figure 3). Igniter housing 76 is threadingly coupled within the lower end of connector housing 74 by a left-hand threaded connection. Seal 12 sealingly engages between an outer circumference of igniter housing 76 and an interior diameter of pressure chamber 8 to prevent fluid flow therebetween. Seal 84 sealingly engages between an outer circumference of igniter housing 76 and an interior diameter of the lower end of connector housing 74 to prevent fluid flow therebetween.

Cartridge cap 86 retains primary igniter 78 within an upper end of igniter housing 76. Seal 88 sealingly engages between cartridge cap 88 and primary igniter 78. Secondary igniter 80 is held within igniter housing 76 by snap ring 90.

Electrical connector assembly 91 is utilized to electrically connect a wireline, or wireline tool string, to primary igniter 78. Electrical connector assembly 91 includes upper connector pin 92, connector spring 94, and lower connector pin 95. Electrical connector assembly 91 is insulated by insulator sleeve 96 and pin insulator 97 to prevent electrical continuity between connector housing 74 and electrical connector assembly 91. Insulator sleeve 96 and pin insulator 97 are made from suitable insulating materials, such as, for example, polytetrafluoroethylene, which is available from E.I. DuPont De Nemours and Company under the registered trademark TEFLON*. Connector lock ring 98 threadingly engages within connector housing 74 to hold insulator sleeve 96, pin insulator 97, and electrical connector assembly 91 in place within connector housing 74.

Connector spring 94 is a biasing member which, in the preferred embodiment of the present invention, pushes between both upper connector pin 92, and lower connector pin 95 to provide electrical continuity therebetween. Connector spring 94 also urges upper connector pin 92 upwards and lower connector pin 95 downward and into electrical contact with the upper end of primary igniter 78.

Still referring to Figure 3, bore 100 extends longitudinally through igniter housing 76 for providing a portion of an ignition pathway extending between primary igniter 78 and secondary igniter 80. Hydrostatic activated ballistic blocker 102 is shown in Figure 3 disposed within igniter housing 76 in a blocking position, obstructing bore 100.

Hydrostatic activated ballistic blocker 102 includes: valve plug 104 having passageway 106, and bias spring 108. Valve plug 104 is a valve member which, in the preferred embodiment of the present invention, is a steel cylindrical plug which inserted into a cylindrical bore extending laterally into igniter housing 76, across bore 100, and retained within igniter housing 76 by snap ring 110. In the preferred embodiment of the present invention, valve plug 104 does not provide a fluid tight seal across bore 100, but rather obstructs bore 100 to prevent sufficient thermal energy for igniting secondary igniter 80 from passing through bore 100. Passageway 106 is a groove cut circumferentially into valve plug 104 to form a necked down section for selectably providing another portion of the ignition pathway between primary igniter 78 and secondary igniter 80.

Valve plug 104 is a blocking member which may be selectably moved within igniter housing 76 for selectably obstructing bore 100 for blocking the ignition pathway between primary igniter 78 and secondary igniter 80, and for selectably aligning passageway 106 with bore 100 for providing an ignition pathway therethrough.

Valve plug 104 further includes a wetted surface 112 which is exposed to a wellbore fluid when firing head 4 and downhole well tool 2 are lowered downhole within a wellbore containing the wellbore fluid. Seals 114 seal between valve plug 104 and igniter housing 76 to prevent wellbore fluid from flowing therebetween. When valve plug 104 is lowered within a wellbore into a wellbore fluid having a hydrostatic pressure, seals 114 prevent the hydrostatic pressure from pressing against the non-wetted portions of valve plug 104, thus providing a net force acting longitudinally across valve plug 104 between wetted surface 112 and the non-wetted portions of valve plug 104.

Bias spring 108 is a coiled wire spring which provides a biasing means for urging valve plug 104 to obstruct bore 100. Bias spring 108 is, in the preferred embodiment of the present invention, inserted about a portion of valve plug 104 which extends within bias spring 108 to provide a stop for restraining valve plug 104 from moving beyond a position in which passageway 106 is aligned with bore 100.

Vent hole 116 passes longitudinally into the lower face of igniter housing 76 to assure that air pressure will not be trapped between igniter housing 76 and the non-wetted portions of valve plug 104 which would prevent activation of hydrostatic activated ballistic blocker 102. Shear pin 118 (shown in phantom) extends laterally between valve plug 104 and igniter housing 76 for assuring that valve plug 104 will not move from the position shown in Figure 3 until after a force is exerted against shear pin 118 sufficient for severing shear pin 118.

In the preferred embodiment of the present invention, wetted surface

112, bias spring 108, and shear pin 118 are included together to provide an actuator for activating hydrostatic ballistic blocker 102. When downhole well tool 2 is lowered within a wellbore, wellbore fluids press against wetted surface 112 to provide a force which pushes against shear pin 118 and bias spring 108.

When downhole well tool 2 is lowered to wellbore depths having a hydrostatic pressure level substantially equal to or above an activation hydrostatic pressure, wellbore fluids will press against wetted surface 112 with sufficient force to sever shear pin 118 and overcome a biasing force exerted by bias spring 108, to move valve plug 104 from a blocking position to an ignition position.

With reference to Figure 4, firing head 4 is shown with valve plug 104 depicted in the ignition position, after moving from the blocking position depicted in Figure 3. Referring now to Figures 3 and 4, when hydrostatic activated ballistic blocker 102 is activated by a wellbore fluid, valve plug 104 moves from a blocking position shown in Figure 3, in which valve plug 104 obstructs bore 100, to an ignition position shown in Figure 4, in which passageway 106 is aligned with bore 100 for providing an ignition pathway therethrough.

Shear pin 118, bias spring 108, and the difference between the opposing surface area of wetted surface 112 and the non-wetted surface areas of valve plug 104, among other dimensions of downhole well tool 2, are selectable for determining the hydrostatic activation pressure for hydrostatic actuated ballistic blocker 102. An actuation pressure should be chosen for assuring that downhole well tool 2 cannot be operated until downhole well tool 2 is lowered to a depth downhole within a wellbore.

It should be noted, however, that although hydrostatic activated ballistic blocker 102 is disposed between primary igniter 78 and secondary igniter 80 in the preferred embodiment of the present invention, in other embodiments of the present invention, hydrostatic activated ballistic blocker 102 may be disposed in alternative positions, such as, for example, between secondary igniter 80 and power charge 70 to prevent secondary igniter 80 from igniting power charge 70 until after downhole well tool 2 is lowered to a downhole position within a wellbore having a hydrostatic pressure which is higher than the activation hydrostatic pressure for ballistic blocker 102.

Operation of downhole well tool 2 is now discussed with reference to the Figures, beginning now with reference to Figure 2. Downhole well tool 2 is lowered downhole within a wellbore having wellbore fluids therein, until downhole well tool 2 reaches a wellbore depth where a wellbore fluid about firing head 4 has a hydrostatic pressure level substantially equal to or above the activation hydrostatic pressure level for hydrostatic activated ballistic blocker 102. At this wellbore depth, and below within the wellbore, the wellbore fluid will pass through pressure ports 68, and referring now to Figure 3, push against wetted surface 112 of valve plug 104 to move valve plug 104 from the blocking position of Figure 3, to the ignition position shown in Figure 4, in which passageway 106 is aligned with bore 100. Referring to Figure 4, primary igniter 78 can now be ignited for igniting power charge 70 and setting packer

P once downhole well tool 2 is lowered to a selected position within wellbore B.

Referring to Figure 1, electrical power is then selectively applied from electrical power supply E, through wireline W, and to wireline tool string T. Electrical power then passes from wireline tool string T, through, referring back to Figure 4, power conductor 72 and electrical connector assembly 91, and to primary igniter 78. The electrical circuit is completed by primary igniter 78 contacting connector housing 74. Still referring to Figure 4, connector housing 74 and igniter housing 76 provide an electrical ground for completing an electrical circuit between power conductor 72 and primary igniter 78 and power supply E (shown in Figure 1).

With reference to Figures 1 and 4, power charge 70 is ignited by passing electrical current from an electrical power supply, such power supply E, and through a wireline W to a wireline tool string T, through electrical connector assembly 91, and to primary igniter 78. Primary igniter 78 includes a gunpowder load which is ignited by the electrical current conducted through electrical connector assembly 91. Primary igniter 78 burns to generate thermal energy which passes through bore 100 and passageway 106, which together provide an ignition pathway for the thermal energy to pass through between primary igniter 78 and to secondary igniter 80, for igniting secondary igniter 80. Referring to Figure 2, secondary igniter 80 is ignited and generates heat which then ignites chemical components 71 within power charge 70. Power charge 70 then burns in a self-sustained combustion reaction to generate a gas, having a pressure which pushes floating piston 18 downward.

In the preferred embodiment of the present invention, power charge 70 will burn in a self-sustained chemical reaction, which, in the preferred embodiment of the present invention, is a combustion reaction for generating the gas. The combustion reaction of the preferred embodiment is a slow combustion reaction, burning at a rate so that a maximum level of gas pressure within pressure chamber 8 will not be reached before a one second period of time has elapsed. This is to be distinguished from explosive reactions in which explosive material is either detonated, deflagrated, or generally burns with a rate of reaction wnich takes no more than a time period of several milliseconds to burn the explosive materials.

Referring to Figures 1 and 2, movement of floating piston 18 downward pushes hydraulic fluid 66 through orifice 28 and flow port 26 to push secondary piston 34 downward. Secondary piston 34 is connected to piston rod 38, cross link 56, and sleeve 58. Movement of secondary piston 34 downward within lower cylinder 30 moves sleeve 58 downward with respect to mandrel 48. Relative movement of sleeve 58 with respect to mandrel 48 is applied to a downhole tool, such as packer P, for applying a force over a distance to set packer P within casing C. (Packer P not shown in a set position.)

If downhole well tool 2 is not operated after lowering into a wellbore to a depth having a wellbore fluid with a sufficient hydrostatic pressure for activating hydrostatic ballistic blocker 102, bias spring 108 will reset hydrostatic activated ballistic blocker 102 for obstructing bore 100 during removal from the wellbore. Bias spring 108 will move valve plug 104 back to the blocking position upon raising downhole well tool 2 above depths at which bias spring 108 overcomes hydrostatic pressure forces pushing against wetted surface 112, and urges valve plug 104 back into the blocking position.

The preferred embodiment of the present invention offers several advantages over prior art wellbore pressure setting assemblies. One advantage is that the primary igniter cannot ignite the secondary igniter, or the power charge, until after the tool string is lowered downhole within the wellbore to sufficient wellbore depths at which a wellbore fluid has a high enough hydrostatic pressure to activate the hydrostatic ballistic blocker, which urges the valve plug to move from the blocking position to the ignition position for providing an ignition pathway therethrough.

Further, the preferred embodiment of the present invention provides a downhole well tool for automatically providing an ignition pathway between an igniter and a power charge within a wellbore pressure setting assembly only after the downhole well tool is lowered downhole within a wellbore.

Additionally, the preferred embodiment of the present invention provides a low cost method and apparatus for preventing actuation of a wellbore pressure setting assembly prior to running the wellbore pressure setting assembly to a position downhole within a wellbore. Although the downhole well tool of the present invention has been described herein as including a wireline conveyed pressure setting assembly, other embodiments of the present invention may include other types of wellbore pressure setting assemblies, such as, for example, a tubing convened pressure setting assembly, and thus is not limited to either wireline conveyed pressure setting assemblies, or tubing conveyed pressure setting assemblies. Further, the downhole well tool of the present invention is not limited to use with either pyrotechnic, or explosive actuators, but may also be used with nonexplosive power charge igniters. While the invention has been shown in only one of its forms, it is thus not limited but is susceptible to various changes and modifications without departing from the spirit thereof.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for use in a wellbore to prevent an igniter from igniting a power charge within a wellbore pressure setting assembly until after said wellbore pressure setting assembly is disposed downhole within said wellbore, said apparatus comprising:

a housing having a passageway extending therein, said passageway providing an ignition pathway through which said igniter reacts for igniting said power charge within said wellbore pressure setting assembly;

a blocking member which is movable between a plurality of positions for obstructing said passageway to block said ignition pathway and prevent said igniter from igniting said power charge; and

an actuator for lowering downhole within said wellbore with said wellbore pressure setting assembly to a depth within said wellbore having a wellbore fluid exerting substantially at least a selectable level of hydrostatic pressure, at which said actuator is activated and moves said blocking member from a blocking position obstructing said passageway to an ignition position for allowing said igniter to ignite said power charge.

2. The apparatus of claim 1 , wherein said igniter is a primary igniter which is included within said housing, and said apparatus further comprises:

a secondary igniter disposed within said housing for igniting said power charge in response to being ignited by said primary igniter; and

said blocking member, when in said blocking position is disposed between said primary and secondary igniters for preventing said primary igniter from igniting said secondary igniter, and thus preventing said primary igniter from igniting said power charge.

3. The apparatus of claim 1 , wherein said actuator moves said blocking member to said ignition position by moving said blocking member in a linear path of travel.

4. The apparatus of claim 1 , wherein said actuator includes a bias means which urges said blocking member into said blocking position.

5. The apparatus of claim 1, wherein said actuator positions said blocking member into said blocking position during removal of said wellbore pressure setting assembly from said wellbore, at least when said igniter has not been ignited.

6. The apparatus of claim 1 , wherein said actuator is automatically activated upon reaching said depth having said wellbore fluid exerting substantially at least said selectable level of hydrostatic pressure; and

wherein said igniter is selectively operated for igniting said power charge after said actuator is activated.

The apparatus of claim 1, further comprising:

said wellbore pressure setting assembly.

8. The apparatus of claim 7, wherein said wellbore pressure setting assembly is a wireline pressure setting assembly.

9. The apparatus of claim 1, further comprising:

explosive materials which are used within said igniter.

10. The apparatus of claim 1, further comprising:

said blocking member including a necked down section, which is aligned with said ignition pathway when said blocking member is in said ignition position for providing at least a portion of said ignition pathway therethrough.

11. An apparatus for use in a wellbore to prevent an igniter from igniting a power charge within a wellbore pressure setting assembly until after said wellbore pressure setting assembly is disposed downhole within said wellbore, said apparatus comprising:

a tubular housing having a passageway extending longitudinally therein, said passageway providing an ignition pathway through which said igniter reacts for igniting said power charge within said wireline pressure setting assembly,

a valve member which is movable between a plurality of positions for selectably obstructing said passageway to block said ignition pathway and prevent said igniter from igniting said power charge;

a biasing means which urges said valve member into a blocking position obstructing said passageway; and

a wetted surface exposed to a wellbore fluid after running downhole within said wellbore with said wellbore pressure setting assembly to a depth having a wellbore fluid exerting substantially a predetermined level of hydrostatic pressure, which exerts a force against said wetted surface for urging said valve member from a blocking position obstructing said passageway to an ignition position for allowing said igniter to ignite said power charge.

12. The apparatus of claim 11, wherein said valve member is a singular rigid member.

13. The apparatus of claim 12, wherein said valve member includes said wetted surface.

14. The apparatus of claim 11, wherein said predetermined level of hydrostatic pressure is selectable for determining at least one fluid pressure level below which said valve member selectively obstructs said passageway.

15. The apparatus of claim 11, wherein said actuator positions said valve member into said blocking position during removal of said wireline pressure setting assembly from said wellbore, at least when said igniter has not been ignited.

16. The apparatus of claim 11, comprising:

a wireline pressure setting assembly.

17. An apparatus for use in a wellbore to operate a downhole well tool only after said downhole well tool is disposed downhole within said wellbore, said apparatus operating said downhole tool by converting a chemical pressure source into a force exerted over a distance, said apparatus comprising:

a pressure chamber within which a propellant is selectively initiated to interact in a slow chemical reaction for generating a gas having a pressure; a power charge within which said propellant is included, said propellant made from a plurality of chemical components which are selectively initiated within said pressure chamber to interact in a slow chemical reaction which generates said gas having said pressure, said slow chemical reaction for generating said gas taking at least one second to generate a maximum level of said pressure within said pressure chamber;

a means for igniting said power charge, wherein said means is selectively actuated by electrical energy to initiate said chemical reaction for generating said gas having said pressure;

a pressure responsive member which is selectively moved by said gas having said pressure pushing against said pressure responsive member with at least part of said force to urge a volumetric expansion within a volume which includes, at least in part, said pressure chamber;

a driven member to which said pressure responsive member is connected for transferring from said pressure at least part of said force over at least part of said distance;

a valve member which is movable between a plurality of positions for selectably obstructing said passageway to block said ignition pathway and prevent said means for igniting said power charge from igniting said power charge;

a biasing means which urges said valve member into a blocking position obstructing said passageway; and a wetted surface exposed to a wellbore fluid after running downhole within said wellbore to a depth having a wellbore fluid exerting substantially a level of hydrostatic pressure, which exerts a force against said wetted surface for urging said valve member from a blocking position obstructing said passageway to an ignition position for allowing said means for igniting said power charge to ignite said power charge.

18. The apparatus of claim 17, wherein a portion of said valve member provides said wetted surface.

19. The apparatus of claim 17, further comprising:

said downhole well tool, for urging by said driven member into a setting engagement within said wellbore.

20. A method for preventing an igniter from igniting a power charge within a wellbore pressure setting assembly until after said wellbore pressure setting assembly is disposed downhole within a wellbore, said method comprising the steps of:

securing a housing to said wellbore pressure setting assembly so that a passageway extending within said tubular housing extends between said igniter and said power charge;

obstructing said passageway with a blocking member for preventing said igniter from igniting said power charge;

providing an actuator which is operable for moving said blocking member between a plurality of positions;

lowering said wellbore pressure setting assembly and said housing downhole within said wellbore; and activating said actuator, which operates to move said blocking member from a position obstructing said passageway to a position for allowing said igniter to ignite said power charge.

21. The method of claim 20, wherein said actuator moves said blocking member to said position for allowing said igniter to ignite said power charge by moving said blocking member along a linear path of travel.

22. The method of claim 20, wherein said actuator is selectably activated.

23. The method of claim 20, wherein said actuator is activated by exposure to a wellbore fluid, which exerts a hydrostatic pressure substantially having at least a predetermined level.

24. The method of claim 23, further comprising the step of:

selecting said predetermined level of said hydrostatic pressure prior to lowering said wellbore pressure setting assembly and said housing downhole within said wellbore.

25. The method of claim 20, wherein said actuator positions said blocking member into said position obstructing said passageway to prevent said igniter from igniting said power charge during removal of said wellbore pressure setting assembly from said wellbore, at least when said igniter has not been ignited.

26. A method for preventing an igniter from igniting a power charge within a wellbore pressure setting assembly until after said wellbore pressure setting assembly is disposed downhole within a wellbore, said method comprising the steps of: securing a tubular housing to a wellbore pressure setting assembly so that a passageway extending longitudinally within said tubular housing extends between said igniter and said power charge;

providing an actuator which is operable for moving said blocking member between a plurality of positions; and

lowering said wellbore pressure setting assembly and said tubular housing downhole within said wellbore to a depth at which a wellbore fluid having substantially a predetermined level of hydrostatic pressure activates said actuator, which operates to move said blocking member from a position obstructing said passageway to a position for allowing said igniter to ignite said power charge.

27. The method of claim 26, wherein said actuator moves said blocking member to said position for allowing said igniter to ignite said power charge by moving said blocking member along a linear path of travel.

28. The method of claim 26, further comprising:

selectably activating said actuator by selecting said predetermined level of hydrostatic pressure and lowering said tubular housing within said wellbore.

29. The method of claim 26, wherein said actuator positions said blocking member into said position obstructing said passageway to prevent said igniter from igniting said power charge during removal of said wellbore pressure setting assembly from said wellbore, at least when said igniter has not been ignited.

30. The method of claim 26, wherein said blocking member is a valve member, wherein said actuator includes a biasing means and said valve member, and wherein said predetermined level of hydrostatic pressure is selectable.