Source: http://www.google.fr/patents/US4690227
Timestamp: 2013-05-19 19:29:22
Document Index: 60380947

Matched Legal Cases: ['art 206', 'art 218', 'arts 202', 'art 206', 'art 206', 'arts 202']

Brevet US4690227 - Gun firing head - Google�BrevetsRecherche Images Maps Play YouTube Actualit�s Gmail Drive Plus » Recherche avanc�e dans les brevets | Historique Web | Connexion Recherche avanc�e dans les brevets BrevetsThe method and apparatus for actuating a perforating gun by pressure includes a pressure actuated gun firing head disposed on the perforating gun for detonating the shaped charges of the gun. The gun is attached to a pipe string and located downhole adjacent the formation to be perforated. The pressure...http://www.google.fr/patents/US4690227?utm_source=gb-gplus-shareBrevet US4690227 - Gun firing head Num�ro de publicationUS4690227 AType de publicationOctroi Num�ro de demande06/738,617 Date de publication1 sept. 1987 Date de d�p�t28 mai 1985 Date de priorit�31 mars 1983 InventeursFlint R. GeorgeMarlin R. Smith Cessionnaire d'origineHalliburton CompanyVann Systems Inc.Geo International Corporation Classification aux �tats-Unis175/4.56175/4.54 Classification internationaleE21B43/11E21B43/1185E21B43/116 Classification coop�rativeE21B43/1185E21B43/116 Classification europ�enneE21B 43/116E21B 43/1185R�f�rencesCitations de brevets (4) R�f�renc� par (11)Liens externesUSPTO Cession USPTO EspacenetGun firing headUS 4690227 A R�sum� The method and apparatus for actuating a perforating gun by pressure includes a pressure actuated gun firing head disposed on the perforating gun for detonating the shaped charges of the gun. The gun is attached to a pipe string and located downhole adjacent the formation to be perforated. The pressure actuated firing head includes a housing with a plug and piston. The piston has a firing pin adapted for engagement with the initiator of a perforating gun upon reciprocation within the housing. Initially, the piston is pressure balanced until the time of actuation. The plug is responsive to fluid pressure of a predetermined magnitude at the time of the actuation of the gun firing head. Upon effecting pressure on the plug, the plug unbalances the piston causing the piston to reciprocate. Upon reciprocation of the piston, the firing pin engages the initiator to detonate the shaped charges of the perforating gun. Pressure may be effected on the firing head through the pipe string, or the annulus, or both. The firing head includes a plurality of passageways, as well as the plug and piston, arranged in a manner whereby should leakage of well fluids into the firing head inadvertently occur, the apparatus is rendered inoperative and therefore the firing head cannot inadvertently be fired due to the occurrence of unforeseen intervening circumstances.
We claim: 1. A well perforating gun firing head comprising: an expansible chamber having a movable wall carrying a firing pin; first valve means for admitting pressure fluid to the chamber; second valve means for equalizing pressure on opposite sides of the movable wall; said first and second valve means being interconnected whereby when the first valve means is closed the second valve means is open and vice versa; primary frangible means holding the movable wall against movement; ancillary frangible means holding the first valve means in closed position; and release means for causing the sequential release of initially the ancillary frangible means and ultimately the primary frangible means.
2. Firing head according to claim 1, wherein said release means includes an area exposed to pressure fluid and acting to move the first valve means toward the open position.
3. Firing head according to claim 1, said release means including an anvile exposed to receive a hammer blow and connected to the first valve means to move the first valve means to the open position upon movement of the anvil in response to such hammer blow.
4. A firing head for detonating a perforating gun in a well comprising: a housing disposed on the perforating gun, and having a chamber; a piston member reciprocably mounted within said chamber and having an armed position and an actuated position within said chamber; valve means within said housing for equalizing the pressure across said piston member when in a first position for permitting a pressure differential across said piston member in a second position; closure means on said housing for moving said valve means from said first position to said second position; said closure means being in communication with the surface and being activated from the surface whereby when activated from the surface, said closure means moves said valve means to said second position to create a pressure differential across said piston member thereby reciprocating said piston member to said actuated position for the detonation of the gun.
5. The firing head according to claim 4 wherein said valve means includes a bore in said piston member extending into one side thereof with a port extending from said bore to the other side of said piston member whereby fluid in said chamber freely flows through said bore and port to equalize the pressure on each side of said piston member.
6. The firing head according to claim 5 wherein said closure means includes a plug member reciprocably disposed in said housing for movement into said piston bore upon activation from the surface thereby closing said port to fluid flow.
7. The firing head according to claim 4 wherein said closure means further includes vent means for admitting pressure into said chamber to create said pressure differential across said piston member.
8. The firing head according to claim 7 wherein said vent means includes a passageway in said housing and said closure means includes a plug member reciprocably disposed in said passageway, said plug member prevents fluid flow through said passageway in one position and allowing fluid flow therethrough in a second position.
9. The firing head according to claim 4 wherein said closue means includes a plug member reciprocably disposed in a passageway in said housing for blocking fluid pressure from the surface into said chamber in one position and permitting the effectuation of fluid pressure into said chamber in another position; said valve means includes a bore in said piston member for receiving said plug member in said another position, said bore permitting fluid flow from one side of said piston member to the other side of said piston member until said plug member is moved from said one position to said another position to permit the effectuation of fluid pressure from the surface into said chamber and onto said piston member.
10. The firing head according to claim 9 wherein said plug member has a smaller pressure area than said piston member whereby the force applied to said plug member from the effectuation of fluid pressure is less than the force applied to said piston member.
11. The firing head according to claim 9 wherein said plug member engages said piston member upon reciprocating from said one position to said another position thereby assisting said piston member to move to said actuated position.
12. The firing head according to claim 9 wherein said plug member includes an extension projecting through said passageway.
13. The firing head according to claim 9 wherein said plug and piston members have seal means for sealingly engaging the walls of said passageway and said chamber respectively.
14. The firing head according to claim 9 wherein said plug member includes first and second seal means, said first seal means sealingly engaging said passageway in said one position and said second seal means sealingly engaging said piston bore in said another position, said first and second seal means being positioned on said plug member so that upon reciprocation of said plug member from said one position to said another position, said second seal means sealingly engages said piston bore before said first seal means unseals said passageway.
15. A firing head for detonating a perforation gun comprising: a housing having an axial passageway which is in communication with the interior of a tubing string when connected thereto; a first length of said axial passageway being spaced from a second length thereof; a first piston reciprocatingly received in sealed relationship within said first length of said axial passageway; a second piston being reciprocatingly received in sealed relationship within said second length of said axial passageway; means associated with said second piston for detonating the perforating gun when reciprocated within said second length of said axial passageway; first chamber formed on one side said second piston and a second chamber formed on the other side of said second piston; a piston passageway formed in said second piston for sealingly receiving said first piston therein; and flow passageway extending from said first chamber, through said piston passageway, and into said second chamber; a flow pasageway extending from an open end of said axial passageawy into said first length of said axial passageway; said first piston precluding flow from the open end of said passageway into said first chamber in one position and being reciprocated into sealed engagement with respect to said piston passageway of the second piston, whereupon pressure can be effected within the open end of said axial passageway to provide a pressure differential across said second piston to thereby move said second piston to detonate the perforating gun.
16. The firing head of claim 15 wherein pressure effected within said axial passageway forces said first piston to move into said piston passageway.
17. The firing head of claim 15 wherein said first piston includes a projecting extension against which a weight is impacted to cause said first piston to move into said piston passageway.
18. The firing head of claim 15 wherein said first and second pistons are releasably held respective to said main housing by shear pins, said shear pin of said first piston requiring a greater pressure to shear as compared to the pressure required to shear said pin of said second piston.
19. The firing head of claim 18 wherein leakage of liquid from said first chamber into said second chamber is effected across the opposite ends of said second piston to cause the pressure differential across said second piston to be equalized so that the gun cannot be detonated.
20. The firing head according to claim 15 wherein said first length of axial passageway extends through a bushing mounted within said axial passageway of said housing and having a portion thereof extending towards the open end of said axial passageway, said extending portion and housing forming an annular passageway therebetween and said bushing having a port extending from said first length of axial passageway to said annular passageway.
21. The firing head according to claim 20 wherein said first piston includes a pressure port extending from a radial inlet at the exterior surface of said first piston to a radial outlet at the exterior surface of said first piston.
22. The firing head according to claim 21 wherein said radial inlet is in communication with said bushing port and said radial outlet communicates with said first chamber upon said first piston reciprocating into sealed engagement with said piston passageway whereby fluid pressure may be effected through said flow passageway, axial passageway, annular passageway, bushing port and into said pressure port for effectuation on said one side of said second piston in said first chamber.
23. The firing head according to claim 21 wherein said first piston includes seals above and below said radial inlet for sealing said radial inlet from fluid communication with the open end of said axial passageway while said first piston is precluding flow through said first length of axial passageway.
24. The firing head according to claim 23 wherein said radial outlet communicates with said first chamber while said firs piston is precluding flow whereby any fluid leaking around said seals will flow through said pressure port and render said firing head inoperable.
25. The firing had according to claim 23 wherein said first piston includes a reduced diameter end extending toward the open end of said axial passageway and said first length of axial passageway includes a reduced diameter portion slidingly receiving the reduced diameter end of said first piston, said seals sealingly engaging the walls of the reduced diameter portion until said first piston reciprocates and said seals move into the larger diameter portion of said first length of said axial passageway whereby fluid flow is permitted through the reduced diameter portion of said first length of said axial passageway.
26. A pressure actuated gun firing head for attachment to a perforating gun, comprising: an apertured first piston slidably received within a first cylinder; a second piston slidably received within said aperture and movable from an unarmed into an armed position; a first chamber above said first piston; a second chamber below said first piston; and an initiator for detonating shaped charges of a gun, said initiator being positioned to be detonated in response to movement of said first piston; means in said head forming a flow path which communicates with the surface of the ground, said flow path extending into said first chamber when said second piston is in the armed position, said flow path being closed when said second piston is in the unarmed position; whereby leakage of incompressible fluid into said first chamber flows through the aperture and renders said first piston immovable, and pressure effected on said second piston moves said second piston into said aperture and is thereby effected across said first piston.
27. A gun firing head for well perforating guns including: a firing means for actuating a detonating device, an expansible chamber including a movable wall; first fluid passage means connecting the interior of said chamber to the exterior of said chamber adjacent said movable wall, second fluid passage means for connecting the interior of said chamber with a third fluid passage means adapted for connection to a source of pressure fluid; first closure means adapted to move to a position closing said first fluid passage means from a normal position in which said first fluid passage means is open, second closure means movable from a normal closed position blocking flow through said second fluid passage means to an open position in which flow through said second fluid passage means is permitted; first shear pin means holding said first closure means when said first closure means is in the normal open position, second shear pin means holding said second closure means in normal closed position; surface means responsive to pressure in said third fluid passage means for overcoming said second shear pin means and moving said second closure means to open position upon existence of at least a certain pressure in said third fluid passage means; means interlocking said first closure means with said second closure means to move said first closure means to closed position when said second closure means moves to open position; means for transferring chamber expansion force on said first closure means to said movable wall when said first closure means is in closed position; and said first shear pin means shearing and said movable wall moving to actuate said detonating device upon the pressure within said expansible chamber rising to said certain pressure.
28. The gun firing head according to claim 27 and further including: an anvil connected by a stem to said second closure means for shearing the second shear pin means upon imposition of a sufficient blow on said anvil whereby said detonating means can also be actuated by pressure in said third fluid passage means less than said certain pressure; said anvil stem having an effective area subject to pressure in said third passage means that is smaller by a differential surface area then the cross-sectional are of said second fluid passage means; seal means sealing said differential surface are of said second closure means from fluid pressure in such third fluid passage means; and fourth fluid passage means interconnecting the sealed off differential surface are with the interior of said expansible chamber but only when said second closure means is in open position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring initially to FIG. 1, there is disclosed a typical well having borehole 10 extending downhole from the surface 12 of the ground through a hydrocarbon-containing formation 14. The borehole 10 is cased by a string of casing 16 hung from wellhead 18 and within surface casing 20. Casing string 16 is cemented into borehole 10 and casing 20 as shown at 22. Casing 16 isolates the wellbore 24 from formation 14. A string of production tubing 26 is suspended within casing 16 and extends from the surface 12 axially through casing 16. Tubing 26 within casing 16 forms borehole annulus 28, and packer 30, disposed on tubing 26, divides the borehole annulus 28 into an upper annulus 32 and a lower annulus 34. Suitable outlets are provided at the surface 12 for the tubing flow bore and each annulus formed by adjacent casing strings with each of the outlets being provided with suitable valves and the like, including valve 36 for the outlet communicating with the borehole annulus 28 and valves 38, 39 for the outlet communicating with the flow bore 40 of tubing string 26. A lubricator 42 is provided for access to tubing flow bore 40 for the use of slick line tools.
In order to complete the well or test the formation, it is necessary to access the hydrocarbons in formation 14 with the wellbore 24. This is accomplished by supproting a perforating gun 50 at the lower end of the tubing string 26. Gun 50 is preferably a jet casing gun, but it should be understood that the term is intended to include any means for communicating the hydrocarbon-producing formation 14 with lower annulus 34. The jet perforating gun of the casing type shoots metallic particles into the formation 14 to form perforations 44 and corresponding channels or tunnels 46. Numerals 44 and 46 broadly indicate a few of a plurality of perforations and tunnels which are formed when the charges 52 of gun 50 are detonated. Perforating objectives include perforations of a desired size and configuration, prevention of further formation invansion and contamination during the perforating process, and maximum capacity to move the hydrocarbons from formation 14 to lower annulus 34.
Mandrel 66 includes a reduced diameter portion or pin 76 which is telescopingly received within box 74 of cylinder 64. Pin 76 is threadingly engaged to box 74 at 78 by external threads on pin 76 and internal threads on box 74. Pin 76 forms an annular shoulder 82 for seating the lower end of cylinder 64 upon complete attachment. Set screws 84 are provided in threaded bores in the lower end of cylinder 64 to engage the outer suface of pin 76 and prevent any inadvertent disengagement of cylinder 64 and mandrel 66. Pin 76 has annular seal grooves in which are disposed sealing members 112, 114 for sealing engagement with the internal surface of box 74 to prevent leakage at connection 78.
At the upper end of cylinder 64 is a tapered threaded pin 86 and tapered shoulder 88 for making connection with one of the pipe members making up tubing string 26. The piper member of string 26 adjacent pin 86 has a threaded box which threadingly receives pin 86 for mounting firing head 60 onto tubing string 26. Pipe readily available at the well site is often used for tubing string 26. Since that pipe may often be drill pipe or drill collars, the connection on the upper end of housing 62 may be a rotary shouldered connection compatible with such pipe.
Mandrel 66 includes a lower threaded box end 92 for threadingly receiving a sub 51 on the upper end of perforating gun 50. Pin 76, extending above box end 92, has a central bore 80 generally having the same internal diameter as axial passageway 70 in cylinder 64. Central bore 80 has a lower counterbore 84 adjacent box end 92 for receiving initiator 90 as hereinafter described, and is restricted by an inwardly directed annular shoulder 96 located near the upper end of pin 76. Annular shoulder 96 includes an upwardly facing seat 98 forming an insert counterbore 102 with the upper portion of bore 80 and a downwardly facing seat 104 forming a chamber 100 with the lower portion of bore 80. Insert counterbore 102 receives closure assembly 100, hereinafter described, and chamber 100 houses piston 120, hereinafter described. The upper end of bore 80 is bevelled at 106 for receiving closure assembly 110, and pin 76 is reduced in outer diameter at 108 along its upper end.
Initiator 90 is mounted within a bore 122 in an initiator support 124 which is telescopingly received within lower counterbore 94 of central bore 80. Support 124 has O-rings 126 disposed in annular grooves therearound for sealing with the internal surface forming counterbore 94. Counterbore 94 and bore 80 form a downwardly facing annular shoulder 128 for abutting the upper face 130 of support 124. As the sub 51 of perforating gun 50 is threaded into box and 92, the upper end of the sub 51 engages the lower face 132 of support 124 and the lower end of initiator 90 to secure support 124 and initiator 90 within lower counterbore 94. Initiator 90 supports a plurality of seal rings 134 on its exterior for sealing engagement with the inner surface of bore 122 and has an elastomeric ring 135 on its upper end to take up any end play as sub 51 is threaded into end 92. A prima cord 53 extends from initiator 90 to the shaped charges 52 of gun 50 whereby upon the initiation of initiator 90, charges 52 are detonated. The upper end of bore 122 is reduced in diameter forming an entry bore 136 for a firing pin to be described.
Piston 120 includes a reduced diameter lower end 138 which supports a firing pin 140 positioned on piston 120 to be received by entry bore 136 when piston 120 is moved to its lowermost position. Firing pin 140 has threads on one end which is threaded into a hole at 142 in the lower face of end 138 and secured by a set screw (not shown), and a point 146 for impacting and setting off initiator 90. As best shown in FIG. 2, initially piston 120 is secured by shear pins 150 in an uppemost position against lower seat 104 in chamber 100. Shear pins 150 are sized to shear upon the application of a predetermined pressure force on the upper face of piston 120.
Bonnet bore 164 is part of a fluid flow path which ultimately extends to the surface 12. A plurality of radial fluid ports 180, located adjacent bottom 172 of bonnet bore 164, extend from blind bore 174 to the exterior of bonnet 152 and axial fluid flow passageway 70 of cylinder 64. Shoulder 176 of stem 174 prevents plug 160 from moving over bonnet ports 180 so as to damage O-ring seal members 182, 184. Initially, as shown in FIG. 2, plug 160 is in the upper and bonnet port sealing position preventing any fluid flow from passageway 70 to chamber 100. Plug 160 is held in the upper position by shear pin 188 sized to shear upon the application of a predetermined fluid pressure in passageway 70 through bonnet ports 180 and that portion of bonnet bore 164 above plug 160. Roll pins 189 pass through closure assembly 110 to hold shear pin 188 in position.
Shear pins 188 determine the amount of fluid pressure required in passageay 70 to actuate firing head 60. Where head 60 is to be actuated solely by fluid pressure, i.e. without the use of a bar, shear pins 188 are sized to shear at a predetermined pressure approximately 2000 to 3000 psi above hydrostatic pressure. The hydrostatic pressure is the heavier of the hydrostatic head in the casing annulus 28 or the tubing flow bore 40. If the predetermined pressure were calculated based on the tubing flow bore hydrostatic and the casing annulus hydrostatic was greater than the predetermined pressure set to shear pins 188, a leak from the casing annulus into the tubing flow bore might raise the fluid pressure in passageway 70 to the predetermined pressure and prematurely detonate gun 50. Thus, shear pins 188 must be heavy enough to insure that pins 188 will not be sheared by the largest hydrostatic head in the well.
Referring now also to FIG. 4, pressure actuated firing head 60 is shown fully actuated. By unsealing bonnet ports 180, the fluid from axial passageway 70 now flows into upper chamber 100A. Further, because plug 160 has now sealed piston ports 190, a pressure differential is effected across piston 120. Upon the application of this increased fluid pressure onto the upper face of piston 120 and the impact of plug 160 engaging bottom 192 of piston bore 166, pins 150 are sheared. Shear pins 150 for piston 120 may be larger than shear pins 188 for plug 160 because the cross-section of piston 120, i.e. pressure area, is greater than the cross-section of plug 160. Since piston 120 is substantially heavier than plug 120, pins 150 need to be larger to pass the drop test. Pins 150 are not strong enough to withstand the hydrostatic head and would shear.
In operation, fluid pressure is effected into passageway 70 to actuate head 60. Although normally the fluid pressure will be hydraulic pressure from a liquid, it is possible that a gas may be used to actuate head 60. Further, fluid pressure may be effected in passageway 70 by pressuring down the flow bore 40 of tubing string 26, or pressuring down the casing annulus 28, or pressuring down both the tubing flow bore 40 and casing annulus 28, or pressuring down a flow path made up of portions of tubing flow bore 40 and casing annulus 28 to communicate with passageway 70.
A substantial pressure differential is created across plug 160. On the upper face of plug 160 and stem 174 is hydrostatic pressure plus 2000 to 3000 psi and on the lower face of plug 160 is atmospheric pressure since cylinder 162 and chamber 100 are at atmospheric. As plug 160 moves downward under the pressure differential, seal 182 continues to seal with bonnet 152 until after lower seal 184 has sealingly engaged the walls of cylinder 162 of piston 120. As plug 160 moves into cylinder 162, any trapped pressure is exhausted through piston ports 190. Once plug 160 is received within cylinder 162 and seal 184 has sealed with piston 120, ports 190 in piston 120 are closed preventing free fluid flow between upper and lower chambers 100A and 100B. At that time upper seal 182 disengages with bonnet 152 and permits the fluid pressure of passageway 70 to pass into upper chamber 100A and be applied to the cross-section of piston 120. Fluid from passageway 70 flows through hole 168 between stem 174 and bonnet 152and through bonnet ports 180 into blind bore 164 in bonnet 152. The fluid then passes from bore 164 into upper chamber 100A.
The box end 210 includes an axial bore 214 which is reduced in diameter at 216. The outside diameter of the upper end of the lower main body part 206 is reduced in diameter commencing at 204 to provide reduced diameter part 218. Outer surface 218 and inner surface 220 are made in close fitting relationship relative to one another so that one slidably receives the other in a telescoping manenr therewithin. The before mentioned coacting threaded areas 203 releasably fasten the upper and lower main body parts 202, 206 together.
An annular boss 224 projects inwardly from housing 200 an is internally threaded at 226. The boss 224 increases in diameter to proivde a cylindrical portion 228, which again increases in inside diameter at 230 to provide the illustrated upper constant diameter inner surface which terminates at the upper terminal end thereof in the form of a shoulder 232.
As best shown in FIG. 6, bushing 242 is secured to lower body part 206, and is provided with a contoured entrance at 260. Bushing 242 further includes an outer surface area defined by outside diameter 262. The bushing is spaced from the wall of axial bore 70, thereby forming an upwardly opening annulus 264. The annulus 264 communicates with bore 256 by means of the illustrated radial passageway 270. The upper reduced diameter end of piston plug 250 includes at least one radial passageway 272 which communicate with an axial passageway 274 which leads to a lower radial passageway 276. Radial passagway 276 communicates, via axial passageway 274, with the upper end of piston plug 250 which is isolated from well fluids by means of the spaced O-rings 244 and 246.
Should well fluids leak past seal 244 or 246 to act on the upper end of piston plug 250, it will also be conducted by passages 272, 274, 276 to lower end 258 of piston plug 250 and exert there a balancing force so that piston plug 250 will not be moved. The upper end of piston plug 250 is releasably affixed to bushing 242 by means of radially disposed shear pins 278. Shear pins 278 are selected to fail upon the application of a predetermined foce, as will be more fully discussed hereinafter.
In this embodiment of the present invention, shear pins 278 may be somewhat smaller. Because that portion of bore 248 between seals 244, 246 communcates with upper chamber 284, via ports 272, 274, 276, there is atmospheric pressure on both sides of the small diameter portion of plug 250 having little tendency for moving plug 250. The only down force on plug 250 is the difference in cross-sectional area between the larger lower portion of piston 250 and the smaller upper portions of piston 250. Thus the smaller pins 278 can pin against a high hydrostatic.
Large piston 280 has an upwardly opening passageway 282 formed therewithin which is in communication with an upper chamber 284 when the firing head is in the standby configuration as shown in FIG. 5. Lateral ports 286 place the lower chamber 288 in communication with piston passagway 282.
Initiator support 202 underlies the piston 280 and has an outside diameter 294 fitting closely within the before mentionend axial bore 214. The support 292 is provided with an axial bore 296 which sealingly receives the initiator 290 in sealed relationship therewithin, noting the plurality of spaced O-rings located between the initiator 290 and the bore 296. O-rings 298 seal the interface between outside diameter 294 and axial bore 214. Piston 280 is reduced in diameter at lower end 302 thereof. The upper face 304 of piston 280 is dispsoed within the interior of chamber 284. Lower face 308 of piston 280 is disposed within lower chamber 288. The lower end of piston 280 is again reduced at 310 to provide a firing pin 300 at the lower extremity thereof.
Radial shear pins 312 are formed through the sidewall of the lower main part 206 and extend into bores formed in a sidewall of piston 280. Shear pins 312 are sized to insure that pins 312 do not shear due to the weight of piston 280 or due to head 60 being accidentaly dropped. O-rings 314 seal against fluid flow across the shear pins 312 and across the threads 203. O-rings 316 further seal against flow which may occur across shear pins 312 or from upper chamber 284 into lower chamber 288 under certain conditions of operation, as will be further discussed later on in this disclosure.
Locking screws 318 prevent inadvertent relative motion between the upper and lower main body parts 202 and 206. Prima cord 320 is routed through passageway 322 of sub 51 associated with gun 50. The prima cord 320 is attached to the initiator 290, and to the shaped charges 52 so that when the firing pin 300 strikes face 324 of initiator 290, initiator 290 explodes, which in turn explodes prima cord 320, and this action instantaneously detonates all of the shaped charges 42 associated with the gun 50. In actual practice, the initiator explodes and thereafter the prima cord 320 is progressively exploded, with each of the shaped charges 52 being sequentially exploded; however, the time frame within which this explosive train occurs is of such a short duration that one could call this action "instantaneous", although those skilled in the art of measuring phenomena that occur within a millisecond would probably consider that the explosion train requires a time duration.
Referring now to FIG. 7 showing partial actuation, shear pin 278 is sheared by increasing the fluid pressure in passageway 70 which, when applied to the cross-sectional area of shaft 238 projecting into passageway 70 and to the remaining crosssectional area of piston plug 250 in bore 256 via ports 270, the force will reach the predetermined amount which will shear pins 278. As piston plug 250 and shaft 238 move downwardly, the lower end of piston plug 250 with O-ring seal 254 enters piston passageway 282 where O-ring seal 254 sealingly engages piston plug 250 and large piston 280 to close off lateral ports 286 in large piston 280. Then, O-ring seals 244 on shaft 238 and seal ring 246 on the upper end of piston plug 250 move into enlarged bushing bores 248, 256, respectively whereby seals 244, 246 disengage their sealing engagement with bushing 242. Further, as piston plug 250 moves out of bore 256 of bushing 242, O-ring seal 252 also unseals with bushing 242. However, prior to the disengagement of seals 244, 246 and 252, the lower seal 254 on piston plug 250 sealingly engage the cylindrical wall of bore 282 in piston 280 which in turn seals off piston ports 286. When plug 250 bottoms in cylinder 282 of piston 280, radial ports 272 are in communication with ports 270.
Another application of the present invention is illustrated in FIG. 10. In this application the present invention is used to test a plurality of payzones through a single tubing string. Referring to FIG. 10, there is shown a casing 350 extending through a plurality of payzones such as upper payzone 352 and lower payzone 354. The tool string includes an upper packer 356, an upper vent 358, an upper pressure actuated firing head 360, an upper perforating gun 362, a lower packer 366, a lower vent 368, a lower pressure actuated firing head 370, a lower perforating gun 372 and a bull plug 364, all suspended on tubing string 374. Bull plug 370 closes the lower end of tubing string 374. Although only two payzones and corresponding perforating guns are shown, it should be understood that any number of payzones could be tested by adjacent perforating guns mounted on tubing string 374. Upper and lower pressure actuated firing hads 360, 370 and upper and lower perforating guns 362, 372 are mounted on the exterior of tubing string 374. Each pressure actuated firing head is in fluid communication with the tubing flow bore of tubing string 374 by means of a ported connector whereby pressure effected down the tubing flow bore of string 374 is applied to the respective plugs of firing heads 360, 370. Vents 358, 368 may be sliding sleeves or one-way valves for the passage of production fluids into the tubing flow bore of string 374 after perforaton. It should be obvious that a bar cannot be used in this situation since the perforating guns are disposed outside the tubing string. The shear pins 188 in firing heads 360, 370 are set at 500 psi intervals whereby the lowest firing head 370 and gun 372 will be actuated first. Thus lower pressure actuated firing head 370 has shear pins 188 set to shear at a predetermined pressure 500 psi lower than the predetermined pressure set to shear the pins 188 in upper pressure actuated firing head 360. In operation, lower packet 366 is set to isolate payzone 354. When the invention is used in a new well such that the annulus below packers 356, 366 can be pressurized, lower vent 368 may be a sliding sleeve which is opened using a wireline prior to perforating. Pressure is then effected down tubing string 374 until shear pins 188 of lower firing head 370 are sheared and gun 372 is detonated. Production is then permitted into tubing string 374 via lower vent 368. After lower payzone 354 is tested, lower vent 368 is closed and upper packer 356 is set if it has not already been set. Upper vent 358 is then opend and pressure is again applied through tubing string 374 until pins 188 in upper firing head 360 are sheared and payzone 352 is perforated for testing. Production is then permitted into tubing string 374 via upper vent 358. Where the annulus below packers 356, 366 cannot be pressurized, as for example where there are existing perforations already in payzones 352, 354, vents 358, 368 may be one-way valves which are opened to the flow of production fluids after perforation either by bleeding the pressure off from tubing string 374 or swabbing string 374 to open the one-way valve.
A still another application of the present invention is with a workover operation where the well has previously been perforated. As shown in FIG. 1, a tool string with a packer 30, vent assembly 56, releasable coupling 58, pressure actuated firing head 60, and jet perforating gun 50 suspended on tubing string 26 is run into the well with the vent assembly 56 closed. Tubing string 26 is filled with fluid. Packer 30 is hydraulically set. Pump pressure is applied down the flow bore 40 of tubing string 26 to actuate firing head 60 and fire gun 50. Vent assembly 56 is then opened, and the pump pressure is bled off or the tubing string is swabbed to bring in the well. Vent assembly 56 could not have been opened prior to detonation due to the old perforations in the payzone. Vent assembly 56 may be a sliding sleeve or a check valve which opens when the pressure in the tubing string is reduced. No underbalance, i.e. downhole pressure less than formation pressure, is used. The same procedure may be used in a new well where an overbalance is desired, i.e. downhole pressure greater than formation pressure. Gun 50 may be dropped by using releasable coupling 58.
In a variation to the above, the bar initiates activation of the pressure actuated firing head but additional pressure must be added to the tubing flow bore to complete actuation. The tool string is lowered into the well with a normally closed vent assembly. In operation a bar is dropped downhole. The bar opens vent assembly 56 and impacts against head 178, thereby driving the plug 160 into the piston passageway 162 and forming a flow path from the tubing string into the upper chamber 100A. The gun firing head 160 now is the "armed" or "cocked" position and the gun 50 is ready to fire upon the addition of sufficient pressure being effected within the tubing string 26. The vent 56 can be opened using wireline, bar, or packet actuated devices. Further pressure is then applied. This preferably is accomplished using N.sub.2, CO.sub.2, or flue gases, although a liquid could be employed to elevate the tubing hydrostatic head or fluid pressure to the valve required to shear the piston pin 150. After the pressure differential across the piston 120 has sheared the piston pins 150, the piston 120 strokes downhole, thus forcing firing pin 146 to strike the initiator 90, and explode the prima cord 53, which detonates the individual shaped charges 52. After the casing 16 has been perforated, the tubing is swabbed until production is achieved. In some instances it may be necessary for the well to be put on a pumpjack unit because of the low downhole formation pressure. In the above example, it is, of course, necessary to contain the downhole pressure by the provision of a hydrostatic head achieved by the use of a suitable well fluid.
A still another application of the present invention is shown in FIG. 11 where a pressure actuated firing head is used as an alternate firing head. Referring now to FIG. 11, there is shown a casing 380 extending though a formation 382. A tool string with a packer 384, vent assembly 386, releasable coupling 388, bar actuated firing head 390, perforating gun 392, and pressure actuated firing head 394 suspended on a drill string 396, is lowered in the borehole until the perforating gun 392 is adjacent formation 382. The packer 384 is set to isolate formation 382 and a bar is dropped to actuate bar actuated firing head 390. Vent assembly 386 is either packer actuated or bar actuated. If, for some reason, bar-actuated firing head 390 does not actuate, pressure actuated firing head 394 may be actuated by pressuring down tubing string 396 and through open vent assembly 386 into lower annulus 398. Pressure actuated firing head 394 is in fluid communication with the lower annulus 398, and therefore pressure is effected on pressure actuated firing head 394 to detonate gun 392. Thus, pressure actuated firing head 394 serves as a back-up firing head.
Those skilled in the art, having digested the above description of this invention, will appreciate that the gun firing head can be actuated by (1) pressure of a predetermined magnitude; (2) bar and pressure combination; or (3) bar and elevated tubing pressure in two distinct steps.
One advantage of the present invention is to fire a perforating gun or guns under conditions which prevent firing with a bar. Once such condition would be to pressure the tubing or the annulus to fire a lower gun prior to firing an upper gun with the upper gun and lower gun being attached to one another. The upper gun can thus be fired by dropping a bar. Therefore, the present invention enables the charges of a casing gun to be detonated commencing at the bottom-most cahrge and proceeding uphole until the uppermost charge has been fired. This may be accomplished by inverting the gun and gun firing head, thereby locating the gun firing head on the bottom of the gun "looking downhole". The vent assembly by the lower gun must be opened in order to fire the lower gun by elevating the bottom hole pressure as in (1) above. A bar cannot be used as in (2) above in this instance.
Should this primary valve leak and fluid enter the expansible chamber, the movable wall would move the firing pin to detonate this gun. This is the problem faced and solved by this invention.
It is to be understood that although it is preferred that the upper shear pins break at a higher pressure than the lower shear pins, as that operation without the use of a bar, i.e. all pressure operation, will cause a snap action of the firing head, it would also be possible to provide a firing head in which the upper shear pins sheared at a lower tubing pressure than the loewr shear pins, whereby a two stage all pressure operation could be achieved, the head first being armed by raising the tubing pressure to a certain value to shear the upper shear pins and thereafter at any time the pressure could be raised to a higher pressure sufficient to shear the lower shear pins and move the lower piston to detonate the gun.
FIG. 1 is a fragmentary, partly schematic, partly diagrammatic, partly cross-sectional view of a well with substantially vertical borehole and an apparatus made in accordance with the present invention associated therewith;
FIG. 9 is a fragmentary, partly schematic, partly diagrammatic, partly cross-sectional view of a highly deviated well and an apparatus made in accordance with the present invention associated therewith;
FIG. 10 is a partly schematic, partly diagrammatic view of a well for perforation of multiple portions of the cased borehole using a plurality of apparatus made in accordance with the present invention associated therewith; and
FIG. 11 is a fragmentary, partly schematic, partly diagrammatic, party cross-sectional view of a well and a perforating gun having both a bar-actuated firing head and the apparatus of the present invention.
BACKGROUND OF THE INVENTION After a wellbore has been formed into the ground and the casing has been cemented into place, the hydrocarbon containing zone usually is communicated with the casing interior by forming a plurality of perforations through the casing which extend radially away from the casing and out into the formation, thereby communicating the hydrocarbon producing zone with the interior of the casing.
A bar actuated firing head cannot be used in certain situations and sometimes it is desirable to be able to detonate the charges of a perforating gun without the use of a bar. Particularly it would be advantageous to actuate the gun by effecting a pressure within the pipe string or annulus or both, but a gun firing head which could be detonated in response to pressure effected within the borehole has been considered to be highly dangerous by many logging and completion engineers for the reason that leakage across some of the critical seals of the firing head could inadvertently detonate the firing head and prematurely explode the shaped charges of the gun. Should this misfire occur at an inappropriate time, untold damage could be done to the wellbore if, for example, the explosion occurred while running the gun into the hole, or if the explosion occurred before proper flow passageways back to the surface had been provided for the competed formation. If a pressure actuated gun is to be safe, it is necessary that the firing head be unable to detonate the shaped charges until the gun has been lowered downhole and properly located relative to the formation to be completed.
U.S. Pat. No. 3,189,094 to Hyde discloses a hydraulically operated firing apparatus on a gun perforator for purposes of formation testing. The firing apparatus assembly includes a tubing string having a conventional formation tester valve in a housing and a conventional packer secured below the housing. Firing apparatus housings, along with the gun perforator, are series connected to the tubing string below the packer. In conducting a formation test, the assembly is lowered into a fluid filled wellbore so that, externally, all parts of the assembly are subjected to the submergence pressure exerted by the fluid in the well. The formation tester valve is initially closed so that the pressure within the empty tubing string is essentially at atmospheric pressure. When the packer is set, the zone opposite the gun is isolated from the region above the packer. Thereafter, when the formation tester valve is opened, the zone opposite the gun is exposed essentially to atmospheric pressure, or at least to a pressure which is greatly lower than the submergence pressure of the fluid in the well. Although various embodiments of the firing apparatus are disclosed, all of the embodiments utilize the submergence pressure to arm the firing apparatus during descent of the assembly and then utilize the low pressure condition created when the packer has been set and the formation tester valve opens to cause a pressure differential which operates the firing apparatus and fires the gun. The gun perforator penetrates the surrounding formation so that the formation fluids flow into the tubing string to complete the formation testing operation.
SUMMARY OF THE DISCLOSURE According to the invention there is provided a pressure actuated firing head for detonating the shaped charges of a perforating gun to which the head is connected. The gun is suspended downhole in a borehole on a tubing string, and the firing head is in fluid communication with the surface so that pressure can be effected at the surface down to the firing head to detonate the gun. The firing head is set to detonate the shaped charges of the gun at a predetermined pressure.
The pressure is elevated to a predetermined value, thereby moveing a plug located in the head in response to the pressure. This action closes ports located in a piston of the head, whereby pressure can now be effected on the upper face of the piston, thereby driving the piston into engagement with an explosive initiator. The initiator, when detonated by the piston movement, causes the shaped charges of the gun to be detonated.
Prior to movement of the plug, the flow path from the surface to an upper chamber, located above the piston, is closed, and the ports through the piston into a lower chamber, located between the piston and the initiator, are open. Should leakage of well fluids into the upper chamber of the firing head inadvertently occur, the apparatus is rendered inoperative because the leaking fluid flows through the ports of the piston to the lower chamber so that equal fluid pressure is placed on opposed faces of the piston, thereby rendering the piston immovable and non-responsive to pressure.
In a more specific embodiment of the invention, the firing head includes an enlongated main housing having a passageway which is in fluid communication with a flow path to the surface.
A relatively small inside diameter length of the passageway is spaced from a relatively large inside diameter length thereof. a relatively small outside diameter plug in the form of a piston or plunger, is reciprocatingly recieved in sealed relationship with the relatively small inside diameter length of the passageway. A relatively large outside diameter piston is reciprocatingly received in sealed relationship within the relatively large inside diameter length of the passageway.
In one embodiment of the invention, a bore extends from near the upper end of the plug, through the plug, and into the upper chamber above the piston to equalize pressure around the plug should seals leak around a stem connected to an extending from the upper end of the plug.
The above objects are attained in accordance with the present invention by the provision of a method for use with apparatus faabricated in a manner substantially as described in the above abstract and summary.
This application is a continuation application Ser. No. 481,069, filed Mar. 31, 1983. now abandoned.
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