US3040808A - Method and apparatus for perforating oil wells - Google Patents

Description

June 26, 1962 H. B. SCHRAMM ET AL 3,040,808

METHOD AND APPARATUS FOR PERFORATING OIL WELLS Filed Feb. 17, 1959 5 Sheets-Sheet 1 IN V EN TOR5 HAPPY 6. sfHPAMM mica-4550) by JQf'PH/NESCf/PAMM (FIECUTI/X) June 26, 1962 H. B. SCHRAMM ET AL METHOD AND APPARATUS FOR PERFORATING OIL WELLS Filed Feb. 17, 1959 Ana-3 5 Sheets-Sheet 2 FIG -4- o INVENTORS C4 APE/V66 1/595 June 26, 1962 H. B. SCHRAMM ET AL 3,040,808

METHOD AND APPARATUS FOR PERFORATING OIL WELLS Filed Feb. 17, 1959 5 Sheets-Sheet 3 June 26, 1962 H. B. SCHRAMM ET AL 3,040,808

METHOD AND APPARATUS FOR PERFORATING OIL WELLS-- Filed Feb. 17, 1959 5 Sheets-Sheet 4 fins-7 a;

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IN VEN TORS HA PP) 9. .SCHPA MM (05645509 b y Josipm/vffnrpmwMfflricure/A C4 APE/V6.6 P. A AEHEPT ATTOPA/[YJ June 26, 1962 H. B. SCHRAMM ET AL METHOD AND APPARATUS FOR PERFORATING OIL WELLS Filed Feb. 17, 1959 5 Sheets-Sheet 5 IIIIIIIII INVENTORS [MFA-was" P. 055597 5/.- WWW United States This invention relates to a method and apparatus for perforating oil Wells, and has for its primary object the provision of a novel method and means whereby all of the perforating operations are carried out and controlled by fluid pressure exerted in the well from the well head.

Another object is to provide a method and apparatus whereby the perforating means is inserted in the well, landed and locked in place in the well at a desired location therein with a perforating device suspended therefrom and located adjacent a production zone to be perforated, detonated, and removed from the wellsolely by means of fluid pressure exerted in the Well from the well head, and without the use of wire line or similar equipment.

Another object is to provide apparatus for perforating a well which apparatus can be pumped into a well through a tubing string which has one or more curved portions each with a substantially small radius of curvature.

A further object is to provide a detonator operable in response to an extended duration of a fluid pressure of a predetermined magnitude.

Still another object of the invention is to provide a method and apparatus for locating and positioning a perforating device in a well adjacent to a production zone to be perforated.

Other objects and advantages will become apparent in the course of the following detailed description.

In the drawings, forming a part of this application, and in which like parts are designated by like reference numerals throughout the same,

FIG. 1 illustrates schematically a well drilled at a water location with the perforating gun shown suspended from v the well tubing and adjacent the production formation to be perforated.

FIG. 2 is a detail view, partly in section, of the extension hanger used in FIG. 1 to suspend the perforator gun in place.

FIG. 3 is a detail view, partly in section, of a modification of the extension hanger shown in FIG. 2, and also showing a sectional view of a ball joint used between the extension hanger and detonator.

FIG. 4 is a sectional view of the detonator used in the assembly shown in FIG. 1.

FIGS. 5A, 5B and 5C are continued elevational views of the flexible plug means used in the present invention to install and remove the perforating assembly in and from the well tubing string by fluid pressure exerted from the well head.

FIG. 6 is a partial view of the system shown in FIG. 1 illustrating a modification of the manner in which the well tubing strings are located and packed to the casing string.

FIG. 7 is an elevational view, partly in section, of a portion of the flexible plug means shown in FIGS. 5A, 5B and 5C, illustrating the details thereof.

FIG. 8 is a generally schematic view, similar to FIG. 1, illustrating a modification of the invention in which the tubing-casing annulus is used as a flow path.

FIG. 9 is a partial view of a system similar to that of "ice FIG. 8, illustrating another manner in which the tubingcasing annulus is used as a flow path.

In terms of general description, the present invention finds particular use in carrying out well perforating operations in offshore well locations wherein a pair of well tubing strings extends from an onshore well head out to an offshore well and then generally vertically down through the cased bore of the well. One of these tubing strings is provided with a landing nipple made up therein which is spaced above the desired zone of the well to be perforated at a distance therefrom which is determined in a manner to be more fully described.

At the onshore well head, a well perforating device is flexibly connected to an extension hanger and pressure actuated detonator at a distance therefrom equal to the I above determined distance from the well zone to the landing nipple. The extension hanger is connected to an elongated flexible plug and the whole assembly is inserted within one of the tubing strings. Fluid pressure is then'applied to this tubing string to force the plug through the length thereof, until the extension hanger lands in the landing nipple which prevents further downward movement of the extension hanger in the tubing. The perforating device will now be suspended in the Well below the bottom of the tubing string and adjacent the zone of the well to be perforated.

In one embodiment of the invention, the extension hanger is locked against vertical movement in the landing nipple when landed therein. Fluid pressure is then applied from the onshore well head to the other tubing string, which fluid pressure enters the lower end of the first tubing string and disconnects the plug member from the locked in place extension hanger. This same fluid pressure then forces the plug member back through the first tubing string to the well head, where it is removed. Fluid pressure is then reapplied at the well head to the first tubing string at a pressure suflicient to actuate the detonator which in turn causes the perforating device to fire. The plug member is then inserted into the first tubing string, with a pulling, or retrieving, tool connected thereto, and is pumped through the tubing stn'ng until the retrieving tool engages the extension hanger. Fluid pressure is again applied at the well head to the second tubing string to force the plug and extension hanger back up through the first tubing string to the wellhead, to'complete the operation.

In another embodiment of the invention, the extension hanger is landed in the landing nipple by pumping the plug member through the first tubing string, as above described, but the extension hanger is not locked in the landing nipple against upward vertical movement therefrom. In this embodiment, the plug member is not removed from the extension hanger before the perforating device is fired. Rather, the fluid pressure in the tubing string is increased, and a fluid by-pass is provided past the plug member so that the increased pressure will actuate the detonator to fire the perforating device. After firing, fluid pressure in applied to the other tubing string to force the plug member and extension hanger back up through the first tubing string to complete the operation.

Referring now to the drawings, and particularly to FIG. 1 thereof, thereference numeral 10 indicates anPumps 19 and 20 are provided at the well head, for thetubing strings 14 and 15, respectively, so that desired fluid pressures may be built up in these strings from the well head. Thetubing strings 14 and 15 are'each provided with an enlargedinternal diameter portion 21; and 22, respectively, bent on a short radius from the top of the casing towards the onshore well head. r

Thetubing string 14 has alanding nipple 23 made up therein adjacent the 'bottom thereof, to receive anextension hanger 24 which will be supported therein against downward movement therethrough. Aball joint 25 flexibly connects the extension hanger to .aconnector member 26, which in turn is connected to thedetonator device 27. A flexiblelink spacer assembly 28 extends downwardly from the detonator housing to a flexible, multiplegunperforating device 29. Theextension hanger 24, shown in detail in FIG. 2, is generally of the type more fully illustrated and described in the Fredd Patent No. 2,798,559, and comprises amain mandrel 31 having alongitudinal bore 32 therethrough. A pair ofselector keys 33 and 34 is carried on the main mandrel, the keys being biased outwardly from themandrel 31 bysprings 35. As'is seen in FIG. 2, when the extension-hanger 24 is landed inlanding nipple 23, theselector keys 33 and 34' are biased outwardly into complementary shapedannular grooves 36 and 37. In this position, the engagement of the downwardly facing selectorkey shoulders 39 with the upwardly facinglanding nipple shoulder 40 prevents downward movement of the extension hanger through the landing nipple. Upward movement therefrom is permitted because of the upwardly and inwardly sloping surfaces, 41 and 42, on the selector keys and 41a and 42a on the landing nipple.

Theextension hanger 24 is locked in the landing nipple against upward movement by means of the lockingdogs 43 which are moved outwardly intolocking grooves 44 of the landing nipple and held therein by downward movement of thelocking sleeve 45 relative to themandrel 31, as fully described in the above referred to Fredd patent. Thelocking sleeve 45 is provided with an undercut fishing neck 46-.

Apacking assembly 47 iscarried bymandrel 31 for sealing the interface between the extension hanger and landing nipple to prevent fluid flow therebetween.

Theextension hanger 24, as described in the Fredd patent, has been modified for use in the present invention by providing two passages, 48 and 49, through the lower end thereof in which ball valves, 50 and 51 are disposed to serve as check and relief valves, respectively. Springs 52 and 53 resiliently bias each of these valves to their closed positions. The spring 53 is chosen with astifiness' such that when the fluid pressure within the extension hanger is sufliciently greater than the fluid pressure outside thereof, the ball valve 50 will open, allowing fluid topass from the inside to the outside of the extension hanger. Similarly, 'thespring 52 is of a desired stifiness such that when the exterior pressure is sufii- Thetubular housing member 71 of thedetonator de vice 27, shown in detail in FIG. 4, has abore 72 therethrough which is restricted by the inwardly extendingannular flange 73. Apiston shaft 74 is disposed for longitudinal movement withinbore 72 and has thelower portion 75 thereof of greater cross section than that of theupper portion 76 thereof. Piston heads 77 and 78 are formed onshaft 74 and are disposed above and below theannular flange 73, respectively. O-rings 79 and 80 seal the piston heads 77 and 78 to bore 72, respectively, and O-ring 81 seals thelower portion 75 ofshaft 74 toflange 73. A smalldiameter bleed passage 82 extends longitudinally throughflange 73. Thebore 72 is filled with a suitable hydraulic fluid 83 between piston heads 77 and 78.

Ashear pin 84 passes through thehousing member 71 andpiston head 77 to normally prevent relative longitudinal movement therebetween.Screws 85 and 86 retain the shear pin in place.

Atubular breech 87 is disposed inbore 72 and carries therein afiring pin 88. Aspring 89, within the breech, biases thefiring pin upwardly therein, with the engagement ofbreech pin 90 with the bottom of keyway 91 preventing ejection of the firing pin from the breech. The keyway 91 also permits the firing pin to be moved downwardly within the breech so that the lower end of the firing pin may strike thepercussion cap 92 therebelow. Thefiring pin 83 fits rather loosely inbreech 87 so that fluid can flow therebetween. In this manner, variations in fluid pressure in thebore 72 below thepiston head 78 will not force the firing pin downwardly in the breech.

Acompression spring 93, confined between thelower piston head 78 and thebreech flange 94, serves both to force thepiston head 78 upwardly with a predetermined force and to maintain the breech 87 in place, as shown, so as to space thehammer 95 onpiston head 78 from thefiring pin 88.

Port 96, through thehousingv member 71, provides fluid communication between the interior and exterior of the housing member below thepiston head 78.

Aprima cord 97 extends downwardly from thepercussion cap 92 and passes through thebottom connector 98, secured tohousing member 71, and which has fixed thereto thelink spacer assembly 28.

Thelink spacer assembly 28 comprises a plurality of pin-connectedlinks 99, made up in any desired overall length, as will be discussed hereinafter, and 'is used to. flexibly space the perforating gun device 29 a desired distance below theextension hanger 24.

The perforatinggun device 29, illustrated inFIG. 6, may be any conventional type gun adapted to fire by the ignition ofprima cord 97, as, for example, that illustrated.

and described on page ,64 of the September 23, 1957,

ciently greater than the interior pressure, ball valve 51 will be unseated to allow fluid flow from the outside to the inside of the extension hanger.

The lower end of theextension hanger 24 is connected to theupper tubular member 61 of ball joint 25. As seen in detail in FIG. 3, a lowertubular member 62, provided with an enlargedspherical head 63, is held against theupper member 61 byretainer 64. Theretainer 64 and the lower-end of theupper member 61 are shaped complementary to thespherical head 63 to form a socket therefor in which the spherical head may rotate through a limited degree. O-ring 65 preventsfluid flow'around the exterior of thespherical head 63. The ball joint 25 has alongitudinal bore 66 therethrough in communication with the extension hanger bore 32. The lower tubular member is secured to theconnector member 26, havingbore 67 therethrough, which in turn is connected to the upper end of thedetonator device 27housing member 71.

cu'ssion cap 92, all of the guns 1&2 willbe discharged to.

issue of the Oil and Gas Journal. This perforating device comprises a plurality of pin connectedgun carriers 101, each having a charge-containinggun 102. connected thereto. When the primacord 97- is ignited by the perperforate the casing; and of the well.

FIGS. 5A, 5B, SC'and 7 illustrate the elongated time the adjacent. production zone ible plug means, indicated generally by the reference numeral 110, used for installing and removing theextension hanger 24 in and from the landingnipple 23. The plug means '110'includes upper, intermediate and lower seal assemblies, 111, 112 and 11B, spaced apart from one another by knucklejoint members 114.

As seen in the drawings, the'distance between the upper andlower seal assemblies 111 and 113 is greater than the length of theenlarged tubing portion 21 so'that by the time that the upper seal assembly 111 enters theenlarged tubing portion 21, thelower seal assembly 113 will already be within the normal diameter portion oftubing string 14, thus maintaining a seal with thetubing string 14 at all times to prevent fluid flow between the flexible plug 110 and thetubing string 14.

The upper seal assembly 111 is provided with an undercut fishing neck 116 in the event that it be desired to connect auxiliary equipment thereto. Thelower seal assembly 113 has a knuckle joint connection 117' to arunning tool 118 used for running the extension hanger into the well.

The runningtool 118, illustrated in FIG. 5C, has a dependingskirt 119 adapted to surround the lockingsleeve 45 of theextension hanger 24, to which it is releasably connected, as byshear pin 120, for a purpose to be hereinafter described. Although the runningtool 118 has been illustrated in one specified form in FIG. 5C, it is to be realized that any commercially available running tool usable with theextension hanger 24 may be substituted for that shown.

FIG. 7 illustrates the constructional details of thelower seal assembly 113 and the ball andsocket connection 117, and also shows a pulling, or retrieving,tool 121 connected to the flexible plug means 110. Theseal assembly 113 comprises asolid body member 122 having anupper sub 123 connected thereto and maintained in place byroll pin 124 so that the body member and upper sub constitute essentially an integral part. Upper and lowerannular shoulders 125 and 126 are provided as rigid stop members for the annularresilient seal members 127 and 128.Collars 129 and 130 surround thebody 122 and are compressed against theseal members 127 and 128 byspring 131 to force the outer peripheries thereof outwardly into sealing engagement with the inner wall of thetubing string 14.

Theupper sub 136 of theknuckle joint 117 is con- Elected to thebody member 122 of theseal assembly 113 and held in place therein byroll pin 137. The lower end of theupper sub 136 has secured thereto aball retainer 138 which is maintained in place byroll pin 139.

The lower end of theupper sub 136 and the interior ofretainer 138 are shaped complementary to thespherical head 14!} on the upper end ofstem member 141, which spherical head may rotate therein through a limited degree. Aport 142 is formed through theretainer 138 above thestem head 140.

The pullingtool 121 is connected to stemmember 141 and is held secured thereto byroll pin 143. The pulling tool, illustrated in FIGS. 6 and 7, has a plurality ofresilient fingers 144 thereon provided with upwardly and inwardly extendinghooks 145 which are adapted to engage the undercutfishing neck 46 ofextension hanger 24. A centralizingring 146 is provided on the pulling tool for centering thefingers 144 in thetubing 14 so that they may grapple the extension hanger fishing neck, andlongitudinal passages 147 are provided through this ring to permit fluid flow therethrough.

The seal assemblies 111 and 112 are identical in con struction to the above described construction ofseal assembly 113, and theknuckle joints 114 are generally identical in construction to knuckle joint 117.

In the operation of the equipment thus far described, it is assumed that the well has been cased, and that both of the tubing strings have been installed therein, as illustrated in FIG. 1. After the tubing has been installed and packed in place bypacker 18, a casing collar log is run, to determine the distance between theproduction zone 13 to be perforated and the bottom of thetubing string 14. This distance, plus the known distance from the bottom oftubing string 14 and the landingnipple 23 therein, gives the overall distance from the production zone to the landing nipple.

The perforating assembly is then made up at the onshore well head, with thelink spacer assembly 28 made up of suflicient links to space the perforating gun device 29 a distance from theextension hanger 24 equal to the above mentioned overall distance from the production zone to the landingnipple 23.Theextension hanger 24 is then connected by the runningtool 118 to the flexible plug means 110, and the entire assembly is inserted into thetubing string 14.

Fluid pressure is then applied to thetubing string 14 by pump 19 with suflicient force to move the entire assembly through the tubing until theextension hanger 24 finally rests in landingnipple 23. The flexibility of the perforatinggun device 29, thespacer link assembly 28, the balljoint connection 25 between thedetonator 27 andextension hanger 24, the knuckle joint 117 between the runningtool 118 and the sealing assembly .113, and thevarious knuckle joints 114 of the flexible plug means permit the entire assembly to pass through the short radius bend of theenlarged diameter portion 21. oftubing string 14, as well as through any other deviated portion of thetubing string 14. Thetubing string 15 is open at the top and bottom thereof during this operation to relieve any pressure in the well built up as a result of pumping the above elements down throughtubing string 14.

With the extension hanger landed in place in the landingnipple 23, the fluid pressure built up intubing string 14 by pump 19 forces the plug means 110 downwardly with suflicient force to move the extensionhanger locking sleeve 45 downwardly relative tomandrel 31 which moves the lockingdogs 43 outwardly into locked position in landingnipple groove 44. Additional fluid pressure intubing string 14 causes the running tool shear pin to shear, freeing the running tool from the extension hangenwhich is now locked in place in the landing nipple.

At this time, the perforatinggun device 29 is suspended from the extension hanger and is adjacent theproduction Zone 13 to be perforated.

Pump 19 is now disconnected fromtubing string 14, and fluid pressure is built up intubing string 15 bypump 20. This fluid pressure is now greater than that within theextension hanger 24, causing check valve 50 to open, and allowing fluid to flow into the extension hanger and upwardly against thebottom sealing assembly 113 of the now disconnected flexible plug means. The pressure diflerential on the plug will then cause it to be pumped back up through thetubing string 14 to the well head, so that it may be removed.

It will be noted that this fluid pressure within tubing string '14 will not affect thedetonator 27 because the pressure exerted downwardly onpiston head 77 is balanced by the same pressure acting throughport 96 upwardly onpiston head 78.

After removal of the flexible plug, pump 19 is again used to build up pressure within tubing string '14. This pressure will be exerted on the upper face of thedetonator piston head 77, and when sufiicient pressure is applied,shear pin 84 will fail, freeingpiston shaft 74 for downward movement. Maintaining this pressure causes thepiston head 77 to move downwardly and forcefluid 83 through thebleed passage 82 into the space be- -tween flange 73 andpiston head 73.

The piston head continues to move downwardly slowly until the upper shoulder of thepiston shaft portion 74 passes below O-ring 81, whereupon thehydraulic fluid 83 is allowed to pass through the main bore of theflange 73 into the space between the flange and thelower piston head 78 more rapidly, thus allowing the piston assembly to surge downwardly. This causes thehammer 95 on the lower end ofpiston head 78 to strike the upper end of the firing pin '88, whereupon the lower end of the firing pin strikes the upper end of the percussion cap which explodes and ignites theprima cord 97. When the prima cord is ignited, theperforator 29 is discharged practically simultaneously. It is to be noted that thefluid pressure 82 is merely of suflicient size to permit the piston assembly to move slowly downwardly and that the piston assembly does not surge until the enlargeddiameter shaft portion 75 passes below the O-ring 81. Also,spring 93 offers little opposition to the downward movement of the piston assembly but is employed primarily for the purpose of maintaining the breech 87 in its downward position. The shock waves created by the discharging of the perforator are dissipated upwardly through the circulatingtubing string 15, thus causing relatively little injury to the tools, tubing, casing and packers.

It is to be noted thatspring 93 serves to maintain separation between thepiston head 78 andfiring pin 88 in the event that shear pin 34- fails and the hydraulic fluid leaks fromthe reservoir in which it is contained, until a predetermined force is exerted on thepiston head 77.

It is also to be noted that the primary safety feature of the detonator consists of the size of thebleed passage 82 and theflange 73 arrangement which operates as follows; Should the pressure be increased intubing string 14 inadvertently, thus shearing thepin 84, a predetermined minimum time Will be necessary in order'for the piston assembly to cause thepercussion cap 92 to be discharged as previously described. Therefore, if the pressure is inadvertently built up from the surface for any reason, a minimum time will be allowed in which to correct the error. It is to be further noted that after theshear pin 84 is sheared, the time required to cause firing will vary, depending upon the pressure exerted on the upper end of the piston assembly. The two are proportional. The size of the bleed passage, the viscosity of thehydraulic fluid 83 and its temperature, all

enter into the time required for the piston filing pin to.

strike the percussion cap with a given pressure exerted on thepiston head 77 from above.

After perforation, a pullingtool 121 is connected to the flexible plug means 110 and this assembly is inserted intotubing string 14 and pumped downwardly therethrough by the pressure exerted by pump 19, to engage the fishing neck '46 of the extension hanger. During this downward passage of the plug means, the fluid intubing 14 below the plug means is forced out through therefiet valve 51 in the extension hanger and back uptubing string 15. The relief valve 51 is biased to closed position by spring 53 with suflicient force such that a greater internal pressure is required to open the valve than is necessary to shear theshear pin 84 in the detonator.

After engagement of the pullingtool 121 with theextension hanger 24, fluid pressure is again built up intubing string 15, which again causes check valve to open, so that the pressurized fluid will exert a force underneath the flexible plug, which causes the flexible plug to move upwardly. This in turn pulls the lockingsleeve 45 of the extension hanger upwardly, freeing the lockingdogs 43 for movement from the locking groove '44, and allows the extension hanger to be moved upwardly from the landing nipple. Once the extension hanger sealing means 47 clears the landing nipple, fluid flow may take place between the extension hanger and tubing string to be'exerted on the lower side of the flexible plug. 7

The flexible plug, extension hanger, detonator and the unexpended parts of the perforating gun device are then pumpedthroughtubing string 14 back up to the onshore wellhead, from where they are removed, to complete the operation. 7

'In the foregoing description of operations, it will be noted that a casing collar log had to be run after the tubing was installed, in order to determine the distance between the production zone and landingnipple 23 so that thespacer link assembly 28 could be made up accordingly.

FIG. 6 illustrates a manner in which the necessity for this log is eliminated. During the initial casing of the well, "a casing landing nipple 23a is made up in the casing string 11, which landing nipple is generally similar the particular details of the casing landing nipple 23a and a tubing-casing packer 18a laudable therein form no part of the invention other than their use therewith, these elements have only been indicated schematically. Any commercially available elements usable 'for this purpose may be used, such as those shown on page 4136 of'the Composite Catalog. of Oil Field Equipment and Service, 1957 edition.

After the casing string has been installed, the usual casing collar log which is run after casing installation, will indicate the distance from the production zone 1.3 to the casing landing nipple 23a. Prior to installation of the tubing strings 14 and 15, thetubing string 14 is made up with the packer 18a and landingnipple 23 therein, at a known distance apart. Thetubing string 14 is then run into the casing until the packer 18a is landed in the casing landing nipple 23a, and the packer is set to seal between the tubing and casing.Tubing string 15 is then run into the casing and packed to the other bore of the packer 18a by conventional methods to complete the installation,

,With this installation, the distance from theproduction zone 3 to thetubing landing nipple 23 is the sum of the known distances from the production zone to the casing landing nipple 23a and from the packer 18a to thetubing landing nipple 23, and thus there is no need for a further casing collar log after the tubing is installed to find the overall distance from theproduction zone 13 and thetubing landing nipple 23.

to thetubing landing nipple 23, and which has an internal v profile adapted to receive the packer 18a therein. Since There are also various times in which it is not necessary that the extension hanger be locked in the landing nipple or that the flexible plug means be removed from the well after installing the extension hanger and before firing the perforating device.

In these instances, a modifiedextension hanger 24a, illustrated in FIGS. 3 and 6, is employed. Theextension hanger 24a is generally the same asextension hanger 24 previously described, in that it hasselector keys 33a and 34a spring biased outwardly into the landing nipple grooves -36 and 37, which keys have a downwardly facingshoulder 3 9a engageable with landingnipple shoulder 40 to prevent downward movement of the extension hanger through the landing nipple. Sealing means 47a, carried by the extension hanger, seals against the landing nipple.

Extension hanger 2.4a has been modified from that previously described in that no lockingdogs 43 are used to lock intolanding nipple groove 44, and that the check and relief valves 50 and 51 are eliminated.

In the operation of the invention, using extension hanger 240, the same initial preparations are made, as previously described, and the flexible plug means 110 is connected to the extension hanger by a pullingtool 121 engaging thefishing neck 46a of the extension hanger, or by some other permanent connection. The entire assembly is then pumped down thetubing string 14, until theextension hanger 24a is landed in landingnipple 23, with thedetonator 27 and perforatinggun device 29 suspended therebelow.

' The fluid pressure intubing string 14 is then increased by pump 19. When the pressure is sufficiently high, it will overcome the force exerted on the sealingelements 127 and 128 of the plug means bysprings 131 which compress the sealing elements against the tubing, and will force fluid past these sealing elements and through theextension hanger 24a and ball joint 25 to be exerted on thepiston head 77 in the detonator. The force of this high fluid pressure will again causeshear pin 84 to shear to actuate the detonator as previously described.

After firing of the perforator, fluid pressure is built up intubing string 15, which pressure is exerted on the exterior oftheextension hanger 24a, forcing it upwardly intotubing string 14. Once the seal between theextension hanger 24a and the landing nipple 2B is broken,-the fluid pressure willbe exerted on the flexible plug means 110. causing it to move upwardly through thetubing string 14 to the well head, carrying theextension hanger 24a,detonator 27 and the unexpanded portions of theperforator 29. These elements are then removed from the tubing string to complete the operations.

FIG. 8 illustrates a modification of the invention in which thetubing string 14 is used as one flow path, and the tubing-casing annulus A is used as the other flow path. Thetubing string 14 is anchored to the casing string 11 by means of a tubing anchor 18b fixed in the tubing string and laudable in the casing landing nipple 23b. The tubing anchor 18b may be any commercially available element usable for this purpose, again such as the casing packer shown on page 4136 of the Composite Catalog of Oil Field Equipment and Services, 1957 edition, however with the packing elements removed. The tubing anchor 18b does not seal thetubing string 14 to the casing 11, and thus fluid flow may take place in the tubing-casing annulus A past the tubing anchor 18b.

The upper end of the casing string 11 is sealed bypacker 17a to theflange 14a of thetubing string 14, and conduit 15a extends from'the tubing-casing annulus A to theonshore pump 20.

The method of operation is the same in this modification as that previously described, that is, the perforating apparatus is again made up as described above and is pumped throughtubing string 14 by pump 19 until theextension hanger 24 lands in landingnipple 23. Thedetonator 27 is again actuated in response to the fluid pressure created by pump 19 to fire the perforatinggun device 29 to perforate theproduction zone 13 of the we The perforating apparatus is removed by fluid pressure created bypump 20 which pumps fluid through conduit 15a, through the tubing-casing annulus A past the tubing anchor 18b and up throughtubing string 14. The removal of the perforating apparatus thus occurs in the same manner as previously discussed.

FIG. 9 illustrates another tubing-casing annulus A is used as a flow path. In this modification, thetubing string 14 is anchored to the casing string by adual bore packer 18, as in FIG. 1. Or, if desired, a dual bore tubing casing packer of the type shown in FIG. 6 maybe used.

Thetubing string 15 is sealed to the top of the casing string by packer 17', as in FIG. 1, but does not extend down in the casing string topacker 18, as previously described.

In operation, the perforating apparatus is again pumped throughtubing string 14 and landed in thetubing landing nipple 23. In removal, fluid is pumped throughtubing string 15, through the tubing-casing annulus A, through bore B ofpacker 18 and up through thetubing string 14.

Thus, the only significant diflerence between the modifications of FIGS. 8 and 9 and the forms earlier described, is that the tubing-casing annulus is used as a flow path in place oftubing string 15 within the casing string. The selection of the system to use will be determined primarily by the necessity of fluidly separating theproduction zone 13 from the zones abovepacker 18. If separation is not necessary or desired, then the systems of FIGS. 8 and 9 may be used. If separation is necessary, thentubing string 15 must extend down to belowpacker 18, withpacker 18 being used to seal the tubing strings 14 and 15 to the casing 11.

Thus, by means of the present invention, well perforating operations can be completely carried out without the use of wire line or similar devices, with tions being performed and controlled by regulating the modification by which the all of the operafluid pumps 19 and 20 at the onshore well head to provide the desired fluid pressure in the two tubing strings.

It is to be further realized that the methods and apparatus described are preferred embodiments of the invention and that various changes may be made in the shape,

10 size and arrangement of parts without departing from the spirit of the invention or the scope of the attached claims. Having thus described our invention, what'we claim and desire to secure by Letters Patent is:

l. A method for perforating a desired zone of an oil well having a fluid flow path extending from the well head of said well down to above said zone and in which said fluid flow path has apoint therein spaced a known distance above said zone, comprising: connecting a well perforator to a plug at a distance therebetween equal to said known distance, forcing said well perforator and plug down through said fluid flow path by fluid pressure in said flow path exerted from said well head, arresting downward movement of said plug in said fluid flow path at said point therein with said well perforator suspended therebelow, and detonating said well perforator in response to an increase in fluid pressure exerted in said fluid flow path from said well head.

2. A method for perforating a desired zone of an oil well having two separate fluid flow paths extending from the well head of said well down to above said zone and in which one of said fluid flow paths has a point therein spaced a known distance above said zone, comprising: connecting a well perforator to a plug at a distance there between equal to said known distance, pumping said well perforator and plug down through said one fluid flow path by fluid pressure in said one flow path exerted from said Well head, arresting downward movement of said plug in said one fluid flow path at said point therein with said well perforator suspended therebelow, detonating said well perforator in response to a fluid pressure exerted in said first fluid flow path from said well head, pumping fluid under pressure down the other of said fluid flow paths and forcing said plug back up through said one fluid flow path by said last named fluid.

3. A method for perforating a desired zone of an oil well having two separate fluid flow paths extending from the well head of said Well down to above said zone and in which one of said fluid flow paths has a point therein spaced a known distance above said zone, comprising: connecting a well perforator to a plug at a distance there between equal to said known distance, pumping said well perforator and plug down through said one fluid flow path by fluid pressure in said one flow path exerted from said well head, landing said extension hanger in said one fluid flow path at said, point therein with said well perforator suspended therebelow, increasing the fluid pressure in said one flow path, detonating said well perforator in response to an extended duration of said increased fluid pressure, pumping fluid under. pressure from said well head down the other of said fluid flow paths, and forcing said plug back up through said one fluid flow path by said last named fluid.

4.A method for perforating oil wells comprising installing a well casing string having a landing nipple made up therein in said well, logging the distance from a desired zone of perforation to said casing landing nipple, making up a tubing string having a casing packer and a landing nipple made up therein at a predetermined spacing from one another, installing the tube string in the casing string to land the packer in the casinglanding nipple, connecting a well perforator to an extension hanger at a distance therefrom equal to the distance from said desired zone of perforation to said casing landing nipple plus the distance that said tubing landing nipple is above said packer, pumping said well perforator and extension hanger down through saidiubing string by fluid pressure exerted in said tubing string from the upper end thereof, landing said extension hanger in said tubing landing nipple, and detonating said well perforator by said fluid pressure.

5. A method for perforating oil wells, comprising: installing a well casing string having a landing nipple made up therein in said well, logging the distance from a de- 1 1 sired zone of perforation to said casing landing nipple, making up a tubing string having a casing packer and a landing nipple made up therein at a predetermined spacing from one another, installing the tubing string in the casing string to land the packer in the casing landing nipple, connecting a well perforator to an extension hanger at a distance therefrom equal to the distance from said desiredzone of perforation to said casing landing nipple plus the distance that said tubing landing nipple is above said packer, pumping said well perforator and extension hanger down through said tubing string by fluid pressure exerted in said tubing string from the upper end thereof, landing said extension hanger in said tubing landing nipple, increasing the fluid pressure in said tubing string from the upper end thereof, detonating said well perforator after a predetermined interval while maintaining the increase of fluid pressure in said tubing string, pumping said extension hanger back up through said tubing string by fluid pressure exerted in said tubing string from the lower end thereof.

6. A methodof perforating an oil well having a zone to be perforated and a casing therein, comprising: forming first and second fluidly separated fluid flow. paths within said casing from the well head of said well down to above said zone with a landing nipple made upin said first fluid flow path and with said second fluid flow path being in fluid communication'with said first fluid flow path below the landng nipple therein, connecting a well perforating device to an extension hanger at a distance therefrom equal to the distance between the zone to be perforated and the first fluid fiow path landing nipple, pumping the perforating device 'and extension hanger from the well head down through said first fluid flow path by fluid pressure exerted from said well head, landing the extension hanger in the first fluid flow path landing nipple with the Well perforating device suspended therehelow, increasing the fluid pressure within said first fluid flow path, and detonating said well perforating device in response to a fluid pressure of a predetermined amount within said first fluid flow path exerted therein from said well head. V

7. A method of perforating an oil well having a zone to be perforated and a casing therein, comprising: forming first and second fluidly separated fluid flow paths within said casing from the well head of said well down to above said zone with a landing nipple made up in said first fluid flow path and with said second fluid flow path being in fluid communication with said first fluid flow path below the landing nipple therein, packing said fluid paths above the lower ends thereof to said casing, connecting a well perforating device to an extension hanger at a distance therefrom equal to the distance between the zone to be perforated and the first fluid flow path land- I ing nipple, pumping the perforating device and extension hanger from the well head down through said first fluid flow path by fluid pressure exerted. from said well head, landing the extension hanger in the first fluid flow path landing nipple with the well perforating device, suspended therebelow, detonating said well perforating device in response to an extended duration of the presence of a fluid pressure of a predetermined amount within said first fluid flow path exerted therein from said well head, purnping fluid under pressure from said well head down through said second fluid flow path, and forcing said extension hanger back up through said first fluid flow path to said Well head.

8. A method of perforating an oil well having a casing therein provided with a landing nipplerspaced a known distance above a desired zone to be perforated, comprising: forming first and second fluidly separated fluid flow paths within said casing from the well head of said well down to said casing landing nipple with a landing nipple in said first fluid flow path spaced a known distance from said casing landing nipple'and with said second fluid flow path being in fluid communication with said first fluid flow path below the landing nipple therein, connecting a well perforating device to an extension hanger at a distance therefrom equal to the distance between the zone to be perforated and the first fluid flow path landing nipple, pumping the perforating device and extension hanger from the well head down through said first fluid flow path by fluid pressure exerted fi'om said well head, landing the extension hanger in the first fluid flow path landing nipple with the well perforatingdevice suspended therebelow, and'detonating said well perforating device in response to a fluid pressure of a predetermined amount within said first fluid flow path exerted therein from said well head.

9. A method of perforating an oil well having a casing therein provided with a landing nipple spaced a known distance above a desired zone to be perforated, compris ing: forming first and second fluidly separated fluid flow paths within said casing from the well head of said well down to said casing landing nipple with a landing nipple in said first fluid flow path spaced a known distance from said casing landing nipple and with said second fluid flow path being in fluid communication with said first fluid flow path below the landing nipple therein, connecting a well perforating device to an extension hanger at a distance therefrom equal to the distance between the zone to be perforated and the first fluid flow path landing nipple, pumping the perforating device and extension hanger from the well head down through said first fluid flow path by fluid pressure exerted therein from said well head, landing the extension hanger in the first fluid flow path landing nipple with the well perforating device suspended therebelow, detonating said well perforating device by a fluid pressure of a predetermined amount within said first fluid flow path exerted therein from said well head, pumping fluid under pressure from said well head down through said second fluid flow path, and forcing said extension hanger back up through said first fluid flow path to said well head by said last named fluid under pressure.

10. A method of perforating an oil well having a casing therein provided with a landing nipple spaced a known distance above a desired zone to be perforated, comprising: forming first and second fluidly separated fluid flow paths within said casing from the well head of said well down to said casing landing nipple with a landing nipple in said first fluid flow path spaced a known distance from said casing landing nipple and with said second fluid flow path being in fluid communication with said first fluid flow path below the landing nipple therein, connecting a well perforating device to an extension hanger at a distance therefrom equal to the distance between the zone to be perforated and the first fluid flow path landing nipple, pumping the perforating device and extension hanger from the well head down through said first fluid flow path by fluid pressure exerted from said well head, landing the extension hanger in the first fluid flow path landing nipple with the well perforating device suspended therebelow, increasing the fluid pressure within said first fluid flow path from said well head, detonating said well perforating device in response to an extended duration of the presence of increased fluid pressure within said first fluid flow path, pumping fluid under pressure from said well head down through said second fluid flow path, and forcing said extension hanger back up through said first fluid flow path to said well head by said last named fluid under pressure. I

11. Apparatus for perforating a desired zone of a well bore comprising a casing string lining said well bore, a tubing string extending down through said casing string with the lower end of said tubing string being above said zone, a landing nipple in said tubing string, a tubular extension hanger movable through said tubing string and removably landed in said landing nipple, an elongated flexible plug means pumpable through said tubing string by a fluid pressure therein, means connecting said plug means to said extension hanger, a Well perforating gun, means suspending said perforating gun from said extension hanger at a distance therebelow approximately equal to the distance from said zone to said landing nipple whereby said perforator device is suspended adjacent said zone, a detonator housing member connected to said extension hanger for movement therewith, means providing fluid communication between the interiors of said detonator housing member and said extension hanger, means responsive to the presence of a predetermined high fluid pressure for providing fluid flow through said first tubing string from above said plug means to the interior of said extension hanger, fluid pressure actuated detonator means in said detonator housing, and means responsive to actuation of said detonator for firing said perforating gun.

12. Apparatus for perforating a desired zone of a well bore comprising a casing string lining said well bore, first and second tubing strings extending down through said casing string with the lower ends of said tubing strings being above said zone, packer means for sealing said tubing strings to said casing string, a landing nipple in said first tubing string, said first tubing string being open from below the landing nipple therein to the interior of said casing string below said packer means and said second tubing string being also open to the interior of said casing string, below said packer means, a tubular extension hanger movable through said first tubing string and removably landed in said landing nipple, means sealing the exterior of said extension hanger to said landing nipple to prevent fluid flow therebetween, an elongated flexible plug means pumpable through said first tubing string by a fluid pressure therein and disposed in said tubing string above said extension hanger, means connecting said plug means to said extension hanger, a well perforating gun, means suspending said perforating gun from said extension hanger at a distance therebelow equal to the distance from said zone to said landing nipple whereby said perforating gun is suspended adjacent said zone, a detonator housing member connected to said extension hanger for movement therewith, means providing fluid communication between the interiors of said detonator housing member and said extension hanger, means responsive to the fluid pressure within said first tubing string exerted on said plug and operable to provide fluid flow through said first tubing string from above said plug means to the interior of said extension hanger when said fluid pressure Within said first tubing string exerted on said plug is above a predetermined value, fluid pressure actuated detonator means in said detonator housing, and means responsive to actuation of said detonator means for firing said perforating gun.

13. Apparatus for perforating a desired zone of a well bore comprising a casing string lining said well bore, a landing nipple in said casing string above said zone, first and second tubing strings extending down through said casing string with the lower ends of said tubing strings being above said zone and below said casing string landing nipple, packer means fixed to said first tubing string and landed in said casing string landing nipple to seal said tubing strings to said casing string, a landing nipple in said first tubing string, said first tubing string being open from below the landing nipple therein to the interior of said casing string below said packer means and said second tubing string being also open to the interior of said casing string below said packer means, a tubular extension hanger movable through said first tubing string and removably landed in said first tubing string landing nipple, means sealing the exterior of said extension hanger to said first tubing string landing nipple to prevent fluid flow therebetween, an elongated flexible plug means pumpable through said first tubing string by a fluid pressure therein, means connecting said plug means to said ex tension hanger, a well perforating gun, means suspending said perforating gun from said extension hanger at a distance therebelow approximately equal to the distance from said zone to said first tubing string landing nipple whereby said perforating gun is suspended adjacent said zone, a detonator housing member flexibly connected to said extension hanger for movement therewith, means providing fluid communication between the interiors of said detonator housing member and said extension hanger, means responsive to the fluid pressure within said first tubing string exerted on said plug and operable to provide fluid flow through said first tubing string from, above said plug means to the interior of said extension hanger when said fluid pressure within said first tubing string exerted on said plug is above a predetermined value, a percussion cap in said detonator housing, hammer means within said detonator housing responsive to an extended duration of the presence of said predetermined fluid pressure therein to strike said percussion cap, and means responsive to the striking of said percussion cap for firing said perforating gun.

14. Apparatus for perforating a desired zone of a well bore comprising a casing string lining said well bore, a tubing string extending down through said casing string with the lower endof said tubing string being above said zone, a landing nipple in said tubing string, a tubular extension hanger movable through said tubing string and removably landed in said landing nipple, a plug means pumpable through said tubing string by a fluid pressure therein, means detachably connecting said plug means to said extension hanger, means including a check valve for allowing fluid flow from the exterior of said extension hanger to the interior thereof, a well perforating gun,

' means suspending said perforating gun from said extension hanger at a distance therebelow approximately equal to the distance from said zone to said'tubing string landing nipple, a detonator housing member connected to said extension hanger, means providing fluid communication betweenthe interiors of said detonator housing member and said extension hanger, fluid pressure actuated detonator means in said detonator housing, means responsive to actuation of said detonator for firing said perforating gun, and means including'a relief valve to provide fluid flow from the interior of said extension hanger to the exterior thereof.

15. Apparatus for perforating a desired zone of a well bore comprising a casing string lining said well bore, first and second tubing strings extending down through said casing string with the lower ends of said tubing strings being above said zone, packer means for sealing said tubing strings to said casing string, a landing nipple in said first tubing string, said first tubing string being open from below the landing nipple therein to the interior of said casing string below said packer means and said second tubing string string being also open to the interior of said casing string below said packer means, a tubular extension hanger movable through said first tubing string and removably landed in said landing nipple, means sealing the exterior of said extension hanger to said landing nipple to prevent fluid flow therebetween, an elongated flexible plug means 'pnmpablethrough said first tubing string by a fluid pressure therein, means detachably connecting said plug means to said extension hanger thereabove, means including a check valve for allowing fluid flow from the exterior of said extension hanger below said sealing means to the interior of said extension hanger, a Well perforating gun, means suspending said perforating gun from said extension hanger at a distance therebelow equal to the distance from said zone to said landing nipple, a detonator housing member connected to said extension hanger for movement therewith, mans providing fluid communication between the interiors of said detonator housing member and said extension hanger, fluid pressure actuating detonator means in said detonator housing, means responsive to actuation of said detonator means for firing said perforating gun, and means including a relief valve to provide fluid flow from the interior of said extension hanger to the exterior thereof below said sealing means.

16. Apparatus for perforating a desired zone of a well bore comprising a casing string lining said well bore, a landing nipple in said casing string above said zone, first and second tubing strings extending downithrough said casing string with the lower ends of said tubing strings being above said zone and below said casing string landing nipple, packer means fixed to said first tubing string and landed in said casing string landing nipple to seal said tubing strings to said casing string, a landing nipple in said first tubing string, said first tubing string being open from below thelanding nipple therein to the interior of said casing string below said packer means and said second tubing string being also open to the interior of said casing string below said packer means, a' tubular ex tension hanger movable through said first tubing string and removably landed in said first tubing string landing nipple, means sealing the exterior of said extension hanger to said first tubing string landing nipple to prevent fluid flow therebetween, an elongated flexible plug means pumpable' through said first tubing string by a fluid pressure therein, means detachably connecting said plug means to said extension hanger, means including a check valve for allowing fluid flow from the exterior of said extension hanger below said sealing means to the interior of said extension hanger, a well perforating gun, flexible means suspending said perforating gun from said extension hanger at a distance therebelow approximately equal to the distance from said zone to said first tubing string landing nipple whereby said perforator device is suspended adjacent said zone, a detonator housing member flexibly connected to said extension hanger for movement therewith, means providing fluid communication between the interiors of said detonator housing member and said extension hanger, a percussion cap in said detonator housing, hammer means within said detonator housing responsive to an extended duration of the presence of a predetermined fluid pressure therein to strike said percussion cap, means responsive to striking of said percussion cap for firingsaid perforating gun, and means including a relief valveopenable by a fluid pressure in said first tubing string substantially greater than said predetermined pressure to provide fluid flow from the interior of said extension hanger to the exterior thereof below said sealing means.

17. Apparatus for perforating a desired zone of a well bore comprising a casing string lining said well bore, a tubing string extending down through said casing string with the lower end of said tubing string being above said zone, a landing nipple in said tubing string; an elongated flexible plug member in said tubing string and having an annular shoulder on each end thereof, a pair of collars surrounding said plug member with one each adjacent one of said shoulders, spring means biasing said collars towards said shoulders adjacent thereto with a predetermined force, an annular resilient seal member disposed against each of said shoulders and compressed thereagainst by said collars, the outer surfaces of said seal members being sealingly engaged with said tubing string by said spring means; a tubular extension hanger flexibly connected at one end thereof to one end of said plug member, said extension hanger having means thereon engaged with said landing nipple to prevent movement of said extension hanger through said landing nipple, packing means on said extension hanger sealing against said landing nipple; a detonator housing flexibly connected to the other end of said extension hanger, means providing fluid communication between the interiors of said detonator housing and said extension hanger, a detonator in said detonator housing, a fluid pressure actuated detonator actuator in the interior of said detonator housing responsive to the presence of an extended duration of a fluid pressure therein of a predetermined amount for actuating said detonator; a well perforating means flexibly connected to said detonator housing at a distance therefrom approximately equal to the distance from said zone to be perforated to said tubing string landing nipple; and

means to operate said perforating'means in response to actuation of said detonator.

18. Apparatus for perforating a desired zone of a well bore comprising a casing string lining said well bore, first and second tubing strings extending down through said casing string with the lower ends of said tubing strings being above said zone, packer means sealing said tubing strings to said casing string, a landing nipple in said first tubing string, said first tubing'string being open from below the landing nipple therein to the interior of said casing string below said packer means and said second tubing string being also open to the interior of said casing string below said packer means; an elongated flexible plug member in said first tubing stringjand having an annular shoulder on each end thereof, a pair of collars surrounding said plug member with one each adjacent one of said shoulders, spring means biasing said collars towards said shoulders adjacent thereto with a predetermined force, an annular resilient seal member disposed against each of said shoulders and compressed thereagainst by said collars, the outer surfaces of said seal members being sealingly engaged with said tubing string by said spring means; a tubular extension hanger flexibly connected at one end thereof to one end of said plug member, said extension hanger having means thereon engaged with said landing nipple to prevent movement of said extension hanger through said landing nipple, packing means on said extension hanger sealing against said landing nipple; a detonator housing flexibly connected to the other end of said extension hanger, means providing fluid communication between the interiors of said detonator housing and said extension hanger, a detonator in said detonator hous ing, a fluid pressure actuated detonator actuator in the interior of said detonator housing responsive to the presence of an extended duration of a fluid pressure therein of a predetermined amount for actuating said detonator; a well perforating means flexibly connected to said detonator housing at a distance therefrom approximately equal to the distance from said zone to be perforated to said tubing string landing nipple; and means to operate said perforating means in response to actuation of said detonator.

19. Apparatus for perforating a desired zone of a well bore comprising: a casing string lining said well bore, a landing nipple in said casing string above said zone, first and second tubing strings extending down through said casing string with the lower ends of said tubing strings being above said-zone and below said casing string landing nipple, packer means fixed to said first tubing string and landed in said casing string landing nipple to seal said tubing-strings to said casing string, a landing nipple in said first tubing string, said first tubing string being open from below the landing nipple therein to the interior of said casing string below said packer means and said second tubing string being also open to the interior of said casing string below said packer means; an elongated flexible plug member in said first tubing string and having an annular shoulder on each end thereof, a pair of collars surrounding said plug member with one each adjacent one of said shoulders, spring means biasing said collars towards said shoulders adjacent thereto with a predetermined force, an annular resilient seal member disposed against each of said shoulders and compressed thereagainst by said collars, the outer surfaces of said seal members being sealingly engaged with said tubing string by said spring means; a tubular extension hanger flexibly connected at one end thereof to one end of said plug member, said extension hanger having means thereon engaged with said landing nipple to prevent movement of said extension hanger through said landing nipple, packing means on said extension hanger sealing against said landing nipple; a detonator housing flexibly connected to the other end of said extension banger, means providing fluid communication between the interiors of said detonator housing and said extension hanger, a detonator in said detonator housing, a fluid pressure actuated detonator actuator in the interior of said detonator housing responsive to the presence of an extended duration of a fluid pressure therein of a predetermined amount for actuating said detonator; a well perforating means flexibly connected to said detonator housing at a distance therefrom approximately equal to the distance from said zone to be perforated to said tubing string landing nipple; and means to operate said perforating means in response to actuation of said detonator.

20. Apparatus for perforating a desired zone of a well bore comprising a casing string lining said well bore, first and second tubing strings extending down through said casing string with the lower ends of said tubing strings being above said zone, packer means sealing said tubing strings to said casing string, a landing nipple in said first tubing string, said first tubing string being open from below the landing nipple therein to the interior of said casing string below said packer means and said second tubing string being also open to the interior of said casing string below said packer means; an elongated flexible plug member in said first tubing string having an annular shoulder on each end thereof, a pair of collars surrounding said plug member with one each adjacent one of said shoulders, spring means biasing said collars towards said shoulders adjacent thereto with a predetermined force, an annular resilient seal member disposed against each of said shoulders and compressed thereagainst by said collars, the outer surfaces of said seal members being sealingly engaged with said tubing string by said spring means; a tubular extension hanger flexibly and removably connected at one end thereof to one end of said plug member, said extension hanger having means thereon engageable with said landing nipple to lock said extension hanger against longitudinal movement relative to said landing nipple, packing means on said extension hanger to seal against said landing nipple, said extension hanger having first and second passages from the interior thereof to the exterior thereof below said sealing means, relief valve means in said first passage openable when the pressure within said extension hanger is sufliciently higher than the external pressure thereon for permitting fluid flow from the interior to the exterior thereof, check valve means in said second passage openable when the pressure exterior of said extension hanger is sufliciently greater than the pressure therein for permitting fluid flow from the exterior thereof to the interior thereof; a detonator housing flexibly connected to the other end of said extension hanger, means providing fluid communication bet-ween the interiors of said detonator housing and said extension hanger, a detonator in said detonator housing, a fluid pressure actuated detonator actuator in the interior of said detonator housing responsive to the presence of an extended duration of a' fluid pressure therein of a predetermined amount for actuating said detonator; a well perforating means flexibly connected to said detonator housing at a distance therefrom approximately equal to the distance from said zone to be perforated to said tubing string landing nipple; and means to operate said perforating means in response to actuation of said detonator.

21. Apparatus for perforating a desired zone of a well bore comprising a casing string lining said well bore, a landing nipple in said casing string above said zone, first and second tubing strings extending down through said casing string with the lower ends of said tubing strings being above said zone and below said casing string landing nipple, packer means fixed to said first tubing string and landed in said casing string landing nipple to seal said tubing strings to said casing string, a landing nipple in said first tubing string, said first tubing string being open from below the landing nipple therein to the interior of said casing string :below said packer means and said second tubing string being also open to the interior of said casing string below said packer means; an elongated flexible plug member in said first tubing string having an annular shoulder on each end thereof, a pair of collars surrounding said plug member with one each adjacent one of said shoulders, spring means biasing said collars towards said shoulders adjacent thereto with a predetermined force, an annular resilient seal member disposed against each of said shoulders and compressed thereagainst by said collars, the outer surfaces 'of said seal members being sealingly engaged with said tubing string by said spring means; a tubular extension hanger flexibly and removably connected at one end thereof to one end of said plug member, said extension hanger having means thereon engageable with said landing nipple to lock said extension hanger against longitudinal movement relative to said landing nipple, packing means on said extension hanger to seal against said landing nipple, said extension hanger having first and second passages from the interior thereof to the exterior thereof below said sealing means, relief valve means in said first pasage openable when the pressure within said extension hanger is sufliciently higher than the external pressure thereon for permitting fluid flow from the interior to the exterior thereof, check valve means in said second passage openable when the pressure exterior of said extension hanger is sufficiently greater than the pressure therein for permitting fluid flow from the exterior thereof to the interior thereof; a detonator housing flexibly connected to the other end of said extension hanger, means providing fluid communication between the interiors of said detonator housing and said extension hanger, a detonator in said detonator housing, a fluid pressure actuated detonator actuator in the interior of said detonator housing responsive to the presence of an extended duration of a fluid pressure therein of a predetermined amount for actuating said detonator; a well perforating means flexibly connected to said detonator housing at a distance therefrom approximately equal to the distance from said zone to be perforated to said tubing string landing nipple; and means to operate said perforating means in response to actuation of said detonator.

22;. Apparatus for perforating oil wells and passable through a tubing string having a landing nipple made up therein, comprising: an elongated flexible plug member having an annular shoulder thereon, a collar surrounding said plug member adjacent said shoulder, spring means biasing said collar towards said shoulder with a predetermined force, an annular resilient seal member disposed against said shoulder and compressed thereagainst by said collar, the outer surface of said seal member being sealingly engageable with said tubing string by said spring means when said plug member is inserted in said tubing string; a vertically disposable tubular extension hanger flexibly connected at one end thereof to one end of said plug member, said extension hanger having means thereon engageable with said landing nipple to prevent longitudinal movement of said extension hanger through said landing nipple; a detonator housing connected to the other end of said extension hanger, means providing fluid communication between the interiors of said detonator housing and said extension hanger, a fluid pressure actuated detonator means in the interior of said detonator housing responsive to the presence of a fluid pressure therein of a predetermined amount for actuation thereof; a well perforating means flexibly connected to said detonator housing at a predetermined distance therefrom; and means to operate said perforating means in response to actuation of said detonator means. I

23. Apparatus for perforating oil wells and passable through a tubing string having a landing nipple" made up therein, comprising: an elongated flexible plug member, an annular resilient seal member disposed on each end of said plug member, the outer surfaces of said seal members being sealingly engageable with said tubing string when said plug member is inserted in said tubing string; a vertically disposable tubular extension hanger removably connected at one end thereof to one end of said i9 plug member, said extension hanger having means thereon engageable with said landing nipple to lock said extension hanger against longitudinal movement relative to said landing nipple, said extension hanger having first and second passages from the interior to the exterior thereof,

relief valve means in said first passage openable When the pressure within said extension hanger is sufiiciently higher than the external pressure thereon for permitting fluid flow from the interior to the exterior thereof, check valve means in said second passage openable when the pressure exterior of said extension hanger is sufiiciently greater than the pressure therein for permitting fluid flow from the exterior thereof to the interior thereof; a detonator housing flexibly connected to the other end of said extension hanger, means providing fluid communication between the interiors of said detonator housing and said extension hanger, a fluid pressure actuated detonator means in the interior of said detonator housing responsive to the presence of a fluid pressure therein of a predetermined amount for actuation thereof; a well perforating means flexibly connected to said detonator housing at a predetermined distance therefrom; and means to operate said perforating means in response to actuation of said detonator means.

24. Apparatus for perforating oil wells and passable through a tubing string having a landing nipple made up therein, comprising: an elongated flexible plug member having an annular shoulder on each end thereof, a pair of collars surrounding said plug member with one each adjacent one of said shoulders, spring means biasing said collars towards said shoulders adjacent thereto with a predetermined force, an annular resilient seal member disposed against each of said shoulders and compressed thereagainst by said collars, the outer surfaces of said seal members being sealingly engageable with said tubing string by said spring means when said plug member is inserted in said tubing string; a vertically disposable tubular extension hanger flexibly connected at one end thereof to one end of said plug member, said extension hanger having means thereon engageable with said landing nipple to prevent longitudinal movement of said extension hanger through said landing nipple, packing means on said extension hanger to seal against said landing nipple; a detonator housing flexibly connected to the other end of said extension hanger, means providing fluid communiaction between the interiors of said detonator housing and said extension hanger, a detonator in said detonator housing, a fluid pressure actuated detonator actuator in the interior of said detonator housing responsive to the presence of an' extended duration of a fluid pressure therein of a predetermined amount for actuating said detonator; a well perforating means flexibly connected to said detonator housing at a predetermined distance therefrom; and means :to operate said perforating means in response to actuation of said detonator.

25. Apparatus for perperfating oil wells andpassable through a tubing string having a landing nipple made up therein, comprising: an elongated flexible plug member having an annular shoulder on each end thereof, a pair of collars surrounding said plug member with one each adjacent one of said shoulders, spring means biasing said collars towards said shoulders adjacent thereto with a predetermined force, an annular resilient seal member disposed against each of said shoulders and compressed thereagainst by said collars, the outer surfaces of said seal members being sealingly engageable with said tub ing string by said spring means when said plug member is inserted in said tubing string; a vertically disposable tubular extension hanger flexibly and removably connected at one end thereof to one end-of said plug member, said extension hanger having means thereon engageable with said landing nipple to lock said extension hanger against longitudinal movement relative to said landing nipple, packing means on said extension hanger to seal against said landing nipple, said extension hanger having first and second passages from the interior thereof to the exterior thereof below said sealing means, relief valve means in said first passage openaole when the pressure Within said extension hanger is sufficiently higher than the external pressure thereon for permitting fluid flow from the interior to the exterior thereof, check valve means in said second passage openable when the pressure exterior of said extension hanger is suificiently greater than the pressure therein for permitting fluid flow from the exterior thereof to the interior thereof; a detonator housing flexibly connected to the other end of said extension hanger, means providing fluid communication between the interiors of said detonator housing and said extension hanger, a detonator in said detonator housing, a fluid pressure actuated detonator actuator in the interior of said detonator housing responsive to the presence of an extended duration of a fluid pressure therein of a predetermined amount for actuating said detonator; a well perforating means flexibly connected to said detonator housing at a predetermined distance therefrom; and means to operate said perforating means in response to actuation of said detonator.

26. A detonator comprising an elongated tubular member having an axial bore therethrough and a restriction in said bore intermediate its ends, a percussion cap mounted in said housing member, a firing pin spaced from said percussion cap and mounted in said housing member bore for movement thereof into percussive engagement with said percussion cap, a piston member mounted in said housing member for axial movement in said bore and disposed on the side of said bore restriction away from said firing pin, a shaft member passing through said bore restriction and connected to said piston member, said shaft member having a portion of its length remote from said piston member of greater cross section than the pontion of its length adjacent to said piston member, a firing pin engaging hammer carried by said shaft, said shaft and piston member being movable in said bore between a first position wherein said hammer is spaced from said firing pin and a second position wherein said hammer engages said firing pin and moves said pin into percussive engagement with said percussion cap, a quantity of hydraulic fluid filling said bore between said piston member and said bore restriction, and shear pin means connecting said piston member to said housing member when said piston member is in said first position.

27. A detonator comprising an elongated tubular member having an axial bore therethrough and a restriction in said bore intermediate its ends, a percussion cap mounted in said housing member, a firing pin spaced from said cap and mounted in said housing member bore for movement thereof into percussive engagement with said cap, a piston member mounted in said housing member for axial movement in said bore and disposed on the side of said bore restriction away from said firing pin, a shaft member passing through said bore restriction and connected to said piston member, said shaft member having a portion of its length remote from said piston member of greater cross section than the portion of its length adjacent to said piston member, means sealing between said bore restriction and said greater cross-sec tion portion of said shaft member, a hammer carried by said shaft for engagement with said firing pin, said shaft and piston member being movable in said bore between a first position wherein said hammer is spaced from said firing pin and a second position wherein said hammer engages said firing pin and moves said pin into percussive engagement with said cap, a quantity of hydraulic fluid filling said bore between said piston member and said bore restriction, spring means resiliently biasing said piston member to said first position, and shear pin means connecting said piston member to said" housing member when said piston member is in said first position.

28. A detonator comprising an elongated tubular member having an axial bore therethrough and a restriction in said bore intermediate its ends, a percussion cap mounted in said housing member, a firing pin spaced from said cap and mounted in said housing member for movement thereof into percussive engagement withsaid cap, first and second spaced apart piston members mounted in said housing member for axial movement in said bore and disposed one on each side of said bore restriction, a shaft member passing through said bore restriction and connecting said piston members for unitary movement thereof, said shaft member having a portion of its length adjacent said first piston member of greater cross section than the remainder thereof, said shaft and piston members being movable in said bore between a first position wherein said first piston member is spaced from said firing pin and a second position wherein said first piston member engages said firing pin and moves said pin into percussive engagement with said cap, a quantity of hydraulic fluid filling said bore between said piston members, and shear pin means connecting said piston members to said housing member when said piston members are in said first position.

29. A detonator comprising an elongated tubular member having an axial bore therethrough and a restriction in said bore intermediate its ends, a percussion cap mounted in said housing member, a firing pin spaced from said cap and mounted in said housing member for movement into percussive engagement with said cap, first and second spaced apart piston members mounted in said housing member for axial movement in said bore and disposed one on each side of said bore restriction, a shaft member passing through said bore restriction and connecting said piston members for unitary movement thereof, said shaft member having a portion of its length adjacent said first piston member of greater cross section than the remainder thereof, said shaft and piston members being movable in said bore between a first position wherein said first piston member is spaced from said firing pin and a second position wherein said first piston member engages said firing pin and moves said pin into percussive engagement with said cap, a quantity of hydraulic fluid filling said bore between said piston members, shear pin means connecting said piston members to said housing member when said piston members are in said first position, and means forming an opening through said housing member into said bore to provide fluid communication between the exterior of said housing and the face of said first piston member engageable with said firing pin.

30. A detonator comprising an elongated tubular member having an axial bore therethrough and a restriction in said bore intermediate its ends, a percussion cap mounted in said housing member, a firing pin spaced from said cap and mounted in said housing member for movement thereof into percussive engagement with said cap, first and second spaced apart piston members mounted in said housing member for axial movement in said here and disposed one on each side of said bore restriction, a shaft member passing through said bore restriction and connecting said piston members for unitary movement thereof, said shaft member having a portion of its length adjacent said first piston member of greater cross section than the remainder thereof, means sealing between said bore restriction and said greater cross-section portion of said shaft member, means forming a restricted passage from one side of said bore restriction to the other side thereof, said shaft and piston members being movable in said bore between a first position wherein said first piston member is spaced from said firing pin and a second position wherein said first piston member engages said firing pin and moves said pin into percussive engagement with said cap, a quantity of hydraulic fluid filling said bore between said piston members, spring means resiliently biasing said piston members 22 to said first position, and shear pin means connecting said piston members to said housing member when said piston members are in said first position.

31. A detonator comprising an elongated tubular member having an axial bore therethrough and a restriction in said bore intermediate its ends, a percussion cap mounted in said housing member, a firing pin mounted in said housin-g member for movement between a first position wherein said pin engages said cap and a second position wherein said pin is spaced from said cap, first spring means resiliently biasing said pin to its second position, first and second spaced apart piston head members mounted in said housing member for axial movement in said bore and disposed one on each side of said bore restriction, a shaft member passing through said bore restriction and connecting said piston head members for unitary movement thereof, said shaft having a portion of its length adjacent said first piston head of greater cross section than the remainder thereof, means sealing between said bore restriction and said greater cross-section portion of said shaft, means forming a restricted bleed passage from one side of said bore restriction to the other side thereof, said shaft and piston heads being movable in said bore between a first position wherein said first piston head is spaced from said firing pin and a second position wherein said first piston head engages said firing pin and moves said firing pin against said percussion cap, a quantity of hydraulic fluid filling said bore between said piston heads, second spring means resiliently biasing said shaft to said first position, shear pin means connecting said shaft and piston head members to said housing member when said shaft and piston head members are in said first position, and means forming an opening through said housing member into said bore to provide fluid communication between the exterior of said housing and the face of said first piston head member engageable with said firing pin.

32. A method for perforating oil wells comprising installing a well casing string having a landing nipple made up therein in said well, logging the distance from a desired zone of perforation to said casing landing nipple, making up a tubing string having a tubing anchor and a landing nipple made up integrally therein at a predetermined spacing from .one another, installing the tubing string in the casing string to land the tubing anchor in the casing landing nipple, connecting a well perforator to an extension hanger at a distance therefrom equal to the distance from said desired zone of perforation to said casing landing nipple plus the distance that said tubing landing nipple is above said tubing anchor, pumping said well perforator and extension hanger down through said tubing string by fluid pressure exerted in said tubing string from the upper end thereof, landing said extension hanger in said tubing landing nipple, and detonating said well perforator by said fluid pressure.

33. A method for perforating oil wells, comprising: in-

, stalling a well casing string having a landing nipple made up therein in said Well, logging the distance from a desired zone of perforation to said casing landing nipple, making up a tubing string having a tubing anchor and a landing nipple made up therein at a predetermined spacing from one another, installing the tubing string in the casing string to land the tubing anchor in the casing landing nipple, connecting a well perforator to-an extension hanger at a distance therefrom equal to the distance from said desired zone of perforation to said casing landing nipple plus the distance that said tubing landing nipple is above said tubing anchor, pumping said well perforator and extension hanger down through said tubing string by fluid pressure exerted in said tubing string from the upper end thereof, landing said extension hanger in saidtubing 23 tubing string by fluid pressure exerted in said tubing 2,785,754 string from the lower end thereof. 2,805,718 r 2,810,440 References Cited in the file of thispatent 2,8,10 442 UNITED STATES PATENTS 5 2,304,408 Holifield Dec. 8, 1942 241 True Mar. 19, 1957 Tausch Sept. 10, 1957 Kenneday et a1 Oct. 22, 1957 Tausch Oct. 22, 1957 Long Nov. 11, 1958 Dmmmond Mar. 31, 1959

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