US3116689A

US3116689A - Well perforating apparatus and switch

Info

Publication number: US3116689A
Application number: US825517A
Authority: US
Inventors: Cyril R Sumner
Original assignee: Halliburton Co
Current assignee: Halliburton Co
Priority date: 1959-07-07
Filing date: 1959-07-07
Publication date: 1964-01-07
Anticipated expiration: 1981-01-07

Description

Jan. 7, 1964 c. R. SUMNER WELL PERFORATING APPARATUS AND SWITCH 3 Sheets-Sheet 1 Filed July 7, 1959 Jan. 7, 1964 c. R. SUMNER 3,116,689

WELL PERFORATING APPARATUS AND SWITCH Filed July 7, 1959 3 Sheets-Sheet 2- !l 1 74 hl! 'Illi r-1 I 7/ 77 I 72 8o- ---a/ 78 76 2 FIG. 4

INVENTOR.

FIG- 3 CYRH. R. SUMNER Jan. 7, 1964 c. R. SUMNER 3,116,639

WELL PERFORATING APPARATUS AND SWITCH Filed July 7, 1959 3 Sheets-Sheet 3 INVENTOR. 56 CYRIL R. SUMNER United States Patent 3,116,68? WELL PERFORATHNG APPARATUS AND SWITCH Cyril R. Sumner, Fort Worth, Tex., assignor to Halliburton Company, a corporation of Delaware Filed July 7, 1959, er. No. 825,517 4 Claims. (Cl. 102-28) This invention relates to well perforating apparatus including a switch mechanism for sequentially firing explosive components of the apparatus and to a switch mechanism for such purposes.

Shaped charge and bullet well perforators include a plurality of electrically fired explosive components such as squibs, blasting caps, shaped charge perforating units, bullet gun units and the like. It is often desired to fire two or more of such components or groups of components in time sequence and at predetermined intervals.

[One type of perforating apparatus that requires, in operation, the sequential firing of an electric squib and an electric blasting cap is disclosed in the copending application of Blake M. Caldwell and Harrold D. Owen, Serial No. 461,236, filed October 8, 1954, for Well Perforating Assembly and Perforating Unit Therefore, now Patent No. 3,067,679, which patent is assigned to the assignee of the present application.

The aforementioned Caldwell and Owen application discloses well perforating apparatus, illustrated generally in FIGS. 1 and 2 of this application, wherein a plurality of shaped charge perforating units are pivotally mounted on an elongated carrier and are interlocked in axial disposition. The shaped charge units may be maintained in interlocked axial disposition by an electric squib while the apparatus is lowered into the well through tubing. When the squib is fired, after the apparatus has emerged from the bottom of the tubing, the shaped charge units are released for pivotal movement to dispositions laterally of the carrier. The charge units are pivoted to such lateral dispositions by means of springs or the like. When the shaped charge units have assumed lateral disposition, they are ready to be fired to perforate a portion of the well casing and the surrounding formation. The units are detonated by a length of detonating fuse, such as Primacord, arranged in detonating relation to the units the Primacord being fired from one end by an electric blasting cap.

In operating the apparatus of the foregoing Caldwell et al. application, it is desirable that, after release of the charge units by the firing of the electric squib, at least sufficient time be allowed for all of the charge units to reach lateral disposition before the electric blasting cap is fired. Thus, all of the charge units will be pointed in the horizontal direction and optimum perforation of the we l will be accomplished.

T he foregoing Caldwell and Owen perforating apparatus has an arming switch that maintains the electric blasting cap in disarmed condition until after the electric squib has been fired. The arming switch has an actuating mechanism that is spring biased to move the switch to arm the electric blasting cap, the actuating mechanism being restrained in switch-disarming position by engagement with the uppermost of the pivoted shaped charge units. The actuating mechanism is released, upon initial pivotal movement of the uppermost shaped charge unit, to allow the arming switch to close and to fire the electric blasting cap.

It has been found that, because of great hydrostatic force acting on the plunger of the actuating mechanism of the arming switch, the arming switch often closes to fire the blasting cap and the Primacord before the upper shaped charge units have had time to pivot to full lateral 3,llfi,fi39 Patented Jan. 7, 1964 dispositions. Thus, the upper charge units may fail to fire because they have not reached full lateral disposition, or if they should be detonated, the resulting perforations are directed downwardly from the horizontal and at an angle other than that desired. In either event, the firing is characterized as a malfunction.

The present invention provides a reverse-acting stepswitch mechanism that can be incorporated in the foregoing basic Caldwell and Owen well perforating apparatus, with only minor changes in the latter, to obviate premature firing of the shaped charge units. The well perforating apparatus, thus modified, is an improvement in the Caldwell and Owen apparatus and it is with such improvement that the present application is concerned. Although the present application, in order to enable the invention to be described fully, clearly, concisely and exactly, discloses much of the basic Caldwell and Owen well perforating apparatus, no claim is made herein to such basic apparatus per se.

It is, therefore, an object of the invention to provide a reverse-acting step-switch mechanism that may be employed in a well perforator or the like for successively firing a plurality of explosive components.

Another object of the invention is to provide a reverseacting step-switch wherein the intervals between movements of the switch are under complete control of the operator.

Another object is to provide a reverse-acting step switch wherein the cooperating contact elements of the switch are stationary when the switch is conducting current and wherein switching movement takes place with no voltage across the switch.

Still another object is to provide a well perforating apparatus incorporating a step-switch of the foregoing type to fire in controlled sequence a plurality of electrically actuated exposive devices.

A further object is to provide a well perforating apparatus including a step-switch of the foregoing type wherein two electrically actuated explosive devices may be fired in controlled sequence and predetermined order irrespective of the initial positions of the movable switch components.

These and other aims, objects and advantages of the invention are achieved in well perforating apparatus includi-ng a carrier; means for lowering the carrier into a well; a plurality of well perforating units pivotally mounted in axial disposition on the carrier and pivotable to lateral disposition; means including an electric squib restraining the units in axial disposition and adapted to permit the units to pivot to the lateral disposition upon the squib being fired; an electric blasting cap for firing the units when they have pivoted to the lateral disposition; a step-switch mounted on the carrier, the stepsswitch including a fixed switch component having two contact elements mounted thereon, a movable switch arm positioned to contact either of the two contact elements as the switch arm is moved, and electrically powered stepping means to move the switch arm from either one of the contact elements to the other of the contact elements; circuit means including a feed conductor and a return conductor arranged to conduct electricity from the surface of the earth to the carrier; means electrically connecting the movable switch arm to one of the conductors; means electrical connecting the electric squib for firing between the other of the conductors and one of the two contact elements; means including a normally open arming switch for electrically connecting the electric blasting cap for firing between the same conductor to which the squib is connected and the other of the two contact elements; means for closing the normally open arming switch in response to the firing of the electric squib; means electrically connecting the electrically powered stepping means across the conductors; a source of electric power at the surface of the earth; and a control switch at the surface of the earth for connecting the power source to and disconnecting the power source from the circuit means.

The reverse-acting solenoid step-switch mechanism will be described hereinafter and its method of operation in the perforating apparatus will be set forth.

The invention will be described with greater particularity with reference to the drawings in which:

FIG. 1 is a vertical axial sectional view through a portion of an oil well showing, in axial section, a well perforating apparatus in accordance with the invention suspended within the tubing, the shaped charge perforating units being disposed in axial alignment;

FIG. 2 is a vertical axial sectional view similar to FIG. 1 but showing the perforating apparatus suspended in the casing with the perforating units below the bottom of the tubing and pivoted to lateral disposition;

FIG. 3 is an enlarged vertical axial sectional view of a portion of the well perforating apparatus shown in FIGS. 1 and 2;

BIG. 4 is a sectional view taken along the line 4-4 of FIG. 3 looking in the direction of the arrows;

.FIG. 5 is an enlarged detail view of the arming switch of the perforating apparatus shown in FIGS. 1 and 2; and

FIG. 6 is a diagrammatic view of well perforating apparatus in accordance with the invention.

Referring to the drawings, particularly to FIGS. 1 and 2 thereof, the reference numeral 10 designates an oil well casing in which is suspended a production tubing 11. Within the tubing is a perforating device including a step-switch sub 12 to the bottom of which is threaded a firing head 13. Carried by the firing head is an elongated tubular carrier 14 through which passes the detonating fuse 15. Pivoted to the carrier are a number of shaped explosive charge well perforating units 16 each having a cap 17 and a .case 18. The perforating units are biased to pivot through apertures in the carrier to the horizontal positions illustrated in FIG. 2 by springs 19 tensioned between the carrier and the charge units. The charge units have

complementary detents

20 and 21 that are interlocked as seen in FIG. 1 to hold the units in axial alignment in the carrier as the per-forator is lowered through the tubing.

The charge units 16 are maintained in axial alignment in the carrier by an electric squib 22 seated in a recess in the bull nose 23 attached to the bottom of the carrier 14. The upper end of the squib is engaged by the detent 20 of the lowermost charge unit to prevent the unit from pivoting to lateral disposition while the apparatus is being lowered through the tubing. The other charge units are interlocked in axial disposition by inter-engagement of their

respective detents

20 and 21. The detent 2.1 of the uppermost shaped charge unit is engaged by a cooperating detent 24 of an arm 25 pivoted to the carrier at 26 and .urged to a lateral disposition by a spring 27 tensioned between the arm and the carrier.

A plunger 28 is slidably mounted in the firing head 13 and the lower end of the plunger is attached to the arm 25 by a link 29 pivoted to the plunger and to the arm. When the arm 25 swings to the lateral disposition of FIG. 2, the plunger 28 is moved upwardly in the firing head to actuate an arming switch 30 in a manner to be described more fully hereinafter.

When the squib 22 is exploded, the upper end of the squib is destroyed as shown in FIG. 2 and the interlocked charge units and arm 25 pivot to their lateral dispositions. The charge units are then in position to direct their perforating jets through the casing lit and into the surrounding earth formation when the detonating fuse is fired. The detonating fuse is initiated by an electric blasting cap 31 in the firing head as will be described more fully hereinafter. It will be understood that, be-

fore the squib 22 is fired to release the pivoting members, the perforating apparatus is lowered out of the bot tom of the tubing 11 at leastsufficiently far so that the charge units and arm 25 may pivotwithout interference to their firing positions. It 'will also be understood that the perforating apparatus is lowered through the tubing by means of a conductor cable (not shown), the cable not only serving to support the perforating apparatus but also to deliver electric current to the apparatus for releasing the charge units and for firing them.

Referring to FIGS. 3 and 4, the step-switch in the sub 12 has a ratchet wheel 32 fixedly mounted on a shaft 33 journaled in a bearing block 34 that is electrically insulated from the supporting structure. The shaft 33 has alfixed to it a switch arm 35 carrying a movable contact element 36. The step-switch has a fixed switch member 37 in the form of an insulating plate which carries the fixed contact elements 38 that are disposed in circular arrangement to be contacted in succession by the movable contact element 36.

The ratchet wheel 32 is made of suitable insulating material and has teeth formed on the periphery corresponding in number and spacing to the fixed contact elements 38. A spring finger 4t? mounted on the transverse plate 41 follows the periphery of the ratchet wheel and falls successively into the interdental spaces as the ratchet wheel is rotated in the counter-clockwise direction, as seen in FIG. 3, to prevent the ratchet wheel from turning in the reverse direction.

The mechanism for advancing the ratchet wheel one tooth at a time includes a plunger 42 having an armature 43 at the upper end, the armature and plunger being drawn upwardly when the solenoid coil 44 is energized. A plunger return spring 45 is attached at one end to the bottom of the plunger and at the other end to an anchor 46 on the cross plate 47. The return spring 45 is stretched when the plunger is drawn upwardly by the solenoid and, when the solenoid is de-energized, the spring pulls the plunger down. The plunger 4-2 carries a pawl 48 mounted on a pivot .49. The pawl is urged upwardly against a stop 5t) by means of a spring 51. The pawl is free to ride over the teeth of the ratchet wheel when the plunger is drawn up, but engages a tooth of the ratchet wheel when the plunger moves down to advance the ratchet wheel a distance of one tooth in a forward direction. Each time the ratchet wheel is advanced one tooth, the moveable contact element 36 moves from one of the fixed contact elements 38 to the next fixed contact element.

Referring to FIG. 6, the electrical circuit of the perforating apparatus is diagrammatically shown, together with certain associated components. Some ,of the on-carrier parts, such as the step-switch, the squib 22, the blasting cap 31 and the arming switch 34 have already been referred to. Other on-carrier components of the electrical system include a fixed condenser 52 and a rectifier 53. The conductor cable by which the perforating apparatus is lowered'into the well is designated by the reference numeral 54. At the surface of the ground is located a source of alternating current designated by the general reference numeral 55.

One terminal 56 of the source of alternating current is grounded and the other terminal 57 is connected through a manually-operated switch 58 to the insulated conductor wire 59 of the conductor cable 54. The conductor cable has a metallic sheath 60 which is grounded and which may also be electrically connected to the stepswitch sub 12 to ground the latter. Wire 59 is connected to one side of the rectifier 53 and the other side of the rectifier is connected through a Wire 61 to an insulated terminal 62. Terminal 62 is led to ground 63 through the condenser 52 by wires .64 and 65. A wire 66 connects the terminal 62 to one end of the solenoid coil 44, the opposite end of the solenoid being grounded by the wire 67. A conductor 63 leads from the ungrounded end of the solenoid coil to the step-switch shaft 33 and thence through the shaft and switch arm 35 to the moveable contact element 36. Contact between the wire 68 and the shaft 33 is established through a wiper 69, as shown in FIG. 4.

As will be seen from the diagram of FIG. 6, there is an even number of fixed contact elements 38, the elements being equally spaced around the fixed switch member 37. Alternate fixed contact ele rents are connected through suitable wires to a common conductor 70, the latter being connected by a wire 71 to the right hand center pole 72 of the arming switch 36. The remaining fixed contact elements 33 of the step-switch are similarly connected through suitable wiring to a second common conductor 73 which, in turn, is connected by wire '74 to the upper left pole 75 of the arming switch.

The bridge wire of the squib 22 is connected between the lower right hand pole '76 of the arming switch and ground by suitable wiring, as seen in FIG. 6.

The bridge wire of the electric blasting cap 31 is connected between the left hand center pole 77 of the arming switch and the left hand lower pole 78, the latter pole being grounded. The right hand upper pole 79 of the arming switch is not used in the circuit illustrated in FIG. 6.

The arming switch Ed has a pair of contact sliders 8d and 81 that are actuated in unison by the plunger 28 (FIG. 1). When the plunger is in the down position of FIG. 1, the sliders occupy the positions shown in FIGS. 5 and 6 with the slider 84 interconnecting poles 7'7 and 78 and the slider 81 interconnecting the

switch poles

72 and 76. When the plunger has moved to the up position of FIG. 2, the slider 89 is shifted to interconnect

switch poles

75 and 77 and the slider 81 is moved to interconnect

switch poles

79 and 72.

In operation, the perforating apparatus of the invention is lowered through the production tubin to a position in the well below the bottom of the tubing at which the casing and surrounding formation is to be perforated. The perforating units 16 are interlocked in axial disposition as illustrated in FIG. 1. With the parts of the reverse acting solenoid step-switch mechanism in the positions shown in FIG. 6, the line energizing switch 58 at the surface of the earth is closed to deliver current to the perforating apparatus suspended in the well. Current is delivered to the bridge wire of the squib 22 through the rectifier 53, the

conductors

66 and 68, the step-switch, the common conductor 70, the wire 71 and the contact slider 81 of the arming switch 39, the circuit being completed through ground as shown in FIG. 6. Thus the squib is fired. The perforating units 16 pivot to the lateral dispositions shown in FIG. 2. The sliders of the arming switch 39 are moved to their upper positions, as described hereinbefore, by upward movement of the arming switch plunger 28. The low impedance path through the squib is thus opened and current flows through the high impedance solenoid coil 44 to draw the plunger 42 upwardly against the tension of the spring 45, the pawl 4-8 riding over the teeth of the ratchet wheel 32. Upon such movement of the plunger 42, the switch arm remains in the position shown in FIG. 6. Although the slider fit) of the arming switch has completed the circuit through the bridge wire of the blasting cap 31 from the step-switch to ground, the blasting cap is not fired because the step-switch is open to the common conductor 73. This condition obtains as long as the operating switch 58 at the surface of the earth remains closed.

In order to fire the blasting cap 31 and the perforating units, the operating switch 58 is opened. The solenoid coil 44 of the step-switch is thus deenergized and the spring 45 returns the plunger 42 to its lower position, the pawl 48 advancing the ratchet wheel 32 one tooth as the plunger moves from its upper to its lower position. The arm 35 of the switch is thereby advanced to the next fixed contact element.

However, the blasting cap 31 is not at this moment fired because the operating switch 58 is open. When the operating switch 58 is again closed, the blasting cap 31 is fired, the fuse 15 is detonated, and the perforating units are fired to perforate the well. It is seen that the step-switch 37 advances only when the line conducting the current to the perforating apparatus is de-energized so that inadvertent firing of the blasting cap is avoided. It is only when the operating switch 58 is closed the second time that the blasting cap is fired.

Upon firing, the perforating units and the carrier are substantially destroyed. The firing head, the step-switch sub and the cable head are not destroyed and may be retrieved from the well.

If the switch arm 35 should happen to be in contact with one of the contact elements connected to the com mon conductor 73 when the perforating apparatus is lowered to the location to be perforated, the first closure of the operating switch 53 at the surface of the earth will not effect firing of the blasting cap because the slider 89 of the arming switch 34) is in the lower position and the circuit to the blasting cap is open between the arming

switch terminals

75 and 77. Such first closure of the switch 53 does, however, energize the solenoid coil 4-4 and, when the operating switch 58 is opened, the contact arm 35 is advanced to a position completing the circuit to the common conductor 76 leading to the bridge wire of the squib 22. Upon a second closure of the operating switch 58, the squib Z2 is fired, as described hereinbefore. Then, upon opening the operating switch 58 and closing it a third time, the blasting cap 31 is fired to effect perforation of the well. Therefore, no matter in what position the switch arm 35 of the step-switch may be, if the switch 58 is closed three times, the desired firing sequence of the squib and the blasting cap is assured.

The reverse-acting solenoid step-switch of the invention is not restricted to use in the particular perforating apparatus disclosed by way of illustration. It may be used for sequentially firing any desired number of electrically operated explosive devices of either a shaped charge perforating apparatus or a bullet perforating apparatus. The reverse-acting solenoid step-switch mechanism of the invention also finds general utility in the electrical arts.

As pointed out hereinbefore, the conductor cable 54 has a grounded metallic sheath 60. It is not essential that the sheath be grounded if it is a good electrical conductor, and it is not essential that the sheath be conductive if the electrical circuit is completed through ground or another conductor. Thus, the expression twoconductor line as used herein is intended to include all such lines and their equivalents.

The expression one-way clutch as used herein is intended to embrace not only the particular ratchet-andpawl mechanism shown by way of illustration for advancing the switch elements one step at a time, but also other equivalent mechanisms well known in the art.

I claim:

1. A well perforating assembly comprising:

(a) a carrier;

(b) means for lowering said carrier into a well;

(c) a p'luratliy of well perforating units pivotally mounted in axial disposition on said carrier and pivotable to lateral disposition;

(d) means including an electric squib restraining said units in said axial disposition and adapted to permit said units to pivot to said lateral disposition upon said squib being fired;

(e) an electric blasting cap for firing said units when they are pivoted to said lateral disposition;

(f) a step-switch mounted on said carrier, said stepswitch including a fixed switch component having two contact elements mounted thereon, a movable switch arm positioned to contact either of said two contact elements as said switch arm is moved, and electrically powered stepping means to move said switch arm from either one of said contact elements to the other of said contact elements;

(g) circuit means including a feed conductor and a return conductor arranged to conduct electricity from the surface of the earth to said carrier;

(h) means electrically connecting said movable switch arm to one of said conductors;

(i) means electrically connecting said electric squib for firing between the other of said conductors and one of said two contact elements;

(j) means including a normally open arming switch for electrically connecting said electric blasting cap for firing between the same said conductor to which said squib is connected and the other of said two contact elements;

(k) means for closing said normally open arming switch in response to the firing of said electric squib;

(1) means electrically connecting said electrically powcred stepping means across said conductors;

(m) a source of electric power at the surface of the earth; and

(n) a control switch at the surface of the earth for connecting said power source to and disconnecting said power source from said circuit means.

2. A well perforating assembly comprising:

(a) a carrier;

(b) means for lowering said carrier into a well;

(c) a pluratliy of well perforating units pivotally mounted in axial disposition on sm'd carrier and pivotable to lateral disposition;

(e) an electric blasting cap for firing said units when they have pivoted to said lateral disposition;

(7) a step-switch mounted on said carrier, said stepswitch including a fixed switch component having an even number, comprising at least four, of contact elements mounted thereon, alternate contact elements being electrically connected to a first common lead, the remaining contact elements being electricdly connected to a second common lead, a movable switch arm positioned to contact each one of said contact elements in succession as said switch arm is moved,

and electrically powered stepping means to move said i electrically connecting said electric blasting cap for firing between the same said conductor to which said squib is connected and the other of said common leads;

(1) means electrically connecting said electrically po-wered stepping means across said conductors;

(m) a source of electric power at the surface of the earth; and

3. A well perforating assembly as defined in claim 2 wherein:

(a) said arming switch has a center pole, two terminal poles, and a movable contact member for connecting said center pole to either one of said terminal poles;

(b) said means electrically connecting said electric blasting cap for firing further includes means electrically connecting one of said terminal poles to the same conductor to which said squib is connected, and means electrically connecting the other of said terminal poles to said other of said common leads, and means electrically connecting said blasting cap between said center pole and said one of said terminal poles;

(c) said movable contact member connects said center pole to said one of said terminal poles to short out said blasting cap; and

(d) said means for closing said arming switch includes means for moving the movable contact member of said arming switch to disconnect said one of said terminal poles from said center pole, thereby to unshort said blasting cap, and to connect said center pole to said other of said terminal poles, thereby to complete the blasting cap firing circuit from said same said conductor to which said squib is connected to said other of said common leads. 5

4. A well perforating assembly as defined in claim 2 wherein References Cited in the file of this patent UNITED STATES PATENTS Stick Oct. 5, 1943 Hooker Sept. 14, 1954 Cheltz Oct. 25, 1955 Schlumberger Feb. 28, "1956 Bricaud Ian. 24, 1956 Caldwell Apr. 28, 1959

Claims

1. A WELL PERFORATING ASSEMBLY COMPRISING: (A) A CARRIER; (B) MEANS FOR LOWERING SAID CARRIER INTO A WELL; (C) A PLURATLIY OF WELL PERFORATING UNITS PIVOTALLY MOUNTED IN AXIAL DISPOSITION ON SAID CARRIER AND PIVOTABLE TO LATERAL DISPOSITION; (D) MEANS INCLUDING AN ELECTRIC SQUIB RESTRAINING SAID UNITS IN SAID AXIAL DISPOSITION AND ADAPTED TO PERMIT SAID UNITS TO PIVOT TO SAID LATERAL DISPOSITION UPON SAID SQUIB BEING FIRED; (E) AN ELECTRIC BLASTING CAP FOR FIRING SAID UNITS WHEN THEY ARE PIVOTED TO SAID LATERAL DISPOSITION; (F) A STEP-SWITCH MOUNTED ON SAID CARRIER, SAID STEPSWITCH INCLUDING A FIXED SWITCH COMPONENT HAVING TWO CONTACT ELEMENTS MOUNTED THEREON, A MOVABLE SWITCH ARM POSITIONED TO CONTACT EITHER OF SAID TWO CONTACT ELEMENTS AS SAID SWITCH ARM IS MOVED, AND ELECTRICALLY POWERED STEPPING MEANS TO MOVE SAID SWITCH ARM FROM EITHER ONE OF SAID CONTACT ELEMENTS TO THE OTHER OF SAID CONTACT ELEMENTS; (G) CIRCUIT MEANS INCLUDING A FEED CONDUCTOR AND A RETURN CONDUCTOR ARRANGED TO CONDUCT ELECTRICITY FROM THE SURFACE OF THE EARTH TO SAID CARRIER; (H) MEANS ELECTRICALLY CONNECTING SAID MOVABLE SWITCH ARM TO ONE OF SAID CONDUCTORS; (I) MEANS ELECTRICALLY CONNECTING SAID ELECTRIC SQUIB FOR FIRING BETWEEN THE OTHER OF SAID CONDUCTORS AND ONE OF SAID TWO CONTACT ELEMENTS;