Patent Publication Number: US-9903695-B1

Title: Method and device for initiating an explosive train

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional application claiming the benefit of U.S. Provisional Patent Application No. 61/595,224, filed 6 Feb. 2012, which is hereby incorporated in its entirety herein. 
    
    
     FIELD 
     The invention relates to an arming apparatus and, more particularly, to a method and device for initiating an explosive train to detonate an explosive, such as with a perforating gun. 
     BACKGROUND 
     Many known explosives require significant shock, heat, force or other stimuli to detonate, generally referred to as a secondary explosive. As such, an explosive train is often used to efficiently detonate these explosives, where the explosive train often includes a detonator and an intermediary. To provide ease of use, detonators generally are constructed using easily detonated primary explosives. 
     Given the ease of ignition of a detonator, precautions are taken to prevent accidental initiation of the detonator or to interrupt the explosive train extending to the explosive. 
     A first known approach is to physically isolate the detonator from the rest of the explosive train until just before the desired detonation. This requires an operator to physically connect the detonator to the rest of the explosive train at the final location of usage. While advantageous in that the explosive train is not complete prior to connection, the initiation device must be connected before detonation is needed and, in perforating a wellbore, before the explosive is positioned. 
     Another approach is the use of a deflagration to detonation device, exploding bridgewire or exploding foil initiator to directly detonate an explosive train constructed solely of secondary explosives. While effective, these systems are limited by the technology available, reliability and/or the high cost and complexity of the electrical systems. 
     An alternative approach includes interrupting the explosive train so that, even if the primary explosive detonator is initiated, at least a portion of the explosive train is not “in line” with the rest, so that the explosive at the end of the explosive train is left undetonated. These systems generally can be classified as either blocking or misaligned. In a blocking system, a barrier or other blockage is positioned so as to interrupt the explosive train. In practice, while the barrier may be exposed to the detonator or other portion of the explosive train, the barrier prevents the explosive train from continuing therepast. 
     In a misaligned system, at least one portion of the explosive train is shifted so as to not be aligned with the rest of the explosive train. With the system misaligned, the progress of the explosive train is limited by the misaligned location, thereby ending the explosive train extending between the detonator and the explosive. However, with the misaligned portion shifted back into aligned with the remainder, the explosive train can be initiated and maintained to detonate the explosive. 
     One method of accomplishing the interruption of the explosive train, whether misaligned or blocked, is for an operator to physically remove the barrier or realign the explosive train prior to use. This allows for a safe system up to the point of being physically manipulated. However, once realigned or unblocked, the explosive train is intact. As such, physically interacting with the arming device requires access to the arming device and may result in further handling the armed device prior to actual use. 
     An alternative method is utilized in ballistic applications in which the interrupted system automatically shifts to an uninterrupted state (i.e., unblocked or aligned) upon the presence of specific external forces or environmental conditions. For a given application, specific environmental or external factors associated with a desired arming condition are determined. For example, a specific impact force applied to the arming device, velocity of the arming device or angular rotation of the arming device can be utilized. Additionally, environmental factors, such as pressure or temperature, can be utilized to transition an arming device to an armed state. However, care must be taken in the selection of the external forces and environmental conditions utilized to arm the arming device as once the external force or environmental condition is encountered the arming device will be armed whether intended or not. 
     SUMMARY 
     A device for initiating an explosive train is provided which can be armed just prior to initiation. The device includes an electronic switch for receiving and transmitting signals. An orientation mechanism connected to the switch operates to transition the device from an out-of-line orientation, where a detonation path of a detonator connected to the switch does not extend to the explosive train, to an in-line orientation, where the detonation path extends from the detonator to the explosive train. 
     In another embodiment, a detonation device is provided which can be remotely armed. In this regard, an explosive train associated with the detonation device can be armed just prior to detonation of a detonator of the detonation device. The detonation device further includes a barrier member positioned between the detonator and the explosive train to inhibit detonation of the explosive train by detonation of the detonator. A biasing member engaged against the barrier member is counteracted by a blocking mechanism engaged by the barrier member. A frangible member of the blocking mechanism is configured to break upon receiving a signal so that the force applied by the biasing member urges the barrier member out from between the detonation device and the explosive train. 
     Additionally, a method of detonating an explosive train is provided that allows an arming device to be armed just prior to detonation of the explosive train. The method includes transmitting a signal to reposition an arming device to provide a direct path between a detonator and an explosive train. Once the arming device is repositioned the detonator is detonated, along with the explosive train. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a perforating gun having an explosive connected to a detonating device; 
         FIG. 2  is a top perspective view of the detonating device of  FIG. 1  showing a barrier positioned to provide an out-of-line orientation of the detonating device; 
         FIG. 3  is a bottom perspective view of the detonating device of  FIG. 1 ; 
         FIG. 4  is a top perspective view of the detonating device of  FIG. 1  showing the barrier shifted to provide an in-line orientation of the detonating device; 
         FIG. 5  is a bottom perspective view of the detonating device of  FIG. 1  showing the barrier shifted to provide an in-line orientation of the detonating device; 
         FIG. 6  is a perspective view of another embodiment of the detonating device of  FIG. 1  in an out-of-line orientation; 
         FIG. 7  is a perspective view of the detonating device of  FIG. 6  showing a barrier rotated to provide an in-line orientation of the detonating device; 
         FIG. 8  is a perspective view of another embodiment of the detonating device of  FIG. 1  in an out-of-line orientation with the detonator misaligned with the explosive train; and 
         FIG. 9  is a perspective view of the detonating device of  FIG. 8  in an in-line orientation with the detonator aligned with the explosive train. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a system  2  is shown having a detonation device  4  connected to an explosive train  6 . The explosive train  6 , such as a detonation cord, extends from the detonation device  4  toward an explosive or otherwise ignitable material. The detonation device  4 , as shown, is configured to be shifted from an out-of-line orientation  8 , such that initiation of the detonation device  4  does not result in ignition of the explosive train  6 , and an in-line orientation  10  that allows for ignition of the explosive train  6  upon initiation of the detonation device  4 . The detonation device  4  includes an electronic switch  12  for receiving a signal from a remote location, which allows for reorientation of the detonation device  4  without physical interaction by an operator and just prior to initiation of the detonation device  4 . As such, the detonation device  4  can remain in an out-of-line orientation  8  until the detonation device  4  is in a predetermined position and the explosive is ready to be ignited. 
     As shown in  FIG. 2 , the detonation device  4  includes a detonator  14  connected to the switch  12 . The detonator  14  contains a primary explosive or otherwise ignitable material. The detonator  14  can be initiated by known methods, such as an electrical current. As shown in  FIG. 2 , the detonator  14  can be connected to the switch  12 , such as by a wire, so that upon receipt of a signal by the switch  12  the switch  12  can relay an electrical current to sufficient to initiate the detonator  14 . 
     The detonator  14  can include known explosive material, including primary explosives and secondary explosives. Primary explosives include, but are not limited to lead azide, lead styphnate, mercury fulminate and combinations thereof. Secondary explosives include, but are not limited to, TNT, PETN, RDX, HMX, HNS, NONA and combinations thereof. Initiation of the detonator  14  results in the dissipation of energy along a detonation path  16  defined thereby. 
     The detonation device includes an orientation mechanism  18  to transition the device from the out-of-line orientation  8 , as shown in  FIGS. 2 and 3 , to an in-line orientation  10 , as shown in  FIGS. 4 and 5 . Initiation of the detonator  14  causes energy to be released. In the out-of-line orientation  8  the energy dissipated along the detonation path  16  does not extend to the explosive train  6 . As such, with the detonation device  4  in the out-of-line orientation  10 , the explosive train  6  will not ignite as a result of initiation of the detonator  14 . In contrast, in the in-line orientation  10 , the detonation path  16  provided by the detonator  14  extends to the explosive train  6  so that the explosive train  6  is ignited. 
     As shown in  FIGS. 2-5 , the orientation mechanism  18  includes a barrier member  20  shiftable from a blocking position  22  between the detonator  14  and the explosive train  6 , corresponding to the out-of-line orientation  8  of the detonation device  4 , and an offset position  24  out from between the detonator  14  and the explosive train  6  corresponding to the in-line orientation  10  of the detonation device  4 . 
     As shown in  FIGS. 2-4 , the barrier member  20  is a formed metal member, however it is contemplated that the barrier member can be formed of ceramic, plastic, carbon fiber or other suitable material. Alternatively, the barrier member  20  includes a plastic section facing the detonator  14  so that, upon initiation with the barrier member  20  in place, the plastic section is first impacted. The plastic section absorbs the impact and reduces the force transmitted through the metal member. The reduced force transmission limits or eliminates the production of shrapnel from a back side of the barrier member  20  facing the explosive train  6  and the possibility of ignition of the explosive train  6  by the shrapnel. 
     The orientation mechanism  18 , as shown in  FIGS. 2-5 ; further includes a biasing member  26 , such as a spring, for urging the barrier member  20  toward the offset position  24 . To resist the urging provided by the biasing member  26 , the orientation mechanism  18  includes a blocking mechanism  28  configured to be engaged by the barrier member  20  and resist shifting of the barrier member  20  from the blocking position  22  to the offset position  24 . As shown in  FIGS. 3 and 5 , the blocking mechanism  28  includes a blocking member  30  pivotably connected to a structural member  32 , such as the switch. As shown in  FIGS. 2-5 , the barrier member  20  extends through an opening  34  of the structural member  32 . However, it is contemplated that no structural member is required. 
     The blocking member  30  of the blocking mechanism  28  can be shifted away from the barrier member  20  by known methods, including the use of mechanical power, such as a motor, and hydraulic pressure, such a via a control system including hydraulic lines, fluid reservoir, or a solenoid valve. Alternatively, such as with a motor, the barrier member  20  could be shifted directly the motor, such as with a lead screw. 
     Alternatively, as shown in  FIGS. 2-5 , the blocking mechanism  28  includes a biasing mechanism  36 , such as a spring, engaged against the blocking member  30  and configured to urge the blocking member  30  away from the barrier member  20  so that the barrier member  20  can shift to the offset position  24 . 
     A frangible member  38  of the blocking mechanism  28  can be positioned in engagement with the blocking member  30  to prevent the blocking member  30  from moving out of engagement with the barrier member  20 . As shown in  FIGS. 2-5 , the frangible member  38  is secured to and extends from the structural member  32 . The frangible member  38  is further connected to the switch  12  to receive a signal therefrom. Upon receipt of the signal, the structural integrity of the frangible member  38  is compromised such that the blocking member  30  can shift therepast and thereby allow the barrier member  20  to shift to the offset position  24 . 
     As shown in  FIGS. 2-5 , the frangible member  38  is a resistor. The resistor is selected so that, upon receipt of the electrical signal from the switch  12 , the resistor breaks. The biasing force applied to the blocking member  30  by the biasing member  36  is sufficient to overcome the resistance provided by the broken resistor. As a result, the biasing member  36  shifts the blocking member  30  out of engagement with the barrier member  20 , thereby allowing the barrier member  20  to shift to the offset position  24  and resulting in the detonation device  4  being in the in-line orientation  10 . 
     As shown in  FIGS. 6-9 , alternative detonation devices  38  and  40  are depicted. In  FIGS. 6 and 7 , the barrier member  42  rotates from an out-of-line orientation  44 , as shown in  FIG. 6 , to an in-line orientation  46 , as show in  FIG. 7 . The barrier member  42  is connected to a pivot member  48 , such as a pin, extending therethrough which allows the barrier member  42  to pivot therearound from the out-of-line orientation  44  to the in-line orientation  46 . The barrier member  42  is biased toward the in-line orientation  44  by a biasing member  50 , such as a spring. Rotation of the barrier member  42  is impeded by a blocking mechanism  52 . As shown in  FIGS. 6 and 7 , the blocking mechanism  52  is a resistor  54 . It is contemplated that, as an electric signal from the switch  12  flows through the resistor  54 , the resistor  54  will break, melt or otherwise move or cause a member to move so that the barrier member  42  can be shifted toward the in-line orientation  44  by the spring  50 . 
     As shown in  FIGS. 8 and 9 , a detonation device  40  can include a portion  56  of the detonator  14  or the explosive train  6  which can rotate from an out-of-line orientation  58 , as shown in  FIG. 8 , and an in-line orientation  60 , as shown in  FIG. 9 . Similar to detonation device  38  shown in  FIGS. 6 and 7 , the detonation device  40  includes a pivotable portion  62  including a pivot member  64 , such as a pin. The pivotable portion  62  includes either a portion of the detonator  14  or explosive train  6 . The pivotable portion  62  is biased toward the in-line orientation  60  by a biasing mechanism  66 , such as a spring  68 . Rotation of a pivotable portion  62  is impeded by a blocking mechanism  70 . As shown in  FIGS. 8 and 9 , the blocking mechanism  70  is a resistor. It is contemplated that, as an electric signal from the switch  12  flows through the resistor, the resistor will break, melt or otherwise move or cause a member to move so that the pivotable portion can be shifted toward the in-line orientation  60  by the spring  68 . 
     As shown in  FIG. 9 , with the detonation device  40  in the in-line orientation  60 , the detonator  14 , explosive train  6  and pivotable portion  62  are positioned relative to one another so that upon initiation of the detonator  14  the explosive train  6  is ignited. Conversely, as shown in  FIG. 8 , the space between the explosive train  6  and the detonator  14  is sufficient to prevent initiation. 
     Alternatively, the entire detonator  14  can be rotated so that, in the out-of-line orientation  58 , the entire detonator  14  is positioned so that it is not in-line with any part of the explosive train  6 . 
     The resistors disclosed herein can include a carbon composition resistor, which is known to fracture when overloaded. Further, the resistor can be configured to optimize its function as a mechanical release device. In particular, the resistor can include a groove, hole or reinforced leads to further buttress its mechanical blocking capability. 
     In an alternative embodiment, the frangible member can include a meltable portion which, upon the application of heat or electricity, melts so that the structural integrity of the frangible member is compromised. The meltable portion can include a body formed from an electrically conductive plastic which is connected to electrical leads, which may or may not be integrated therewith. Passing electricity through the electrically conductive plastic causes the plastic to melt, and thereby reduces the structural integrity of the plastic. Alternatively, a plastic or otherwise meltable material can be positioned to be engaged by the blocking member. A resistor, or other electrical component, is positioned adjacent the meltable material so that, as electricity flow through the resistor and breaks the resistor, the resulting energy melts the meltable material. 
     It is contemplated that two barrier members or out-of-line mechanism can be implemented in a detonation device. The mechanisms for creating the out-of-line mechanism can be the same or different from one another. 
     It is contemplated that the switch is an addressable switch, such as described in U.S. Pat. Nos. 7,347,278 and 7,505,244, incorporated by reference in its entirety herein. In particular, the addressable switch can control the release or positioning of the blocking mechanism by sending an electrical signal to a motor, control system, solenoid valve or other known systems. Further, it is contemplated that the addressable switch can provide feedback on the status of the system as a whole and its integrity. 
     It is further contemplated that the switch sends a series of signals to the detonating device, such as at least two signals, and the repositioning of the detonating device occurs as a result of the receipt of the two signals within a specified period of time. Alternatively, other known methods and devices for confirming an instruction, such a detonation instruction, can be utilized. 
     In addition, it is contemplated that an external testing device can be utilized to query and report the status of the system and any safety protocols. Such a device could be utilized to verify the existence and/or integrity of the barrier member and/or blocking mechanism. For example, a current could be run through the blocking member, with the current being utilized to establish the existence, integrity and/or placement of the barrier member. 
     One use of the disclosed system is to arm a perforating gun remotely, after it is downhole and at a specific depth, regardless and independent of other factors such as pressure, temperature, movement, depth, or the presence of markers providing a signal to the system or a member within the wellbore engaging the system. 
     While various embodiments have been described herein with respect to a limited number of examples, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments and variations thereof can be devised which do not depart from the scope disclosed herein. Accordingly, the scope of the claims should not be unnecessarily limited by the present disclosure.