Patent ID: 12252963

DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION

In the following description, certain terms have been used for brevity, clarity, and examples. No unnecessary limitations are to be implied therefrom and such terms are used for descriptive purposes only and are intended to be broadly construed. The different apparatus, systems and method steps described herein may be used alone or in combination with other apparatus, systems and method steps. It is to be expected that various equivalents, alternatives, and modifications are possible within the scope of the appended claims.

Terms such as booster may include a small metal tube containing secondary high explosives that are crimped onto the end of detonating cord. The explosive component is designed to provide reliable detonation transfer between perforating guns or other explosive devices, and often serves as an auxiliary explosive charge to ensure detonation.

Detonating cord is a cord containing high-explosive material sheathed in a flexible outer case, which is used to connect the detonator to the main high explosive, such as a shaped charge. This provides an extremely rapid initiation sequence that can be used to fire several shaped charges simultaneously.

A detonator or initiation device may include a device containing primary high-explosive material that is used to initiate an explosive sequence, including one or more shaped charges. Two common types may include electrical detonators and percussion detonators. Detonators may be referred to as initiators. Electrical detonators have a fuse material that burns when high voltage is applied to initiate the primary high explosive. Percussion detonators contain abrasive grit and primary high explosive in a sealed container that is activated by a firing pin. The impact of the firing pin is sufficient to initiate the ballistic sequence that is then transmitted to the detonating cord.

An example embodiment may comprise a modular perforating gun system in which the selective switch is embodied in the end fitting of the loading tube assembly of the perforating gun. The top or bottom end fitting is designed to hold a selective switch, a feed through contact and orifices to insert the detonator from one end and the detonating cord from the other. The opposite end fitting is designed to connect to a pressure bulkhead containing the feed through contact. Ground is made through charge tube to the end fitting to bulkhead to baffle to gun body. The loading tube is prewired and terminated to the pressure bulkhead feed through contact at one end and the selective switch at the other end. The gun carrier is box by pin with bottom of gun carrier having a swaged and threaded end. Alternatively, may have a thin shoulder pin-pin tandem sub.

An example embodiment is shown inFIGS.1-3. The example embodiment includes a perforating gun assembly10having a cylindrical body housing11, in the charge tube14, with a lower end32and an upper end33. A baffle12with a pressure bulkhead bottom contact17disposed therein is further coupled to the lower end32of the cylindrical body housing11.

A charge tube14is loaded with shaped charges18and disposed within, and coupled to, the cylindrical body housing11. In this example embodiment, the charge tube14may be pre-wired. The baffle12is adjacent to the lower end fitting13which is coupled to the lower end34of the charge tube14. A charge tube is also known as a loading tube. The charge tube14has loading tube cutouts29located proximate to the lower end34and loading tube cutouts28located proximate to the upper end35. The charge tube14has a lower end fitting13located proximate to the lower end34and a upper end fitting50located proximate to the upper end35. A locking means for shaped charges18may include the tabs30located on shaped charges18. A detonator cord locking means may include the retainer fitting31located on the end of the shaped charges18. The selective switch20is grounded to the cylindrical body via ground wire61coupled to grounding screw62. Signal wire60is used to send signals through perforating gun10and is pre-wired into the charge tube14. Signal wire60is insulated from the cylindrical body11, which is conductive and acts as a ground. A detonating cord40is coupled to each of the shaped charges18. A ground wire61from the selective switch20is coupled to the charge tube14via fastener62. The upper end fitting50includes a door80that is adapted to receive the detonator21. Door80is hinged, it opens outward, and it snaps into a closed position in a recess, aligning the detonator in a side-by-side configuration with the end of the detonating cord, in the end fitting50. The signal is conducted through the upper end fitting50via feed thru spring82and the ground is conducted through the upper end fitting50via ground spring81.

The upper end fitting50includes a selective switch20, a wireless detonator21, a detonating cord orifice19, and a top contact16inFIG.2. A closer view of upper end fitting50is shown inFIG.2. The ground lug62and ground wire61allows the selective switch20to be grounded to the charge tube14. The selective switch20is connected to the wireless detonator21via the modular connector assembly85. The modular connector assembly85has an auto-shunting feature whereby the wireless detonator21is shunted until the correct connector is inserted. A detonating cord40wraps around the outside of the charge tube14, connecting to each of the shaped charges18via connectors31, and terminates within the charge tube14, through the loading tube cutout28, and into the detonating cord orifice19, which is located proximate to the wireless detonator21. The detonating cord40may be located in an end-to-end or side-by-side configuration with the wireless detonator21. The modular connector assembly85may include the example embodiments inFIGS.12A-18, as disclosed herein.

The lower end34of the perforating gun assembly10is shown inFIG.3including a baffle12coupled to the lower end34and located proximate to the lower end fitting13. The pressure bulkhead bottom contact17is coupled to an insulated wire27. The loading tube14includes shaped charges18having locking tabs30for locking into the loading tube14. The shaped charges18have detonating cord locking clips31that couple to a detonating cord40wrapped along the outside of the loading tube14. Ground contact with the charge tube14is maintained by spring connection76coupled to the lower end fitting13via fastener75.

Two perforating guns, a lower gun100and an upper gun200are shown inFIG.4depicting a close up of the gun-to-gun connection. The two perforating guns100and200are configured similarly and this example embodiment shows how the guns are coupled together. The perforating gun100has a charge tube114located within a cylindrical body111. The charge tube114contains shaped charges118coupled to detonating cord140and an upper end fitting150. Upper end fitting150contains a selective switch120coupled to a wireless detonator121, which is further located adjacent to a detonating cord end119. Detonating cord end119may include a booster. Pressure Bulkhead bottom contact217is disposed within and coupled to bottom end fitting212. Perforating gun200also contains a charge tube214located within a cylindrical body211and containing perforating charges250coupled to detonating cord240. Perforating gun200also has an upper fitting250that contains a selective switch220coupled to a wireless detonator221via modular connector assembly285, which is further located adjacent to a detonating cord end219. Detonating cord end219may have a booster. Signal wire160is used to send signals through perforating gun100and is pre-wired into charge tube. Signal wire160is insulated from the cylindrical body111, which is conductive and acts as a ground. The selective switch120is grounded to the cylindrical body via ground wire161coupled to grounding screw162. Signal wire260is used to send signals through perforating gun200and is pre-wired into charge tube. Signal wire260is insulated from the cylindrical body211, which is conductive and acts as a ground. The selective switch220is grounded to the cylindrical body via ground wire261coupled to grounding screw262. Bulkhead contact117provides the signal continuity to signal wire160. Ground spring strap176coupled to the end fitting via fastener175grounds the charge tube114. Upper end fitting150contains an outward opening door180that is coupled via modular connector assembly185to detonator121. Door180is hinged, it opens outward, and it snaps into a closed position in a recess, aligning the detonator in a side-by-side configuration with the end of the detonating cord, in the end fitting150. Feed thru spring182provides signal continuity through the upper end fitting150. Ground spring181provides ground continuity between the upper end fitting150and the bottom end fitting212. Ground spring strap276coupled to the end fitting213via fastener275further grounds the charge tube214. Charge tube214contains shaped charges218. The modular connector assembly185and285may include the example embodiments inFIGS.12A-18, as disclosed herein.

An example embodiment is disclosed inFIG.5of a perforating gun assembly310. It includes a gun body314containing a charge tube311. The first end of the charge tube311is coupled to the first end of the gun body314via lower end fitting. The second end of the charge tube311is coupled to the second end of the gun body314via upper end fitting350. Upper end fitting350includes an integrated switch and contains a detonator underneath detonator door380. Door380is hinged, it opens outward, and it snaps into a closed position in a recess, aligning the detonator in a side-by-side configuration with the end of the detonating cord, in the end fitting350. The charge tube includes cutouts329for the shaped charges318. A signal wire360carries an electrical signal to the switch located in the upper end fitting350. The shaped charges318are contained in the charge tube311. The shaped charges318are coupled to the detonating cord340. Electrical wire360transmits signals to the integrated switch located into the upper end fitting350.

An example embodiment is disclosed inFIG.6of the upper end fitting350. Upper end fitting350includes an integrate switch320and a detonator321contained underneath detonator door380. It also includes a ground spring381for maintaining a ground connection through the upper end fitting350. It also includes a feed thru spring382for conveying electrical signals through the upper end fitting350. Ground spring381conveys the ground through the upper end fitting.

An example embodiment is disclosed inFIG.7of the upper end fitting350installed within a perforating gun assembly310. Housing311contains an upper end fitting350includes an integrated switch320and a detonator321contained underneath detonator door380. It also includes a ground spring381for maintaining a ground connection through the upper end fitting350. It also includes a feed thru spring382for conveying electrical signals between the electrical pin383, the integrated switch320, and the signal wire360. Sub384contains electrical pin383that contacts with feed thru spring382. Detonating cord340is coupled to the shaped charges318located in the charge tube314.

An example embodiment is disclosed inFIGS.8A and8Bof the upper end fitting350partially outside of the gun body314. Upper end fitting350includes an integrated switch320and a detonator321contained underneath detonator door380. It also includes a ground spring381for maintaining a ground connection through the upper end fitting350. It also includes a feed thru spring382for conveying electrical signals through the upper end fitting350. Detonating cord340is detonated by the detonator321located in detonator door380. Signal wire360sends the initiation signal to the initiator321. The detonator321is received by modular connector assembly385which may include an auto-shunting feature. The modular connector assembly385may include the example embodiments inFIGS.12A-18, as disclosed herein.

An example embodiment is disclosed inFIGS.9A,9B, and9Cof the upper end fitting350. Upper end fitting350includes an integrated switch320and a detonator321contained underneath detonator door380. It also includes a ground spring381for maintaining a ground connection through the upper end fitting350. It also includes a feed thru spring382for conveying electrical signals through the upper end fitting350. The detonator install tool386is shown having a handle391, a head390, with an extension389having a radial opening392for holding a detonator321. The pins393and tap387help hold the detonator321in place when installing or removing. Tap387engages tab388to positively engage with the detonator321. The detonator321is plugged into connector381.

An example embodiment is disclosed inFIG.10of the upper end fitting350. Upper end fitting350includes an integrated switch320and a detonator321contained underneath detonator door380. It also includes a ground spring381for maintaining a ground connection through the upper end fitting350. It also includes a feed thru spring382for conveying electrical signals through the upper end fitting350. In this view the shaped charges318are secured by locking tabs into the charge tube311. Charge tube311containing shaped charges318is slideably engaged with the gun housing314. Signal wire360and detonating cord340are wrapped around the charge tube311. The gun housing314has internal threads having a thread cutout395for allowing the nut394on the upper end fitting350to slide past the threads.

An example embodiment is disclosed inFIGS.11A and11Bof the upper end fitting350. Upper end fitting350includes an integrated switch320and a detonator321contained underneath detonator door380that closes into recess398. It also includes a ground spring381for maintaining a ground connection through the upper end fitting350. It also includes a feed thru spring382for conveying electrical signals through the upper end fitting350. The detonator321is plugged into connection381having a header connector396and a receptacle connector397.

A modular initiator is depicted inFIG.12AandFIG.12B. The modular initiator serves the purpose of providing a high energy output to initiate a second explosive device such as a detonating cord, a booster, a power charge, or propellant. The modular initiator requires electrical input to transfer electrical energy into a high energy output. The modular initiator contains a rigid connector for the purpose of assembling the initiator to a receiving circuit or installing in a contact block such that it may function as a standalone unit. The modular initiator may be used in a variety of explosive systems requiring electrical initiation.

A contact block provides electrical feed through to allow the modular initiator to function without the need for additional electrical connections. The electrical circuit may be a printed circuit board, flexible circuit board, or other commonly used electrical boards or combinations. There may be many features included in the circuitry including switches, safety features, RF isolation, two-way communication with the surface, temperature measurement circuitry, pressure measurement circuitry, and other features not directly required for initiating the modular initiator. Electrical energy will pass through the electrical circuit to initiate the modular initiator through a rigid connector.

Referring toFIGS.12A,12B, and12C, a modular connector assembly410has a receptacle412having a latch416and contacts420are coupled to the connector413. Connector413includes contact blades419that engage with the contacts420. The contact blades419are further coupled to the resistors417aand417bvia resister leads418. Resister leads418, which may be continuous portions of contact blades419, are coupled to corresponding resistors417. A shell411is crimped onto the connector413. Wire414and415are coupled to the receptacle412. The design is such that each wire414or415has a corresponding contact20, a corresponding contact blade419, a corresponding resistor lead418, and a corresponding resistor417aor417b. Latch416locks the receptacle412into the connector413.

Referring toFIGS.13A,13B,13C,13D,13E, and13F, a side cross section and corresponding side cross section of the modular connector assembly410are shown in different stages of engagement. Stage 1 is depicted byFIGS.13A and13B. In stage 1 the receptacle412is partially inserted into the connector413, approximately one-third or less of the way inserted, there is no electrical connection between the receptacle412and connector413and the shunt, represented by shunt contacts422aand422b, are in the shunted position. In this configuration the modular connector assembly410is self-protected from radio frequency signals and stray voltages. As can be seen inFIG.13B, the shunt contacts422aand422bare electrically in contact with each other, forming an electrical shunt between contact blades419aand419b. The latch416is not engaged. The signal contacts420aand420bare not engaged with the corresponding blades419aand419b. The separator421, a non-conductive wedge shaped part of the receptacle412, is not engaged with the shunt contacts422aand22b. Contact blades419aand419bhave corresponding resistor contacts418aand418b. The wires414and415can be arranged side by side, or opposite of each other, depending on the application.

Stage 2 is depicted inFIGS.13C and13Dwhen the receptacle412is approximately between one third and two thirds of the way inserted into the connector413. Here electrical connections have been established between the receptacle412and the connector413while the shunt remains in place due to shunt contacts422aand422bstill being in contact. In this state the modular connector assembly410is electrically protected by the initiator shunt and the circuit connected to the receptacle and is in a transition state. As can be seen inFIG.13D, the shunt contacts422aand422bare electrically in contact with each other, forming an electrical shunt between contact blades419aand419b. The latch416is deflected, but not engaged. The signal contacts420aand420bare engaged with the corresponding blades419aand419b. The separator421, is beginning to make contact with the shunt contacts422aand422b, but it has not yet separated them.

Stage 3 is depicted inFIGS.13E and13Fwhen the receptacle412is more than two thirds of the way inserted into connector413. The receptacle412is in electrical communication with the connector413and is no longer shunted. As can be seen inFIG.13F, the shunt contacts422aand422bare not electrically in contact with each other due to separator421wedging them apart, therefore contact blades419aand419bare unshunted. The latch416is engaged into the connector413. The signal contacts420aand420bare engaged with the corresponding blades419aand419b.

FIGS.14A and14Bshow additional detail of the connector413. The contact blades419aand419band their corresponding shunt contacts422aand422bare shown. Furthermore, contact blades149aand419bhave corresponding resistor contacts418aand418b.

FIGS.15A and15Bshow additional detail of the receptacle412. The latch416is integrally formed to the receptacle. The wires414and415can be arranged side by side, or opposite of each other, depending on the application. InFIG.15Aone wire is strain-relieved while the other is not. InFIG.15Bboth wires are strain relieved.

Referring toFIGS.16A,16B,16C,16D,16E, and16Fa side cross section and corresponding side cross section of the modular connector assembly500are shown in different stages of engagement. A modular connector assembly500has a receptacle512having contacts520are coupled to the connector513. Connector513includes contact blades519that engage with the contacts520. The contact blades519are further coupled to the resistors517aand517bvia resister leads518. Stage 1 is depicted byFIGS.16A and16B. In stage 1 the receptacle512is partially inserted into the connector513, approximately one-third or less of the way inserted, there is no electrical connection between the receptacle512and connector513and the shunt, represented by shunt contacts522aand522b, are in the shunted position. In this configuration the modular connector assembly500is self-protected from radio frequency signals and stray voltages. As can be seen inFIG.16B, the shunt contacts522aand522bare electrically in contact with each other, forming an electrical shunt between contact blades519aand519b. A latch may be used in this configuration to ensure a positive and locking engagement, but it is not shown. The signal contacts520aand520bare not engaged with the corresponding blades519aand519b. Therefore, the wires514and515are not connected. The separator521, a non-conductive part of the receptacle512, is not engaged with the shunt contacts522aand522b. Housing531is coupled to connector513.

Stage 2 is depicted inFIGS.16C and16Dwhen the receptacle512is approximately between one third and two thirds of the way inserted into the connector513. Here electrical connections have been established between the receptacle512and the connector513while the shunt remains in place due to shunt contacts522aand522bstill being in contact. In this state the modular connector assembly500is electrically protected by the initiator shunt and the circuit connected to the receptacle and is in a transition state. As can be seen inFIG.16D, the shunt contacts522aand522bare electrically in contact with each other, forming an electrical shunt between contact blades519aand519b. The signal contacts520aand520bare engaged with the corresponding blades519aand519b, however, because of the shunting, the signal contacts520aand520b, and their corresponding wires514and515, are connected. The separator521, is beginning to make contact with the shunt contacts522aand522b, but it has not yet separated them.

Stage 3 is depicted inFIGS.16E and16Fwhen the receptacle512is more than two thirds of the way inserted into connector513. The receptacle512is in electrical communication with the connector513and is no longer shunted. As can be seen inFIG.16F, the shunt contacts522aand522bare not electrically in contact with each other due to separator521wedging them apart, therefore contact blades519aand519bare unshunted, and thus wires514and515are no longer in contact with each other. The signal contacts520aand520bare engaged with the corresponding blades519aand519b.

An example embodiment of a shunting initiator connection may include modular connector assembly700with contact circuit is shown inFIGS.17A and17B. It has a detonator shell701, a short/shunt tab702, a shunt lift mechanism703, an electrical contact pin704, a connector housing705, and an electrical contact circuit706. There may be a plurality of pins704that are shunted by a single short/shunt tab702.FIG.17Ashows an example where the modular connector assembly700is partially inserted andFIG.17Bshows an example where the modular connector assembly700is fully inserted.

An example embodiment of a self-shunting coaxial connector is shown inFIG.18. A coaxial male connector800has an electrically conductive line803, it may be coupled to a positive wire, and an outer electrically conductive spring contact802, that may be coupled to a negative wire. The spring contact802is by default in contact with line803due to a springing action, which provides a self-shunting feature for the male connector800. The female connector801has an outer electrically conductive radial portion804, a radial insulator806, and an inner receptacle805that is electrically conductive. Inner receptacle805is coupled to a line807. When the male connector800is initially inserted into the female connector800, the spring contact802makes electrical contact with the radial portion804and the line803makes electrical contact with the receptacle805. The curvature808of the spring contact902interfacing with the curvature809of the female connector forces the spring contact802away from the line803as the male connector800is fully inserted into the female connector801, thus removing the shunt after first establishing electrical contact.

Wireless detonator, as used in this specification, is defined as a detonator that is pre-wired prior to installation and does not require any wiring in the field to function. This wireless capability allows the detonator to become effectively a plug-and-play device that establishes the necessary electrical connections for its function by plugging it into the perforating gun.

The example embodiments disclose a modular gun system that is a box by pin design consisting of a steel loading tube with an end fitting pre-installed at each end. One end fitting centers and orients the loading tube and embodies a selective switch, feed through contact and orifices to insert a wireless detonator from the outer end and detonating cord into the inner end.

The loading tube is pre-wired with insulated wire which is terminated at the selective switch in one end fitting and the pressure bulkhead at the opposite end. The opposite end fitting centers the loading tube and provides electrical contact from the pre-installed insulated wire on the loading tube to the pressure bulkhead contact adjacent to the end fitting. The pressure bulkhead is pre-installed into a baffle in the pin end of the gun carrier. The selective switch is grounded to the loading tube which is electrically connected to the baffle which is threaded into the gun carrier.

Charges are inserted into the loading tube and held in place by locking features fixed to the shaped charge. Detonating cord is inserted into the back of each charge via locking features fixed to the shaped charge. The detonating cord terminates into the detonating cord orifice in the end fitting. A wireless detonator is inserted into the end fitting from outside of the gun assembly such that the explosive load end of the detonator is adjacent to the detonating cord in an end to end position. The wireless detonator has an auto-shunting feature that does not un-shunt until a mating receptacle is inserted.

The selective switch has a ribbon pigtail with the un-shunting receptacle attached. After inserting the wireless detonator, the connector receptacle connected to the switch is attached to the end of the detonator, disengaging the shunt of the detonator. The loaded and armed modular gun assemblies are screwed together such that the top contact makes electrical contact to the bottom contact of the adjacent gun assembly. The box by pin gun configuration is accomplished by swaging and threading the outer diameter of one end of the gun. Alternatively, the pin end is accomplished by installing a pin by pin tandem sub into one box end of a box by box gun body.

The end fitting is purposefully designed via a mold or machining method to house a selective switch designed to selectively initiate the detonator of a perforating gun. The end fitting is pre-assembled with a spring-loaded top contact wired to the input of the selective switch. The end fitting is pre-assembled such that the through wire of the selective switch is connected to the insulated wire pre-installed onto the loading tube. The end fitting is pre-assembled such that the output wires of the selective switch are insulated ribbon or wires which has the detonator connector receptacle affixed to its end. The end fitting is purposefully designed via a mold or machining method to insert detonating cord through the inner end and a detonator from the outer end such that the detonator is adjacent to the detonating cord on the horizontal axis of the gun body. Alternatively, the end fitting is designed such that the detonating cord and detonator overlap each other such that the end of the detonating cord and detonator are side by side.

The pressure bulkhead is pre-installed into the baffle of the pin end of the gun carrier. Alternatively, the pressure bulkhead is pre-installed into the pin by pin tandem sub which is inserted into one end of the gun carrier. Alternatively, the pressure bulkhead is pre-installed to the end of the charge tube end fitting. The gun assembly is armed by inserting a wireless electric detonator, connector end facing up, into the end fitting detonator orifice, followed by attaching the connector receptacle attached to the end fitting into the outer end of the detonator.

The selective switch is attached to, or contained within, the pre-wired loading tube and the wires with the detonator connector receptacle pass through the upper end fitting. The selective switch is contained within the lower end fitting, wherein the insulated wire is connected to the switch within the same lower end fitting and the detonator connector receptacle wire runs the length of the loading tube and the receptacle end passes through the upper end fitting.

The application for the example embodiments may be used with different types of initiators including resistor based bridgewire initiators, exploding bridge wire initiators, exploding foil initiators, and any other style of electric or electronic initiator. The modular initiator in the example embodiment is a packaged unit, which may include resistors, capacitors, or other electrical components. It may include a circuit board or other electronic circuitry. The modular initiator may be assembled or incorporated into an electrical circuit as a new assembly. The modular initiator may function as a standalone unit. A contact assembly without electronic circuitry may be employed which would receive the initiator and pass through electrical signals to the initiator.

The modular initiator includes a shell containing a high explosive such as lead azide, RDX, HMX, HNS, a bridge element or foil initiator, and electrical components such as resistors, capacitors, spark gaps, electronic circuits, etc. The modular initiator may contain a rigid connector. The rigid connector may be incorporated in many configurations. The rigid connector may be a male pin-style or female style socket. The connector may incorporate a shunting mechanism. The purpose of the shunting mechanism is to act as a protective barrier against radio frequency (RF) energy and stray electrical energy by electrically shorting the contacts. The short length and removal of leg wires also creates RF resistance. The modular initiator must be protected from RF when transported off-site on public roads. The modular initiator could be installed to an electronic circuit with its own RF protection during the installation process. For situations where the shunt must be removed, a safety housing can be employed to protect personnel if the modular initiator were to initiate during installation. Robotics installation methods could also be used when shunting is not available.

Auto-Shunting Electrical Connection or Auto-Shorting Electrical Connection (ASEC)—An ASEC is an electrical connection comprising at least one connector with a self-contained feature which electrically shorts two or more electrical contact paths of the connector when the connector is disconnected from, in the process of being disconnected from, or is being connected to a mating connector which includes at least one design feature which disengages the shorting feature of the first connector after electrical contact is established or allows the shorting feature of the first connector to reengage before electrical contact is broken.

Auto-Shunting Electric Initiator or Auto-Shorting Electric Detonator (ASED)—An ASED is an electric or electronic initiator of any variety in which electrical energy is converted to an high energy output wherein the electric or electronic initiator includes the attached connector of an ASEC with the self-contained feature to electrically short two or more electrical contact paths and the electrical contact paths of the ASEC connector include the electrical contact paths of the electric or electronic initiator and at least part of the path through which electrical energy is converted to a high energy output.

Initiators may be used to initiate a perforating gun, a cutter, a setting tool, or other downhole energetic device. For example, a cutter is used to cut tubulars with focused energy. A setting tool uses a pyrotechnic to develop gases to perform work in downhole tools. Any downhole device that uses an initiator may be adapted to use the modular connector assembly disclosed herein.

Although the invention has been described in terms of embodiments which are set forth in detail, it should be understood that this is by illustration only and that the invention is not necessarily limited thereto. For example, terms such as upper and lower or top and bottom can be substituted with uphole and downhole, respectfully. Top and bottom could be left and right, respectively. Uphole and downhole could be shown in figures as left and right, respectively, or top and bottom, respectively. Generally downhole tools initially enter the borehole in a vertical orientation, but since some boreholes end up horizontal, the orientation of the tool may change. In that case downhole, lower, or bottom is generally a component in the tool string that enters the borehole before a component referred to as uphole, upper, or top, relatively speaking. The first housing and second housing may be top housing and bottom housing, respectfully. In a gun string such as described herein, the first gun may be the uphole gun or the downhole gun, same for the second gun, and the uphole or downhole references can be swapped as they are merely used to describe the location relationship of the various components. Terms like wellbore, borehole, well, bore, oil well, and other alternatives may be used synonymously. Terms like tool string, tool, perforating gun string, gun string, or downhole tools, and other alternatives may be used synonymously. The alternative embodiments and operating techniques will become apparent to those of ordinary skill in the art in view of the present disclosure. Accordingly, modifications of the invention are contemplated which may be made without departing from the spirit of the claimed invention.