Patent Publication Number: US-11655693-B2

Title: Perforation gun system

Description:
PRIORITY CLAIM 
     This application is a continuation of U.S. patent application Ser. No. 17/201,552, filed Mar. 15, 2021, which claims priority to U.S. Provisional Patent Application No. 62/989,279 filed on Mar. 13, 2020 and entitled “PERFORATION GUN SYSTEM”. The contents of each of the above applications is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments of the invention are in the field of oilfield equipment and, in particular, perforation guns. 
     BACKGROUND 
     In conventional methods a user may couple perforation guns together and then use explosives within the guns to fracture rock formations. Oil may then flow through the fractured rock formations. This may involve hydraulic “Tracking”, which involves injecting liquid at high pressure into subterranean rocks, boreholes, and the like to force open existing fissures and extract oil or gas. A typical perforation gun may include a long tube that includes charges. These guns may couple together with a coupler, which is sometimes called a “tandem sub” (https://***.yjoiltools.com/Wireline-Subs/Tandem-Sub). The coupler&#39;s external threads mate with internal threads of the gun. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features and advantages of embodiments of the present invention will become apparent from the appended claims, the following detailed description of one or more example embodiments, and the corresponding figures. Where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements. 
         FIG.  1 A  includes a cross-sectional view of an embodiment of a single gun having inner and outer conduits, proximal and distal connectors (e.g., caps), and a coupler.  FIG.  1 B  includes a front view of the same. 
         FIG.  2 A  includes a perspective view of an embodiment of a coupler (also known as a sub assembly) having a bulkhead.  FIG.  2 B  includes a cross-sectional view of the same.  FIG.  2 C  provides a front view of the same. 
         FIG.  3 A  includes a perspective view of an embodiment of a coupler (also known as a sub assembly) having a bulkhead.  FIG.  3 B  includes a cross-sectional view of the same.  FIG.  3 C  provides a front view of the same. 
         FIG.  4 A  includes a cross-sectional view of an embodiment of a distal cap (also referred to as a bottom cap).  FIG.  4 B  includes a rear view of the same. 
         FIG.  5 A  includes a perspective view of an embodiment of a proximal cap (also referred to as a top cap).  FIG.  5 B  includes a cross-sectional view of the same.  FIG.  5 C  includes a front view of the same. 
         FIG.  6 A  includes a side view of an embodiment of an inner conduit.  FIGS.  6 B and  6 C  provide cross-sectional views of the same.  FIG.  6 D  provides a rear view of the same. 
         FIG.  7    includes an embodiment of a system having two gun assemblies. 
         FIG.  8    includes a cross-sectional view of an embodiment of a distal connector.  FIGS.  9 A,  9 B,  9 C,  9 D,  9 E  depict assembly, rear, front, perspective, and cross-sectional views of an embodiment of a coupler to mate with the distal connector of  FIG.  8   . 
         FIGS.  10 A and  10 B  provide perspective and assembly views for an embodiment a proximal connector. 
         FIGS.  11 A and  11 B  provide side views of an embodiment of an inner tube.  FIG.  11 C  provides a front view of a proximal connector.  FIG.  11 D  provides a view of a distal connector. 
         FIG.  12 A  includes a perspective view of an embodiment of a bulkhead electric contact or conductor.  FIG.  12 B  provides a cross-sectional view of the contact and  FIG.  12 C  provides a front view of the contact. 
         FIG.  13 A  includes a side view of an embodiment of a bulkhead electric contact (also referred to as a bulkhead conductor).  FIG.  13 B  provides a front view of the contact. 
         FIGS.  14 A and  14 B  provide cross-sectional views of an embodiment of a perforation gun system.  FIG.  14 C  provides a rear or bottom view of the same. 
         FIGS.  15 A,  15 B, and  15 C  provide perspective, cross-sectional, and front views of an embodiment of a bulkhead. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings wherein like structures may be provided with like suffix reference designations. In order to show the structures of various embodiments more clearly, the drawings included herein are diagrammatic representations of structures. Thus, the actual appearance of the fabricated structures, for example in a photograph, may appear different while still incorporating the claimed structures of the illustrated embodiments. Moreover, the drawings may only show the structures useful to understand the illustrated embodiments. Additional structures known in the art may not have been included to maintain the clarity of the drawings. “An embodiment”, “various embodiments” and the like indicate embodiment(s) so described may include particular features, structures, or characteristics, but not every embodiment necessarily includes the particular features, structures, or characteristics. Some embodiments may have some, all, or none of the features described for other embodiments. “First”, “second”, “third” and the like describe a common object and indicate different instances of like objects are being referred to. Such adjectives do not imply objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. “Connected” may indicate elements are in direct physical or electrical contact with each other and “coupled” may indicate elements co-operate or interact with each other, but they may or may not be in direct physical or electrical contact. Phrases such as “comprising at least one of A and B” include situations with A, B, or A and B. 
     Applicant determined conventional systems are cost-prohibitive, difficult to manufacture, and difficult to work with in the field. However, described herein are embodiments that address these concerns. Advantages of certain embodiments are, without limitation: (1) easier for field users to assemble since there are fewer threaded joints to assemble, (2) fewer threaded parts provide economic efficiencies (i.e., the coupler lacking threads saves costs normally used to impart threads on a tandem sub), and (3) the direct outer conduit to outer conduit connection provides a smaller chance of fluid getting leaking into a gun (in some embodiments there is a need for fewer O rings because there are fewer coupling surfaces). Other advantages are listed further below. 
       FIG.  1 A  illustrates a hydraulic fracturing system comprising a perforating gun. The gun includes an outer conduit  1 , an inner conduit  3 , a proximal cap  11  (a cap is a form of connector), a distal cap  10 , a coupler  2  and a bulkhead  22 . The inner conduit is included within the outer conduit. The outer conduit includes proximal and distal ends, the proximal end including outer threads  8  (male threads) and the distal end including inner threads  9  (female threads). 
     The distal cap includes a first distal electric contact  12  and a second distal electric contact  14 . The first distal electric contact is resiliently coupled to a body of the distal cap via a distal resilient member  13 . The second distal electric contact is resiliently coupled to the body of the distal cap via the distal resilient member. The first distal electric contact includes at least one metal, the at least one metal including at least one of stainless steel, bronze, brass, tin-plated metal, or combinations thereof. 
     The proximal cap includes a first proximal electric contact  15  and a second proximal electric contact  16 . The first proximal electric contact is resiliently coupled to a body of the proximal cap via a second resilient member  17 . The second proximal electric contact is resiliently coupled to the body of the proximal cap via the second resilient member. The first proximal electric contact includes at least one metal, the at least one metal including at least one of stainless steel, bronze, brass, tin-plated metal, or combinations thereof. The proximal cap includes an aperture  19  ( FIG.  5 C ) and the aperture includes an electrical switch  18 . The electrical switch couples at least one cable that is proximal to the proximal cap to at least one cable that is distal to the proximal cap. The proximal cap includes an additional aperture  20  and the additional aperture includes a detonator  21 . 
       FIG.  7    shows an additional perforating gun, which includes an additional outer conduit  1 ′, an additional inner conduit  3 ′, an additional proximal cap  11 ′, and an additional distal cap  10 ′. The additional proximal cap includes an additional first proximal electric contact  15 ′ and an additional second proximal electric contact  16 ′. The additional first proximal electric contact is resiliently coupled to a body of the additional proximal cap via an additional second resilient member  17 ′. The additional second proximal electric contact is resiliently coupled to the body of the additional proximal cap via the additional second resilient member. The additional first proximal electric contact includes at least one metal, the at least one metal including at least one of stainless steel, bronze, brass, tin-plated metal, or combinations thereof; 
     Coupler  2  has no external threads (although all embodiments are not limited in this way). Bulkhead  22  is included within the coupler. The bulkhead includes no resilient members (not including items such as o-rings), such as coils or springs. The bulkhead directly contacts both the first distal electrical contact  12  and the additional first proximal electrical contact  15 ′ of  FIG.  7   . The first resilient member  13  biases the first distal electrical contact towards the bulkhead in a first direction and the additional second resilient member  17 ′ biases the additional first proximal electrical contact towards the bulkhead in a second direction that is opposite the first direction. 
     Contact  31  has no spring-induced physical bias and is configured to directly contact the first distal electrical contact  12  and another contact of another gun (e.g., contact  15  of another gun). First resilient member  13  is configured to bias the first distal electrical contact  12  towards contact  31 . 
     Any of the contacts may be made of a material that is not easily magnetized or corroded, such as stainless steel. As a result, system reliability is enhanced considering the system may be exposed in the field to caustic and/or magnetic field environments. Embodiments may use stainless steel, brass, bronze, tin-based alloys, tin-plated metals, or combinations thereof. 
     In an embodiment, contact  15  has a non-circular cross-section. For example, see flat portions  29  and/or  30  of  FIG.  5 C . Such a keyed profile ensures the contact does not rotate within the cap when screw  32  is tightened, which consequently promotes a more reliable electrical path for data signals, and the like. Contact face  32  has a larger surface area than contact  31  of the bulkhead. 
     In an embodiment, contact  12  has a non-circular cross-section. For example, see flat portions  29 ′ and/or  30 ′ of  FIG.  4 B . Such a keyed profile ensures the contact does not rotate within the cap when screw  33  is tightened, which consequently promotes a more reliable electrical path for data signals, and the like. Contact face  32 ′ has a larger surface area than contact  31  of the bulkhead. 
     Regarding the bulkhead of  FIG.  1 A , the bulkhead provides advantages over conventional systems that conduct data signals through resilient members, such as springs. With vibrating environments common to oilfields, this conduction path can be less than reliable. However, in the embodiment of  FIGS.  1 A and  7    contacts  12  and  15  (or the version of  15  on a neighboring gun, which is seen in  FIG.  7   ) are biased towards contact  31 . The path then conducts directly from contact  12 , to contact  31 , to contact  15  (or the version of  15  on a neighboring gun, which is seen in  FIG.  7   ). This path has fewer physical interfaces than conventional systems (i.e., there is no interface between a pin contact and spring and a metal sealing surface and then to a spring and to another pin contact), which promotes reliability for conduction of signals. Contacts  12 ,  15  utilize springs  13 ,  17  to maintain continuity despite vibrations and the like that are inherent to operating conditions in the oilfield. Wires/cables are secured to contacts  12 ,  15  by wrapping around screws  32 ,  33  (referred to above as contacts  16 ,  14 ). 
     In an embodiment, coupler  2  is keyed to the distal cap  10 . For example, in  FIG.  1 A  projection  23  is keyed to void  24  to ensure the distal cap (and the rest of the inner tube) are oriented in only one way to the coupler. As a result, and for example, void  27  (which holds a charge as shown in  FIG.  7   ) aligns with void  28 , thereby aligning a charge with void  28 . 
     In an embodiment coupler  2  is included entirely within the outer conduit. 
     In the embodiment of  FIG.  7    the additional outer conduit includes additional proximal and distal ends. The additional proximal end includes additional outer threads  8 ′ and the additional distal end includes additional inner threads  9 ′. The additional outer threads  8 ′ directly couple to the inner threads  9 . By allowing two guns to mate directly to each other (at a single junction) there is one less junction compared to previous technologies. For example, with a coupler or tandem sub there are two interfaces at the two spots where the tandem sub interfaces the two guns. These interfaces are an area where drilling fluids and the like can enter the gun and prevent charges from detonating. However, decreasing the number of interfaces for such leakage provides another advantage for embodiments described herein. 
     In an embodiment the outer conduit includes long axis  38  that intersects the proximal and distal caps. A plane, which is orthogonal to the long axis, intersects the additional outer threads, the inner threads, and the coupler. 
     In the embodiment of  FIG.  1 A  inner threads  9  are keyed to coupler  2 . For example, projection  25  is keyed to void  26  to ensure the coupler is oriented in only one way to the outer tube. 
       FIG.  1 A  also discloses top thread protector  5 , retaining ring  4 , bottom thread protector  6 , and o-ring  7 .  FIG.  2 B  discloses a bulkhead retainer unit  34 .  FIG.  3 B  shows a modified version of contact  31  of  FIG.  2 B .  FIG.  4 A  discloses washer  35 .  FIG.  5 B  discloses detonator plug  36  and washer  37 . 
     Example 1: A hydraulic fracturing system comprising: a perforating gun, the perforating gun including an outer conduit ( 1 ), an inner conduit ( 3 ), a proximal cap ( 11 ), a distal cap ( 10 ), a coupler ( 2 ), a bulkhead ( 22 ); wherein the inner conduit is included within the outer conduit; wherein the outer conduit includes proximal and distal ends, the proximal end including outer threads ( 8 ) and the distal end including inner threads ( 9 ); wherein (a)(i) the distal cap includes a first distal electric contact ( 12 ) and a second distal electric contact ( 14 ), (a)(ii) the first distal electric contact is resiliently coupled to a body of the distal cap via a distal resilient member ( 13 ), (a)(iii) the second distal electric contact is resiliently coupled to the body of the distal cap via the distal resilient member, (a)(iv) the first distal electric contact includes at least one metal, the at least one metal including at least one of stainless steel, bronze, brass, tin-plated metal, or combinations thereof; wherein (b)(i) the proximal cap includes a first proximal electric contact ( 15 ) and a second proximal electric contact ( 16 ), (b)(ii) the first proximal electric contact is resiliently coupled to a body of the proximal cap via a second resilient member ( 17 ), (b)(iii) the second proximal electric contact is resiliently coupled to the body of the proximal cap via the second resilient member, (b)(iv) the first proximal electric contact includes at least one metal, the at least one metal including at least one of stainless steel, bronze, brass, tin-plated metal, or combinations thereof; (b)(v) the proximal cap includes an aperture ( 19 ) and the aperture includes an electrical switch ( 18 ), (b)(vi) the electrical switch couples at least one cable that is proximal to the proximal cap to at least one cable that is distal to the proximal cap; (b)(vii) the proximal cap includes an additional aperture ( 20 ) and the additional aperture includes a detonator ( 21 ); an additional perforating gun, the additional perforating gun including an additional outer conduit, an additional inner conduit, an additional proximal cap, an additional distal cap, the additional proximal cap including (c)(i) an additional first proximal electric contact and an additional second proximal electric contact ( 16 ), (c)(ii) the additional first proximal electric contact is resiliently coupled to a body of the additional proximal cap via an additional second resilient member, (c)(iii) the additional second proximal electric contact is resiliently coupled to the body of the additional proximal cap via the additional second resilient member, (c)(iv) the additional first proximal electric contact includes at least one metal, the at least one metal including at least one of stainless steel, bronze, brass, tin-plated metal, or combinations thereof; wherein (d)(i) the coupler has no external threads, (d)(ii) the bulkhead is included within the coupler, (d)(iii) bulkhead includes no resilient members, (d)(iv) the bulkhead directly contacts both the first distal electrical contact and the additional first proximal electrical contact, (d)(v) the first resilient member biases the first distal electrical contact towards the bulkhead in a first direction and the additional second resilient member biases the additional first proximal electrical contact towards the bulkhead in a second direction that is opposite the first direction. 
     Example 2. The system of example 1 wherein the inner threads are keyed to the coupler. 
     Example 3. The system of example 2 wherein the coupler is keyed to the distal cap. 
     Example 4. The system of example 1, wherein the coupler is included entirely within the outer conduit. 
     Example 5. The system of example 4, wherein: the additional outer conduit includes additional proximal and distal ends, the additional proximal end including additional outer threads and the additional distal end including additional inner threads; the additional outer threads directly couple to the inner threads. 
     Example 5.1. The system of example 5, wherein: the outer conduit includes a long axis that intersects the proximal and distal caps; a plane, which is orthogonal to the long axis, intersects the additional outer threads, the inner threads, and the coupler. 
     Example 6. The system of example 4, wherein: the additional outer conduit includes additional proximal and distal ends, the additional proximal end including additional outer threads and the additional distal end including additional inner threads; the additional inner threads directly couple to the outer threads. 
     Example 6.1. The system of example 6, wherein: the outer conduit includes a long axis that intersects the proximal and distal caps; a plane, which is orthogonal to the long axis, intersects the outer threads, the additional inner threads, and the coupler. 
     Example 7. The system of example 4 wherein the outer conduit directly contacts the additional outer conduit. 
     Example 8. The system of example 7, wherein: the outer conduit includes a long axis that intersects the proximal and distal caps; a plane, which is orthogonal to the long axis, intersects the outer conduit, the additional outer conduit, and the coupler. 
     Example 9. The system of example 7, wherein: the outer conduit includes a long axis that intersects the proximal and distal caps; a plane, which is orthogonal to the long axis, intersects the outer conduit, the additional outer conduit, and the additional first proximal electric contact. 
     Example 10. A hydraulic perforating gun system comprising: an outer conduit ( 1 ); an inner conduit ( 3 ); a proximal cap ( 11 ); a distal cap ( 10 ); a coupler ( 2 ); a bulkhead ( 22 ); wherein the inner conduit is proportioned to be included within the outer conduit; wherein the outer conduit includes proximal and distal ends, the proximal end including outer threads ( 8 ) and the distal end including inner threads ( 9 ); wherein (a)(i) the distal cap includes a first distal electric contact ( 12 ) and a second distal electric contact ( 14 ), (a)(ii) the first distal electric contact is resiliently coupled to a body of the distal cap via a distal resilient member ( 13 ), (a)(iii) the second distal electric contact is resiliently coupled to the body of the distal cap via the distal resilient member, (a)(iv) the first distal electric contact includes at least one metal; wherein (b)(i) the proximal cap includes a first proximal electric contact ( 15 ) and a second proximal electric contact ( 16 ), (b)(ii) the first proximal electric contact is resiliently coupled to a body of the proximal cap via a second resilient member ( 17 ), (b)(iii) the second proximal electric contact is resiliently coupled to the body of the proximal cap via the second resilient member, (b)(iv) the first proximal electric contact includes at least one metal; (b)(v) the proximal cap includes an aperture ( 19 ) and the aperture includes an electrical switch ( 18 ), (b)(vi) the electrical switch couples at least one cable that is proximal to the proximal cap to at least one cable that is distal to the proximal cap; (b)(vii) the proximal cap includes an additional aperture ( 20 ) and the additional aperture includes a detonator ( 21 ); wherein (c)(i) the coupler has no external threads, (c)(ii) the bulkhead is included within the coupler, (c)(iii) the bulkhead includes no resilient members, (d)(iv) the bulkhead is configured to directly contact the first distal electrical contact and another contact of another gun, (d)(v) the first resilient member is configured to bias the first distal electrical contact towards the bulkhead. 
     Example 11. A hydraulic perforating gun system comprising: an outer conduit ( 1 ); an inner conduit ( 3 ); a proximal cap ( 11 ); a distal cap ( 10 ); a coupler ( 2 ); a bulkhead ( 22 ); wherein the inner conduit is proportioned to be included within the outer conduit; wherein the outer conduit includes proximal and distal ends, the proximal end including outer threads ( 8 ) and the distal end including inner threads ( 9 ); wherein (a)(i) the distal cap includes a first distal electric contact ( 12 ) and a second distal electric contact ( 14 ), (a)(ii) the first distal electric contact is resiliently coupled to a body of the distal cap via a distal resilient member ( 13 ), (a)(iii) the second distal electric contact is resiliently coupled to the body of the distal cap via the distal resilient member, (a)(iv) the first distal electric contact includes at least one metal; wherein (b)(i) the proximal cap includes a first proximal electric contact ( 15 ) and a second proximal electric contact ( 16 ), (b)(ii) the first proximal electric contact is resiliently coupled to a body of the proximal cap via a second resilient member ( 17 ), (b)(iii) the second proximal electric contact is resiliently coupled to the body of the proximal cap via the second resilient member, (b)(iv) the first proximal electric contact includes at least one metal; wherein (c)(i) the coupler has no external threads, (c)(ii) the bulkhead is included within the coupler, (c)(iii) the bulkhead includes no resilient members, (d)(iv) the bulkhead is configured to directly contact the first distal electrical contact and another contact of another gun, (d)(v) the first resilient member is configured to bias the first distal electrical contact towards the bulkhead. 
     Example 12. An apparatus comprising: proximal and distal caps; a conduit configured to couple to the distal and proximal caps; wherein (a)(i) the distal cap includes a first distal electric contact ( 12 ) and a second distal electric contact ( 14 ), (a)(ii) the first distal electric contact is resiliently coupled to a body of the distal cap via a distal resilient member ( 13 ), (a)(iii) the second distal electric contact is resiliently coupled to the body of the distal cap via the distal resilient member, (a)(iv) the first distal electric contact includes at least one metal; wherein (b)(i) the proximal cap includes a first proximal electric contact ( 15 ) and a second proximal electric contact ( 16 ), (b)(ii) the first proximal electric contact is resiliently coupled to a body of the proximal cap via a second resilient member ( 17 ), (b)(iii) the second proximal electric contact is resiliently coupled to the body of the proximal cap via the second resilient member, (b)(iv) the first proximal electric contact includes at least one metal. 
     Example 13. A coupler comprising: a bulkhead; a plurality of O-rings; wherein (a)(i) the coupler has no external threads, (a)(ii) the bulkhead is included within the coupler, (a)(iii) the bulkhead includes no resilient members. 
     Example 14. A hydraulic perforating gun system comprising: an outer conduit ( 1 ); an inner conduit ( 3 ); a proximal cap ( 11 ); a distal cap ( 10 ); a coupler ( 2 ); wherein the inner conduit is proportioned to be included within the outer conduit; wherein the outer conduit includes proximal and distal ends, the proximal end including outer threads ( 8 ) and the distal end including inner threads ( 9 ); wherein (a)(i) the distal cap includes a first distal electric contact ( 12 ) and a second distal electric contact ( 14 ), (a)(ii) the first distal electric contact is resiliently coupled to a body of the distal cap via a distal resilient member ( 13 ), (a)(iii) the second distal electric contact is resiliently coupled to the body of the distal cap via the distal resilient member, (a)(iv) the first distal electric contact includes at least one metal; wherein (b)(i) the proximal cap includes a first proximal electric contact ( 15 ) and a second proximal electric contact ( 16 ), (b)(ii) the first proximal electric contact is resiliently coupled to a body of the proximal cap via a second resilient member ( 17 ), (b)(iii) the second proximal electric contact is resiliently coupled to the body of the proximal cap via the second resilient member, (b)(iv) the first proximal electric contact includes at least one metal; wherein (c)(i) the coupler has no external threads, (c)(ii) an additional electrical contact is included within the coupler, (c)(iii) the additional electrical contact has no spring-induced physical bias, (d)(iv) the additional electrical contact is configured to directly contact the first distal electrical contact and another contact of another gun, (d)(v) the first resilient member is configured to bias the first distal electrical contact towards the additional contact. 
     Example 1A. A hydraulic fracturing system comprising: a perforating gun that includes an outer conduit, an inner conduit included in the outer conduit, proximal and distal connectors, a coupler, and a bulkhead included in the coupler; wherein (a)(i) the distal connector includes a distal electric contact resiliently coupled to a body of the distal connector via a distal resilient member, and (a)(ii) the proximal connector includes a proximal electric contact resiliently coupled to a body of the proximal connector via a proximal resilient member; wherein (b)(i) the proximal connector includes a first aperture that includes an electrical switch that couples at least one cable that is proximal to the proximal connector to at least one cable that is distal to the proximal connector; and (b)(ii) the proximal connector includes a second aperture to receive a detonator; wherein (c)(i) the coupler is unthreaded, (c)(ii) the bulkhead includes a bulkhead electric contact and the bulkhead includes no resilient members, (c)(iv) the bulkhead electric contact directly contacts the distal electrical contact and is configured to directly contact an additional proximal electrical contact of an additional perforating gun&#39;s additional proximal connector, (d)(v) the distal resilient member biases the distal electrical contact towards the bulkhead in a first direction and the proximal resilient member biases the proximal electrical contact in a second direction that is opposite the first direction. 
     In an embodiment, the distal or proximal connectors may include caps that cap off opposing ends of the inner conduit. Such connectors may include plugs or other means to plug or close, fully or partially, opposing ends of the inner conduit. Such connectors may provide means for energy (e.g., an electrical signal, a percussive surge) to traverse the gun across the inner tube. 
     As used herein, an aperture includes an opening, hole, or gap. In an embodiment, portions of the first and second apertures connect to one another. 
     Another version of Example 1A. A hydraulic fracturing system comprising: a perforating gun that includes an outer conduit, an inner conduit included in the outer conduit, proximal and distal connectors, a coupler, and a bulkhead included in the coupler; wherein (a)(i) the distal connector includes a distal electric contact resiliently coupled to a body of the distal connector via a distal resilient member, and (a)(ii) the proximal connector includes a proximal electric contact resiliently coupled to a body of the proximal connector via a proximal resilient member; wherein (b)(i) the proximal connector includes a first aperture that includes an electrical switch that couples at least one cable that is proximal to the proximal connector to at least one cable that is distal to the proximal connector; and (b)(ii) the proximal connector includes a second aperture to receive a detonator; wherein (c)(i) the coupler is unthreaded, (c)(ii) the bulkhead includes a bulkhead electric contact and the bulkhead electric contact includes no resilient members, (c)(iii) the bulkhead electric contact directly contacts the distal electrical contact and is configured to directly contact an additional proximal electrical contact of an additional perforating gun&#39;s additional proximal connector, (c)(iv) the distal resilient member biases the distal electrical contact towards the bulkhead in a first direction and the proximal resilient member biases the proximal electrical contact in a second direction that is opposite the first direction. 
     Example 2A. The system of example 1A, wherein the bulkhead electric contact is monolithic and includes no welds, seems, or resilient members. 
     As used herein, monolithic means formed of a single piece of material. For example, the bulkhead electric contact may be formed via machining or removing material from a single piece of metal via a lathe process or the like. 
     Example 3A. The system of example 2A, wherein: the outer conduit includes a long axis that intersects the proximal and distal connectors; a first plane, which is orthogonal to the long axis, intersects the bulkhead and the bulkhead electric contact; and a second plane, which is orthogonal to the long axis, intersects the bulkhead electric contact but not the bulkhead. 
     For example, see axes  38 ,  39 ,  40 . 
     Example 4A. The system of example 2A, wherein: the bulkhead includes a gasket; the gasket directly contacts the bulkhead electric contact; the outer conduit includes a long axis that intersects the proximal and distal connectors; and a first plane, which is orthogonal to the long axis, intersects the bulkhead electric contact and the gasket. 
     For example, an o-ring is a type of gasket. For instance, see  FIG.  15 B . 
     Example 5A. The system of example 2A, wherein: the outer conduit includes a first long axis that intersects the proximal and distal connectors; and the bulkhead electric contact includes a second long axis that is collinear with the first long axis. 
     For example, see  FIG.  2 B . 
     Example 6A. The system of example 5A, wherein: the bulkhead electric contact includes first and second portions; the first portion includes a first width that is oriented orthogonal to the second long axis; the second portion include a second width that is oriented orthogonal to the second long axis; the first width is unequal to the second width; a first plane, which is orthogonal to the second long axis, intersects the bulkhead and first portion; and a second plane, which is orthogonal to the second long axis, intersects the bulkhead and the second portion. 
     For example, see widths  41 ,  42  of  FIG.  3 B . 
     Example 7A. The system of example 6A, comprising an overmold, wherein: the overmold includes a non-metal material; the bulkhead includes the overmold; and the overmold directly contacts the first and second portions of the bulkhead electric contact. 
     Another version of Example 7A. The system of example 6A, comprising a mold, wherein: the mold includes a non-metal material; the bulkhead electric contact includes metal; the bulkhead includes the mold; and the mold directly contacts and is form-fitted to the first and second portions of the bulkhead electric contact. 
     As used herein, over molding includes the use of layering effects in polymer application techniques. This process is centered around the use of a liquidous resin to add additional layers of shape and structure to an existing component. An example of such a resin could be a polymer that has been heated to a temperature just above its glass transition temperature. The existing component to which the resin is being added is often injection molded as well (but that is not necessarily the case for embodiments used herein), and may be near its own glass transition temperature. 
     Another embodiment may utilize insert molding, which is a similar process to overmolding but instead uses a preformed part, often metal, that is loaded into a mold where it is then overmolded with a thermoplastic resin to create a final component. When the run is complete, parts are boxed and shipped shortly thereafter. 
     Regardless of overmolding or insert molding, embodiments include a material that is molded to the bulkhead electric contact. 
       FIG.  12 B  provides a view of overmold  54 . In an embodiment, overmold  54  includes polyether ether ketone (PEEK). Gaskets (e.g., o-rings)  55  reside within voids  56  formed, at least partially, in the overmold. 
     Example 8A. The system of example 1A, wherein: the outer conduit includes internal threads; the coupler includes a projection; and the internal threads are keyed to the coupler&#39;s projection. 
     This keying may help ensure the inner conduit&#39;s charges properly align with the outer conduit&#39;s voids. Thus, voids  27 ,  28  align with each other. 
     Example 9A. The system of example 8A, wherein the coupler is keyed to the distal connector. 
     Example 10A. The system of example 1A, wherein: the outer conduit includes a long axis that intersects the proximal and distal connectors; a first plane, which is orthogonal to the long axis, intersects the distal electric contact; the distal electric contact includes a non-circular cross-section within the first plane; a second plane, which is orthogonal to the long axis, intersects the proximal electric contact; the proximal electric contact includes a non-circular cross-section within the second plane. 
     Such an orientation is advantageous because, for example, tightening a screw or fastener such as contact  32  or  33  occurs more easily if contact  15  or  13  resists turning with the tightening of a screwdriver. This helps reduce forces applied to cabling coupled to the contacts. 
     Example 11A. The system of example 1A, wherein: the distal connector has a proximal face and a distal face, and the proximal face is between the distal face and the proximal connector; the distal face includes first, second, and third projections; a proximal face of the coupler includes first, second, and third recesses, the first projection is keyed to the first recess and the second and third projections are respectively keyed to the second and third recesses; the outer conduit includes a long axis that intersects the proximal and distal connectors; a plane, which is orthogonal to the long axis, intersects the first projection but neither of the second or third projections. 
     For example, in  FIGS.  8 ,  9 A,  9 B, and  9 C , distal face  46  of the distal connector includes first projection  43 , first recess  44 , and second recess  45 . Proximal face  50  of coupler  2  includes a recess  47 , first projection  48 , and second projection  49 . Projection  43  is keyed to the recess  47 . Projections  48 ,  49  are respectively keyed to recesses  44 ,  45 . 
     Another version of Example 11A. The system of example 1A, wherein: the distal connector has a proximal face and a distal face, and the proximal face is between the distal face and the proximal connector; the distal face of the distal connector includes a first projection and a first recess; a proximal face of the coupler includes a second recess and a second projection; the first projection is keyed to the first recess and the second projection is keyed to the second recess; the outer conduit includes a long axis that intersects the proximal and distal connectors; a plane, which is orthogonal to the long axis, intersects the first projection but not the first recess. 
     Another version of Example 11A. The system of example 1A, wherein: the distal connector has a proximal face and a distal face, and the proximal face is between the distal face and the proximal connector; the distal face of the distal connector includes a projection and one of a first recess and a first projection; a proximal face of the coupler includes another of the first recess and the first projection; the first projection is keyed to the first recess; the outer conduit includes a long axis that intersects the proximal and distal connectors; a plane, which is orthogonal to the long axis, intersects the first projection but not the one of a first recess and a first projection. 
     Example 12A. The system of example 11A, wherein none of the first, second, or third projections includes metal. 
     Another version of Example 12A. The system of example 11A, wherein neither of the first projection or the first recess includes metal. 
     This is advantageous in that a user desiring a fixed orientation of the inner conduit  3  with regard to the outer conduit  1  may couple projection  43  with recess  47 . However, a user desiring a variable orientation between the tubes may remove projection  43 . For example, projection  43  may be formed from a polymer and projection  43  may be cut or otherwise removed from face  46 . As a result, the user is then able to rotate face  46  to align the proper recess (one of recesses  44 ,  45 ) with one of projections  48 ,  49 . Projections  48 ,  49  may be biased away from face  46  and towards face  50 . Projections may include spring loaded ball plungers. 
     Example 13A. The system of example 11A, wherein the second projection couples to a resilient member that biases the projection away from the proximal face of the coupler and towards the distal connector. 
     For instance, the resilient member may be included in a spring-loaded ball plunger. 
     FIGS. 10A and 10B provide perspective and assembly views for an embodiment a proximal connector.  FIG.  11 C  shows an embodiment of a proximal connector  11 . 
     Example 14A. A system comprising: (a)(i) a first perforating gun including first proximal and distal connectors on opposing ends of a first inner conduit; and (a)(ii) a second perforating gun including second proximal and distal connectors on opposing ends of a second inner conduit; and a coupler that includes a bulkhead; wherein (b)(i) the first distal connector is resiliently coupled to a first distal electric contact via a first distal resilient member, and (b)(ii) the second proximal connector is resiliently coupled to a second proximal electric contact via a second resilient member; wherein (c)(i) the bulkhead includes a bulkhead electric contact that includes no resilient members, (c)(ii) the bulkhead electric contact directly contacts the first distal electrical contact and the second proximal electrical contact, (c)(iii) the first distal resilient member biases the first distal electrical contact towards the bulkhead in a first direction and the second proximal resilient member biases the second proximal electrical contact towards the bulkhead in a second direction that is opposite the first direction. 
     Embodiments provide multiple options that promote ease of indexing to more easily align shots. For example,  FIGS.  1    (indexed distal connector and coupler),  2 A, and  8  (element  43 ) provide one form of indexing (a single index position) while removing element  43  allows  FIG.  8    to have many different index positions. Thus, the user may decide what is best for a particular situation and then quickly and easily adjust the gun system to meet the need. Another advantage concerns the non-circular contacts of  FIGS.  5 B and  5 C , which help a user tighten a contact (e.g., screws  32 ,  33 ) without applying force to cabling connected to the contact. Yet another advantage includes the ability to view the detonation cord/proximal connector interface after the inner tube is fully seated within the outer tube. Other advantages concern, for example, the contact of  FIG.  15 B . If an explosion causes a gap to form between the bulkhead material (e.g., PEEK) and the metal contact, a gasket contacting the contact will prevent or lessen fluid flow between neighboring guns (which can improve reliability of neighboring guns). Another advantage concerns the use of a monolithic single-piece bulkhead electric contact. Such a contact may be machined from a single piece of metal. This reduces costs and increases reliability for the entire bulkhead. Further, such a contact may include machined voids (e.g., element  56 ), which foster better coupling between the molding and contact of the bulkhead. 
     The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. This description and the claims following include terms, such as left, right, top, bottom, over, under, upper, lower, first, second, etc. that are used for descriptive purposes only and are not to be construed as limiting. For example, terms designating relative vertical position refer to a situation where a side of a substrate is the “top” surface of that substrate; the substrate may actually be in any orientation so that a “top” side of a substrate may be lower than the “bottom” side in a standard terrestrial frame of reference and still fall within the meaning of the term “top.” The term “on” as used herein (including in the claims) does not indicate that a first layer “on” a second layer is directly on and in immediate contact with the second layer unless such is specifically stated; there may be a third layer or other structure between the first layer and the second layer on the first layer. The embodiments of a device or article described herein can be manufactured, used, or shipped in a number of positions and orientations. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above teaching. Persons skilled in the art will recognize various equivalent combinations and substitutions for various components shown in the Figures. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.