Patent ID: 12252965

DETAILED DESCRIPTION

The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the central axis. For instance, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance means a distance measured perpendicular to the central axis. Any reference to up or down in the description and the claims is made for purposes of clarity, with “up”, “upper”, “upwardly”, “uphole”, or “upstream” meaning toward the surface of the borehole and with “down”, “lower”, “downwardly”, “downhole”, or “downstream” meaning toward the terminal end of the borehole, regardless of the borehole orientation.

Referring now toFIG.1, a system10for completing a wellbore4extending into a subterranean formation6is shown. In the embodiment ofFIG.1, wellbore4is a cased wellbore including a tubular casing string12secured to an inner surface8of the wellbore4using cement (not shown). In some embodiments, casing string12generally includes a plurality of tubular segments coupled together via a plurality of casing collars. In this embodiment, completion system10includes a wireline deployable digital gun system or tool string20disposed within wellbore4and suspended from a wireline22that extends to the surface of wellbore4. Wireline22comprises an armored cable and includes at least one electrical conductor for transmitting power and electrical signals between tool string20and a control system or firing panel15(shown schematically inFIG.1) positioned at the surface.

In some embodiments, system10may further include suitable surface equipment for drilling, completing, and/or operating completion system10and may include, for example, derricks, structures, reels, pumps, electrical/mechanical well control components, etc. Tool string20is generally configured to perforate casing string12to provide for fluid communication between formation6and wellbore4at predetermined locations to allow for the subsequent hydraulic fracturing of formation6at the predetermined locations.

In this embodiment, tool string20has a central or longitudinal axis25and generally includes a cable head24, a casing collar locator (CCL)26, a direct connect sub500, a plurality of perforating guns300A,300B, a switch sub100, a plug-shoot firing head600, a setting tool30, and a downhole or frac plug34. Cable head24is the uppermost component of tool string20and includes an electrical connector for providing electrical signal and power communication between the wireline22and the other components (CCL26, perforating guns300A,300B, setting tool30, etc.) of tool string20. CCL26is coupled to a lower end of the cable head24and is generally configured to transmit an electrical signal to the surface via wireline22when CCL26passes through a casing collar, where the transmitted signal may be recorded at the surface as a collar kick to determine the position of tool string20within wellbore4by correlating the recorded collar kick with an open hole log. The direct connect sub500(shown schematically inFIG.1) is coupled to a lower end of CCL26and is generally configured to provide a connection between the CCL26and the portion of tool string20including the perforating guns300A,300B and associated tools, such as the setting tool30and downhole plug34.

Perforating guns300A,300B (shown schematically inFIG.1) of tool string20are coupled to direct connect sub500and are generally configured to perforate casing string12and provide for fluid communication between formation6and wellbore4. Particularly, perforating guns300A,300B each include a plurality of perforating or shaped charges that may be detonated by a signal conveyed by the wireline22to produce an explosive jet directed against casing string12. In some embodiments, perforating guns300A,300B may comprise a hollow steel carrier (HSC) type perforating gun, a scalloped perforating gun, a retrievable tubing gun (RTG) type perforating gun, as well as other types of perforating guns. In addition, each perforating gun300A,300B may comprise a wide variety of sizes such as, for example, 2¾″, 3⅛″, or 3⅜″, wherein the above listed size designations correspond to an outer diameter of perforating guns300A,300B.

In this embodiment, switch sub100(shown schematically inFIG.1) of tool string20is coupled between the pair of perforating guns300A,300B and includes an electrical conductor and switch generally configured to allow for the passage of an electrical signal to a lower perforating gun300B of tool string20. Tool string20further includes plug-shoot firing head600(also shown schematically inFIG.1) coupled to a lower end of the lower perforating gun300B. Plug-shoot firing head600couples the perforating guns300A,300B of the tool string20to the setting tool30and downhole plug34, and, as will be described further herein, is generally configured to pass a signal from the wireline22to the setting tool30of tool string20. In this embodiment, plug-shoot firing head600also includes electrical components to fire the setting tool30of tool string20.

In this embodiment, tool string20further includes setting tool30and downhole plug34, where setting tool30is coupled to a lower end of plug-shoot firing head600and is generally configured to set or install downhole plug34within casing string12to isolate desired segments of the wellbore4, as will be discussed further herein. Once downhole plug34has been set by setting tool30, an outer surface of downhole plug34seals against an inner surface of casing string12to restrict fluid communication through wellbore4across downhole plug34. Downhole plug34of tool string20may be any suitable downhole or frac plug known in the art while still complying with the principles disclosed herein. Although in this embodiment tool string20generally includes cable head24, CCL26, direct connect sub500, perforating guns300A,300B, switch sub100, plug-shoot firing head600, setting tool30, and downhole or frac plug34, in other embodiments, the configuration of tool string20may vary. For instance, in some embodiments, tool string20may comprise weight bars and/or a fish neck at an upper or uphole end thereof. In certain embodiments, tool string20may comprise a release tool for releasing at least a portion of tool string20in the event that tool string20becomes stuck in wellbore4. In some embodiments, tool string20may also comprise a safety sub.

Referring toFIGS.2-5, embodiments of the switch sub100, perforating guns300A,300B, direct connect500, and plug-shoot firing head600of the tool string20ofFIG.1are shown inFIGS.2-5. In the embodiment ofFIGS.2-5, tool string20includes a first or upper perforating gun300A coupled between direct connect500and switch sub100, and a second or lower perforating gun300B connected between switch sub100and plug-shoot firing head600; however, in other embodiments, tool string20may comprise varying numbers of switch subs100, and perforating guns300A,300B, and/or direct connect sub500positioned in varying configurations, as well as additional components besides switch sub100, perforating guns300A,300B, and direct connect sub500.

In this embodiment, switch sub100generally includes an outer housing102, an electronic first or gun switch120, a multi-contact bulkhead connector160, and a second or single-contact bulkhead connector220. Housing102of switch sub100has a first or upper end104, a second or lower end106, a central bore or passage defined by a generally cylindrical inner surface108extending between ends104,106, and a generally cylindrical outer surface110extending between ends104,106. The central passage of housing102includes a switch receptacle112, an upper bulkhead receptacle114extending between upper end104and switch receptacle112, and a lower bulkhead receptacle116extending between switch receptacle112and the lower end106of housing102. An annular first or upper shoulder113of the inner surface108separates upper bulkhead receptacle114and switch receptacle112while an annular second or lower shoulder115of inner surface108separates lower bulkhead receptacle116from switch receptacle112. Gun switch120is disposed in switch receptacle112, multi-contact bulkhead connector160is disposed in upper bulkhead receptacle114, and single-contact bulkhead connector220is disposed in lower bulkhead receptacle116. In this embodiment, the outer surface110includes a pair of annular first or upper seal assemblies117A positioned thereon, a pair of annular second or lower seal assemblies117B positioned thereon, and a pair of releasable or threaded connectors118formed thereon and positioned at the ends104,106of housing102.

Referring toFIGS.3,6A-7B, an embodiment of gun switch120of switch sub100is shown inFIGS.6A-7B. Gun switch120has a central or longitudinal axis125(shown inFIG.6A), an axial maximum length120L (extending along central axis125), and a maximum diameter120D (extending orthogonal central axis125). In the embodiment ofFIGS.3,6A-7B, gun switch120generally includes a printed circuit board (PCB)122having an electrical circuit124(shown schematically inFIG.6A) including electronic components positioned thereon. In this embodiment, the electronic components of electrical circuit124generally include a processor and a memory, such as a reprogrammable memory; however, in other embodiments, the electronic components of electrical circuit124may vary. PCB122and electrical circuit124are centrally positioned in a housing or potting compound126(shown as transparent inFIG.6Afor clarity) having a cylindrical outer surface128. Potting compound126comprises a solid or gelatinous material configured to provide electrical insulation and resistance to shock and/or vibration at elevated temperatures (e.g., 300-350 degrees Fahrenheit or greater) to thereby protect electrical circuit124. In some embodiments, potting compound126comprises an epoxy resin; however, in other embodiments, the material from which potting compound126is comprised may vary.

In this embodiment, the electrical circuit124positioned on the PCB122of gun switch120includes a first or upper electrical connector130, a second or lower electrical connector140, and a pair of circumferentially spaced radial ground contacts150. As shown particularly inFIG.6A, contacts130,140each extend along central axis125while ground contacts150are spaced from central axis125and extend radially outwards therefrom. As shown particularly inFIG.6C, upper electrical connector130comprises a wireline circuit or female contact132and a pair of detonator circuits or female contacts134. Thus, in this embodiment, upper electrical connector130comprises a multi-contact connector. As shown particularly inFIG.6D, lower electrical connecter140comprises a single wireline circuit or female contact142. The wireline contacts132,142of electrical connectors130,140allow for electrical signals and/or data to be selectably communicated from wireline22to components of tool string20positioned downhole of switch sub100(e.g., lower perforating gun300B, plug-shoot firing head600, etc.).

The detonator contacts134of upper electrical connector130allow for electrical signals to be selectably communicated between wireline22and a detonator of upper perforating gun300A, as will be described further herein. Ground contacts150extend radially outwards from the outer surface128of potting compound126and are configured to contact inner surface108of the switch receptacle112of housing102to thereby ground the electrical circuit124of gun switch120to housing102. In some embodiments, each ground contact150comprises a biasing member configured to bias ground contacts150into engagement with the inner surface108of housing102, thereby maintaining contact between ground contacts150and housing102during operation of tool string20.

Referring toFIGS.3,8A, and8B, an embodiment of the multi-contact bulkhead connector160of switch sub100is shown inFIGS.8A,8B. In the embodiment ofFIGS.3,8A,8B, multi-contact bulkhead connector160has a central or longitudinal axis165(shown inFIG.8A) and generally includes a housing162and a PCB (not shown inFIGS.8A,8B) housed therein. Housing162has a first or upper end164, a second or lower end166, and a generally cylindrical outer surface168extending between ends164,166. In this embodiment, the outer surface168of housing162includes an annular shoulder169and a pair of annular seal assemblies170. Seal assemblies170are configured to sealingly engage the inner surface108of the upper bulkhead receptacle114of housing102when multi-contact bulkhead connector160is positioned therein, thereby restricting fluid communication between upper bulkhead receptacle114and the switch receptacle112of housing102.

Additionally, multi-contact bulkhead connector160is configured to act as a pressure bulkhead isolating switch120from pressure in upper perforating gun300A (due to the firing of gun300A, for example) and/or pressure in the environment surrounding switch sub100. In other words, multi-contact bulkhead connector160is configured to restrict the communication of fluid pressure between upper end164and lower end166. The outer surface168of multi-contact bulkhead connector160comprises an annular engagement surface171extending from upper end164and a pair of opposing flanking engagement surface173extending from annular engagement surface171. In this embodiment, annular engagement surface171comprises a planar surface extending between opposing ends of an arcuate surface of annular engagement surface171. Additionally, in this embodiment, flanking engagement surfaces173are circumferentially spaced approximately 180 degrees about a longitudinal axis of multi-contact bulkhead connector160.

The PCB of multi-contact bulkhead connector160includes an electrical circuit that comprises electronic components including a first or upper electrical connector172, a second or lower electrical connector180in signal communication with upper electrical connector172, and a pair of circumferentially spaced radial circuits or contacts190in signal communication with lower electrical connector180. Connectors172,180each extend along central axis165while radial contacts190are spaced from central axis165and extend radially outwards therefrom. In this embodiment, upper electrical connector172comprises a pair of detonator circuits or female contacts. Lower electrical connector180comprises a wireline circuit or male contact182and a pair of detonator circuits or male contacts184. Radial contacts190are electrically connected to the wireline contact182of lower electrical connector180, thereby permitting signals and/or data to be transmitted from wireline22to the electrical circuit124of switch sub100via the insertion of the wireline contact182of lower electrical connector180into the wireline contact132of the upper electrical connector130of switch120.

In this embodiment, the PCB of multi-contact bulkhead connector160does not include transistors, resistors, or other electronic components beyond electrical connectors172,180,190, and the electrical conductors extending therebetween; however, in other embodiments, the PCB of multi-contact bulkhead connector160may include additional electronic components. Additionally, in this embodiment, housing162is overmolded to the previously formed PCB to form multi-contact bulkhead connector160, where housing162comprises one of Polyether ether ketone (PEEK), Ultem, or a similar material; however, in other embodiments, the material from which housing162is comprised may vary. In some embodiments, housing162may comprise one or more strengthening materials, such as glass.

Additionally, the detonator contacts of upper electrical connector172are electrically connected to detonator contacts184of lower electrical connector180. In this configuration, electrical signals may be selectably communicated between the detonator of upper perforating gun300A and electrical circuit124of switch120via the insertion of the detonator contacts184of lower electrical connector180into the detonator contacts134of the upper electrical connector130of switch120. In this embodiment, switch sub100includes an annular first or upper retainer200(shown inFIG.3) having an outer surface that includes a releasable or threaded connector202which releasably or threadably connects to a corresponding threaded connector formed on the inner surface108of upper bulkhead receptacle114to couple upper retainer200to housing102. Additionally, an inner surface of upper retainer200includes an annular shoulder that matingly engages the annular shoulder169of multi-contact bulkhead connector160to thereby retain upper bulkhead connector160within upper bulkhead receptacle114and limit relative axial movement between multi-contact bulkhead connector160and housing102. In this embodiment, force applied to upper bulkhead connector160due to pressure applied to the upper end164of upper bulkhead connector160is transferred to housing102via contact between the lower end166of upper bulkhead connector160and the upper shoulder113of housing102, thereby restricting pressure applied to upper end164of upper bulkhead connector160from being communicated to switch120.

As shown particularly inFIG.3, the single-contact bulkhead connector220generally includes a generally cylindrical electrical conductor222including a first or upper male contact224, and a second or lower male contact226. Upper male contact224of electrical conductor222is insertable into the female contact142of the lower electrical connector140of switch120to provide an electrical connection between the electrical circuit124of switch120and single-contact bulkhead connector220. Additionally, single-contact bulkhead connector220includes an insulation sleeve230surrounding conductor222, and a pair of annular seal assemblies232surrounding insulation sleeve230. Insulation sleeve230electrically insulates electrical conductor222from housing102while seal assemblies232restrict fluid communication between lower bulkhead receptacle116and switch receptacle112.

Additionally, single-contact bulkhead connector220is configured to act as a pressure bulkhead isolating switch120from pressure in lower perforating gun300B (due to the firing of gun300B, for example) and/or pressure in the environment surrounding switch sub100. In this embodiment, switch sub100includes an annular second or lower retainer240having an outer surface that includes a releasable or threaded connector242which releasably or threadably connects to a corresponding threaded connector formed on the inner surface108of lower bulkhead receptacle116to couple lower retainer240to housing102. Additionally, an inner surface of lower retainer240includes an annular shoulder that matingly engages an annular shoulder formed on the outer surface of the insulation sleeve230of single-contact bulkhead connector220to thereby retain lower bulkhead220within lower bulkhead receptacle116and limit relative axial movement between single-contact bulkhead connector220and housing102. In this embodiment, force applied to single-contact bulkhead connector220due to pressure applied to a lower end of bulkhead connector220is transferred to housing102via contact between an upper end of bulkhead connector220and the lower shoulder115of housing102, thereby restricting pressure applied to the lower end of bulkhead connector220from being communicated to switch120.

Referring again toFIGS.2-5, embodiments of perforating guns300A,300B of the tool string20are shown therein. Each perforating gun300A,300B generally includes an outer housing302, and a charge tube320positioned therein. The housing302of each perforating gun300A,300B has a first or upper end304, a second or lower end306, and a central bore or passage308defined by a generally cylindrical inner surface310that extends between ends304,306. In the embodiment ofFIGS.2-5, a generally cylindrical outer surface of housing302includes a plurality of indentations or scallops312configured to fracture or break-apart during the firing of perforating guns300A,300B; however, in other embodiments, housing302may not include scallops312. In this configuration, an upper threaded connector118of the housing102of switch sub100releasably or threadably connects to a threaded connector formed on the inner surface310of the lower end306of upper perforating gun300A, and a lower threaded connector118of the housing102of switch sub100releasably or threadably connects to a threaded connector formed on the inner surface310of the upper end304of lower perforating gun300B. Additionally, upper seal assemblies117A of the housing102of switch sub100sealingly engage the inner surface310of the housing302of upper perforating gun300A while lower seal assemblies117B of the housing102of switch sub100sealingly engage the inner surface310of the housing302of lower perforating gun300B.

The charge tube320of each perforating gun300A,300B is generally cylindrical and has a first or upper end322, a second or lower end324, and a central bore or passage326extending between ends322,324. As will be described further herein, charge tube320is configured to receive a plurality of explosive perforating or shaped charges (not shown inFIGS.2-5) positioned in openings formed in charge tube320. The shaped charges are configured to fire in response to the actuation of a detonator assembly400, each shaped charge being axially and circumferentially aligned with one of the scallops312of housing302. For convenience, inFIGS.3-5the detonator assemblies400of tool string20are shown as a first or upper detonator assembly400A and a second or lower detonator assembly400B; however, in this embodiment, the detonator assemblies400of tool string20are each similarly configured. Additionally, a first or upper charge tube endplate330is coupled to the upper end322of each charge tube320and a second or lower charge tube endplate334is coupled to the lower end324of each charge tube320. In this embodiment, each endplate330,334generally comprises a nonmetallic, non-electrically conductive material (e.g., a plastic, etc.).

In this embodiment, upper endplate330of each perforating gun300A,300B includes a central bore or passage332that receives a first or upper electrical connector340that includes a generally cylindrical electrical conductor342and a biasing member344that biases electrical conductor342towards the single-contact bulkhead connector220of switch sub100. Particularly, biasing member344acts against an annular shoulder of electrical conductor342to maintain contact between an upper end of electrical conductor342and a lower end226of the electrical conductor222of single-contact bulkhead connector220, thereby providing an electrical connection between the upper electrical connector340of lower perforating gun300B and the single-contact bulkhead connector220of switch sub200. Additionally, a lower end of electrical conductor342is connected to a signal conductor or charge tube cable346that extends between an upper end and a lower end of the charge tube320of lower perforating gun300B. In this configuration, signals and/or data may be selectably communicated from wireline22to charge tube cable346(and components of tool string20positioned downhole of lower perforating gun300B) via the electrical connection formed between single-contact bulkhead connector220of switch sub100and the upper electrical connector340of lower perforating gun300B.

In this embodiment, lower endplate334of each perforating gun300A,300B includes a central bore or passage that receives a second or lower electrical connector350. Referring toFIGS.3,5, and13A-15D, the lower electrical connector350of each perforating gun300A,300B is shown in detail inFIGS.13A-15D. In the embodiment ofFIGS.3,5, and13A-15D, lower electrical connector350includes a housing352(shown semi-transparently inFIGS.13A,13Bfor clarity) and an electrical conductor380disposed within housing352. In this embodiment, housing352generally comprises a nonmetallic, non-electrically conductive material (e.g., a plastic, etc.); however, in other embodiments, the material from which housing352is comprised may vary. Housing352has a first or upper end354, a second or lower end356, a central bore or passage358extending between ends354,356, and an outer surface360extending between ends354,356. In this embodiment, the electrical conductor380of lower electrical connector350is overmolded to form housing352, where housing352comprises one of Polyether ether ketone (PEEK), Ultem, Nylon, or a similar material; however, in other embodiments, the material from which housing352is comprised may vary. In some embodiments, housing352of lower electrical connector350may comprise one or more strengthening materials, such as glass.

In this embodiment, the outer surface360of housing352includes a plurality of circumferentially spaced flexible or snap connectors362positioned proximal to the lower end356of housing352. Snap connectors362are configured to connect housing352to an inner surface of the lower endplate334of charge tube320. At least a portion of the central passage358of housing352forms a detonator receptacle364extending from the upper end354of housing352, wherein detonator receptacle364extends along central axis355. As will be described further herein, detonator receptacle364is configured to receive one of the detonator assemblies400A,400B and permit relative rotation between lower electrical connector350and detonator assembly400A,400B when detonator assembly400A,400B is received in detonator receptacle364.

Additionally, housing352includes a detonator cord or “detcord” receptacle366that also extends into the lower end366of housing352in a direction parallel with, but radially offset from, central axis355. Detcord receptacle366is configured to receive an end of a detonator cord or detcord connected to the shaped charges of charge tube320. Additionally, detcord receptacle366, being positioned adjacent detonator receptacle364, is configured to position the end of the detcord adjacent one of the detonator assemblies400A,400B such that the detonator assembly400A,400B may selectably initiate or ignite the detcord and thereby fire the shaped charges coupled to charge tube320. Housing352further includes an electrical stab connector368positioned adjacent upper end354. Stab connector368includes a receptacle370extending into housing352in a direction parallel with, but radially offset from, central axis355. Stab connector368additionally includes a protrusion372formed on outer surface360of housing352.

As shown particularly inFIG.14, in this embodiment, the electrical conductor380of lower electrical connector350includes an annular or ring-shaped contact382and an elongate contact384extending therefrom. Annular contact382is positioned proximal the lower end356of housing352, and an inner surface of annular contact382is exposed to the central passage358of housing352. Elongate contact384extends at least partially through the receptacle of the stab connector368of housing352. In this configuration, the charge tube cable346includes an electrical connector that contacts the elongate contact384to provide an electrical connection between the electrical conductor380of lower electrical connector350and charge tube cable346, where the connector of charge tube cable346is secured to lower electrical connector350via the protrusion372of housing352. Additionally, annular contact382of electrical conductor380contacts the radial contacts190of multi-contact bulkhead connector160, thereby providing an electrical connection between the electrical conductor380of lower electrical connector350and the electrical circuit of multi-contact bulkhead connector160such that signals and/or data from wireline22may be selectably communicated between lower electrical connector350and multi-contact bulkhead connector160while also permitting relative rotation between lower electrical connector350and multi-contact bulkhead connector160.

Referring toFIGS.3,9A-11, an embodiment of a detonator assembly400is shown in detail inFIGS.9A-11. The detonator assemblies400A,400B shown inFIGS.2-5are configured similarly as the detonator assembly400shown inFIGS.9A-11. In the embodiment ofFIGS.3,9A-11, detonator assembly400includes a detonator402and a connector housing420coupled to detonator402. Detonator402of detonator assembly400includes a detonator housing404, one or more explosive or flammable materials (not shown inFIGS.3,9A-11) housed within detonator housing404, and a pair of electrical conductors or wires406extending therefrom. Detonator402is generally configured to produce a thermal reaction igniting the detcord of charge tube320in response to the passage of an electrical signal through wires406. An outer surface of detonator housing404includes an annular ridge or shoulder405formed thereon. In this embodiment, wires406are at least partially sheathed by electrical insulators408. Additionally, detonator402includes a pair of electrical terminals or contacts410, where each male terminal410is connected to a terminal end of a corresponding wire406.

The connector housing420of detonator assembly400has a first end422, a second end424opposite first end422, and a central bore or passage defined by a generally cylindrical inner surface426extending between second end424and a base425. Additionally, connector housing420comprises separate, connectable components to assist with assembling connector housing420with detonator402. In this embodiment, connector housing420comprises a first arcuate portion421and a second arcuate portion423. A flexible snap connector428formed along an edge of second arcuate portion423may be matingly inserted into a corresponding groove formed in first arcuate portion421to couple arcuate portions421,423together. When arcuate portions421,423of connector housing420are in an assembled configuration, inner surface426of connector housing420forms an annular groove430in which the annular shoulder405of detonator housing404may be received to restrict relative axial movement between connector housing420and detonator402when detonator assembly400is in an assembled configuration.

In this embodiment, connector housing420includes a pair of apertures432that extend through base425and are configured to allow for the passage of terminals410of detonator402therethrough. Terminals410of detonator assembly400may be inserted into the female contacts of the upper electrical connector172of multi-contact bulkhead connector160to provide an electrical connection therebetween. In this manner, an activation or firing signal may be selectably transmitted from the electrical circuit124of switch120to the detonator402of detonator assembly400.

In this embodiment, connector housing420includes a flexible or snap connector434extending from base425and configured to matingly engage the engagement surfaces171,173of multi-contact bulkhead connector160. Particularly, snap connector434includes a pair of circumferentially spaced arms436configured to matingly engage the flanking engagement surfaces173of multi-contact bulkhead connector160. Arms436permit snap connector434to latch to multi-contact bulkhead connector160, inhibiting or preventing disconnection of snap connector434from bulkhead connector160while also restricting relative rotation between connector housing420and bulkhead connector160.

Mating engagement between arms436of connector housing420with flanking engagement surfaces173of multi-contact bulkhead connector160assists with angularly aligning detonator assembly400with multi-contact bulkhead connector160such that terminals410of detonator assembly400may be axially inserted into the corresponding female contacts of the upper electrical connector172of multi-contact bulkhead connector160, thereby providing an electrical connection between detonator402and the electrical circuit124of switch120via multi-contact bulkhead connector160. In some embodiments, a compliant material (e.g., rubber) may be positioned and compressed at the interface between snap connector434and multi-contact bulkhead connector160to dampen or prevent vibration and to further inhibit disconnection of the snap connector434from the multi-contact bulkhead connector160. Additionally, as described above, detonator assembly400fits within the detonator receptacle364of lower electrical connector350. Moreover, detonator assembly400is configured to permit relative rotation between lower electrical connector350and multi-contact bulkhead connector160when detonator402is electrically connected to the upper electrical connector172of multi-contact bulkhead connector160.

In this embodiment, prior to installation of detonator assembly20within one of the components of tool string20, detonator assembly400includes a shunt cap440configured to prevent the accidental initiation of detonator402. Particularly, when detonator assembly400is in the assembled configuration (shown inFIGS.9A-9C), shunt cap440may be coupled to terminals410to directly short electrically connect terminals410. Shunt cap440may be removed prior to the assembly of tool string20to permit the electrical connection of detonator402with another component of tool string20, such as multi-contact bulkhead connector160. Referring briefly toFIG.12, another embodiment of a detonator assembly460is shown. In the embodiment ofFIG.12, detonator assembly460includes detonator402, a connector housing462(similar in functionality as the connector housing420ofFIGS.9A-11), and an integrated shunt or spring connector464that provides a direct electrical connection or electrical short between terminals410of detonator402.

Integrated shunt464is affixed or coupled to a first of the terminals410A of detonator assembly460and is biased into contact with a second of the terminals410B to provide a direct electrical connection between terminals410A,410B. Unlike the shunt cap440of detonator assembly400, integrated shunt464does not need to be mechanically removed from detonator assembly460prior to the assembly of tool string20. Instead, as terminals410A,410B of detonator402are inserted into the female contacts of the upper electrical connector172of multi-contact bulkhead connector160, the upper electrical connector172contacts integrated shunt464and bends or flexes shunt464out of contact with the second terminal410B, thereby removing the electrical short formed between terminals410A,410B. Direct electrical contact or an electrical short may be reestablished between terminals410A,410B by uncoupling detonator assembly460from multi-contact bulkhead connector160, thereby permitting integrated shunt464to flex into contact with second terminal410B. Thus, integrated shunt464may be biased into contact with second terminal410B. Thus, integrated shunt464may prevent inadvertent initiation of detonator402while reducing the time required for assembling tool string20by eliminating the need to insert and remove a mechanical shunt from detonator assembly460prior to coupling detonator assembly460with multi-contact bulkhead connector160.

Referring again toFIGS.2-5, the direct connect sub500of tool string20is shown inFIG.4. In the embodiment ofFIGS.2-5, direct connect sub500generally includes an outer housing502, an electronic second or safety switch520, a single-contact bulkhead connector220, and a single-contact biased bulkhead connector560. Housing502of direct connect sub500has a first or upper end504, a second or lower end506, a central bore or passage defined by a generally cylindrical inner surface508extending between ends504,506, and a generally cylindrical outer surface510extending between ends504,506. In this embodiment, the upper end504forms a neck or pin511that is insertable into a lower end of the CCL26of tool string20. The outer surface510of housing502includes a pair of annular first or upper seal assemblies512A, a pair of annular second or lower seal assemblies512B, and a pair of releasable or threaded connectors513positioned at the ends504,506of housing502. Lower seal assemblies512B of housing502sealingly engage the inner surface310of the housing302of upper perforating gun300A while the threaded connector513positioned at lower end506releasably or threadably connects to a corresponding threaded connector positioned at the upper end304of housing302.

In this embodiment, the central passage of housing502includes a switch receptacle514, an upper bulkhead receptacle515extending between upper end504and switch receptacle514, and a lower bulkhead receptacle516extending between switch receptacle514and the lower end506of housing502. An annular first or upper shoulder517of the inner surface508of housing502separates upper bulkhead receptacle515and switch receptacle514while an annular second or lower shoulder519of inner surface508separates lower bulkhead receptacle516from switch receptacle514. Safety switch520is disposed in switch receptacle514, biased bulkhead connector560is disposed in upper bulkhead receptacle515, and single-contact bulkhead connector220is disposed in lower bulkhead receptacle516. Although in this embodiment safety switch520is housed within direct connect sub500, in other embodiments, safety switch520may be located in a component of tool string20other than direct connect sub500. For example, in an embodiment where tool string20comprises a release tool configured to release at least a portion of tool string20, safety switch520may be positioned in a safety sub located between CCL26and the release tool, the release tool being positioned between the safety sub and direct connect sub500.

Referring toFIGS.3,16A-17B, an embodiment of safety switch520of direct connect sub500is shown inFIGS.16A-17B. As will be described further herein, safety switch520of direct connect sub500is configured to selectably restrict signal and/or data communication between wireline22and components of tool string20positioned downhole of direct connect sub500(e.g., switch sub100, perforating guns300A,300B, plug-shoot firing head600, etc.). Thus, safety switch520is configured to act as a safety feature to prevent premature activation of electrical components of tool string20positioned downhole of direct connect sub500.

Safety switch520has a longitudinal or central axis525, an axial maximum length520L (extending along central axis525), and a maximum diameter520D (extending orthogonal central axis525). In the embodiment ofFIGS.3,16A-17B, safety switch520generally includes a printed circuit board (PCB)522having an electrical circuit524(shown schematically inFIG.16A) including electronic components positioned thereon. In this embodiment, the electronic components of electrical circuit524include a processor and a memory, such as a reprogrammable memory; however, in other embodiments, the electronic components of electrical circuit524may vary. PCB522and electrical circuit524are centrally positioned in a housing or potting compound526(shown transparently inFIG.16Afor clarity) having a cylindrical outer surface528. In this embodiment, the outer surface528of potting compound526comprises an annular shoulder530which, in at least one respect, differentiates the exterior shape of safety switch520from the gun switch120shown inFIGS.6A-6D.

By providing safety switch520with an exterior shape which differs from an exterior shape of gun switch120, safety switch520may be easier to visually distinguish from gun switch120in the field by operators or personnel of completion system10, thereby reducing the likelihood of a safety switch520being mistakenly installed in a switch sub100and/or a gun switch120being mistakenly installed in a direct connect sub500by personnel of completion system10. In some embodiments, the maximum length520L and/or maximum diameter520D of safety switch520differs from the maximum length120L and/or maximum diameter120D of gun switch120to further distinguish safety switch520from gun switch120. Potting compound526comprises a solid or gelatinous material configured to provide electrical insulation and resistance to shock and/or vibration at elevated temperatures (e.g., 300-350 degrees Fahrenheit or greater) to thereby protect electrical circuit524. In some embodiments, potting compound526comprises an epoxy resin; however, in other embodiments, the material from which potting compound526is comprised may vary. Additionally, the potting compound526of safety switch520may comprise a material which differs from the material comprising the potting compound126of gun switch120.

In this embodiment, the electrical circuit524positioned on the PCB522of safety switch520includes a first or upper electrical connector535, a second or lower electrical connector540, and a pair of circumferentially spaced ground contacts550. Electrical connectors535,540each extend along central axis525while ground contacts550are offset from central axis525and extend radially outwards therefrom. As shown particularly inFIG.16C, upper electrical connector530comprises a single wireline circuit or female contact536. As shown particularly inFIG.16D, lower electrical connecter540comprises a single wireline circuit or female contact542. The wireline contacts536,542of electrical connectors535,540, respectively, allow for electrical signals and/or data to be selectably communicated from wireline22to components of tool string20positioned downhole of direct connect sub500(e.g., switch sub100, perforating guns300A,300B, plug-shoot firing head600, etc.).

In this embodiment, the ground contacts550of electrical circuit524extend radially outwards from the outer surface528of potting compound526and are configured to contact inner surface508of the switch receptacle514of housing502to thereby ground the electrical circuit524of safety switch520to housing502. In some embodiments, each ground contact550comprises a biasing member configured to bias ground contacts550into engagement with the inner surface508of housing502, thereby maintaining contact between ground contacts550and the housing502of direct connect sub500.

As shown particularly inFIG.4, the biased bulkhead connector560generally includes a housing562, a biasing member572, a generally cylindrical first or upper electrical conductor574, and a generally cylindrical second or lower electrical conductor576. Housing562is positioned in upper bulkhead receptacle515the housing502of direct connect sub500and includes a generally cylindrical outer surface564extending between opposing ends thereof. In this embodiment, outer surface564of housing562includes a pair of annular seal assemblies566positioned thereon which sealingly engage the inner surface508of housing502. Additionally, housing562includes a central bore or passage568in which biasing member572is received. A lower end of upper electrical conductor574couples to an upper end of biasing member572, forming an electrical connection therebetween. In this embodiment, an inner surface of an upper end of housing562may have an electrical insulator positioned or formed thereon to prevent direct electrical contact between upper electrical conductor574and housing562. An annular first or upper retainer590releasably or threadably couples to the inner surface508of housing502at the upper end504thereof. Upper retainer590retains or locks biased bulkhead connector560within upper bulkhead receptacle515of housing502.

The lower electrical conductor576of biased bulkhead connector560includes a first or upper male contact578, and a second or lower male contact580. Upper male contact578of lower electrical conductor576is coupled to biasing member572, forming an electrical connection between upper electrical conductor574and lower electrical conductor576. Additionally, the lower end580of lower electrical conductor576is insertable into the female contact536of the upper electrical connector535of safety switch520, thereby providing an electrical connection between lower electrical conductor576and the electrical circuit524of safety switch520.

An annular insulation sleeve582surrounds lower electrical conductor576to prevent direct electrical contact from forming between lower electrical conductor576and the inner surface of housing562. Additionally, a pair of annular seal assemblies584surround insulation sleeve582and sealingly engage the inner surface of housing562. In this configuration, seal assemblies578disposed about housing562and seal assemblies584disposed about insulation sleeve582restrict fluid communication between the upper bulkhead receptacle515and the switch receptacle514of housing502. In this embodiment, biasing member572acts against upper electrical conductor574to bias conductor574in a first or upwards axial direction. Additionally, biasing member572acts against lower electrical conductor576to bias conductor576in a second or lower axial direction, opposite the upper axial direction. In this manner, biasing member572biases upper electrical conductor574into electrical contact with a corresponding electrical connector of CCL26(not shown inFIG.4), and biases lower electrical conductor576into electrical contact with safety switch520. In this embodiment, force applied to biased bulkhead connector560due to pressure applied to an upper end biased bulkhead connector560is transferred to housing502via contact between a lower end of biased bulkhead connector560and the upper shoulder517of housing102, thereby restricting pressure applied to the upper end of biased bulkhead connector560from being communicated to safety switch520.

As described above, a single-contact bulkhead connector220, similar in configuration as the bulkhead connector220of switch sub100, is positioned in the lower bulkhead receptacle516of housing502. The upper male contact224of the electrical conductor222of single-contact bulkhead connector220is insertable into the female contact542of the lower electrical connector540of safety switch520, thereby providing an electrical connection between electrical conductor222of single-contact bulkhead connector220and the electrical circuit524of safety switch520. Additionally, the lower male contact226of electrical conductor222is configured to contact the electrical conductor342of the upper endplate330of upper perforating gun300A to form an electrical connection between the electrical conductor222of single-contact bulkhead connector220and the charge tube cable346of upper perforating gun300A. An annular second or lower retainer592releasably or threadably couples to the inner surface508of housing502at the lower end506thereof. Lower retainer592retains or locks single-contact bulkhead connector220within the lower bulkhead receptacle516of housing502. In this embodiment, force applied to single-contact bulkhead connector220due to pressure applied to a lower end of bulkhead connector220is transferred to housing502via contact between an upper end of bulkhead connector220and the lower shoulder519of housing502, thereby restricting pressure applied to the lower end of bulkhead connector220from being communicated to safety switch520.

Referring again toFIGS.2-5,18A-19B, the plug-shoot firing head600of tool string20is shown inFIG.5. In the embodiment ofFIGS.2-5,18A-19B, plug-shoot firing head600generally includes an outer housing602, an electronic third or combination switch620, and a multi-contact bulkhead connector160. Housing602of plug-shoot firing head600has a first or upper end604, a second or lower end606, a central bore or passage defined by a generally cylindrical inner surface608extending between ends604,606, and a generally cylindrical outer surface610extending between ends604,606. In this embodiment, the lower end606forms a neck or pin611that is insertable into tool30of tool string20. The outer surface610of housing602includes a pair of annular first or upper seal assemblies612A, a pair of annular second or lower seal assemblies612B, and a pair of releasable or threaded connectors613positioned at the ends604,606of housing602. Upper seal assemblies612A of housing602sealingly engage the inner surface310of the housing302of lower perforating gun300B while the threaded connector613positioned at lower end606releasably or threadably connects to a corresponding threaded connector positioned at an upper end of setting tool30.

In this embodiment, the central passage of housing602includes a switch receptacle614, an upper bulkhead receptacle615extending between upper end604and switch receptacle614, and an igniter receptacle616extending between switch receptacle614and the lower end606of housing602. An annular first or upper shoulder617of the inner surface608of housing602separates upper bulkhead receptacle615and switch receptacle614while an annular second or lower shoulder619of inner surface608separates igniter receptacle616from switch receptacle614. Combination switch620is disposed in switch receptacle614, multi-contact bulkhead connector160is disposed in upper bulkhead receptacle515, and an igniter assembly700of the setting tool30(not shown inFIG.5) is partially received in igniter receptacle616.

As shown particularly inFIGS.18A-19B, an embodiment of combination switch620of plug-shoot firing head600is shown inFIGS.18A-19B. As will be described further herein, combination switch620of plug-shoot firing head600is configured to selectably actuate both the setting tool30and lower perforating gun300B of tool string20. Combination switch620has a longitudinal or central axis625(shown inFIG.18A), an axial maximum length620L (extending along central axis625and shown inFIG.18B), and a maximum diameter620D (extending orthogonal central axis625and shown inFIG.18B). In the embodiment ofFIGS.5,18A-19B, combination switch620generally includes a printed circuit board (PCB)622having an electrical circuit624(shown schematically inFIG.18A) including electronic components positioned thereon. In this embodiment, the electronic components of electrical circuit624include a processor and a memory, such as a reprogrammable memory; however, in other embodiments, the electronic components of electrical circuit624may vary. PCB622and electrical circuit624are centrally positioned in a housing or potting compound626(shown transparently inFIG.18Afor clarity) having a cylindrical outer surface628. Potting compound626comprises a solid or gelatinous material configured to provide electrical insulation and resistance to shock and/or vibration at elevated temperatures (e.g., 300-350 degrees Fahrenheit or greater) to thereby protect electrical circuit624. In some embodiments, potting compound626comprises an epoxy resin; however, in other embodiments, the material from which potting compound626is comprised may vary. Additionally, the potting compound626of combination switch620may comprise a material which differs from the material comprising the potting compound126of switches120,520.

Combination switch620has an exterior shape that differs from the exterior shapes of switches120,520. For example, the maximum length620L and/or maximum diameter620D of combination switch620may differ from the maximum lengths120L,520L and/or maximum diameters120D,520of switches120,520, respectively. In other embodiments, the exterior shape of combination switch620may differ from the exterior shapes of switches120,520in other ways (e.g., a different cross-sectional shape, the inclusion of surface features, etc.). By providing combination switch620with a different exterior shape than the exterior shapes of switches120,520, combination switch620is easier to distinguish from switches120,520in the field by personnel of completion system10.

In this embodiment, the electrical circuit624positioned on the PCB622of combination switch620includes a first or upper electrical connector630, a second or lower electrical connector640, and a pair of circumferentially spaced ground contacts650. As shown particularly inFIG.18C, upper electrical connector630comprises a wireline circuit or female contact632and a pair of detonator circuits or female contacts634. As shown particularly inFIG.18D, lower electrical connecter640comprises a single wireline circuit or female contact642. The wireline contacts632,642of electrical connectors630,640allow for electrical signals and/or data to be selectably communicated from wireline22to components of tool string20positioned downhole of plug-shoot firing head600(e.g., setting tool30).

The detonator contacts634of upper electrical connector630allow for electrical signals to be selectably communicated between wireline22and a detonator of lower perforating gun300B, as will be described further herein. Ground contacts650extend radially outwards from the outer surface628of potting compound626and are configured to contact inner surface608of the switch receptacle614of housing602to thereby ground the electrical circuit624of combination switch620to housing602. In some embodiments, each ground contact650comprises a biasing member configured to bias ground contacts650into engagement with inner surface608, thereby maintaining contact between ground contacts650and housing602.

As shown particularly inFIG.5, multi-contact bulkhead connector160, received in upper bulkhead receptacle615of housing602, electrically connects with the lower electrical connector350and lower detonator assembly400B, thereby providing an electrical connection between combination switch620and both the charge tube cable346and lower detonator assembly400B. In this embodiment, plug-shoot firing head600includes an annular retainer660having an outer surface that includes a releasable or threaded connector which releasably or threadably connects to a corresponding threaded connector formed on the inner surface608of upper bulkhead receptacle615to couple retainer660to housing602. Additionally, an inner surface of retainer680includes an annular shoulder that matingly engages the annular shoulder169of multi-contact bulkhead connector160to thereby retain upper bulkhead connector160within upper bulkhead receptacle615and limit relative axial movement between multi-contact bulkhead connector160and housing602. [moo] In this embodiment, force applied to the multi-contact bulkhead connector160of plug-shoot firing head600due to pressure applied to the upper end164of upper bulkhead connector160is transferred to housing602via contact between the lower end166of bulkhead connector160and the upper shoulder617of housing602, thereby restricting pressure applied to upper end164of upper bulkhead connector160from being communicated to combination switch620. Additionally, force applied to igniter assembly700due to pressure applied to a lower end thereof is transferred to housing602via contact between an upper end of igniter assembly700and the lower shoulder619of housing602, thereby restricting pressure applied to the lower end of igniter assembly700from being communicated to combination switch620.

Having described structural features of tool string20, an embodiment of a method for assembling and operating tool string20will now be described. As will be described further herein, at least some components of tool string20may be assembled by the manufacturer, or the end user or operator of tool string20prior to transporting tool string20to a well site (e.g., the location of wellbore4) of completion system10. The remaining components of tool string20may be assembled at the wellsite of completion system10but prior to the insertion of tool string20into wellbore4.

In this embodiment, detonator assemblies400A,400B of tool string20are assembled by the manufacturer, with required safeguards in place, prior to transportation of tool string20to the wellsite of completion system10. Referring toFIGS.20-23, in an embodiment, each detonator assembly400may be assembled by first cutting and stripping a portion of each electrical insulator408from each wire406to expose a predetermined length of each wire406to the surrounding environment. As shown particularly inFIG.20, following the cutting and stripping of electrical insulators408, terminals410are attached to the terminal ends of the exposed wires406. In some embodiments, terminals410may be crimped to wires406; however, in other embodiments, terminals410may be attached to wires406via other mechanisms.

As shown inFIG.21, with terminals410attached to the terminal ends of wires406, terminals410are inserted through apertures432of the first arcuate portion421of connector housing420, and the shoulder405of detonator housing404is snapped into the groove430of first arcuate portion421thereby coupling detonator housing404to the first arcuate portion421of connector housing420. As shown particularly inFIG.22, with detonator housing404coupled to the first arcuate portion421of connector housing420, the second arcuate portion423of connector housing420is coupled to first arcuate portion421via the insertion of the snap connector428of second arcuate portion423into the corresponding groove formed in first arcuate portion421. In this embodiment, as shown inFIG.23, terminals410are inserted into shunt cap440to prevent the inadvertent initiation of the detonator402of detonator assembly400. Shunt cap440is removed from detonator assembly400when tool string20is assembled at the well site of completion system10. In other embodiments, an integrated shunt (e.g., integrated shunt464shown inFIG.12) may be utilized, eliminating the need to insert terminals410into shunt cap464as well as the need to remove shunt cap464prior to installation of detonator assembly400within one of the components of tool string20.

Prior to assembling perforating guns300A,300B with the other components of tool string20, as will be discussed further herein, the charge tube320of each perforating gun300B is assembled and installed within its corresponding housing302.

Particularly, in this embodiment, with charge tube320disposed external of its respective housing302, endplates330,334are attached by a user of perforating guns300A,300B and/or tool string20(e.g., a manufacturer, end user, etc., of tool string20or components thereof) to the ends322,324, respectively of charge tube320to thereby assemble charge tube320. Lower electrical connector350is attached to lower endplate334prior to coupling lower endplate334to the lower end324of charge tube320. In some embodiments, charge tube cable346, which extends through charge tube320, is electrically connected to the elongate contact of lower electrical connector350prior following the coupling lower endplate334to the lower end324of charge tube320; however, in other embodiments, charge tube cable346is connected to lower electrical connector350prior to the coupling of lower endplate334to charge tube320.

In this embodiment, following the assembly of endplates330,334, lower electrical connector350, and charge tube cable346, the user positions a plurality of explosive shaped charges in the openings formed in charge tube320, and ballistically couples the detcord to each of the shaped charges coupled to charge tube320. With the plurality of explosive shaped charged positioned in the openings of the charge tube320, the user may insert an end of the detcord into the detcord receptacle366of lower electrical connector350. An interference fit is formed between the end of the detcord and an inner surface of the detcord receptacle366, and thus, friction between the end of the detcord and the inner surface of the detcord receptacle366prevents, or at least inhibits, removal of the end of the detcord from detcord receptacle366. With the end of the detcord inserted into detcord receptacle366, charge tube320may be loaded into its respective housing302by the user of perforating guns300A,300B, and/or tool string20.

Referring again toFIGS.2-5, in this embodiment, at least the lower portion of tool string20is assembled “top to bottom” with the assembly of direct connect sub500and upper perforating gun300A occurring prior to the assembly of the components of tool string20configured to be positioned downhole from direct connect sub500and upper perforating gun300A (e.g., switch sub100, lower perforating gun300B, plug-shoot firing head600, etc.); however, in other embodiments, the lower portion of tool string200may be assembled “bottom to top” with the assembly of plug-shoot firing head600and lower perforating gun300B occurring prior to the assembly of components of tool string20configured to be positioned uphole from lower perforating gun300B and plug-shoot firing head600(e.g., direct connect sub500, upper perforating gun300A, switch sub100, etc.). Particularly, in this embodiment, the upper electrical connector535of safety switch520is first electrically connected to the biased bulkhead connector560of direct connect sub500. With safety switch520connected to biased bulkhead connector560, safety switch520and biased bulkhead connector560are then inserted into the central passage of housing502, with safety switch520being received in switch receptacle514and biased bulkhead connector560being received in upper bulkhead receptacle515.

In some embodiments, the lower electrical connector540of safety switch520is electrically connected to the single-contact bulkhead connector220of direct connect sub500, which is received in lower bulkhead receptacle516of housing502, when safety switch520is inserted into the switch receptacle514of housing502; however, in other embodiments, single-contact bulkhead connector220may be inserted into lower-bulkhead receptacle516and connected to safety switch520following the insertion of safety switch520into switch receptacle514. Following the insertion of biased bulkhead connector560and single-contact bulkhead connector220into housing502, retainers590,592are coupled to the inner surface508of housing502to lock safety switch520and bulkhead connectors560,220in the central passage of housing502, and thereby complete the assembly of direct connect sub500.

Following the assembly of direct connect sub500, the lower end506of the housing502of direct connect sub500is inserted into the upper end304of the housing302of upper perforating gun300A. As housing502of direct connect sub500is inserted into the housing302of upper perforating gun300A, housing502is rotated relative to housing302to threadably connect a threaded connector513of housing502with a corresponding threaded connector positioned at the upper end304of housing302. Additionally, as the housing502of direct connect sub500is inserted into the housing302of upper perforating gun300A, lower male contact226of the single-contact bulkhead connector220of direct connect sub500contacts electrical conductor342of the upper electrical connector340of upper perforating gun300A, thereby forming an electrical connection between safety switch520and the charge tube cable346of upper perforating gun300A.

Referring toFIGS.2-5, and24, in this embodiment, following the assembly of direct connect sub500with upper perforating gun300A, switch sub100of tool string20may be assembled with upper perforating gun300A and lower perforating gun300B. In this embodiment, the upper electrical connector130of gun switch120is electrically connected to lower electrical connector180of the multi-contact bulkhead connector160of switch sub100. With gun switch120connected to multi-contact bulkhead connector160, gun switch120and connector160are inserted into the central passage of housing102, with gun switch120being received in switch receptacle112and multi-contact bulkhead connector160being received in upper bulkhead receptacle114.

In some embodiments, the lower electrical connector140of gun switch120is electrically connected to single-contact bulkhead connector220, which is received in lower bulkhead receptacle116of housing102, when gun switch120is inserted into the switch receptacle112of housing102; however, in other embodiments, single-contact bulkhead connector220may be inserted into lower-bulkhead receptacle116and connected to gun switch120following the insertion of gun switch120into switch receptacle112. Following the insertion of multi-contact bulkhead connector160and single-contact bulkhead connector220into housing102, retainers200,240are coupled to the inner surface108of housing102to lock gun switch120and bulkhead connectors160,220in the central passage of housing102, and complete the assembly of switch sub100.

In this embodiment, following the assembly of switch sub100, upper detonator assembly400A is connected to the multi-contact bulkhead connector160of switch sub100. Particularly, arms436of the snap connector434of upper detonator assembly400A are circumferentially aligned with the flanking engagement surfaces173of multi-contact bulkhead connector160and the engagement surfaces171,173of connector160are inserted into and latched onto snap connector434. With upper detonator assembly400A connected to multi-contact bulkhead connector160of switch sub100, switch sub100may be connected to the upper perforating gun300A.

Particularly, in this embodiment, upper end104of the housing102of switch sub100is inserted into the lower end306of the housing302of upper perforating gun300A. As housing102of switch sub100is inserted into the housing302of upper perforating gun300A, housing102is rotated relative to housing302to threadably connect a threaded connector118of housing102with a corresponding threaded connector positioned at the lower end306of housing302. Additionally, as housing102of switch sub100is inserted into the housing302of upper perforating gun300A, detonator402of upper detonator assembly400A is axially and slidably inserted into the detonator receptacle364of the lower electrical connector350(indicated by arrow455inFIG.24, where housing102is hidden inFIG.24for clarity), thereby positioning detonator402adjacent the detcord positioned in detcord receptacle366of the lower electrical connector350of upper perforating gun300A.

Also following the assembly of switch sub100, the lower end106of the housing102of switch sub100is inserted into the upper end304of the housing302of lower perforating gun300B. As housing102of switch sub100is inserted into the housing302of lower perforating gun300B, housing102is rotated relative to housing302to threadably connect a threaded connector118of housing102with a corresponding threaded connector positioned at the upper end304of housing302. Additionally, as the housing102of switch sub100is inserted into the housing302of lower perforating gun300B, lower male contact226of single-contact bulkhead connector220contacts electrical conductor342of the upper electrical connector340of lower perforating gun300B, thereby forming an electrical connection between gun switch120and the charge tube cable346of lower perforating gun300B.

Referring again toFIGS.2-5, following the assembly of lower perforating gun300B, the plug-shoot firing head600and setting tool30of tool string20may be assembled. Particularly, in an embodiment, the upper electrical connector630of combination switch620is electrically connected to lower electrical connector180of the multi-contact bulkhead connector160of plug-shoot firing head600. With combination switch620connected to multi-contact bulkhead connector160, assembly620and connector160are inserted into the central passage of housing602, with combination switch620being received in switch receptacle614and multi-contact bulkhead connector160being received in upper bulkhead receptacle615.

In some embodiments, the lower electrical connector640of combination switch620is electrically connected to igniter assembly700when combination switch620is inserted into the switch receptacle614of housing602; however, in other embodiments, igniter assembly700may be connected to combination switch620following the insertion of combination switch620into switch receptacle614. With combination switch620and multi-contact bulkhead connector160received in the central passage of housing602, housing602may be coupled to setting tool30of tool string20. Additionally, retainer660is coupled to the inner surface608of housing602to lock combination switch620and multi-contact bulkhead connector160in the central passage of housing602.

With combination switch620and multi-contact bulkhead connector160received in the central passage of housing602, lower detonator assembly400B is connected to multi-contact bulkhead connector160. Particularly, arms436of the snap connector434of lower detonator assembly400B are circumferentially aligned with the flanking engagement surfaces173of multi-contact bulkhead connector160and the engagement surfaces171,173of connector160are inserted into and latched onto snap connector434, thereby coupling lower detonator assembly400B with multi-contact bulkhead connector160.

Following the assembly of lower perforating gun300B, upper end604of the housing602of plug-shoot firing head600may be inserted into the lower end306of the housing302of lower perforating gun300B. As housing602of plug-shoot firing head600is inserted into the housing302of lower perforating gun300B, housing602is rotated relative to housing302to threadably connect the threaded connector613of housing602with a corresponding threaded connector positioned at the lower end306of housing302. Additionally, as housing602of plug-shoot firing head600is inserted into the housing302of lower perforating gun300B, detonator402of lower detonator assembly400B is axially inserted into the detonator receptacle364of the lower electrical connector350, thereby positioning detonator402adjacent the detcord positioned in detcord receptacle366of the lower electrical connector350of lower perforating gun300B. In this embodiment, detonator402is positioned along the central axis of lower perforating gun300B while the end of the detcord, received in detcord receptacle366, is offset from the central axis of lower perforating gun300B. The positioning of detonator402adjacent the detcord is intended to place the shaped charge in ballistic communication with the gun switch120via the detonator402and detcord.

As detonator402is inserted through detonator receptacle364of the lower electrical connector350, the annular contact382of lower electrical connector350contacts the radial contacts190of the multi-bulkhead connector160of plug-shoot firing head600, thereby providing an electrical connection between the charge tube cable346of lower perforating gun300B and multi-bulkhead connector160. Lower electrical connector350of lower perforating gun300B permits relative rotation between connector350and multi-contact bulkhead connector160as plug-shoot firing head600is rotatably coupled with lower perforating gun300B. In some embodiments, the assembly of plug-shoot firing head600with setting tool30and lower perforating gun300B, as described above, may be accomplished at the well site of completion system10or at a location distal the well site.

In this embodiment, following the assembly of plug-shoot firing head600with lower perforating gun300B and setting tool30, upper end504of the housing502of direct connect sub500may be releasably or threadably connected to a lower end of the CCL26of tool string20. As direct connect sub500is connected to CCL26, electrical conductor574contacts a corresponding conductor of CCL26to establish an electrical connection between the biased bulkhead connector560of direct connect sub500and CCL26. The electrical connection between CCL26and direct connect sub500permits the selectable communication of signals and/or data between wireline22and components positioned downhole of direct connect sub500(e.g., switch sub100, perforating guns300A,300B, plug-shoot firing head600, etc.).

Referring toFIGS.1-5, the component of tool string20, including switch sub100, perforating guns300A,300B, direct connect sub500, and plug-shoot firing head600, comprise “plug-and-play” components that do not need to be electrically wired together during the process of assembling tool string20, thereby substantially reducing the time required for assembling tool string20while also reducing the probability of misassembling (e.g., incorrectly wiring electrical components, etc.) one or more components of tool string20. Particularly, as described above, only the explosive shaped charges and detcord need to be installed in perforating guns300A,300B during the assembly of tool string20, where the installation of detonators402and igniter assembly700, and the electrical connections between components of tool string20being formed in response to rotatably coupling the components of tool string20.

For example, an electrical connection permitting selectable communication of signals and/or data between the safety switch520of direct connect sub500and the gun switch120of switch sub100is formed by or in response to rotatably coupling the housing102of switch sub100to the housing302of upper perforating gun300A and rotatably coupling the housing302of upper perforating gun300A with the housing502of switch sub direct connect sub500. Thus, in order to assemble direct connect sub500, upper perforating gun300A, and switch sub100, the charge tube cable346of upper perforating gun300A does not need to be electrically wired (e.g., by personnel of completion system10) to either gun switch120or safety switch520. Instead, the electrical connection between charge tube cable346with both safety switch520of direct connect sub500and gun switch120of switch sub100is made simply by axially inserting both direct connect sub500and switch sub100into the housing302of upper perforating gun300A.

Similarly, an electrical connection permitting selectable communication of signals and/or data between the gun switch120of switch sub100and the combination switch620of plug-shoot firing head600is formed by or in response to rotatably coupling the housing602of plug-shoot firing head600to the housing302of lower perforating gun300B and rotatably coupling the housing302of lower perforating gun300B with the housing102of switch sub100. Thus, in order to assemble switch sub100, lower perforating gun300B, and plug-shoot firing head600, the charge tube cable346of lower perforating gun300B does not need to be electrically wired (e.g., by personnel of completion system10) to either gun switch120or combination switch620.

In this embodiment, tool string20is configured such that the switches120,520,620may be reused following the firing of perforating guns300A,300B. Particularly, multi-contact bulkhead connector160and the single-contact bulkhead connector220of switch sub100shield gun switch120from the pressure (which may exceed 20,000 pounds per square inch (PSI) in some applications) released following the detonation of the shaped charges of perforating guns300A,300B by inhibiting or preventing the communication of fluid pressure from perforating guns300A,300B to the switch receptacle112of housing102, thereby preventing damage from occurring to gun switch120from the activation of perforating guns300A,300B. Additionally, biased bulkhead connector560and the single-contact bulkhead connector220of direct connect sub500shield safety switch520from the pressure released following the detonation of the shaped charges of perforating guns300A,300B by inhibiting or preventing the communication of fluid pressure from perforating guns300A,300B to the switch receptacle514of housing502, thereby preventing damage from occurring to safety switch520from the activation of perforating guns300A,300B. Further, in some embodiments, igniter assembly700comprises a pressure bulkhead such that multi-contact bulkhead connector160of plug-shoot firing head600and the pressure bulkhead of igniter assembly700shield combination switch620from the pressure released following the detonation of the shaped charges of perforating guns300A,300B by inhibiting or preventing the communication of fluid pressure from perforating guns300A,300B to the switch receptacle614of housing602, thereby preventing damage from occurring to combination switch620from the activation of perforating guns300A,300B.

Due to the protection afforded to switches120,520, and620by pressure bulkheads160,560and the pressure bulkhead of igniter assembly700, switches120,520, and620may be reused following the perforation of casing string12by perforating guns300A,300B so that switches120,520, and620may be employed in a plurality of separate and distinct completion operations. Given that the cost of manufacturing switches120,520,620may be relatively expensive compared to the cost of manufacturing the other components of switch sub100, direct connect sub500, and plug-shoot firing head600, the ability to reuse switches120,520,620may reduce the cost of operating tool string20and perforating casing string12. In some embodiments, pressure bulkheads160,560and the pressure bulkhead of igniter assembly700may be sacrificial, and thus, not reused for multiple completion operations.

Referring still toFIGS.1-5, following the assembly of tool string20, tool string20is lowered though to a desired or predetermined depth or axial position17(shown inFIG.1) within wellbore4of completion system10. In some embodiments, CCL26of tool string20may be utilized to assist in determining when tool string20is disposed in the predetermined position17in wellbore4. In an embodiment, once tool string20is disposed in the predetermined position17, a first or enabling signal is transmitted from control system15to an electronic shunt (e.g., an FET) of electrical circuit524of the safety switch520of direct connect sub500via wireline22, which actuates safety switch520into a closed configuration by closing the electronic shunt of the safety switch520such that signal and/or data communication is permitted between control system15and electrical components of tool string20positioned downhole of safety switch520(e.g., detonator assemblies400A,400B, gun switch120, combination switch620, etc.). Thus, prior to being activated by the transmission of the first signal from control system15, safety switch520acts to prevent signal and/or data communication between control system15and electrical components of tool string20positioned downhole of safety switch520to thereby prevent the inadvertent activation or firing of components positioned downhole of safety switch520.

In this embodiment, following the actuation (via the closing of the FET in this example) of the safety switch520into the closed configuration, a second or enabling signal is transmitted from control system15to the combination switch620of plug-shoot firing head600via wireline22to enable combination switch620and thereby actuate combination switch620from an “open” configuration into a “closed” configuration. A third or arming signal is then transmitted from the control system15to the combination switch620via wireline22to arm combination switch620for initiating an igniter of igniter assembly700by closing an electronic shunt (e.g., an igniter FET) of the electrical circuit624of combination switch620which thereby completes a circuit path to the igniter of igniter assembly700. A firing signal comprising electricity or electrical energy is then transmitted from control system15down wireline22to igniter assembly700to initiate the igniter of igniter assembly700and thereby actuate setting tool30and set frac plug34whereby fluid communication across frac plug34is restricted.

In this embodiment, following the actuation of setting tool30and the setting of frac plug34, a fourth or arming signal is transmitted from the control system15to the combination switch620via wireline22to arm combination switch620for initiating the detonator402of lower detonator assembly400B by closing an electronic shunt (e.g., a detonator FET) of the electrical circuit624of combination switch620, thereby completing a circuit path to detonator402. A firing signal comprising electricity or electrical energy is then transmitted from control system15down wireline22to the detonator402of lower detonator assembly400B to thereby initiate detonator402. The initiation of detonator402of lower detonator assembly400B detonates the explosive shaped charges of lower perforating gun300B, forming a first or lower set of perforations in casing string12.

In this embodiment, following the detonation of the shaped charges of lower perforating gun300B, a fifth or enabling signal is transmitted from control system15to the gun switch120of switch sub100to enable gun switch120. A sixth or arming signal is then transmitted from the control system15to the gun switch120via wireline22to arm gun switch120for initiating the detonator402of upper detonator assembly400A by closing an electronic shunt (e.g., a detonator FET) of the electrical circuit124of gun switch120, thereby completing a circuit path to detonator402. A firing signal comprising electricity or electrical energy is then transmitted from control system15down wireline22to the detonator402of upper detonator assembly400A to thereby initiate detonator402. The initiation of detonator402detonates the explosive shaped charges of upper perforating gun300A, forming a second or upper set of perforations in casing string12that are spaced from the lower set of perforations formed by lower perforating gun300B. In this embodiment, following the detonation of the shaped charges of upper perforating gun300A, tool string20(sans frac plug34) is retracted from wellbore4and the formation6is hydraulically fractured via a fluid delivered to formation6via the upper and lower sets of perforations formed in casing string12by perforating guns300A,300B.

In some embodiments, tool string20is retrieved from the wellbore4and gun switch120is recovered from the tool string20. The gun switch120may be inspected (e.g., at the wellsite at which wellbore4is located and/or at a location distal the wellsite) to verify that, following the detonation of the explosive shaped charges of perforating guns300A,300B, the gun switch120is intact and operable for reuse with a new tool string that is different from tool string20.

In another embodiment, the new tool string (which may be similar to tool string20) is assembled to include one or more new perforating guns (different from perforating guns300A,300B of tool string20) each having one or more new perforating charges located therein (e.g., a first new perforating charge located in a first new perforating gun, a second new perforating charge located in a second perforating gun, etc.). The new tool string is also assembled to include the original gun switch120which is connected to at least one of the new perforating guns of the new tool string whereby the original gun switch is placed in communication (e.g., ballistic communication) with the one or more new perforating charges of at least one of the one or more new perforating guns of the new tool string. The original gun switch may be located internally or externally of the new perforating gun to which it is connected. Additionally, the assembly of the new tool string may occur at the location of the wellbore or at a location that is remote from the wellbore.

In another embodiment, the assembled new tool string is inserted into a wellbore (which may be the same as, or different from, the original wellbore4) and a signal may be delivered to the original gun switch120to initiate a detonation of at least one of the new perforating charges of the new tool string. The new tool string may then be retrieved from the wellbore and the original gun switch120may be retrieved from the new tool string. In some embodiments, the original gun switch120may be inspected following the detonation of the at least one new perforating charge to verify that the original gun switch120may be reused with a third tool string which is different from both tool string20and the new tool string.

While exemplary embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the invention. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.