Modular Perforating Gun System

This application is a Continuation Application of and claims priority to U.S. patent application Ser. No. 18/546,999 filed Aug. 18, 2023, which is a national stage entry of International PCT Patent Application PCT/EP2022/055014 filed Feb. 28, 2022, which claims the benefit of U.S. Provisional Patent Application 63/155,902 filed Mar. 3, 2021, U.S. Provisional Patent Application 63/166,720 filed Mar. 26, 2021, U.S. Provisional Patent Application 63/271,846 filed Oct. 26, 2021, United States Provisional Patent Application 63/276,103 filed Nov. 5, 2021, and U.S. Provisional Patent Application 63/309,674 filed Feb. 14, 2022, the entire contents of each of which are incorporated herein by reference.

Hydrocarbons, such as fossil fuels (e.g. oil) and natural gas, are extracted from underground wellbores extending deeply below the surface using complex machinery and explosive devices. Once the wellbore is established by placement of casing pipes after drilling and cementing the casing pipe in place, a perforating gun assembly, or train or string of multiple perforating gun assemblies, are lowered into the wellbore, and positioned adjacent one or more hydrocarbon reservoirs in underground formations.

Assembly of a perforating gun may require assembly of multiple parts. Such parts typically include a housing or outer gun barrel containing or connected to perforating gun internal components such as: an electrical wire for relaying an electrical control signal such as a detonation signal from the surface to electrical components of the perforating gun; an electrical, mechanical, and/or explosive initiator such as a percussion initiator, an igniter, and/or a detonator; a detonating cord; one or more explosive and/or ballistic charges which are held in an inner tube, strip, or other carrying device; and other known components including, for example, a booster, a sealing element, a positioning and/or retaining structure, a circuit board, and the like. The internal components may require assembly including connecting electrical components within the housing and confirming and maintaining the connections and relationships between internal components. The assembly procedure may be difficult within the relatively small free space within the housing. Typical connections may include connecting the electrical relay wire to the detonator or the circuit board, coupling the detonator and the detonating cord and/or the booster, and positioning the detonating cord in a retainer at an initiation point of each charge. In addition, typical perforating guns may not provide components that are size-independent and therefore available for use in different perforating guns with, e.g., different gun housing inner diameters.

The housing may also be connected at each end to a respective adjacent wellbore tool or other component of the tool string such as a firing head, tandem seal adapter or other sub assembly, or the like. Connecting the housing to the adjacent component(s) typically includes screwing the housing and the adjacent component(s) together via complementary threaded portions of the housing and the adjacent components and forming a connection and scal therebetween.

Known perforating guns may further include explosive charges, typically shaped, hollow, or projectile charges, which are initiated, e.g., by the detonating cord, to perforate holes in the casing and to blast through the formation so that the hydrocarbons can flow through the casing. In other operations, the charges may be used for penetrating just the casing, e.g., during abandonment operations that require pumping concrete into the space between the wellbore and the wellbore casing, destroying connections between components, severing a component, and the like. The exemplary embodiments in this disclosure may be applicable to any operation consistent with this disclosure. For purposes of this disclosure, the term “charge” and the phrase “shaped charge” may be used interchangeably and without limitation to a particular type of explosive, charge, or wellbore operation, unless expressly indicated.

The perforating guns may be utilized in initial fracturing process or in a refracturing process. Refracturing serves to revive a previously abandoned well in order to optimize the oil and gas reserves that can be obtained from the well. In refracturing processes, a smaller diameter casing is installed and cemented in the previously perforated and accessed well. The perforating guns must fit within the interior diameter of the smaller diameter casing, and the shaped charges installed in the perforating guns must also perforate through double layers of casing and cement combinations in order to access oil and gas reserves.

The explosive charges may be arranged and secured within the housing by the carrying device which may be, e.g., a typical hollow charge carrier or other holding device that receives and/or engages the shaped charge and maintains an orientation thereof. Typically, the charges may be arranged in different phasing, such as 60°, 90°, 120°, 180°, 270°, etc. along the length of the charge carrier, so as to form, e.g., a helical pattern along the length of the charge carrier. Charge phasing generally refers to the radial distribution of charges throughout the perforating gun, or, in other words, the angular offset between respective radii along which successive charges in a charge string extend in a direction away from an axis of the charge string. An explosive end of each charge points outwardly along a corresponding radius to fire an explosive jet through the gun housing and wellbore casing, and/or into the surrounding rock formation. Phasing the charges therefore generates explosive jets in a number of different directions and patterns that may be variously desirable for particular applications. On the other hand, it may be beneficial to have each charge fire in the same radial direction. A charge string in which each charge fires in the same radial direction would have zero-degree (0°) phasing. Still further, a gravitationally oriented shaped charge may be beneficial in certain applications. Ensuring the orientation of the shaped charges before firing may also be a critical step for ensuring accurate and effective perforating and therefore eliminating the need for multiple perforating operations for a single section of the wellbore.

Once the perforating gun(s) is properly positioned, a surface signal actuates an ignition of a fuse or detonator, which in turn initiates the detonating cord, which detonates the explosive charges to penetrate/perforate the housing and wellbore casing, and/or the surrounding rock formation to allow formation fluids to flow through the perforations thus formed and into a production string.

Typical perforating guns may suffer from shortcomings with respect to, for example, simplifying the assembly procedures for components, providing size-independent components that may be used in various gun housings having different inner diameters, and achieving the potential benefits of adaptable charge phasing including accurate orientation of shaped charges once the perforating gun is downhole (i.e., deployed within the wellbore). For example, various components of the perforating gun may require assembly and wiring on site and certain components must be specific to the perforating gun housing with the particular inner diameter that is being assembled. Metal charge tubes and other charge carriers that are not easily reconfigurable are not easily adaptable for use with different numbers of charges in different phasing and/or may not be capable of gravitational orientation. The number and phasing of charges in such rigid carriers may be limited by the number and orientation of charge holes/receivers in the particular charge carrier. Machining different charge carriers for every possible desired arrangement and number of charges in the perforating gun is not practically desirable.

In addition, a charge carrier that provides a very high charge phasing (i.e., a relatively severe angle between successive charges in the charge carrier) requires that a detonating cord make relatively drastic bends, especially for charges arranged with a relatively short distance between them, as it is routed between the initiating end of successive shaped charges. The detonating cord must be precisely positioned on the initiating end, above an initiation point, of the shaped charge to ensure that the detonating cord initiates detonation of the shaped charge. The detonating cord is retained at the initiation point of the shaped charge by a variety of known detonating cord retaining components. Typically, the forces and stresses on the detonating cord, especially at the detonating cord retaining components, increases as the phasing increases and the distance decreases between successive charges. The forces and stresses may damage the detonating cord and/or cause the detonating cord to become misaligned with the initiation point either to a side of the initiation point or in a direction away from the initiation point in which the detonating cord is pulling away from the retaining component.

Accordingly, a modular perforating gun platform system and corresponding perforating gun that may address one or more of the above shortcomings would be beneficial.

An exemplary embodiment of a system for use within a gun housing of a perforating gun may include a centralizer and a detonator holder. The centralizer may include a centralizer body and a centralizer bore extending through the centralizer body. The detonator holder may be disposed within the centralizer bore and may include a first detonator holder end configured to receive a detonator and a second detonator holder end comprising a detonator holder coupling. The detonator holder may extend through the centralizer and may be mechanically coupled to the centralizer. The centralizer may be configured to engage with an inner surface of the gun housing.

An exemplary embodiment of perforating gun may include a gun housing, a centralizer disposed within the gun housing, a charge holder module having a first end coupled to the detonator holding coupling, and an end connector coupled to a second end of the shaped charge module opposite the first end of the shaped charge module. The centralizer may include a centralizer body and a centralizer bore extending through the centralizer body. The detonator holder may include a first detonator holder end configured to receive a detonator, a second detonator holder end comprising a detonator holder coupling, a feedthrough contact plate configured to be in electrical communication with a feedthrough terminal of the detonator, and a ground contact plate configured to be in electrical communication with a ground terminal of the detonator, the ground contact plate being in electrical communication with an inner surface of the gun housing. The end connector may include a conductive end contact. A signal relay wire may be provided in electrical communication with the feedthrough contact plate and the conductive end contact. The detonator holder may extend through the centralizer and may be mechanically coupled to the centralizer. The centralizer may be configured to engage with an inner surface of the gun housing.

An exemplary embodiment of a detonator holder for use in a perforating gun may include a detonator holder cap, a detonator holder stem extending from the detonator holder cap along a longitudinal axis, a detonator holder bore extending through the detonator holder stem, a ground plate slot formed in the detonator holder, a ground contact plate having a first portion disposed within the detonator holder cap and a second portion extending through the ground plate slot, a feedthrough plate slot formed in the detonator holder; and a feedthrough contact plate having a first portion disposed within the detonator holder cap and a second portion extending through the feedthrough plate slot.

Various features, aspects, and advantages of the exemplary embodiments will become more apparent from the following detailed description, along with the accompanying drawings in which like numerals represent like components throughout the figures and detailed description. The various described features are not necessarily drawn to scale in the drawings but are drawn to aid in understanding the features of the exemplary embodiments.

The headings used herein are for organizational purposes only and are not meant to limit the scope of the disclosure or the claims. To facilitate understanding, reference numerals have been used, where possible, to designate like elements common to the figures.

Reference will now be made in detail to various exemplary embodiments. Each example is provided by way of explanation and is not meant as a limitation and does not constitute a definition of all possible embodiments. It is understood that reference to a particular “exemplary embodiment” of, e.g., a structure, assembly, component, configuration, method, etc. includes exemplary embodiments of, e.g., the associated features, subcomponents, method steps, etc. forming a part of the “exemplary embodiment”.

For purposes of this disclosure, the phrases “devices,” “systems,” and “methods” may be used either individually or in any combination referring without limitation to disclosed components, grouping, arrangements, steps, functions, or processes.

A modular perforating gun platform and system according to the exemplary embodiments discussed throughout this disclosure may generally include, without limitation, separate and variously connectable or interchangeable (i.e., modular) perforating gun components. The modular components may include size-independent components configured for use with all variants of variable components, each variable component having variants for particular applications and configured for use with the size-independent component(s). Variants may have varying dimensions, geometries, structures, etc. However, each modular component may include standard features and structures (i.e., a platform) for, without limitation, connecting together in various configurations for particular applications.

The application incorporates by reference the following pending patent application in its entirety, to the extent not inconsistent with or incompatible with the present disclosure: U.S. Provisional Patent Application No. 63/166,720, filed Mar. 26, 2021.

With reference now toand, an exemplary embodiment of a perforating gunand perforating gun system, as discussed throughout this disclosure, includes a housingwith a housing first endand a housing second end. Each of the housing first endand the housing second endmay include inner threadsfor connecting to, without limitation, a tandem seal adapteras shown in, or other wellbore tools or tandem/connector subs. In an aspect, the housing first endmay connect to the tandem scal adapterthat is configured for connecting to each of the housing first endof the perforating gun, and a housing second end of an adjacent perforating gun, thus connecting adjacent housings/perforating guns and sealing, at least in part, each housing from an external environment and from each other.

In other embodiments, a housing may have a male connection end at a housing first end. The male connection end may have an external threaded portion corresponding to and configured for connecting to the inner (i.e., female) threadsof the housing second end. The connection between the male connection end external threads and the internal threadsof the housing second endmay connect adjacent housings/perforating guns. A tandem scal adapter may not be required or used between adjacent housings with respective male and female connecting ends, or may be an internal, baffle-style tandem seal adapter. In other embodiments, each of the housing first endand the housing second endmay have external threads for connecting to other tandem/connector subs or adjacent wellbore tools, as applications dictate. A perforating gun housing including respective male and female connecting ends may be such as disclosed in U.S. Pat. No. 10,920,543 issued Feb. 16, 2021, which is commonly owned by DynaEnergetics Europe GmbH and incorporated by reference herein, to the extent not incompatible or inconsistent with this disclosure. An internal, baffle-style tandem seal adapter may be such as disclosed in U.S. Pat. No. 10,844,697 issued Nov. 24, 2020, which is commonly owned by DynaEnergetics Europe GmbH and incorporated by reference herein, to the extent not incompatible or inconsistent with this disclosure

With reference back to, one or more scallopsmay be positioned along the exterior surface of the housingand aligned with shaped charges positioned within an interior of the housing. Scallopsare well known as portions of a perforating gun housing at which the housinghas, e.g., a reduced thickness and/or additional machining to prevent potentially damaging burrs from forming when the shaped charge fires through the housing. Accordingly, perforating guns incorporating a housing with scallopssuch as those shown inmust lock or otherwise ensure that an orientation of the shaped charges within the housing aligns with the scallops, if the scallopsare to be used.

With additional reference to, the exemplary embodiments include a detonatorretained in a detonator holder or sleevethat is positioned within the housingand at or near the housing second end. For purposes of this disclosure, the phrase “at or near” and other terms/phrases describing, for example, a position, proximity, dimension, geometry, configuration, relationship, or order, are used to aid in understanding the exemplary embodiments and without limitation to, e.g., particular boundaries, delincations, ranges or values, etc., unless expressly provided. Further, the phrase “housing second end” may be used interchangeably with the phrase “housing detonator end” with reference to an end of the housingat which the detonatoris positioned or nearest in an assembled perforating gun, to aid in understanding, e.g., the position and relationship between components.

With additional reference to,,,,, and, the detonator holderis retained and centralized within the housingby a centralizer. The exemplary centralizeras shown in, for example,, has a ringencircling a centralizer body such as an axially oriented center tube. The center tubemay define a centralizer bore such as a center tube passageextends through the center tube. The center tubemay receive a detonator holder stemof the detonator holder. In other words, the centralizermay be slid over the detonator holder stemto adjoin a capof the detonator holder. The detonator holder stemmay extend from the detonator holder capalong a longitudinal axis.

With specific reference toand, the detonator holderincludes a relay wire channeland two locking tabsextending axially along the detonator holder stem. A signal relay wire() is routed out of the detonator holdervia the relay wire channel. When the centralizeris slid over the detonator holder stem, such that the detonator holderextends through the centralizer, the center tubecovers the relay wire channelto hold the signal relay wirein place. The center tubeincludes a relay signal outletfor the relay wire channel, thereby allowing the signal relay wireto pass through. The center tubeincludes tab locking structuresfor positively locking against the locking tabs, to hold the detonator holderin the centralizer. In other words, the detonator holdermay be mechanically coupled to the centralizer.

With reference specifically toand, the detonator holderaccording to the exemplary embodiments is, in an aspect, a component that is configured for use with, e.g., a variety of centralizers,,. Each of the centralizers,,is correspondingly configured for use with the detonator holder. For example, each of the centralizers,,will assemble to the detonator holder, and position the detonator holderwithin a perforating gun housing,,, in a similar manner. In an exemplary modular perforating gun platform and without limitation, each of the centralizers,,may be configured, i.e., dimensioned, for use with a particular perforating gun size. The detonator holderand a corresponding centralizer may be used for each of gun sizes (i.e., housing internal diameters) 3.5″ (,), 3⅛″ (,), and 2¾″ (,). For example, a corresponding centralizer,,may have an outer diameter at the ringthat is substantially equal to the housing internal diameter. For purposes of this disclosure, “substantially equal” is used, without limitation, to aid in the understanding of the exemplary embodiments in which, for example, the inner diameter of the housingprovides a barrier against the centralizerto prevent the centralizerfrom tilting or radial misalignment. In an aspect, parts configured for particular gun sizes may be color coded to enhance a production process, while using a detonator holderwith each size variant may improve production logistics. For example, size-independent parts such as the detonator holdermay be a first color such as yellow. Parts corresponding to a 3.5″ gun size system (e.g., centralizer) may be a second color such as cyan, parts for a 3⅛″ gun size system (e.g, centralizer) may be third color such as blue, and parts for a 2¾″ gun size system (e.g., centralizer) may be a fourth color such as green.

With additional reference to, the ring, in an aspect, is connected to the center tubeby spokes, thereby forming open areasthat add to the free gun volume (i.e., volume not occupied by a physical component within the housing) when the centralizeris positioned within the housing.

With reference to,, and, the detonator holderreceives and houses the detonatorin a first detonator holder end. In an aspect, inserting the detonatorinto the detonator holderautomatically makes various wireless electrical connections between electrical contacts on the detonatorand corresponding electrical contacts on the detonator holder, as explained further below. For purposes of this disclosure, “wireless electrical connection” means an electrical connection formed by physical contact between conductive components, without any wires electrically connecting the conductive components. “Electrical contact” means either a conductive component for making a wireless electrical connection, or a state of physical, conductive contact between conductive components, as the context makes clear.

In an aspect and as illustrated inand, the detonator holderincludes a feedthrough contact platepositioned and exposed within the detonator holder cap. The feedthrough contact plateincludes one or more feedthrough contact pinsfor establishing electrical communication with a feedthrough terminal of the detonator. The multiple feedthrough contact pinsmay provide redundancy to insure a stable connection to the feedthrough terminal of the detonator. The feedthrough contact plate may include a first portion disposed within the detonator holder capand a second portion extending through the feedthrough plate slot.

A ground contact plateis also positioned within the detonator holder capand includes one or more ground contact pinsfor establishing electrical communication with a ground terminal of the detonator. The ground contact platemay include a first portion disposed within the detonator holder capand a second portion extending through the ground plate slot. The second portion of the ground contact platemay be configured to provide an electrical path to ground, and may be in electrical communication with an inner surface of the gun housing.

Sliding the centralizerover the detonator holder stemsecures each of the feedthrough contact plateand the ground contact platein position within a respective feedthrough plate slotand ground contact ground plate slotformed in the detonator holder. The feedthrough contact plateand the ground contact plateare secured by corresponding contact plate securing structureson the centralizer. The contact plate securing structuresare configured, i.e., positioned and dimensioned, to cover the feedthrough plate slotand the ground contact ground plate slotwhen the centralizeradjoins the detonator holder cap. In an aspect, the feedthrough contact plateis completely covered by the contact plate securing structure, and not exposed to another outside surface or body above the feedthrough plate slot. Accordingly, the need for a protective shield component for isolating the feedthrough contact platemay be eliminated. In another aspect and as illustrated in, the ground contact plateextends out of the detonator holderthrough a gapbetween the contact plate securing structures, and is configured for making grounding contact with the housingwhen the centralizerand detonator holderare received within the housing. The feedthrough contact plateand ground contact plateare not limited to the “plate” configuration of the exemplary embodiments and may respectively take any form, configuration, shape, etc. consistent with this disclosure. With specific reference to,, and, the detonatoraccording to the exemplary embodiments includes a detonator alignment keyfor properly orienting the detonatorwithin the detonator holder. The detonator alignment keyis positionable within a key slotin the detonator holder, to orient the detonatorwithin the detonator holder. The centralizerincludes a centralizer alignment keyfor orienting the detonator holderand the detonatorwithin the housing. In an aspect, the detonatorincludes an orientation sensor. Thus, the orientation of the detonatorwithin the housingmust be properly established as a reference for the orientation sensor to correctly determine whether the perforating gunis in a desired orientation within the wellbore.

In various aspects, the detonator, detonator holder, and centralizermay individually and via their interaction provide a relatively short assembly for positioning the detonatorwithin the housing, as discussed further below. Thus, the overall length of the perforating gunmay be reduced, and more perforating guns connected as part of a tool string and deployed during one perforation run into the wellbore, because, e.g., perforating gun tool string length may be limited by the cable strength, and rig-up height at the well surface.

With reference to,, and, an exemplary internal gun assemblythat is positioned within the housingof the perforating gunincludes shaped chargesrespectively received and retained in corresponding shaped charge holdersthat are connected together in a chain. For the sake of this disclosure, a charge holder module may be considered to be either a single shaped charge holderor the chainof multiple shaped charge holders. The charge holder module may be coupled to the detonator holder coupling at a first end of the charge holder module. Each shaped chargemay be configured to form a perforation tunnel in a well, and may include a shaped charge case that forms a hollow cavity. Each shaped chargetypically includes an explosive load, for example positioned in the cavity of the shaped charge case. In some embodiments, the explosive load is disposed within the hollow cavity of the shaped charge case, and a liner is disposed adjacent to the explosive load (for example with the explosive load disposed between the liner and the shaped charge case). The liner may be configured to retain the explosive load in the hollow cavity of the shaped charge case. Some shaped chargeembodiments may also include a shaped charge inlay, which may be disposed on top of at least a portion of the liner (e.g. such that at least a portion of the liner is between the inlay and the explosive load). Each shaped chargeis typically configured to form a perforating jet for creating perforation holes in a target (e.g. the casing and/or rock formation of the well). Further details regarding shaped chargesare described in U.S. application Ser. No. 17/383,816. Filed Jul. 23, 2021, and U.S. Pat. No. 11,053,782, issued Jul. 6, 2021, which are hereby incorporated by reference in their entirety to the extent not inconsistent or incompatible with this disclosure.

The detonator holderis connected via the detonator holder stemto a shaped charge holderat a first end of the shaped charge chain. To aid in understanding the exemplary embodiments, this disclosure may refer to the detonator holderand the centralizertogether, without limitation, as a detonator end assemblyof the internal gun assembly. In an aspect, the centralizerincludes one or more finsextending radially outwardly from an exterior of the center tube, for contacting and pressing against an inner surface() of the housingto prevent axial movement of the centralizerand thereby the internal gun assemblywithin the housing. A conductive end connectoris connected to a shaped charge holderat a second end of the shaped charge chain, opposite the first end.

In an aspect, the detonator end assemblyis configured for connecting to a component of the internal gun assemblyand being housed, as part of the internal gun assembly, within the housing. According to the exemplary embodiments, the detonator end assemblyis configured for connecting to the shaped charge holderat the first end of the shaped charge chain. In other embodiments, the detonator end assemblymay connect to another component of the internal gun assembly, such as a spacer (not shown) configured for, e.g., connecting to components of the internal gun assemblyaccording to the exemplary embodiments.

A detonating cordextends from the detonator holderwithin which it is positioned and held in sufficiently close proximity (i.e., “ballistic proximity”) to the detonator, or a ballistic transfer such as a booster in ballistic proximity to each of the detonatorand the detonating cord, such that the detonating cordwill initiate in response to the detonatorinitiating. The detonating cordexits the detonator holdervia a detonating cord channelwhich extends into the detonator holderin a configuration that provides the ballistic proximity between a portion of the detonating cordthat is within the detonating cord channelwithin the detonator holder. In the exemplary embodiments, without limitation, the detonating cord channelis adjacent to a detonator bore() within which the detonatoris housed as explained further below.

The detonating cordextends along the shaped charge chainand connects to each shaped charge holderat a cord clipthat holds the detonating cordin position for initiating the shaped charge. The detonating cordis ultimately held by a terminal cord retainerthat serves to hold the detonating cordat or near an end of the detonating cordand to keep the detonating cordfrom interfering with the assembly, or insertion into the housing, of the internal gun assembly. In the exemplary embodiment, the terminal cord retaineris a blind cylindrical container on the conductive end connector, but may take any form consistent with this disclosure.

The signal relay wireextends via the relay wire channelout of the detonator holder, within which it is positioned and held in electrical contact with the feedthrough contact plateor an electrical relay in electrical contact with each of the feedthrough contact plateand the signal relay wire. In an exemplary embodiment, the signal relay wiremay be in electrical communication with the second portion of the feedthrough contact plate. The signal relay wireextends along the shaped charge chainand is routed through cord slotson each shaped charge holder. The signal relay wireextends to the conductive end connectorand relays and electrical signal between the feedthrough contact plateand the conductive end connector. The signal relay wireis inserted, via a relay wire slot, into the conductive end connector, and positioned in electrical contact with a conductive end contactthat is also positioned within the conductive end connector.

With reference to, a cross-section of the detonator holder, among other things, is shown. The signal relay wireis positioned in the relay wire channelthat extends to the feedthrough plate slot, and a feedthrough contact plate legof the feedthrough contact plateextends into or adjacent to the relay wire channel. In an aspect, the signal relay wiremay be welded to the feedthrough contact plate leg. The detonating cordenters the detonator holdervia the detonating cord channelwhich extends into the detonator holderin a position that puts the detonating cordin ballistic proximity to an explosive portionof the detonator.

shows an arrangement of certain components within the detonator holder, in isolation. The detonator explosive portionis in ballistic proximity to the detonating cord, and the signal relay wireis connected to the feedthrough contact plate leg.

With reference to,, and, an exemplary shaped charge holderfor use with the modular perforating gun platform is shown. Like the detonator holderand the centralizer, the shaped charge holdermay be color coded according to the gun size with which it is used. The shaped charge holdermay include a shaped charge holder bodydefining a shaped charge holder receptaclein which the shaped chargeis inserted. One or more alignment postsmay guide and orient the shaped chargein the shaped charge holder receptacle. One or more retention clipsmay extend from the shaped charge holder body, in a direction that is away from the shaped charge holder receptacle, and may be resilient to move out of the way when the shaped chargeis inserted. The retention clip(s)may be configured to move back into place once the shaped chargeis inserted and may be configured, i.e., positioned and dimensioned, to extend above a height of the shaped chargepositioned within the shaped charge holder receptacle. The one or more retention clipsmay each include a retention tabthat snaps into a depression or divot formed in the external surface of a caseof the shaped charge, to retain the shaped chargewithin the shaped charge holder receptacle.

The shaped charge holdermay have a male connecting sidefor connecting to e.g., an adjacent shaped charge holder, the detonator holder, or an additional component, such as a spacer, of the internal gun assembly. The connections may be standardized between different components. The male connecting sidemay include a knob connectorthat may be a cylindrical extension and include an area of increased diameter at its top, and a slitextending along its length. The area of increased diameter and the slitprovide a structure and resiliency for the knob connectorto engage and positively lock against a corresponding structure formed within, e.g., a central boreof a female connecting sideopposite the male connecting side. The male connecting sidemay include phasing protrusionsthat may fit within phasing holesarranged around the female connecting side, such that adjacent shaped charge holders(or other components) may be oriented at a desired phasing relative to one another by “clocking” (i.e., rotating) adjacent shaped charge holders through the different positions, such as numbers arranged around a clock face, corresponding respectively to different phasing.

As shown in, the detonator holdermay also include a central boreand two or more phasing holesfor connecting to the male connecting sideof a shaped charge holder. In other words, the phasing holesprovided in the detonator holdermay be a detonator holder coupling provided at a second end of the detonator holder. The central boremay serve as a detonator holder bore extending through the detonator holder stem and configured to receive at least a portion of the detonator.

The cord clipfor holding the detonating cordin position for initiating the shaped chargemay include oppositely disposed retention armsthat form a detonating cord receptaclecontoured for retaining the detonating cordin a manner to increase the locking force on the detonating cordas the phasing between adjacent charge holders increases. For example, each oppositely disposed retention armincludes a shaped sidewall portionand a corresponding flangeextending transversely from a top section of the retention arm.

The shaped charge holdermay have a cage structure in which portions of the shaped charge holderare configured with cage barswith cage voidsbetween the cage bars, rather than fully solid pieces. For example, the shaped charge holdermay be configured without solid wall elements, to increase free gun volume. The cage structure may impart a high mechanical strength while increasing the amount of free volume (without limitation, by up to 30% or more) within the housingand decreasing the amount of material required to form the shaped charge holder. Injection molding processes may run more efficiently, and the final product given increased mechanical strength, when a single part is broken up into separate parts with their own thickness. In addition, smaller portions may have a decreased cool-down time, which may benefit injection molding production capacity.

The shaped charge holdermay further include one or more relay wire clips(e.g. also termed cord slots, in) extending transversely from the detonating cord receptacle. The relay wire clipmay be configured to hold the signal relay wireas it is routed across the shaped charge holders. The internal gun assemblymay therefore provide additional flexibility in assembling the internal gun assemblybecause each of the detonating cordand the signal relay wiremay be connected to the shaped charge holdersafter the detonator end assembly, shaped charge holders, and conductive end connectorare assembled together. For example, the detonator end assemblymay be provided assembled with the signal relay wire connected to the feedthrough contact plateand extending out of the detonator end assembly, and the shaped chargesconnected to the detonator end assembly, each other, and the conductive end connector. The signal relay wireand the detonating cordmay then be connected to each shaped charge holderas discussed above (the detonating cordmay first be inserted into the detonating cord channel), and then inserted respectively into the relay wire slotand terminal cord retainer, because each connection (except for the signal relay wire connection to the feedthrough contact plate) is exposed for connections. Increased mechanical strength of the shaped charge holdersmay also eliminate the need to place the shaped chargesin the shaped charge holdersbefore the detonating cordand signal relay wireare connected.

With reference to,,, and, and the exemplary embodiments shown therein, the internal gun assemblyis received within the gun housing. According to an aspect, the internal gun assemblyis housed within the housing. The centralizerand the detonator holder(i.e., the detonator end assembly) is positioned nearest the housing second end(i.e., the housing detonator end). The tandem seal adapteris connected to the housing first end. Finson the centralizermay contact and press against the housing inner surfaceto lock the internal gun assemblyin position within the housing. In an aspect, the finscontact a portion of the housing inner surfacethat is not machined and therefore has a relatively rough texture. The rough texture may aid in, e.g., preventing axial movement of the finsand thereby the internal gun assembly. In an aspect, the ground contact platemay extend to make grounding contact with the housing inner surfaceat a machined portion of the surface, which may be required for effective grounding contact. In an aspect, the internal gun assemblymay be assembled as discussed above and inserted into the housingas a modular piece, locked in position by the fins, and therefore able to be delivered assembled and wired, to, e.g., a wellbore site, where the detonatoris inserted into the detonator holderand electrical connections made by connecting the housing second endto, without limitation, a tandem seal adapter connected to an adjacent perforating gun, as discussed further below. The centralizer alignment keymay be received by a centralizer key slotformed in the housing inner surface, to orient the internal gun assemblywithin the housing. In other words, the centralizermay be engaged with the inner surface of the gun housingvia the centralizer alignment key. Alternatively, the centralizermay be engaged with the inner surface of the gun housingvia contact between the centralizer ringand the inner surface of the gun body.

In the exemplary embodiments, the tandem seal adapterincludes a tandem seal adapter boreextending through the tandem seal adapter. A bulkheadis sealingly received within the tandem seal adapter bore. The bulkheadincludes a bulkhead bodythat may be in contact with an inner circumferential surface bounding the tandem seal adapter borewithin the tandem seal adapter. The bulkheadmay further include one or more scaling assembliespositioned on the bulkhead bodyand in contact with the inner circumferential surface and forming a seal between the bulkhead bodyand the inner circumferential surface. For example, as shown in the exemplary embodiment, the sealing assemblymay include one or more sealing mechanisms, such as elastomeric o-rings, respectively positioned in corresponding recesses on the bulkhead bodyand compressed against the inner circumferential surface. The scaling assemblymay alone, or in combination with the bulkhead body, seal the tandem seal adapter bore, to isolate the interior of the housingfrom, e.g., pressure or fluid from an interior of an adjacent, connected perforating gun housing. In addition, sealing assemblieson the tandem seal adaptermay create a seal against the housing inner surfaceat the housing first end, to seal the interior of the housingfrom, e.g., wellbore fluid or other materials in the environment outside of the housing.

The bulkhead bodyhouses at least a portion of a bulkhead electrical feedthroughfor relaying electrical signals, such as an addressable detonation signal, a diagnostic signal, and the like, between respective electrical connections in adjacent perforating guns. The bulkhead electrical feedthroughmay include, for example and as illustrated in, a first pin connectorand a second pin connector. The first pin connectormay be positioned and dimensioned (i.e., configured) such that when the tandem seal adapteris connected to the housing, the first pin connectoris automatically placed in electrical contact with the conductive end contact, at an end of the first pin connector. The conductive end contactand/or the first pin connectormay be in electrical contact with the signal relay wirewhich may be inserted into a connecting holeon the conductive end contactor otherwise in electrical contact therewith, by known techniques. The second pin connectormay be in electrical contact with an electrical connector in an adjacent perforating gun, as described below, at an end of the second pin connector.