Patent Description:
Novel aspects described herein relate generally to perforating guns that are used in the oil and gas industry to explosively perforate underground hydrocarbon bearing formations. More particularly, the present disclosure describes a perforating gun with improved endplates and an optional zero-tension connector that provides an integrated wiring solution for perforating guns which are easier to manufacture, install, and operate.

A perforating gun is often needed to extract oil and gas from underground formations. The perforating gun is lowered into a casing positioned in a wellbore to a desired rock layer and then fired, creating holes through the casing and into the targeted rock. These perforating holes connect the rock holding the oil and gas to the wellbore, allowing for inflow of hydrocarbons. In many instances, a series of cascaded perforating guns, called a gun string assembly, is used. Each of the perforating guns in the gun string assembly is connected to another perforating gun by a tandem. The tandem houses a detonation transfer apparatus that causes detonation of an adjacent gun in the gun string assembly. Detonation can be initiated from the wireline via electrical, electronic, or pressure-based means.

Gun string assemblies often include numerous components, some of which are formed from costly and complex manufacturing processes. As a result, installation of gun string assemblies is often a complex and time-consuming endeavor. In addition, perforating guns typically lack an integrated wiring solutions, which results in different wireline operators implementing one of a number of conventional, but unreliable methodologies. Therefore, what is needed is an improved perforating gun addressing at least the foregoing deficiencies.

An aspect of the present invention is recited by claim <NUM>, with the dependent claims presenting optional features.

Novel aspects of the present technology are directed to a novel perforating gun, components thereof, and method of assembly. Accordingly, in a first version, the present technology relates to an improved endplate comprising a base with a first end separated from a second end separated by a curved sidewall centered around a longitudinal axis. A set of tube tabs, which is flexibly coupled to the base, extends from the second end. Each of the set of tube tabs is generally oriented in a direction of the longitudinal axis. Further, each of the set of tube tabs comprises a retaining lip for securing the endplate to a charge carrier.

The invention relates to a zero-tension connector having a housing with a first end separated from a second end by a sidewall. A sliding contact is slidably mounted within a cavity of the housing. The sliding contact has a body with a distal end opposite a proximal end, and a portion of the distal end is exposed at the first end of the housing. A through-wire coupled to the proximal end of the sliding contact.

The present technology further relates to a perforating gun comprising a charge carrier having a first end and a second end separated by a curved sidewall centered around a longitudinal axis. The charge carrier further comprises a first set of tube tab receivers at the first end and a second set of tube tab receivers at the second end, and a first endplate releasably coupled to the first end of the charge carrier. The first endplate comprises a first set of flexible tube tabs releasably coupled to the first set of tube tab receivers. The charge carrier also comprises a second endplate releasably coupled to the second end of the charge carrier. The second endplate comprises a second set of flexible tube tabs releasably coupled to the second set of tube tab receivers. The charge carrier is mounted within a gun carrier tube by a set of carrier tabs extending radially outward from an outer surface of the second endplate.

The present technology further relates to a method of assembling the perforating gun comprising a set of novel endplates and a zero-tension connector, the method including the steps of attaching a first endplate to a first end of a charge carrier, wherein the first endplate comprises a first set of tube tabs; attaching a second endplate to a second end of the charge carrier, wherein the second endplate comprises a second set of tube tabs and a set of carrier tabs extending radially outwardly from an outer surface of the second endplate; and sliding the charge carrier into a gun carrier until the set of carrier tabs mates with set of carrier tab receivers on an internal surface of the gun carrier.

Other aspects, embodiments and features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying figures. In the figures, each identical, or substantially similar component that is illustrated in various figures is represented by a single numeral or notation. For purposes of clarity, not every component is labeled in every figure. Nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention.

The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying figures, wherein:.

Novel aspects of the disclosure recognize certain deficiencies in the prior art. For example, a gun string assembly positioned in a wellbore casing with a wireline cable includes a conducting through-wire that provides the electrical connection between a perforating gun and an adjacent tandem. The through-wire is extended down a length of the perforating gun, out the end and then wired directly to the output pin of a firing switch in the tandem. Tension must be maintained on the through-wire to gather up the stack and prevent the through-wire from being pinched between the threads of the perforating gun and the tandem as the two pieces are joined. Oftentimes, too much tension is applied to the through-wire, causing it to disconnect from the output pin of the firing switch. As a result, wireline operators often solder the through-wire to the output pin and apply an optional wrapping of silicone or heat-shrink.

As will be discussed in more detail below, novel aspects of an improved endplate and the perforating gun assembly provide for a zero-tension connector for establishing the electrical connection without the need for the time-consuming wiring steps. in addition, when an improved uphole endplate is outfitted with a zero-tension connector, the firing switch of the attached tandem is protected from inadvertent damage. For context, in conventional systems the firing switch in the tandem is exposed the shaped charges housed in the charge carrier. When the charges are detonated, the firing switch is exposed to shrapnel and overpressure conditions.

In contrast, in one illustrative example described herein, an improved perforating gun includes an uphole endplate with a zero-tension connector that seals the uphole end of the perforating gun and shields the firing switch.

Another deficiency in the prior art is the variability in the methodology in which wireline operators ground gun string assemblies. The variability is attributable to a lack of an integrated grounding solution in perforating guns. One example of a conventionally utilized grounding solution involves scratching through an oxide layer on the surface of a firing switch and affixing the ground wire to the exposed surface. In some instances, the ground wire may be dislodged by vibration and shock during installation or detonation of the gun string assembly. In contrast, novel aspects of the improved perforating gun disclosed herein includes an endplate with an integrated grounding solution that eliminates variability and also simplifies the grounding process.

Additionally, current methods of assembling a gun string assembly require an excessive number of steps that lengthen the assembly procedure. For example, affixing conventional endplates to a charge carrier requires alignment of apertures in the endplate with corresponding apertures in the charge carrier, then joining the two pieces with screws. To align the shaped charges in the charge carrier with the scallops in the gun carrier, an ancillary operation is often required to insert a pin from the charge carrier through a corresponding aperture in the endplate. Further, after the charge carrier is properly oriented within the gun barrel, one or more snap rings are introduced into the gun barrel to engage an annular snap ring recess, which maintains the axial position of charge carrier so that the shaped charges in the charge carrier are properly aligned with the scallops on the outer surface of the gun barrel. Snap ring use increases the number of installation steps as well as the overall cost of the system. As will be discussed in more detail, certain aspects of the disclosure provides for novel perforating gun components with reduced manufacturing costs, reduced number of components, and a reduced number of installation steps.

<FIG> is a perspective view of a perforating gun. Perforating gun <NUM>, which is shown in partial cross-section to more clearly depict the interconnection between individual components, is a generally cylindrical apparatus that includes a hollow gun carrier <NUM> centered around axis <NUM>. A plurality of scallops <NUM> is disposed throughout the outer sidewall <NUM> of the gun carrier. Each of the plurality of scallops <NUM> is a thin-walled portion of the sidewall <NUM> aligned with a shaped charge housed within. Specifically, a charge carrier <NUM> is mounted concentrically within the gun carrier <NUM> which houses shaped charges (not shown). The charge carrier <NUM> is a hollow, cylindrical frame having a first end <NUM> separated from a second end <NUM> by an inner sidewall <NUM>. A plurality of gun ports <NUM> disposed throughout the inner sidewall <NUM> and arranged in a pattern to coincide with the plurality of scallops <NUM> in the gun carrier <NUM>.

The charge carrier <NUM> is sealed on either end by endplates <NUM> and <NUM>. As used herein, the first endplate <NUM> may be referred to in the alternative as the uphole endplate, and the second endplate <NUM> may be referred to in the alternative as the downhole endplate. The first endplate <NUM> and the second endplate <NUM> are molded components formed by injection molding or direct molding from a composite. The endplates <NUM> and <NUM> may also be formed from pure Nylon, glass-filled Nylon, plastic, thermoset polymer, thermoplastic polymer, zinc die cast, steel, composite, magnesium, aluminum, or combinations thereof. Generally, molded components are easier and cheaper to manufacture; however, the first endplate <NUM> and the second endplate <NUM> can be 3D printed or machined from metal. Each of the endplates <NUM> and <NUM> may be formed as unitary components that are not formed of smaller subcomponents that are later attached via permanent, semi-permanent, or removable means.

The second endplate <NUM> has a set of tube tabs <NUM> configured to releasably couple the second endplate <NUM> with the charge carrier <NUM>. As used herein, the term "set of' means one or more. Thus, the set of tube tabs <NUM> can be one tube tab, two tube tabs, or more. Each of the set of tube tabs <NUM> engages a corresponding tube tab receiver <NUM> integrated into the inner sidewall <NUM> of the charge carrier <NUM>. Where the set of tube tabs <NUM> is two or more tube tabs, the set of tube tabs <NUM> are arranged asymmetrically around the circumference of the aperture <NUM> that extends through the second endplate <NUM>. Likewise, the set of tube tab receivers <NUM> in the second end <NUM> of the charge carrier <NUM> is also arranged in a corresponding asymmetric pattern. The asymmetric arrangement of the set of tube tabs <NUM> and the corresponding arrangement of the tube tab receivers <NUM> ensures that the second endplate <NUM> is properly aligned within the charge carrier <NUM>. For example, if the set of tube tabs <NUM> is two tube tabs, placing each of the two tube tabs <NUM>° apart from each other, on opposite sides of the aperture <NUM> allows the second endplate <NUM> to be installed in two separate ways, <NUM>° out of phase. However, placing the two tube tabs at opposite ends of an arc having an angle of less than <NUM>° eliminates variability in the installation process. Proper alignment of the endplates <NUM> and <NUM> with the charge carrier <NUM> along with the proper alignment of the endplates <NUM> and <NUM> with the gun carrier <NUM> necessarily aligns the shaped charges in the charge carrier <NUM> with the plurality of scallops <NUM> in the gun carrier <NUM>.

The second endplate <NUM> also includes a set of carrier tabs <NUM> for releasably coupling the second endplate <NUM> with the gun carrier <NUM>. Each of the set of carrier tabs <NUM> engages a carrier tab receiver <NUM> the interior surface of the gun carrier <NUM> to maintain the axial position of the charge carrier <NUM> within the gun carrier <NUM>. The carrier tab receiver <NUM> is an annular recess conventionally used for engaging a snap ring. Thus, the gun carrier <NUM> may still be used with legacy endplates secured with a snap ring.

To maintain the proper orientation of the second endplate <NUM> within the gun carrier <NUM>, and thus align the shaped charges and corresponding gun port <NUM> with a scallop <NUM>, one or more of the carrier tabs <NUM> includes an alignment pin <NUM>. Each of the one or more alignment pins <NUM> corresponds to an alignment pin receiver <NUM> in the interior surface of the gun carrier <NUM>, which can be seen in more detail in <FIG>. The alignment pin <NUM> is an elongated body integrally formed with the second endplate <NUM>, and aligned with the longitudinal axis <NUM> of the perforating gun <NUM>. The alignment pin receiver <NUM> is one or more elongated recesses sized to receive the one or more alignment pins <NUM>. In the event that two or more alignment pins <NUM> are implemented, the two or more alignment pins <NUM> should be asymmetrically oriented around the second endplate <NUM> to prevent improper alignment of the charge carrier <NUM> within the gun carrier <NUM>. Only one of the carrier tabs <NUM> is formed with an alignment pin <NUM>.

A first endplate <NUM> is releasably coupled to the first end <NUM> of the charge carrier <NUM> by a set of tube tabs <NUM> (omitted for clarity but shown in more detail in <FIG>). Each of the set of tube tabs <NUM> engages one corresponding tube tab receiver <NUM> integrated into the sidewall of the charge carrier <NUM>. when the set of tube tabs <NUM> is two or more tube tabs, the set of tube tabs <NUM> are arranged asymmetrically around the circumference of the corresponding aperture <NUM> in first endplate <NUM>. Likewise, the set of tube tab receivers <NUM> in the first end <NUM> of the charge carrier <NUM> is also arranged in a corresponding asymmetric pattern to maintain the proper orientation of the first endplate <NUM> relative to the charge carrier <NUM>. The asymmetric arrangement of the set of tube tabs <NUM> ensures that the first endplate <NUM> is properly aligned in the first end <NUM> of the charge carrier <NUM>. As already mentioned, proper orientation of the endplates <NUM> and <NUM> relative to the charge carrier <NUM> results in proper alignment of the shaped charges mounted within the charge carrier <NUM> with the gun ports <NUM> and also the scallops <NUM>, which is desirable for optimum recovery of oil and gas.

A zero-tension connector <NUM> is optionally installed into the first endplate <NUM> to simplify the electrical connections in the perforating gun <NUM>, to reduce the number of steps required for installing a gun string assembly, and to protect the firing switch in upstream tandems (not shown). In particular, the zero-tension connector <NUM> eliminates the need to maintain tension on a through-wire <NUM> during installation, obviating the myriad of steps currently undertaken to secure the through-wire <NUM> to the output pin of the firing switch. In addition, the zero-tension connector <NUM> also provides a convenient means for grounding the tandem (not shown) to the gun carrier <NUM> and the ground wire <NUM>. The zero-tension connector <NUM> is described in more detail in <FIG>.

<FIG> is an end view of a gun carrier <NUM>. Located at the end of the gun carrier <NUM> is a carrier tab receiver <NUM>, which is depicted as an annular recess configured to mate with the set of carrier tabs <NUM> on the second endplate <NUM>. To properly align the second endplate <NUM> with the gun carrier <NUM>, the gun carrier also includes a set of alignment tab receivers <NUM>. The set of alignment tab receivers <NUM> is a single elongated recess extending from the set of carrier tab receivers <NUM>. During installation, the endplates <NUM> and <NUM> are attached to opposing ends of the charge carrier <NUM>, and then the charge carrier <NUM> is then inserted axially into the gun carrier <NUM> along the axis <NUM> to allow the set of carrier tabs <NUM> of the second endplate <NUM> to mate with the set of carrier tab receivers <NUM>. While inside the gun carrier <NUM>, the charge carrier <NUM> may be rotated until the alignment pin <NUM> engages the alignment pin receiver <NUM>, which aligns the shaped charges, gun ports <NUM>, and scallops <NUM> as previously mentioned.

<FIG> is a perspective view of a charge carrier <NUM>. The charge carrier <NUM> includes a set of tube tab receivers <NUM> at each end which is configured to receive a set of tube tabs from a corresponding endplate. For example, the set of tube tab receivers <NUM> at the first end <NUM> of the charge carrier <NUM> are configured to receive the tube tabs <NUM> from endplate <NUM>, and the set of tube tab receivers <NUM> at the second end <NUM> of the charge carrier <NUM> are configured to receive the tube tabs <NUM> from endplate <NUM>.

The set of tube tab receivers <NUM> depicted in <FIG> are in the form of apertures extending through the sidewall <NUM> of the charge carrier <NUM>. Each of the set of tube tab receivers <NUM> are shaped to engage the operative surface a corresponding tube tab, which is a retaining lip in the depicted embodiments. Further, each of the set of tube tab receivers <NUM> are positioned to align with the asymmetrically positioned tube tabs so that corresponding endplates will be installed with the proper alignment. The set of tube tab receivers <NUM> at the first end <NUM> of the charge carrier <NUM> are positioned around the charge carrier <NUM> with a different pattern than the set of tube tabs <NUM> at the second end <NUM>, which prevents an endplate from being inadvertently installed at the wrong end of the charge carrier <NUM>.

Although the set of tube tab receivers <NUM> are depicted as apertures, the set of tube tab receivers <NUM> may be recesses that extend only partially through the sidewall <NUM>. The set of tube tab receivers <NUM> may also be projections that extend outwardly from the sidewall <NUM> of the charge carrier.

<FIG> is a perspective view of a downhole endplate <NUM>. The second endplate <NUM> includes a base <NUM> with a first end <NUM> separated from a second end <NUM> by a curved sidewall <NUM> centered around a longitudinal axis <NUM>. The second endplate <NUM> also includes a set of tube tabs <NUM> flexibly coupled to the base <NUM>, extending from the second end <NUM>. Each of the set of tube tabs <NUM> is arranged around an aperture <NUM> in the second end <NUM> of the base <NUM> and generally oriented in a direction of the longitudinal axis <NUM>. Additionally, each of the set of tube tabs <NUM> includes a retaining lip <NUM>, which is an operative surface of a tube tab <NUM> configured to engage a tube tab receiver <NUM>.

The second endplate <NUM> includes a set of structural supports <NUM> fixedly coupled to the base <NUM> at the second end <NUM>, and projects generally in the direction of the longitudinal axis <NUM>. In <FIG>, the set of structural supports <NUM> is a plurality of curved sidewalls arranged around an aperture <NUM> at the second end <NUM> of the base <NUM>. The set of structural supports <NUM> is a projection that protects the tube tabs <NUM> from breakage. For example, before installation, in the absence of the set of structural supports <NUM>, the tube tabs <NUM> would extend from the second end <NUM> of the base <NUM> unprotected, prone to unintended breakage if dropped or improperly packaged prior to shipment. Thus, the set of tube tabs are interspersed between the set of structural supports <NUM>.

Additionally, when the set of structural supports <NUM> is a plurality of curved sidewalls are arranged around the aperture <NUM>, each of the plurality of structural supports <NUM> has a thickness such that the plurality of structural supports <NUM> can be snugly inserted into an end of a charge carrier <NUM>. The plurality of structural supports <NUM> reinforces the connection between the charge carrier <NUM> and the first endplate <NUM> and assumes the forces that would otherwise be asserted on the relatively weaker tube tabs <NUM>.

The second endplate <NUM> also includes a set of carrier tabs <NUM>. The set of carrier tabs <NUM> is one or more fastening devices for securing the second endplate <NUM> and the attached charge carrier <NUM> to the gun carrier <NUM>. The set of carrier tabs <NUM> is partially recessed into the curved sidewall <NUM> of the base <NUM> with a flange <NUM> projecting radially outward relative to the curved sidewall <NUM>. Each of the set of carrier tabs <NUM> is flexibly coupled to the base <NUM> to allow the flange <NUM> to flex relative to the base <NUM>. Each of the set of carrier tabs <NUM> is an L-shaped fastener. During installation, as the charge carrier <NUM> is inserted into the gun carrier <NUM>, the set of carrier tabs <NUM> flexes radially inward until each of the set of flanges <NUM> mates with a carrier tab receiver <NUM> to secure the second endplate <NUM> in the gun carrier <NUM>. As previously mentioned, at least one of the set of carrier tabs <NUM> includes an alignment pin <NUM>, which is configured to align the charge carrier <NUM> in the gun carrier <NUM>.

<FIG> is a perspective view of an uphole endplate <NUM>. The first endplate <NUM> includes a base <NUM> with a first end <NUM> separated from a second end <NUM> by a curved sidewall <NUM> centered around a longitudinal axis <NUM>. The first endplate <NUM> also includes a set of tube tabs <NUM> flexibly coupled to the base <NUM>. In addition each of the set of tube tabs <NUM> is arranged around an aperture <NUM> in the second end <NUM> of the base <NUM> and generally oriented in a direction of the longitudinal axis <NUM>. Additionally, each of the set of tube tabs <NUM> includes a retaining lip <NUM>.

The second endplate <NUM> includes a set of structural supports <NUM> fixedly coupled to the base <NUM>, which extends from the second end <NUM> of the base <NUM>. Each of the set of structural supports <NUM> is generally oriented along the longitudinal axis <NUM>. In <FIG>, the set of structural supports <NUM> is a plurality of curved sidewalls arranged around an aperture <NUM> at the second end <NUM> of the base <NUM>. The set of structural supports <NUM> is a projection that protects the tube tabs <NUM> from breakage. Thus, the set of tube tabs are interspersed between the set of structural supports <NUM>.

Additionally, when the set of structural supports <NUM> is a plurality of curved sidewalls are arranged around the aperture <NUM>, each of the plurality of structural supports <NUM> has a thickness such that the plurality of structural supports <NUM> can be snugly inserted into an end of a charge carrier <NUM>. The plurality of structural supports <NUM> reinforces the connection between the charge carrier <NUM> and the first endplate <NUM> and relieves the forces that would be otherwise asserted on the relatively weaker tube tabs <NUM>.

<FIG> is a perspective view of a zero-tension connector in accordance with the invention. Zero-tension connector <NUM> is generally formed from a housing <NUM> that has a first end <NUM> and a second end <NUM> separated by a sidewall <NUM>. The sidewall <NUM> defines a cavity that houses a sliding contact <NUM>, both of which are shown in more detail in the exploded view depicted in <FIG>. In addition, extending from the second end <NUM> of the housing <NUM> is a ground wire <NUM> that is removably attached to a proximal end of a first ground connection <NUM>. The first ground connection <NUM> is an elongated metallic tab that is secured with the housing <NUM> by passing the first ground connection <NUM> through a slotted aperture in the sidewall <NUM> of the housing <NUM>. However, this method of securing should be deemed exemplary and non-limiting.

The first ground connection <NUM> is electrically connected to a second ground connection, which is a coiled spring <NUM>. In particular, the first ground connection <NUM> is wrapped partially around a coil and optionally secured by the application of solder or other form of conducting weld. Where the second ground connection <NUM> is a coiled spring, the second ground connection <NUM> encircles the first end <NUM> of the housing <NUM> and one end is positioned against an annular flange <NUM> encircling the outer surface of the sidewall <NUM>. The other end of the second ground connection <NUM> extends outwardly beyond the first end <NUM>. When the zero-tension connector <NUM> is installed into a first endplate that is subsequently incorporated into a perforating gun, the first ground connection <NUM> grounds the gun carrier with the ground wire <NUM>. When the perforating gun is attached to a tandem, the second ground connection <NUM> is compressed by a retaining nut in the tandem, which grounds the tandem to ground wire <NUM>. The ground wire <NUM> extends the length of its corresponding perforating gun and connects to a detonator block, which may be connected on its other end to another zero-tension connector affixed to an endplate of a downhole perforating gun. As a result every gun in a string will have a positive, engineered, and redundant ground, which eliminates the common practice for wireline companies to engineer their own grounding solution as perforating guns are loaded.

Also extending from the second end <NUM> of the housing <NUM> is a through-wire <NUM>. The through-wire <NUM> is connected to a proximal end of a sliding contact <NUM>, which is shown in more detail in <FIG>. A distal end of the sliding contact <NUM> is exposed at the first end <NUM> of the housing <NUM> to make contact with an output pin of a firing switch to obviate the need to manually wrap the through-wire around the firing switch and then secure the connection with solder and/or tubing. A spring <NUM> is mounted within the cavity of the housing <NUM> and disposed between the proximal end of the sliding contact <NUM> and the housing <NUM>. The spring <NUM> maintains the sliding contact at the first end <NUM> of the housing with the proximal end exposed and positioned to receive the output pin of a firing switch (not shown).

<FIG> is an exploded view of a zero-tension connector in accordance with the invention. The housing <NUM> of the zero-tension connector <NUM> is depicted as a plurality of pieces that, when assembled, defines a cavity to house sliding contact <NUM>. In particular, the housing is formed from a body 602a that defines cavity <NUM>, which may be sealed by endcap 602b. The endcap 602b may be secured to the body 602a using conventionally available fasteners. For example, the endcap 602b may be threaded and configured to be screwed to the body <NUM>, which is counter-threaded. The endcap 602b includes a set of flexible arms, each with a protruding lip configured to engage a corresponding recess in the sidewall <NUM> of the body 602a.

The sliding contact <NUM> is housed within the cavity <NUM>. The sliding contact includes a proximal end 622a opposite to a distal end 622b. The through-wire <NUM> is electrically connected to the proximal end 622a of the sliding contact <NUM> with the through-wire <NUM> extending out from an aperture in the endcap 602b. The spring <NUM> is oriented along the through-wire <NUM> and positioned so that the spring <NUM> is compressible between the proximal end 622a of the sliding contact <NUM> and the interior surface of the endcap 602b. As previously mentioned, the spring <NUM> provides a compressive force that maintains the sliding contact <NUM> at the first end <NUM> of the housing <NUM> to receive an output pin of a firing switch, as can be seen in more detail in <FIG>.

The first ground connection <NUM> is depicted as a metallic tab with a proximal end 612a and a distal end 612b. The first ground connection <NUM> is wrapped at least partially around a coil in the second ground connection <NUM> and optionally soldered together to maintain the electrical connection. The first ground connection <NUM> and the second ground connection <NUM> may be a single, integrated component that simplifies installation and obviates the need for a soldered joint.

The first ground connection <NUM> is secured with the housing <NUM> via an aperture sized to frictionally engage the first ground connection <NUM>. A bracket or other conventional fastening means may be implemented. Once secured with the housing, the proximal end 612a of the first ground connection <NUM> is coupled to the ground wire <NUM>.

<FIG> is a perspective view of a zero-tension connector coupled to an uphole endplate. The zero-tension connector <NUM> is aligned with the longitudinal axis <NUM> and extended at least partially through the base <NUM> of the first endplate <NUM>. The zero-tension connector <NUM> is mounted with its first end <NUM> projecting outwardly from the first end <NUM> of the base <NUM>. The second end <NUM> of the zero-tension connector <NUM> is obscured in this figure by the curved sidewall <NUM> and the set of structural supports <NUM>, but can be seen in more detail in <FIG>.

The first ground connection <NUM> is wrapped at least partially around the base <NUM> of the first endplate <NUM> so that installation of the endplate <NUM> with a charge carrier <NUM> causes the rim of the charge carrier <NUM> to compress the distal end 612b of the second ground connection <NUM> against the base <NUM> of the first endplate <NUM> to prevent inadvertent misalignment or disengagement during installation or operation.

<FIG> is a cross-sectional view of a portion of a gun string assembly. An uphole end of a perforating gun <NUM> is shown connected to a tandem <NUM>. The tandem <NUM> includes a switch body <NUM> secured in place by a retaining nut <NUM>. Projecting outwardly from the switch body <NUM> is the output pin <NUM>, which is configured to form an electrical connection with a through-wire <NUM> of the attached perforating gun <NUM>. When the perforating gun <NUM> is attached to the tandem <NUM>, the output pin <NUM> engages the distal end 622b of the sliding contact <NUM> that is exposed at the first end <NUM> of the zero-tension connector <NUM>. Contact between the output pin <NUM> and the sliding contact <NUM> is maintained by the force exerted by the spring <NUM>, which is able to absorb and dissipate the vibration and shock generated during operation to prevent inadvertent disengagement.

The perforating gun <NUM> is grounded with a firing switch <NUM> in the tandem <NUM> by the second ground connection <NUM>, which is compressed against the retaining nut <NUM> of the tandem <NUM> when the perforating gun <NUM> is attached to the tandem <NUM>. The second ground connection <NUM> is electrically connected to the grounding wire <NUM> by way of the first ground connection <NUM> that is coupled directly to the ground wire <NUM>. The first ground connection <NUM>, which is shown wrapped partially around a coil of the second ground connection <NUM>, also grounds the gun carrier <NUM> to the ground wire <NUM>. When the charge carrier <NUM> and the endplates <NUM> and <NUM> are assembled and inserted into the gun carrier <NUM>, a portion of the first ground connection <NUM> is secured between the inner surface of the gun carrier <NUM> and the first endplate <NUM>. Thus the gun carrier <NUM> and the firing switch <NUM> is grounded with the ground wire <NUM>.

The switch <NUM> can be configured with its own dedicated ground wire to provide a redundant ground, which can be crucial to proper operation given that tandems are frequently reused and in the absence of through cleaning, deposits on the tandems may prevent a good ground connection. The dedicated ground wire can be attached to the switch <NUM> by conventional means, such as soldering or other forms conducting welds, and placed at a location that does not interfere with installation of the switch into the tandem <NUM>. Thus, the dedicated ground wire is attached to an end portion of the switch <NUM> opposite from the output pin <NUM>.

<FIG> is a high level flowchart of an exemplary method of assembling a perforating gun. A first endplate having a first set of tube tabs is attached to a first end of a charge carrier (Step <NUM>). A second endplate, which has a second set of tube tabs and a set of carrier tabs extending radially outwardly from an outer surface of the second endplate, is attached to a second end of the charge carrier (Step <NUM>). The charge carrier and the attached endplates are slidably inserted into a gun carrier until the set of carrier tabs mates with set of carrier tab receivers on an internal surface of the gun carrier (Step <NUM>).

<FIG> is a flowchart of a particular method of assembling a perforating gun. A zero-tension connector is mounted to a first endplate (Step <NUM>). The first endplate, which has a first set of tube tabs, is attached to a first end of a charge carrier (Step <NUM>). Step <NUM> includes the additional steps of orienting the first set of tube tabs with a corresponding tube tab receiver in a first end of the charge carrier, and then sliding a second end of the first endplate into the first end of the charge carrier until the first set of tube tabs mates with the first set of tube tab receivers.

A second endplate, which has a second set of tube tabs and a set of carrier tabs extending radially outwardly from an outer surface of the second endplate, is attached to a second end of the charge carrier (Step <NUM>). Step <NUM> can also include the additional steps of orienting the second set of tube tabs with a corresponding tube tab receiver in a second end of the charge carrier, and then sliding a second end of the second endplate into the second end of the charge carrier until the second set of tube tabs mates with the second set of tube tab receivers.

One or more alignment pins integrated with the set of carrier tabs is aligned with a corresponding alignment pin receiver positioned on an interior surface of the gun carrier (Step <NUM>). Alignment of the one or more alignment pins with the corresponding alignment pin receiver aligns shaped charges in the charge carrier with a corresponding scallop on an exterior of the gun carrier.

The charge carrier and the attached endplates are slidably inserted into a gun carrier until the set of carrier tabs mates with set of carrier tab receivers on an internal surface of the gun carrier (Step <NUM>). The set of carrier tab receivers is an annular recess. In conventional perforating guns, the annular recess is configured to receive a snap ring to secure the charge carrier within the gun carrier.

<FIG> is a flowchart of a particular method of installing a zero-tension connector into a first endplate. A housing of the zero-tension connector is extended at least partially through an aperture in the first end of the first endplate (Step <NUM>). A second ground connection is coupled to at least a first end of the housing of the zero-tension connector (Step <NUM>). A portion of the second ground connection extends out beyond the first end of the housing, and the second ground connection is a coiled spring. The second ground connection is electrically connected with a first ground connection (Step <NUM>). The first ground connection is an elongated metallic tab. A distal end of the first ground connection is wrapped at least partially around a base of the first endplate (Step <NUM>). A ground wire is attached to a proximal end of the first ground connection (Step <NUM>).

Claim 1:
A zero-tension connector comprising:
a housing (<NUM>) with a first end (<NUM>) separated from a second end (<NUM>) by a sidewall (<NUM>);
a sliding contact (<NUM>) slidably mounted within a cavity of the housing (<NUM>), wherein the sliding contact (<NUM>) has a body with a first end (622b) opposite a second end (622a), wherein a portion of the first end (622b) of the sliding contact (<NUM>) is exposed at the first end (<NUM>) of the housing (<NUM>);
a spring (<NUM>) provided within the cavity of the housing (<NUM>) and configured to bias the sliding contact (<NUM>) against the first end (<NUM>) of the housing (<NUM>); and
a through-wire (<NUM>) extending through the spring (<NUM>) and directly coupled to the second end (622a) of the sliding contact (<NUM>).