Patent ID: 12221865

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. Further, the term “fluid,” as used herein, is intended to encompass both fluids and gasses.

As described above, in rare instances, a perforating gun of a tool string may become stuck downhole as a result of a rod-shaped electrical contact of a damaged perforating gun being partially or fully ejected from the damaged perforating gun. For example, the rod-shaped electrical contact may catch in an opening in the casing (e.g., a perf opening opened by the detonation of the perforating gun) or a joint or other irregularity along the inner surface of the casing string while also, at the same time, being caught somewhere along the tool string. As a result, the damaged perforating gun becomes stuck within the casing string, potentially requiring the wireline system from which the tool string is suspended to break off from the tool sting and gain removal of the tool string from the wellbore via expensive, specialized equipment delaying the completion of the wellbore and substantially increasing the cost for completing the wellbore.

Accordingly, embodiments of frangible electrical contacts for perforating guns are described herein which shear or otherwise yield in the event of the rod-shaped electrical contact jamming or snagging within a casing string. Particularly, the frangible electrical contact may be rod-shaped and may include one or more frangible features intended to reduce the bending strength and shear strength of the rod-shaped electrical contact. Having a reduced shear strength, the tension which may be applied to the wireline connected to the tool string by surface equipment of the wireline system may be sufficient to break apart the jammed rod-shaped electrical contact and thereby dislodge or free the tool string without having to release the wireline from the tool string. In this manner, the freed tool string may be retracted to the surface without the need for performing an expensive and time-consuming removal operation of the once stuck tool string. In some embodiments, the frangible features of the rod-shaped electrical contacts described herein take the form of frangible grooves formed in an outer surface of a frangible conductor rod of the rod-shaped electrical contact. The frangible grooves may define one or more minimum cross-sectional areas of the frangible conductor rod which deliberately weaken the conductor rod to bending and shear forces that may be applied thereto by a wireline system in the event of the frangible conductor rod becoming stuck in the wellbore.

Referring now toFIG.1, a hydrocarbon production location or wellsite generally indicated by the arrow10is shown with wellbore13extending into a subterranean earthen formation17with a generally horizontal segment arranged in a target area of the earthen formation17that is anticipated to contain commercial quantities of hydrocarbons. Wellbore13is a cased wellbore including a casing string12secured and sealed to an inner surface or sidewall of the wellbore13using cement (not shown). The casing string12generally includes a plurality of tubular segments coupled together via a plurality of casing collars.

In this exemplary embodiment, located at the wellsite10is a surface assembly11positioned at the surface5with a tool string20deployed into a subterranean wellbore13. Surface assembly11may comprise any suitable surface equipment for drilling, completing, and/or operating well20and may include, in some embodiments, derricks, structures, pumps, wireline reel, wireline injector, electrical/mechanical well control components, etc. In this exemplary embodiment, among other equipment, surface assembly11includes a control system or firing panel15and a surface wireline unit or winch16, each shown schematically inFIG.1. Tool string20is suspended within wellbore13from a flexible wireline22that extends from surface assembly11located at the surface5. Wireline22generally comprises an armored cable and includes at least one electrical conductor for transmitting power and electrical signals between tool string20and a control system or firing panel15of the surface assembly11located at the surface5.

Tool string20is generally configured to perforate the casing string12to provide for fluid communication between the earthen formation17and the wellbore13at one or more predetermined locations along the wellbore13and to thereby allow for the hydraulic fracturing of the formation17through the perforations formed in the casing string12and the subsequent production of hydrocarbons from the formation17into the wellbore13through the perforations.

In this exemplary embodiment, tool string20generally includes, among other components, a cable head24at an uphole end of the tool string20, a casing collar locator26, a direct connect sub28, a perforating tool or gun100, a setting tool initiator or firing head40, a setting tool50, and a downhole or frac plug60located at a downhole end of the tool string20. It may be understood that in other embodiments the configuration of tool string20may vary from that shown inFIG.1. For example, in other embodiments, tool string20may include a plurality of the perforating guns100, one or more tandem subs connected between adjoining pairs of perforating guns100, and/or other equipment. The one or more tandem subs may provide a pressure barrier preventing a first detonated perforating gun from inadvertently destroying or detonating a second perforating gun of the tool string20that is located uphole from the first detonated perforating gun. It may also be understood that tool string20may include other additional components not shown inFIG.1.

In this exemplary embodiment, 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 of tool string20downhole from the cable head24all the way to the downhole plug60.

Turning toFIG.2, an exemplary perforating gun100is shown which includes one or more shaped charges180detonatable in response to the transmission of one or more electrical signals conveyed by the wireline22from the firing panel15at the surface5. Upon detonation, the one or more shaped charges180of perforating gun100produce one or more corresponding explosive jets (not shown inFIG.2) directed radially outwards and away from the perforating gun100and against casing string12.

Perforating gun100has a central or longitudinal axis105and includes an outer carrier or housing102, a charge carrier assembly142housed within the outer housing102, a plurality of explosive shaped charges180, and an initiator assembly190for selectably detonating the shaped charges180. Outer housing102is generally tubular in shape including a pair of longitudinally opposite ends101, a central bore or passage103defined by a generally cylindrical inner surface104extending between a pair of longitudinally opposite ends101of outer housing102, and a generally cylindrical outer surface106also extending between ends101. In this exemplary embodiment, a plurality of scallops or indentations108are formed in the outer surface106of outer housing102. Each scallop108defines a relatively thin-walled section of outer housing102. As will be described further herein, scallops108are intended to break-apart during detonation of the perforating gun100such that burrs are not formed along the periphery of the outer housing102which could catch against the casing string12. Additionally, the break-up of scallops108may permit the explosive jets generated by shaped charges180to more easily penetrate and punch through the outer housing102. In other embodiments, outer housing102may include a plurality of annular grooves or ring-like channels or indentations formed in outer surface106around the periphery of the housing102in lieu of scallops108. The annular grooves may forego the requirement of angularly aligning the shaped charges180of perforating gun100with scallops108. In still other embodiments, outer housing102may not include either scallops or annular grooves. Outer housing102may additionally include connectors (e.g., threaded connectors) at the ends103thereof for coupling with the direct connect sub28and firing head40(hidden from view inFIG.2), respectively, of tool string20. For example, outer housing102may include a pair of threaded connectors formed on the inner surface104thereof at ends101. Alternatively, outer housing102may include a pair of threaded connectors formed on the outer surface106thereof at one of or both ends101.

Charge carrier assembly140of perforating gun100is slidably received within the central passage103of outer housing102. In this exemplary embodiment, charge carrier assembly140generally includes a generally tubular charge carrier142and a pair of endplates150. Charge carrier142includes a pair of longitudinally opposed ends143and a central bore or passage144extending between the ends143. Charge carrier142may be cylindrical in shape but alternatively could comprise a variety of shapes and configurations including configurations that are not tubular and thus not including a central passage. In this exemplary embodiment, charge carrier142additionally includes a plurality of radial openings146which each receive a corresponding shaped charge180. Each shaped charge180includes a combustive or explosive material housed internally within a charge housing of the shaped charge180. While in this exemplary embodiment perforating gun100includes a plurality of openings146and shaped charges180, in other embodiments, perforating gun100may include only a single shaped charge180in a single corresponding radial opening146formed in the charge carrier142.

Endplates150of charge carrier assembly140are coupled to the ends143of charge carrier142. In this exemplary embodiment, each endplate150comprises a central passage152which houses a corresponding electrical connector160. Electrical connectors160electrically connect with corresponding electrical connectors of the direct connect28and firing head40, respectively, of tool string20to provide signal communication between charge carrier assembly140and the wireline22. In this exemplary embodiment, each electrical connector160generally includes a biasing member or element162and a rod-shaped electrical contact200biased by the biasing element162. The biasing element162of each electrical connector160is coupled to the rod-shaped electrical contact200and is configured to bias contact200outwardly from endplate150along the central axis105of perforating gun100.

In this exemplary embodiment, the rod-shaped electrical contacts200of the pair of electrical connectors160each project outwardly from their respective endplates150, thereby defining the maximum axial length of the charge carrier assembly140. In other embodiments, each electrical connector160may not include biasing element162and instead a counterpart contact may be biased back into contact with the rod-shaped electrical contact200. The rod-shaped electrical contacts200are typically received in concave (e.g., dish-shaped) receptacles of the corresponding electrical contact engaging in a male/female configuration with adjacent components of tool string20such as the direct connect28and firing head40to thereby form an electrical connection between perforating gun100and both the direct connect28and firing head40. Alternatively, electrical contacts200may engage planar surfaces of the corresponding electrical contacts rather than concave surfaces in an end-to-end arrangement. As will be described further herein, the rod-shaped electrical contact200of each electrical connector160has a predefined, intentionally frangible configuration configured to readily yield or break apart should the contact200become jammed or caught between the casing string12following the detonation of perforating gun100.

The initiator assembly190of perforating gun100controls the detonation of the shaped charges180of perforating gun100in response to receiving one or more electrical signals from the firing panel15of surface assembly11. While initiator assembly190is shown within outer housing102, in other embodiments, it may be located external housing102such as within an adjacently positioned tandem sub. Additionally, in this exemplary embodiment, initiator assembly190generally includes an electrical switch192and a detonator194electrically connected (e.g., wired, soldered, etc.) to the switch192. Switch192is connected to each of the electrical connectors160of charge carrier assembly140via a pair of electrical conduits or cables196which extend between switch192and electrical connectors160.

The electrical switch192of initiator assembly190is configured to selectably energize and thereby detonate the detonator194in response to receiving an appropriate firing signal from the firing panel15. In some embodiments, electrical switch192may comprise one or more diodes. In other embodiments, electrical switch192may comprise a digital switch including one or more processors and one or more memory devices coupled to the processor and which are configured to detonate the detonator194in response to receiving a firing signal from the firing panel15which is specifically addressed to the electrical switch192. For example, electrical switch192may detonate the detonator194in response to receiving a firing signal from the firing panel15at the surface5which includes an address which matches an associated address stored in the memory of electrical switch192. In this exemplary embodiment, detonator194is ballistically coupled to each shaped charge180by one or more detonator or “det” cords (not shown inFIG.2). However, in other embodiments, detonator194may alternatively be directly ballistically connected (without an intervening det cord) to one or more of the shaped charges180.

Referring now toFIGS.3-5, an embodiment of a frangible, rod-shaped electrical contact200of perforating gun100is shown. In this exemplary embodiment, rod-shaped electrical contact generally indicated by the arrow200includes an inner, frangible metal conductor rod230and an outer insulating overmolded body202formed on the rod230along with an optional, protective boot220slipped over one end of the rod230. A principal design point for the electrical contact200is to be strong enough to serve as an electrical contact from manufacturing and assembly at the factory through the vibrations and other forces imposed while shipping the perforating gun100(including the electrical contact200) to the wellsite10, running the assembly downhole into wellbore13, and during the detonation of the perforating gun100, but frangible enough to yield or break if dislodged into a bending or shear orientation or arrangement. As installed in the perforating gun100, a majority of the forces encountered by electrical contact200should be compressive with little or no bending force or shear force applied to the electrical contact200. And to the extent that any substantial bending or shear force were ever to be applied to the electrical contact200, the structure and physical integrity of the perforating gun100itself will likely have been compromised as well so the design of the electrical contact200is generally such that the contact200will yield and breakaway well within the forces that may be imposed on the tool string20while the wireline22is still attached.

Noting that the electrical contact200is comprised of two or three elements, depending on whether the boot220is included, the combined strength of these elements is generally what matters if the electrical connection ends up in an inconvenient place or orientation. Generally, most of the physical strength or robustness comes from the conductor rod230. As such, the frangible design of the electrical contact200is most revealed in the design of the conductor rod230. Frangible conductor rod230is shown as male contact inFIGS.3-5although the configuration at a distal end233of the conductor rod230may alternatively have a cup shape to be deemed a female connection. The frangible nature of the design of conductor rod230is less about the maleness or femaleness of the actual connection other than the rod200being elongate and thus capable of catching in the wellbore and causing a stuck tool string within the wellbore.

Additionally, the wireline22has a predefined yield strength, and a working strength that may be approximately between 50% and 60% of the yield strength of the wireline22depending on the given application. A tension applied to the wireline22by the wireline winch16of surface assembly11that is equal to or less than the working strength (e.g., equal to or less than 50% of the yield strength of the physical cable comprising the wireline22) will generally not damage or permanently deform the wireline22. In the event of the electrical contact200of perforating gun100becoming jammed or caught in casing string12, electrical contact200is configured to shear or otherwise yield to free the tool string20in response to applying a tension to the wireline22by wireline winch16that is equal to or less than the working strength of wireline22. It may be understood that typically the force applied to a jammed electrical contact200by the application of tension to wireline22will be a combination of bending and shear loads, and thus the shear strength of electrical contact200is less than the working strength of wireline22to ensure that the combined bending and shear loads applied to the jammed electrical contact200is sufficient to shear or otherwise yield the electrical contact200and thereby free the stuck tool string20such that the tool string20may be successfully retrieved to the surface5using the wireline22. It should be understood that a maximum shear load imposable by wireline winch16on electrical contact200is greater than the designed shear strength to which the electrical contact200is configured to yield such that an inadvertently displaced electrical contact200that has become wedged or otherwise stuck against the casing string12after the shaped charges180have been fired will not prevent recovery of the tool string20. In other words, the wireline operator will have the power required to shear through the stuck electrical contact200at one or more locations along the length of the electrical contact200and thereby continue with operations as normal rather than be forced to abandon the tool string20as stuck in the wellbore13.

As an example, the wireline22may have a yield strength of 11,000 pound-force (lbf) and a corresponding working strength of 5,500 lbf. In some embodiments, conductor rod230of electrical contact200has a shear strength of 1,500 lbf or less, substantially less than the 5,500 lbf working strength of wireline22. In other embodiments, conductor rod230has a shear strength of approximately between 1,000 lbf and 200 lbf such as, for example, 750 lbf, 500 lbf, 350 lbf, 300 lbf, and 250 lbf. It may be understood that the working and yield strengths of wireline22and the associated shear string of conductor rod230may vary substantially depending on the application.

In this exemplary embodiment, conductor rod230is generally long and relatively thin with a longitudinal first or inner end231(located at the left ofFIGS.3-5) and a second or distal end233longitudinally opposed (located on the right inFIGS.3-5) to the inner end231. The conductor rod230further has a generally cylindrical body with an external, peripheral surface marked principally by segments237separated by necked down frangible grooves or voids238spaced along the length of conductor rod230. Distal end233of conductor rod230in this exemplary embodiment is arranged to be inserted into a complimentary socket272of electrical contact270to form an electrical connection therebetween. In other embodiments, instead of being received in a socket, distal end233of conductor rod230may contact a flat surface of electrical contact270in an end-to-end arrangement. In still other embodiments, distal end233of conductor rod230may comprise a female socket configured to receive a male end of the electrical contact270. Frangible conductor rod230comprises an electrically conductive material such as brass, aluminum, copper or other suitable electrically conductive materials. Additionally, while this exemplary embodiment shows frangible conductor rod230as being generally cylindrical, it should be understood that the shape and configuration of conductor rod230may vary in other embodiments without departing from the essential purpose and function.

Insulating body202of rod-shaped electrical contact200is arranged to cover a majority of the length of the conductor rod230with a plastic or other durable and electrically insulating material. In this exemplary embodiment, insulating body202may be overmolded onto the inner contact210and is formed from a polymer such as, for example, a synthetic polymer (e.g., Nylon) while many other options are readily available. However, it should be understood that while outer body202is sufficiently durable to withstand exposure to a wellbore environment, insulating body202is not configured to substantially enhance the bending or shear strength provided by the conductor rod230of the electrical contact200, although some marginal strengthening may be unavoidable.

Insulating body202generally extends along the conductor rod230exposing portions at each of the ends231and233thereof which externally project from the insulating body202. In this exemplary embodiment, insulating body202includes a first or inner end203, a second or outer end205longitudinally opposite inner end203, and a generally cylindrical outer surface204having a collar section206located generally in the longitudinal center of insulating body202and that has an enlarged diameter with respect to the rest of the insulating body202. The collar section206of outer surface204may be used in conjunction with a spring biasing system (not shown inFIGS.3-5) to better secure the physical and electrical connection of the conductor rod230to the female contact270. Additionally, insulating body202is formed as a tubular structure in this exemplary embodiment but it should be understood that the shape and configuration of insulating body202may take other forms.

The insulating body202of rod-shaped electrical contact200is generally configured to prevent or inhibit the conductor rod230from coming into direct electrical contact with another conductive member of perforating gun100such as charge carrier142. In other words, outer body202reduces the likelihood of rod-shaped electrical contact200shorting out while the tool string20is in any part of its operation. In some embodiments, a ratio of the axial length207(shown inFIG.3) of outer body202to the maximum axial length235(shown inFIG.4) of conductor rod230is approximately between 0.5:1 to 0.9:1; however, in other embodiments, the ratio of the axial lengths of outer body202and frangible conductor rod230may vary.

In this exemplary embodiment, protective boot220is provided near the distal end233of conductor rod230having generally tube shape to fit over the distal end233. As shown, the protective boot further220covers outer end205of the outer body202of rod-shaped electrical contact200. Protective boot220is formed from an electrically insulating material but potentially a relatively more pliable material to abut the counterpart connector270to shield the interface between distal end233of conductor rod230and a cup272of the counterpart connector270from having dust, shavings, contaminants or other debris from interfering with or compromising the electrical conductivity therebetween. For example, protective boot220may be formed from a polymer such as silicone other types of pliable electrically insulating materials. Protective boot220may be manually slid over the outer end205of outer body202until a terminal end of boot220abuts shoulder208of outer body202during the initial assembly of charge carrier assembly140or at a wellsite prior to the deployment of the tool string20into the wellbore13.

Referring still toFIGS.3-5, in this exemplary embodiment, a retention groove236is formed in the outer surface234of frangible conductor rod230near the inner end231thereof and which is suited for connecting one of the electrical cables196of perforating gun100. Additionally, in this exemplary embodiment, the plurality of annular frangible grooves238of conductor rod230are formed or cut into the outer surface234of frangible conductor rod230. Although in this exemplary embodiment the frangible conductor rod230comprises frangible grooves238, in other suitable embodiments, the conductor rod230may have different features that are typically configured to yield to shear forces or bending forces. In some embodiments, the number and configuration of frangible grooves238is selected, or the conductor rod230is otherwise configured (e.g., without any grooves but including another feature affecting the shear strength of conductor rod230), so as to provide the conductor rod230with a predefined and desired shear strength which is associated with the yield and working strengths of the wireline (e.g., wireline22) from which the perforating gun100(comprising rod-shaped electrical contact200) is to be deployed from.

In this exemplary embodiment, the frangible grooves238are spaced along the axial length of frangible conductor rod230between the inner end231and outer end233thereof such that any bending resistant segment between the grooves238that might hang up tool string20is relatively short (relative to the maximum length235of conductor rod230) and will less likely prove to be a long enduring catch for the tool string20. In some embodiments, a ratio of a maximum length of a given segment237formed between a pair of adjacent grooves238to the maximum length235of conductor rod230is approximately 1:2 or less. In some embodiments, the ratio of the maximum length of a given segment237formed between a pair of adjacent grooves238to the maximum length235of conductor rod230is 1:4 or less. n certain embodiments, the ratio of the maximum length of a given segment237formed between a pair of adjacent grooves238to the maximum length235of conductor rod230is 1:6 or less. Additionally, the grooves238are spaced at intervals along a majority of the axial length of conductor rod230extending fully around the circumference of the conductor rod230. However, rather than circumferential grooves as with this exemplary embodiment, the grooves may alternatively take the form of notches or other voids formed in the periphery of conductor rod230that do not extend fully around the rod230, but still create designed yield points that can be positioned on opposing sides of conductor rod230.

Each frangible groove238reduces a cross-sectional area of the frangible conductor rod230along the axial length of the frangible groove238, thereby weakening the frangible conductor rod230in shear and in bending at the location of the frangible groove238. Particularly, in this exemplary embodiment, one or more of the frangible grooves238define a minimum cross-sectional area of the frangible conductor rod230. Given that frangible grooves238are spread out across the length of frangible conductor rod230a number of stress risers or locations of reduced shear strength are correspondingly spread at generally regular intervals on outer surface234along the length of frangible conductor rod230. In some embodiments, frangible grooves238may be cut into the outer surface234of frangible conductor rod230during the manufacturing of rod230. Alternatively, grooves238as well as conductor rod230itself may be formed through other processes such as through molding or additive manufacturing processes.

While in this exemplary embodiment a relatively large number of frangible grooves238(e.g., eleven frangible grooves238) are formed in the outer surface234of frangible conductor rod230, in other embodiments, only a small number (e.g., two or three, etc.) or a single frangible groove238may be formed in outer surface234. In still other embodiments, conductor rod230may be of a single diameter that is small enough to shear or otherwise yield in response to the application of a tension force to the wireline22by wireline winch16that is less than a yield strength of the wireline22. However, generally the fewer frangible grooves238conductor rod20may have the greater the axial length of each frangible grooves238will be to ensure the conductor rod230is configured to yield at an equivalent shear or bending load. In each case, the combined axial length of the one or more frangible grooves238formed in outer surface234would comprise a significant share of the total axial length of frangible conductor rod230. For example, in some embodiments, a ratio of the combined or cumulative axial length of the one or more frangible grooves238to the maximum axial length235of conductor rod230ranges between 0.1:1 to 0.5:1; however, it may be understood that the ratio of the combined axial length of the one or more frangible grooves238and the axial length235of the frangible conductor rod230may vary in other embodiments.

As described above, the frangible grooves238of frangible conductor rod230weaken the frangible conductor rod230in shear and in bending. In other words, frangible grooves238are configured to reduce the amount of shear stress and bending force necessary to shear the rod-shaped electrical contact200into two separate pieces or bend the contact to allow the tool string to be withdrawn by the wireline22. For example, applying a sufficiently great shear stress to the rod-shaped electrical contact200will likely result in the rod-shaped electrical contact200breaking apart along one of the frangible grooves238of frangible conductor rod230. The presence of frangible grooves238therefore reduces the shear stress sufficient to result in such breaking apart of the rod-shaped electrical contact200, which may be useful in dislodging a perforating gun100which has become stuck downhole. Moreover, the degree of weakening may be predefined such that the electrical contact200itself is configured to yield in response to a predefined tension load being applied to the wireline22by wireline winch16.

As an example, and referring now toFIG.6, this Figure illustrates an exemplary instance in which perforating gun100has been detonated to form perforations18in casing string12and in which, as a result of the detonation of perforating gun100, one of the rod-shaped electrical contacts200thereof has been partially ejected through an opening109(within one of the scallops108) formed in the outer housing102of perforating gun100as a result of the detonation thereof. As shown inFIG.6, a rod-shaped electrical contact without a frangible design like that of electrical contact200would result in the perforating gun100becoming undesirably locked to the casing string12due to the contact becoming wedged against and between the opening109and the slightly offset perforation18in the casing string12.

Conversely, with the frangible design of electrical contact200shown inFIG.6(contact200is shown schematically inFIG.6), tension applied by wireline22from the surface assembly11is sufficient to cause the electrical contact200to yield by bending or potentially breaking in half, resulting in the perforating gun100being unstuck. The force applied by the wireline cable22produces a shear stress between the perforating gun100and the casing string12. Due to the reduced resistance to shear stress of the rod-shaped electrical contact200produced by frangible grooves238, the rod-shaped electrical contact200shears into multiple pieces (the shearing occurring across one of the frangible grooves238of contact200) or simply bends the electrical contact in response to the application of the wireline force. Additionally, electrical contact200may be configured to yield (e.g., bend or shear apart) in response to the application of a predefined tension force applied by the wireline22to the stuck perforating gun100. The predefined tension force may be associated with a predefined shear or bending force applied by to the stuck electrical contact200that is sufficient to cause the electrical contact200to yield. For example, electrical contact200may be configured (through the configuration of conductor rod230) to yield in response to a tension force applied to wireline22that is approximately equal to or greater than 200 lbf.

In certain embodiments, electrical contact200is configured to yield when only a portion of the reserve tension (e.g., less than 10% of the reserve tension, less than 25% of the reserve tension, less than 50% of the reserve tension, less than 75% of the reserve tension) imposable by wireline winch16is imposed on the wireline22. The “reserve tension” imposable by the wireline winch16is the tension in excess of the current tension imposed by the wireline winch16, where the current tension imposed by winch16may vary depending on the length of wireline22unspooled from the wireline winch16and extending from the wireline winch16to the tool string20positioned in wellbore13. As an example, in an embodiment in which wireline winch16has a reserve tension, in view of the configuration of the current configuration of the wireline system and position of tool string20in wellbore13, of 1,000 lbf, electrical contact200may be configured to yield at less than 200 lbf (20% of the reserve tension), less than 500 lbf (50% of the reserve tension), less than 750 lbf (75% of the reserve tension), etc.

Thus, as described above, by forming one or more frangible grooves238in the frangible conductor rod230of the rod-shaped electrical contact200, the shear strength and bend resistance of the rod-shaped electrical contact200may be reduced by a predefined, desired amount (e.g., to a desired or predefined shear strength) which the wireline22and surface assembly11are capable of applying to the rod-shaped electrical contact200in the event that the contact200should become ejected partially from perforating gun100and caught against the inner surface of casing string12.

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.