Perforating gun assembly having detonator interrupter

A detonator interrupter assembly is provided. The detonator interrupter assembly is designed to inhibit the arming of a detonator within the charge tube of a perforating gun assembly. The detonator interrupter assembly first includes a top end plate. The top end plate is configured to reside between charge tubes. The top end plate has a flange intermediate first and second ends. The detonator interrupter assembly also includes a detonator clip. The detonator clip resides proximate the second end of the top end plate. The detonator clip comprises a first slot configured to receive a detonator cord, and a second slot configured to receive a detonator tube which contains an explosive material. The detonator interrupter assembly also includes an interrupter. The interrupter comprises a handle portion and an opposing blade portion. The blade portion is configured to pass through a through-opening through the flange when an operator removes the interrupter from between the first and second slots. The blade portion is fabricated from an impact resistant material.

Not applicable.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

BACKGROUND OF THE INVENTION

Technical Field of the Invention

The present disclosure relates to the field of hydrocarbon recovery operations. More specifically, the invention relates to a perforating gun assembly used for the perforation of steel casing in a wellbore. Further still, the present disclosure relates to an end plate assembly for a perforating gun assembly, wherein the end plate receives a sliding detonator interrupter.

Discussion of the Background

For purposes of this disclosure, pending U.S. Ser. No. 17/175,651 will be referred to as “the parent application.”

In the drilling of an oil and gas well, a near-vertical wellbore is formed through the earth using a drill bit urged downwardly at a lower end of a drill string. After drilling to a predetermined depth, the drill string and bit are removed and the wellbore is lined with a string of casing. An annular area is thus formed between the string of casing and the formation penetrated by the wellbore.

A cementing operation is conducted in order to fill or “squeeze” the annular volume with cement along part or all of the length of the wellbore. The combination of cement and casing strengthens the wellbore and facilitates the zonal isolation, and subsequent completion, of hydrocarbon-producing pay zones behind the casing.

In connection with the completion of the wellbore, several strings of casing having progressively smaller outer diameters will be cemented into the wellbore. These will include a string of surface casing, one or more strings of intermediate casing, and finally a string of production casing. The process of drilling and then cementing progressively smaller strings of casing is repeated until the well has reached total depth. In some instances, the final string of casing is a liner, that is, a string of casing that is not tied back to the surface.

Within the last two decades, advances in drilling technology have enabled oil and gas operators to “kick-off” and steer wellbore trajectories from a vertical orientation to a near-horizontal orientation. The horizontal “leg” of each of these wellbores now often exceeds a length of one mile, and sometimes two or even three miles. This significantly multiplies the wellbore exposure to a target hydrocarbon-bearing formation. The horizontal leg will typically include the production casing.

The horizontal leg of the wellbore includes a heel and a toe. In order to enhance the recovery of hydrocarbons, particularly in low-permeability formations, the casing along the horizontal section undergoes a process of perforating and fracturing (or in some cases perforating and acidizing). Due to the very long lengths of new horizontal wells, the perforating and formation treatment process is typically carried out in stages.

In one method, a perforating gun assembly is pumped down towards the end of the horizontal leg at the end of a wireline.FIG.1is a side view of an illustrative perforating gun assembly100, or at least a portion of an assembly. The perforating gun assembly100comprises a string of individual perforating guns110. The perforating guns are run into a wellbore at the end of a wireline140. Each gun has sets of charges ready for detonation.

The charges associated with one of the perforating guns are detonated and perforations are “shot” into the surrounding casing (not shown). Those of ordinary skill in the art will understand that a perforating gun has explosive charges, typically shaped, hollow, or projectile charges, which are ignited to create holes in the casing (and, if present, the surrounding cement) and to pass at least a few inches and possibly several feet into the formation. The perforations create fluid communication with the surrounding formation (or pay zone) so that hydrocarbon fluids can flow into the casing.

After perforating, the operator will fracture (or otherwise stimulate) the formation through the perforations (not shown). This is done by pumping treatment fluids into the formation at a pressure above a formation parting pressure. After the fracturing operation is complete, the wireline140will be partially spooled from the surface and the perforating gun assembly100will be positioned at a new location (or “depth”) along the horizontal wellbore. A plug is set below the perforating gun assembly100using a setting tool, and new shots are fired in order to create a new set of perforations. Thereafter, treatment fluid is again pumped into the wellbore and into the formation. In this way, a second set (or “cluster”) of fractures is formed away from the wellbore.

The process of setting a plug, perforating the casing, and fracturing the formation is repeated in multiple stages until the wellbore has been completed, that is, it is ready for production. A string of production tubing (not shown) is then placed in the wellbore to provide a conduit for production fluids to flow up to the surface.

In order to provide perforations for the multiple stages without having to pull the perforating gun assembly100after every detonation, the perforating gun assembly100employs multiple guns110in series. Each perforating gun110represents various components. These typically include a “gun barrel”112which serves as an outer tubular housing. An uppermost gun barrel112is supported by the electric wireline (or “e-line”)140that extends from the surface and delivers electrical energy down to the perforating gun assembly100. Each perforating gun110also includes an explosive initiator, or “detonator” (shown in phantom at129). The detonator129is typically a small aluminum housing having a resistor inside. The detonator129receives electrical energy from the surface and through the e-line140, which heats the resistor.

The detonator129is surrounded by a sensitive explosive material such as RDX. When electrical current is run through the detonator129, a small explosion is set off by the electrically heated resistor. Stated another way, the explosive compound is ignited by the detonator129. This small explosion sets off an adjacent detonating cord (not shown). When ignited, the detonating cord initiates one or more shots, typically referred to as “shaped charges.”

Illustrative shaped charges are shown at320inFIGS.6B and6C. The shaped charges are securely held within an inner tube (shown at310inFIGS.2A,2B, and2C). Some refer to the inner tube310as a charge tube or a carrier tube. As the RDX is ignited, the detonating cord propagates an explosion down its length to each of the shaped charges320along the carrier tube310. The shaped charges then discharge shots through openings115in the selected gun barrel110.

The perforating gun assembly100may include short centralizer subs120. The assembly100also includes the carrier tubes310, which reside within the gun barrel housings112and are not visible inFIG.1. In addition, tandem subs125are used to connect the gun barrel housings112end-to-end. Each tandem sub125comprises a metal threaded connector placed between the gun barrels110. Typically, the gun barrels110will have female-by-female threaded ends while the tandem sub125has opposing male threaded ends. (A tandem sub is seen more clearly at700inFIG.7A.)

The perforating gun assembly100, with its long string of gun barrels (the housings112of the perforating guns110and the carrier tubes310), is carefully assembled at the surface and then lowered into the wellbore at the end of the e-line140. The e-line140extends upward to a control interface (not shown) located at the surface. An insulated connection member130connects the e-line140to the uppermost perforating gun110. Once the perforating gun assembly100is in place within a wellbore, an operator of the control interface sends electrical signals to the perforating gun assembly100for detonating the shaped charges320and for creating perforations in the casing.

After the casing has been perforated and at least one plug has been set, the setting tool and the perforating gun assembly100are taken out of the wellbore and a ball is dropped into the wellbore to close the plug. When the plug is closed, a fluid (e.g., water, water and sand, fracturing fluid, etc.) is pumped by a pumping system down the wellbore (typically through coiled tubing) for fracturing purposes. For a formation fracturing operation, the pump rate will create downhole pressure that is above the formation parting pressure.

As noted, the above operations may be repeated multiple times for perforating and/or fracturing the casing at multiple locations, corresponding to different stages of the well. Multiple plugs may be used for isolating the respective stages from each other during the formation fracturing stages. When all stages are completed, the plugs are drilled out and the wellbore is cleaned using a circulating tool.

A step in the wellbore perforating process is to threadedly connect the various gun barrels110using the tandem subs125. As part of this process, the conductive wires running from gun-to-gun are connected. It can be appreciated that the transporting, handling, and running-in of the gun barrels110could create a hazard to field hands if the electrical connections were made at a location away from the well site (e.g., at a shop) and the perforating guns were armed. For this reason, the approved practice is to leave the individual perforating guns110in a safe or “disarmed” state until just before the perforating guns are assembled into a string and lowered into the wellbore. In many cases, service companies will wait until the parts are delivered to the well site before assembling the string itself. This means removing the charge tubes from the gun barrel housings and then connecting conductor wires.

Those of ordinary skill in the art will appreciate that well sites are not conducive to the manipulation and assembly of small components. In many instances, wells are drilled in remote locations and in harsh weather conditions, including extreme cold and/or wind. This makes the process of assembling and arming perforating guns at the well site a delicate and potentially hazardous operation. Accordingly, it is desirable to make the connections at the shop or field office and limit the electrical connections required to be made in the field.

Accordingly, a need exists for a perforating gun assembly that utilizes a sliding detonator interrupter that can be easily accessed by field technicians at the well site in order to arm a pre-assembled gun string. A need further exists for a detonation system wherein the detonator interrupter passes through an end plate that serves to isolate electronic components in each perforating gun from the pressure wave created during downstream detonation steps. A need further exists for such an end plate that supports a bulkhead and pre-wired signal contact pin.

SUMMARY OF THE INVENTION

A detonator interrupter assembly is first provided. The detonator interrupter assembly is designed to inhibit the ignition, or arming, of a detonator within the charge tube of a perforating gun assembly.

In one aspect, the detonator interrupter assembly first includes a top end plate. The top end plate is a steel plate configured to reside between charge tubes of the perforating gun assembly. The top end plate has a first end, a second end opposite the first end, and a flange intermediate the first and second ends. A through-opening extends through the flange.

The first end of the top end plate comprises a tubular opening. The tubular opening is configured to receive a contact pin for a perforating gun. The contact pin has a contact head at an upstream end.

The detonator interrupter assembly also includes a detonator clip. The detonator clip resides proximate the second (or downstream) end of the top end plate. The detonator clip comprises a first slot configured to receive a detonator cord, and a second adjacent slot configured to receive a detonator tube. The detonator tube contains an explosive material.

The detonator interrupter assembly also includes an elongated interrupter. The elongated interrupter comprises a handle portion at a first end, and a blade portion at a second end. The handle portion resides proximate the first (or upstream) end of the top end plate, while the blade portion resides proximate the second (or downstream) end of the top end plate.

In a preferred embodiment, the detonator clip is fabricated from a polymeric material. The first slot and the second slot are biased inwards towards each other. The blade portion is placed between the first slot and the second slot. The blade portion is fabricated from an impact resistant material (such as steel) to inhibit explosive impact between the detonator cord and the detonator while the blade portion remains between the first and second slots.

The blade portion is configured to pass through the through-opening extending through the flange. An operator will remove the interrupter from between the first slot and the second slot at the well site by pulling on the handle portion of the elongated interrupter.

In one aspect, the detonator clip comprises a pair of wings. A first wing resides adjacent the first slot, and a second wing resides adjacent the second slot. At the same time, the charge tube comprises a window. The first wing and second wing snap into opposing sides of the window.

In one arrangement, the first end of the top end plate comprises a tubular opening. The tubular opening is configured to receive a bulkhead. The bulkhead, in turn, receives a contact pin for a perforating gun. The contact pin has an upstream end and a downstream end. The upstream end of the contact pin extends into a tandem sub for a perforating gun. In this arrangement, the handle portion of the elongated interrupter is adjacent to and runs parallel with the bulkhead.

A method of arming a perforating gun assembly is also provided. In one aspect, the method first comprises providing a charge tube. The charge tube has at least one shaped charge. In addition, the charge tube holds a detonator containing an explosive material, and a detonator cord.

The method also includes providing a detonator clip. The detonator clip comprises a first slot holding a portion of the detonator cord, and a second slot adjacent to the first slot holding the detonator.

The method next includes abutting the charge tube against a top end plate. The top end plate comprises a first end, a second end opposite the first end, and a flange intermediate the first and second ends. In addition, the top end plate has a through-opening extending through a flange.

The method further comprises providing a detonator interrupter. The detonator interrupter is an elongated object that comprises a handle portion and a blade portion.

The method additionally includes sliding the blade portion of the detonator interrupter through the through-opening of the flange in the top end plate. The blade portion is further moved into a position between the first slot and the second slot. This serves to inhibit explosive transfer between the detonator and the detonator cord.

In the method, the first slot and the second slot are biased inwards towards each other. The blade portion is fabricated from an impact resistant material to inhibit explosive energy transfer between the detonator and the detonator cord while the blade portion remains between the first and second slots. In addition, the blade portion is configured to pass back through the through-opening extending through the flange when an operator removes the detonator interrupter from between the first slot and the second slot.

The charge tube and the detonator interrupter are part of a perforating gun assembly. Of course, the perforating gun assembly will include other components such as an addressable switch, a switch housing, and a detonator wire that places the detonator and the addressable switch in electrical communication.

The charge tube abuts the top end plate at the first (or upstream) end of the top end plate. The first end of the top end plate comprises a tubular opening that holds a contact pin. The method then further comprises placing the contact pin in the tubular opening. The contact pin is configured to transmit detonation signals from the surface to the perforating gun assembly.

In a preferred arrangement, the charge tube comprises a window. At the same time, the detonator clip comprises a pair of wings. The method comprises snapping the first wing into a first side of the window, and the second wing into a second side of the window, thereby securing the detonator clip adjacent the upstream end of the top end plate.

The method may further comprise:placing a signal line in electrical communication with the contact pin;placing the detonator in electrical communication with an addressable switch; anddelivering the perforating gun assembly to a well site.

In addition, the method may further comprise:after arrival at the well site, pulling the handle portion of the detonator interrupter from the through-opening of the top end plate, thereby withdrawing the blade portion from between the first slot and the second slot; andsliding an upstream gun barrel housing over the charge tube upstream from the top end plate.

In addition, the method may further comprise:abutting a downstream charge tube to the top end plate at the second end;sliding a downstream gun barrel housing over the downstream charge tube;threadedly connecting the upstream and downstream gun barrel housings to respective opposing ends of a tandem sub, thereby forming the perforating gun assembly; andrunning the perforating gun assembly into a wellbore at the well site, at the end of an electric line, after the detonator interrupter has been withdrawn from the detonator clip.

The method may further comprise sending a detonation signal from a surface, into a wellbore, and down the electric line. The method also includes further sending the detonation signal through a perforating gun and through the signal transmission pin. From there, the method includes further sending the detonation signal to the addressable switch, wherein the addressable switch determines whether the detonation signal is addressed to the perforating gun. The addressable switch resides within a tandem sub below the perforating gun.

The method additionally comprises identifying that the detonation signal is addressed to the perforating gun. In response, the addressable switch sends a detonation signal to a detonator pin and back through the carrier end plate. The method then includes sending the detonation signal to a detonator to initiate explosive charges residing within the perforating gun. Note that the carrier end plate isolates the addressable switch from wellbore fluids and a pressure wave generated in response to the detonation of the explosive charges.

DEFINITIONS

For purposes of the present application, it will be understood that the term “hydrocarbon” refers to an organic compound that includes primarily, if not exclusively, the elements hydrogen and carbon. Hydrocarbons may also include other elements, such as, but not limited to, halogens, metallic elements, nitrogen, carbon dioxide, and/or sulfuric components such as hydrogen sulfide.

As used herein, the terms “produced fluids,” “reservoir fluids” and “production fluids” refer to liquids and/or gases removed from a subsurface formation, including, for example, an organic-rich rock formation. Produced fluids may include both hydrocarbon fluids and non-hydrocarbon fluids. Production fluids may include, but are not limited to, oil, natural gas, pyrolyzed shale oil, synthesis gas, a pyrolysis product of coal, nitrogen, carbon dioxide, hydrogen sulfide, and water.

As used herein, the term “wellbore fluids” includes, produced fluids, but may also include drilling mud, fracturing fluids, or other fluids used in connection with the drilling and completion of a well.

As used herein, the term “fluid” refers to gases, liquids, and combinations of gases and liquids, as well as to combinations of gases and solids, combinations of liquids and solids, and combinations of gases, liquids, and solids.

As used herein, the term “subsurface” refers to geologic strata occurring below the earth's surface.

As used herein, the term “formation” refers to any definable subsurface region regardless of size. The formation may contain one or more hydrocarbon-containing layers, one or more non-hydrocarbon containing layers, an overburden, and/or an underburden of any geologic formation. A formation can refer to a single set of related geologic strata of a specific rock type, or to a set of geologic strata of different rock types that contribute to or are encountered in, for example, without limitation, (i) the creation, generation, and/or entrapment of hydrocarbons, and (ii) the execution of processes used to extract hydrocarbon fluids from the subsurface region.

As used herein, the term “wellbore” refers to a hole in the subsurface made by drilling or insertion of a conduit into the subsurface. A wellbore may have a substantially circular cross-section, or other cross-sectional shape. The term “well,” when referring to an opening in the formation, may be used interchangeably with the term “wellbore.”

Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the present disclosure; instead, the scope of the invention is defined by the appended claims.

The following embodiments are discussed, for simplicity, with regard to attaching two perforating guns to each other through a tandem sub. In the following, the terms “upstream” and “downstream” are being used to indicate that one gun barrel of a perforating gun may be situated above and one below, respectively, within a wellbore. However, one skilled in the art would understand that the present disclosure is not limited only to the upstream gun or only to the downstream gun, but in fact can be applied to either gun. In other words, the terms “upstream” and “downstream” are not necessarily used in a restrictive manner, but only to indicate, in a specific embodiment, the relative positions of perforating guns or other components.

FIG.2Ais a perspective view of an illustrative carrier tube300for a perforating gun110. The carrier tube300defines an elongated tubular body310having a first end302and a second end304opposite the first end302. The tubular body310has an inner bore305dimensioned to receive charges (seen at320inFIGS.6A through6D, and elsewhere). Openings312are provided for receiving the charges320and enabling the charges320to penetrate a surrounding casing string (not shown) upon detonation.

A pair of end plates have been connected to opposing ends302,304of the carrier tube300, forming a part of a perforating gun assembly400. These represent a top end plate420connected at end302, and a bottom end plate430connected at the bottom end304. The end plates420,430have mechanically enclosed the top302and bottom304ends of the tubular body310, respectively. Beneficially, the end plates420,430help center the carrier tube300and its charges320within the outer gun barrel (shown at510inFIGS.6A and6B). For this reason, the end plates420,430may be referred to as “carrier plates.”

It is understood that each opening312along the carrier tube body310will receive and accommodate a separate shaped charge320. Each shaped charge320, in turn, is designed to detonate in response to an explosive signal passed through a detonating cord. An electronic detonator (shown at229inFIG.8A) and a detonating cord (shown at329inFIGS.6C and7B) reside inside the carrier tube300. The carrier tube300is intended to be illustrative of any standard carrier tube, so long as the gun provides a detonator and detonating cord internal to the carrier tube300.

A signal transmission line410is seen extending down from the contact pin470and through the bore305of the elongated tubular body310. The signal transmission line410connects to a signal transmission pin720′ that extends through the bottom end plate430. A signal carried by the signal transmission line410is transmitted to a downstream perforating gun through the signal transmission pin720′ and a next signal transmission line410.

The bottom end plate430has a closed end surface435. Three pins are shown extending out of the closed end surface435. These represent a ground pin710and two electrical pins720′,720″. In one aspect, the ground pin710connects to the bottom end plate430as an electrical ground, while electrical pins720′,720″ connect to white and green wires, respectively. Electrical pin720′ serves as a signal transmission pin while electrical pin720″ serves as a detonator pin.

Note that the ground pin710does not extend through the end plate430but simply extends from the end surface435. In contrast, signal transmission pin720′ and detonator pin720″ do extend through the end plate430. Preferably, signal transmission pin720′ and detonator pin720″ are part of bridged mini-bulkheads as described in U.S. Ser. No. 17/547,016 referenced above and referred to at610and620. (See, e.g., FIGS. 6A and 6B of U.S. Ser. No. 17/547,016.)

FIG.2Bis a first side view of the carrier tube300ofFIG.2A.FIG.2Cis a second side view of the carrier tube300ofFIG.2A, rotated 90° relative to the view ofFIG.2B. In each instance, the charges320have been removed, leaving the signal transmission line410visible. The signal transmission line410feeds into a first end of a bulkhead associated with (and securely connected to) a first end of the signal transmission pin720′. In a similar way, a detonator wire540feeds into a first end of a bulkhead associated with (and securely connected to) a first end of the detonator pin720″.

Of interest, a second end of the signal transmission pin720′ extends out from the end surface435of the bottom end plate430. Also, a second end of the detonator pin720″ extends out from the end surface435of the bottom end plate430. Each of these second ends represents a banana clip808to facilitate an electrical connection.

Pins720′ and720″ reside within separate bulkheads. Because the pins720′ and720″ and their associated bulkheads are small (certainly smaller than bulkhead475ofFIGS.2A-2C), the bulkheads may be referred to as “mini-bulkheads.” In U.S. Ser. No. 17/547,016, a unique “bridged” bulkhead assembly (shown at FIGS. 6A and 6B of U.S. Ser. No. 17/547,016) is provided. The bridged bulkhead assembly provides an efficient way to install pre-wired pins into the carrier end plate430for field-connection with the addressable switch (shown at 760 in the '016 parent application).

A portion of the bridged bulkhead assembly can be seen at600inFIG.2C. The signal transmission line410extending from the bridged bulkhead assembly600feeds signals in a downstream direction. At the same time, wire540is an illustrative detonator wire, sending detonation signals from an addressable switch to a detonator in an upstream direction.

Preferably, the bottom end plate430includes compliant tabs. The tabs are seen partially at425inFIG.2A. The compliant tabs425are configured to mate with slots325in the elongated tubular body310at end304. This ensures a proper orientation of the pins720′,720″. Once the mini-bulkheads are installed, the compliant tabs425engage with slots325, and the mini-bulkheads are unable to back out of the end plate430. This removes the need for retainer nuts or other retention parts.

In the arrangement ofFIGS.2A through2C, the tubular body310and associated gun barrel housing112are downstream from the contact pin470. However, it is understood that a separate carrier tube and gun barrel housing reside upstream from the contact pin470. Similarly, separate carrier tubes310and gun barrel housings112reside downstream from the pins710,720′,720″, forming what may be a long series of perforating guns in a gun barrel string.

FIG.3Ais a perspective view of the top end plate420ofFIG.2A, in one embodiment. The top end plate420has a proximal end424and a distal end422. Intermediate the proximal424and distal422ends is a flange426. The upstream end302of a charge tube300shoulders out against the downstream end of the flange426. At the same time, and as shown inFIG.10Aof the parent application, the flange426receives the upstream end of a gun barrel housing.

The distal end422of the top end plate420comprises a threaded opening421. The threaded opening421is configured to receive a bolt or pin (shown at423inFIGS.2B and2C). The pin423radially fixes the top end plate420to the top of the carrier tube300.

FIG.3Bis a perspective view of the bottom end plate430that is part of the perforating gun assembly400, in one embodiment. The bottom end plate430seats against the upstream end of the tandem sub700(seen inFIG.7A). Note the radial shoulder702of the tandem sub700that serves as a stop member for opposing gun barrel housings112. The bottom end plate430has a proximal end432and a distal end434. Intermediate the proximal432and distal434ends is a flange436.

At the proximal end432of the end plate430are two openings442,444. One of the openings442is dimensioned to receive the detonator pin720″ and the corresponding mini-bulkhead. The other opening444receives the signal transmission pin720′ and its own corresponding mini-bulkhead. As noted, the transmission pin720′ and the detonator pin720″ extend through the bottom end plate430and into a switch housing (shown at 750 in FIG. 10A of the parent application).

The bottom end plate430is slidably connected to the elongated tubular body310of the carrier tube300at end304. A bolt (shown at 810 in FIG. 5A of the parent application) threadedly connects a proximal end432of the carrier end plate430to the lower end304of the carrier tube300. At the same time, the flange436is received in the lowermost end of the gun barrel housing510. The flange436also receives a bolt820.

Flange members436,426associated with the bottom end plate430and the top end plate420, respectively, abut opposing ends of the tandem sub700. Beneficially, the end plates430,420mechanically seal the tandem sub700, protecting the addressable switch from wellbore fluids and debris generated during detonation of the charges320.

During assembly, the signal transmission line410is crimped to a bullet terminal, and the bullet terminal is then connected to the brass signal transmission pin720′. Similarly, the detonator wire540is crimped to a bullet terminal, and the bullet terminal is then connected to the brass detonator pin720″. Over-molding then takes place. The result is that a seamless connection is created, and the “gun shop” is no longer required to connect the terminal and wire to the bulkhead or add insulator boots. This also provides a more secure connection between the components.

The signal transmission pin720′ transmits detonation signals through the end plate430in a first direction. At the same time, the detonator pin720″ transmits the detonation signals back up through the end plate430in a second direction opposite the first direction. Preferably, the first direction is downstream while the second direction is upstream.

FIG.4Ais a side, cross-sectional view of the bulkhead475ofFIG.2A. The contact pin470resides within the non-conductive bulkhead475. The contact pin470is shown in phantom. A first (or proximal) end of the contact pin470extends into the switch housing of the assembly (shown at750inFIG.6C), while a second (or distal) end of the contact pin470extends into the top end plate420. The contact pin470is used to transmit signals through the tandem sub700down to a next perforating gun, while the bulkhead475provides electrical insulation between the conductive contact pin470and the surrounding metal tandem sub700. In a preferred embodiment, the contact pin470comprises an electrically conductive material, for example, brass.

FIG.4Bis a perspective view of the contact pin470and bulkhead475. It can be seen that the bulkhead475defines a generally tubular body810. The tubular body810has an upstream end802and a downstream end804. O-rings850are provided to ensure a seal relative to the surrounding tandem sub700.

Of interest, the downstream end804includes an extended end piece830. The end piece830offers a tip835that is over-molded onto the signal transmission line410. The extended tip825secures the signal transmission line410, preventing the signal transmission line410from becoming separated from the contact pin470during run-in and operation. Preferably, the signal transmission line410is crimped before over-molding to properly secure the signal transmission line410to the contact pin470and prevent movement during the over-molding process. An opposite end of the contact pin470defines a banana clip808. The banana clip808resides within or at least extends well into the tandem sub700.

As discussed above, it is desirable to transport an assembled (or substantially assembled) perforating gun assembly to a well site without the possibility one of the shaped charges320detonating. To address this issue, a novel detonator interrupter assembly is provided herein.

FIG.5Ais a side view of a detonator interrupter assembly500of the present disclosure, in one embodiment. The detonator interrupter assembly500is designed to prohibit explosive energy transfer between the detonator (seen at229inFIG.8A) and an explosive detonation cord (shown at329inFIGS.6C and7B) within a charge tube310. This, in turn, prevents a gun barrel from “going off” (i.e., detonating) prematurely when the electrical wiring is in place.

FIG.5Bis a side view of the detonator interrupter assembly500ofFIG.5A.FIG.5Cis a cross-sectional view of the detonator interrupter assembly500ofFIG.5A.FIG.5Dis a first perspective view of the detonator interrupter assembly500ofFIG.5A.FIG.5Eis a second perspective view of the detonator interrupter assembly500ofFIG.5A. The detonator interrupter assembly500will be described with reference toFIGS.5A through5E, together.

The detonator interrupter assembly500first includes an end plate. In the arrangement ofFIGS.5A through5E, the end plate is a top end plate. The top end plate sits at an upstream end of a charge tube300. The end plate may be, for example, the top end plate420provided inFIG.3A. More preferably, the end plate420is modified to include an opening that receives a sliding detonator interrupter502.).

The proximal (or upstream) end424of the end plate420receives the bulkhead475ofFIG.4B. The bulkhead475, in turn, holds the contact pin470. The distal end (or contact head)472of the contact pin470is visible in these views.

The detonator interrupter assembly500also comprises a detonator clip520. The detonator clip520comprises a thermoplastically molded piece having two slots522,524. A first slot522holds an explosive detonator229, while a second slot524holds the proximal end of a detonator cord329. Both the detonator229and the detonator cord329reside within the tubular body310of the charge tube300. The detonator cord329carries an explosive material from the detonator229to each of the shaped charges320.

The detonator interrupter assembly500also includes the detonator interrupter502. The detonator interrupter502represents an elongated tool that slides through the flange426of the top end plate420. The detonator interrupter502has a proximal end501that represents a handle portion. Of interest, the handle portion501resides adjacent the bulkhead475and contact pin470. The detonator interrupter502also has a distal end that comprises a thin blade, or blade portion503.

In one aspect, the handle portion501is fabricated from a plastic material that has been injection molded. The handle portion501may be about 3 inches in length. At the same time, the blade portion503is fabricated from steel or other more inflexible material. The blade portion503may also be about 3 inches in length. The blade portion503is mechanically connected to the handle portion501.

With specific reference toFIGS.5B and5C, it can be seen that the blade portion503of the detonator interrupter502has been slidably received between the slots522,524of the detonator clip520. The thermoplastically formed material of the detonator clip520is fabricated such that the two slots522,524are biased inward towards each other. In this way, the blade portion503is pinched between the slots522,524, and held in place during transport. This may be referred to as the “run-in” position.

It is noted inFIG.5Ethat the detonator clip520comprises a pair of opposing wings527. One wing527resides proximate slot522, while the other wing527resides proximate slot524. The wings527are designed to plug, snap, or otherwise removably couple into an opening, or window535, formed within the tubular body310of the charge tube300.

FIG.6Ais a first cross-sectional view of a portion of a perforating gun assembly400, in one embodiment. The perforating gun assembly400ofFIG.6Ais intended to duplicate the perforating gun assembly400ofFIGS.2A through2C. In this arrangement, the perforating gun assembly400includes the detonator interrupter assembly500ofFIGS.5A through5E.

FIG.6Bis an enlarged, cross-sectional view of a portion of the perforating gun assembly400ofFIG.6A.FIG.6Cis a cutaway view of a portion of the perforating gun assembly400.FIG.6Dis another cutaway view of a portion of the perforating gun assembly400. Each assembly400ofFIGS.6B,6C and6Dhas the detonator interrupter assembly500ofFIGS.5A and5E. The perforating gun assembly400will be further described with reference toFIGS.6A through6Dtogether.

It is first seen that the perforating gun assembly400includes the top end plate420and the bottom end plate430. The charge tube300resides between the top end plate420and the bottom end plate430. The perforating gun assembly400also includes the outer gun barrel510. The outer gun barrel510passes over each of the top420and bottom430end plates, serving as a housing. Of interest, the top end plate420and the bottom end plate430keep the charge tube300in a concentric state within the outer gun barrel510.

The outer gun barrel510has an upstream end512and a downstream end514. The upstream end512passes over the top end plate420, while the downstream end514encapsulates the bottom end plate430. The upstream end512of the perforating gun assembly400has a thread protector530. The thread protector530is screwed onto the threads of the outer gun barrel510at the upstream end512. The thread protector530will be removed once the perforating gun assembly400is delivered to the well site. The thread protector530not only protects the threads, but also protects the run-in position of the detonator interrupter502.

As noted above, a window535is provided along the gun barrel510. The window535exposes a detonator cord329and an adjacent detonator229. A non-explosive detonating cord seal229′ is also visible. Also seen along the outer gun barrel510is a single shaped charge320. It is understood that the perforating gun assembly400may, and likely will, have several shaped charges320along its length.

At the downstream end514of the outer gun barrel510is a tandem sub700. The tandem sub700represents a small, tubular body that houses electronics for the perforating gun assembly400. The electronics include a switch housing750. Residing within the switch housing750is an addressable switch. The addressable switch is seen at 760 of FIG. 10A in the parent patent application.

Also shown is the bulkhead475. The bulkhead475extends out from the top end plate420in an upstream direction. As noted in connection withFIGS.4A and4B, the bulkhead475holds the contact pin470. The contact pin470includes a contact head472that connects to the signal transmission line410. A banana clip808facilitates the electrical connection between the contact pin470and the signal transmission line410.

Running adjacent to the bulkhead475is the detonator interrupter502. The proximal end of the detonator interrupter502serves as the handle portion501, while the distal end of the detonator interrupter502serves as the blade portion503. In the views ofFIGS.6A through6D, the detonator interrupter502is in its run-in position. Manually pulling the detonator interrupter502will remove the blade portion503from between the slots522,524, allowing energy (or, more accurately, explosive) transfer between the detonator229and the detonator cord329.

FIG.7Ais a perspective view of a portion of the perforating gun assembly400ofFIGS.6A through6D. Here, the tandem sub700is prominently seen. Note that in operation, the tandem sub700is at the downstream end of the charges320and contact pin470. Thus, the view is “backwards” for illustrative purposes. (FIG.6Cshows the correct orientation, recognizing that in oil patch parlance the left side of a wellbore or a tool is the upstream side.)

FIG.7Bis a perspective view of the detonator interrupter assembly500used in the perforating gun assembly400ofFIG.7A. Here, the charge tube300and connected tandem sub700have been removed for illustrative purposes. The detonator cord329is seen extending from one of the slots of the detonator clip522(shown inFIGS.5E,10A, and10B).

FIG.7Cis a first cutaway view of a portion of the perforating gun assembly400ofFIGS.6A through6D. The detonator interrupter assembly500ofFIGS.5A through5Dis also seen.

FIG.7Dis a second cutaway view of a portion of the perforating gun assembly400ofFIGS.6A through6D. The detonator interrupter assembly500ofFIGS.5A through5Dis again seen. The handle portion501of the detonator interrupter502is prominently seen.

FIG.8Ais a first cutaway view of a portion of the perforating gun assembly400ofFIGS.6A through6D. The detonator interrupter assembly500ofFIGS.5A through5Dis again seen.

FIG.8Bis a second cutaway view of a portion of the perforating gun assembly400ofFIGS.6A through6D. The detonator interrupter assembly500ofFIGS.5A through5Dis again seen. The blade portion503of the detonator interrupter502can be seen extending out of the detonator clip520.

FIG.8Cis a third cutaway view of a portion of the perforating gun assembly400ofFIGS.6A through6D. The detonator interrupter assembly500ofFIGS.5A through5Dis again seen. The relative position of the bulkhead475and the handle portion501is well-visible.

FIG.9is a perspective view of the gun barrel housing510of the perforating gun assembly400ofFIG.8A. The handle portion501of the detonator interrupter502is visible.

FIG.10Ais a first perspective view of a detonator clip520as may be used with the detonator interrupter assembly500of the present invention, in one embodiment.

FIG.10Bis a second perspective view of the detonator clip520ofFIG.10A.

In operation, a plurality of perforating guns are assembled at a manufacturing facility or field office. The process for assembling each individual gun includes;placing the addressable switch760within the switch housing750;securing the switch housing750(with the addressable switch760) within a tandem sub700;connecting the signal transmission line410to the signal transmission pin720′;electrically connecting the signal transmission pin720′ to the addressable switch (shown at 760 in FIG. 10A of the parent application);electrically connecting the addressable switch760to the detonator pin720″;electrically connecting the detonator pin720″ to the detonator229using detonator wire (shown at 540 in FIG. 10A in the parent application);placing the detonator229into slot522of the detonator clip520;placing the detonator cord329into slot524of the detonator clip520;securing the detonator clip520along the tubular body310of a charge tube300;electrically connecting the signal transmission pin720′ to the contact head472;sliding the detonator interrupter502through the opening of the top end plate420such that the blade portion503of the detonator interrupter502is moved between slots522,524in the detonator clip520.mechanically connecting an upstream charge tube300to a bottom end plate430(or abutting the upstream charge tube to the bottom end plate430) at the upstream end of the bottom end plate430; andmechanically connecting a downstream charge tube300to a top end plate420(or abutting the downstream charge tube to the top end plate420and then securing using a bolt) at the downstream end of the top end plate420.

When it is time to conduct wireline perforating operations, multiple assembled perforating guns are delivered to a well site. Thereafter, threaded connections are made of the pre-assembled perforating guns to form an elongated perforating gun string200.

Before the perforating gun string200is run into the wellbore, the operator will access the windows535provided in the charge tubes300in order to remove the various detonator interrupters502. The operator will manually access the handle portions501of the detonator interrupters502, and then pull the handle portions501to remove the blade portions503from the detonator clips520. The operator will also remove the thread protectors530. Thereafter, the following steps are taken:sliding the gun barrel housings510over the upstream and downstream charge tube bodies310;threadedly connecting the gun barrel housings510to respective opposing ends of the tandem sub700to form the elongated perforating gun string200(note that an upstream end of the tandem sub700abuts a downstream end of a bottom end plate430(shown inFIG.6C) while the downstream end of the tandem sub700abuts an upstream end of a top end plate420(shown in FIG. 10A of the parent application)); andrun the perforating gun string into the wellbore at the end of an electric line240.

Once the perforating gun string200has been pumped down to the desired depth within the wellbore, a detonation signal is sent from the surface through the electric line240. The signal reaches the perforating gun assembly400(including multiple perforating guns as shown inFIG.2). Typically, a lowest perforating gun is designated for first explosive initiation. In that case, the signal passes along the internal signal transmission line410through each perforating gun210and is then passed along by the applicant's novel transmission pins720′, the addressable switch760in each tandem sub700, and the contact pins470until the signal reaches a lowest tandem sub700and its respective addressable switch760. The addressable switch760then sends a detonation signal back up through the detonator pin720″, through a short detonator wire540, and to the detonator229in the lowest charge tube300.

In connection with the detonator interrupter assembly500, and as described in much greater detail in prior applications, to which the current application claims the benefit, a novel detonation system may be employed. The detonation system provides protection for the electronics within the tandem sub700during detonation of an upstream (or adjacent) perforating gun. In other words, an upstream perforating gun may be activated without damaging the electronic switch assembly in the tandem sub700. The addressable switch assembly760may be reused for another perforation operation. Similarly, the contact pin470, the so-called “big” bulkhead475, and the tandem sub700itself are also protected for later re-use in downhole operations.

In one embodiment, the detonation system first includes the tandem sub700. The tandem sub700defines a generally tubular body having a first end and a second end. The first end and the second end each comprise male connectors. This allows the tandem sub700to be threadedly connected, in series, to respective perforating gun barrels500. Thus, the first end is threadedly connected to a first perforating gun (or, more precisely, a female threaded end of a gun barrel), while the second end is threadedly connected to a second perforating gun (or, again, a female threaded end of an opposing gun barrel).

The first (or upstream) end of the tandem sub700abuts a first (or bottom) end plate. Similarly, the second opposing (downstream) end of the tandem sub abuts a second (or top) end plate. These may be in accordance with the bottom430and top420carrier end plates described above. The result is that the bottom and top end plates straddle the tandem sub700.

An inner bore is formed between the first end and the second end of the tandem sub. An electronic switch housing resides within the inner bore at the first end of the tandem sub. The switch housing holds an addressable switch configured to receive instruction signals from an operator at the surface.

In addition, a receptacle is formed within the inner bore of the tandem sub. The receptacle is dimensioned to closely receive a so-called “big bulkhead.” The big bulkhead, shown at475, comprises:a tubular body having a first end, a second end, and a bore extending there between;an electrical contact pin470having a shaft extending through the bore of the bulkhead body and having an upstream end and a downstream end, wherein the shaft resides within the bore, and wherein the electrical contact pin transmits current from the upstream end to the downstream end; anda contact head472located at the upstream end of the electrical contact pin470outside of the bulkhead body and extending into the switch housing.

The electrical contact pin470and its contact head472are fabricated substantially from a conductive material such as brass. Of interest, the bulkhead is over-molded over a wire that exits the downstream end of the bulkhead.

The bottom end plate430comprises a bore that defines a first opening and a second opening. A signal transmission line720′ extends through the first opening and into the carrier tube300. Instruction signals are sent through the signal transmission pin720′. A separate detonator pin720″ extends through the second opening and into the carrier tube300. The detonator pin720″ is in electrical communication with a detonator229residing within the first perforating gun. The detonator229is configured to receive activation signals from the addressable switch and ignite an explosive material within a detonating cord329.

The signal transmission line410is connected to the signal transmission pin720′ at the first end of the first bulkhead610. At the same time, a detonator wire540is connected to the detonator pin720″ at the first end of the second bulkhead620. This may be in accordance with the bulkhead assembly600ofFIGS.6A and6Bof the parent application, which uses over-molding to protect the wire connections.

The second end of the signal transmission pin720′ extends from the second end of the first bulkhead610and down to a banana clip618. The banana clip618of the signal transmission pin720′ is in electrical communication with the addressable switch760. Similarly, the second end of the detonator pin720″ extends from the second end of the second bulkhead620and also comprises a banana clip628. Note that the detonator pin720″ is never in electrical communication with the signal transmission line410or the signal transmission pin720′.

All electrical connections for the detonation system described herein may be made at the gun building facility, including the wires connecting the detonator and the addressable switch. The end plate on the gun barrel (or gun carrier) is removed, and the pre-wired electronic switch assembly (that is, the switch housing750and encapsulated addressable switch760) is installed. Beneficially, the bulkheads for the two electrical signal pins720′,720″ associated with the bottom end plate430are pre-installed over bulkheads610,620associated with the pins720′,720″ together as part of a novel bridged bulkhead600.

Using the novel detonator interrupter assembly500with the blade portion503residing within a detonator clip520, the detonator229may be installed before the perforating gun assembly400is sent out. In other words, the detonator229may be installed in the shop and still comply with DOT and ATF regulations and API-RP67 recommendations. The detonator interrupter502is slid through an opening427of the top end plate420such that the blade portion503of the detonator interrupter502is moved between slots522,524in the detonator clip520.

The bottom end plate430is slid against the upstream end402of the tandem sub700. The pre-wired switch assembly can be tested at the gun building facility to reduce the chance of a mis-wired or faulty connection.

In addition to the explosive initiation assembly discussed above, a method of arming a perforating gun assembly is also provided. The method is demonstrated in the flow chart ofFIGS.11A and11B, together, and described in steps for a method1100.

In one aspect, the method1100first comprises providing a charge tube. This is seen at Box1105. The charge tube has at least one shaped charge. In addition, the charge tube holds a detonator containing an explosive material, and a detonator cord. In the method1100, the charge tube is an upstream charge tube.

The method1100also includes providing a detonator clip. This is shown at Box1110. The detonator clip comprises a first slot holding a portion of the detonator cord, and a second slot holding the detonator. The first and second slots are adjacent to one another. The clip is fabricated from a non-conductive, elastic material that allows the first and second slots to be biased inwards towards each other.

The method1100next includes abutting the charge tube against a top end plate. This step is provided at Box1115. The top end plate comprises a first end, a second end opposite the first end, and a flange intermediate the first and second ends. In addition, the top end plate has a through-opening extending through the flange. The charge tube is abutted against the flange on the downstream side (second end) of the top end plate. For this reason, the charge tube may be referred to as a downstream charge tube.

The method1100further comprises providing a detonator interrupter. This is indicated at Box1120. The detonator interrupter is an elongated object that comprises a handle portion and a blade portion.

In a preferred arrangement, the downstream charge tube comprises a window. At the same time, the detonator clip comprises a pair of wings. The method1100may comprise snapping (or otherwise removably coupling) the first wing into a first side of the window, and the second wing into a second side of the window. This serves to secure the detonator clip adjacent the upstream end of the charge tube.

The method1100additionally includes sliding the blade portion through the through-opening of the top end plate. This is seen at Box1125. The blade portion is further moved into a position between the first slot and the second slot of the detonator interrupter. This is shown at Box1130. This separation of the first and second slots serves to inhibit explosive transfer between the detonator cord and the detonator.

As noted, in the method1100the first slot and the second slot are biased towards each other. The blade portion is fabricated from an impact resistant material to inhibit explosive initiation between the detonator and the detonator cord while the blade portion remains between the first and second slots. In addition, the blade portion is configured to pass through the through-opening extending through the flange when an operator removes the interrupter from between the first slot and the second slot.

The charge tube and the detonator interrupter are part of a perforating gun assembly. The perforating gun assembly will include other components such as an addressable switch, a switch housing, and a detonator wire that places the detonator and the addressable switch in electrical communication. The addressable switch and the switch housing reside within a tandem sub upstream from the top end plate.

A separate upstream charge tube abuts the top end plate at the first (or upstream) end of the top end plate. The upstream (or first) end of the top end plate comprises a tubular opening that holds a bulkhead and a contact pin. The contact pin transmits detonation signals through the top end plate and into the downstream charge tube. Of interest, the handle portion501of the detonator interrupter502runs alongside the bulkhead475. The method1100may further comprise placing the contact pin in the tubular opening, and placing a signal line in electrical communication with the contact pin.

The method may further comprise:placing the detonator in electrical communication with the addressable switch (Box1135) in the tandem sub;abutting the downstream charge tube to the top end plate at the second (or downstream) end of the top end plate (Box1140);sliding a gun barrel housing over the downstream charge tube (Box1150); anddelivering the perforating gun assembly to a well site (Box1155).

After arrival at the well site, the method1100further comprises pulling the handle portion of the detonator interrupter from the through-opening of the top end plate. This is indicated at Box1160. The step of Box1160results in withdrawing the blade portion from between the first slot and the second slot. Because the first and second slots are biased inward towards each other, this results in the slots contacting one another.

The method1100also includes sliding a gun barrel housing over an upstream charge tube. This is seen at Box1165. In this case, upstream means upstream from the top end plate.

In addition, the method1100may further comprise:threadedly connecting the upstream and downstream gun barrel housings to respective opposing ends of the tandem sub, thereby forming a perforating gun assembly (Box1170); andrunning the perforating gun assembly into a wellbore at the well site, at the end of an electric line (Box1175).

The perforating gun utilizes an addressable switch. The addressable switch is configured to monitor instruction signals received through the signal line and the signal transmission pin. Stated another way, the addressable switch filters instruction signals from the operator at the surface. Thus, the method1100further includes sending the detonation signal through a perforating gun and into the signal transmission pin extending through the top end plate. This is indicated at Box1180.

When an addressable switch receives a signal associated with its tandem sub and perforating gun, the switch is armed and a window of time is opened (typically about 30 seconds) in which to send a detonation signal from the surface. This is provided at Box1185. Upon receiving confirmation, the addressable switch will send a detonation signal through a detonation pin residing in the top end plate, and back up to the detonator. The detonator, in turn, ignites the explosive material that passes through the detonating cord and on to the charges along the upstream charge tube. This is shown at Box1190. The result is that the top end plate isolates the addressable switch from wellbore fluids and the pressure wave generated by detonation of the upstream charges.

If the instruction signal is not recognized as a detonation signal for that tandem sub, the signal is sent on through a contact head residing inside of the switch housing associated with a contact pin. The contact pin resides within a bulkhead. From there, the signal is sent through the contact pin, through a bottom end plate, and on to the downstream perforating gun with its downstream charge tube.

The disclosed embodiments provide methods and systems for preventing electronics located inside a switch sub from being damaged by detonation of an adjacent perforating gun. It should be understood that this description is not intended to limit the present disclosure; on the contrary, the exemplary embodiments are intended to cover alternatives, modifications, and equivalents, which are included in the spirit and scope of the inventions as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.

Further, variations of the detonation system and of methods for using the detonation system within a wellbore may fall within the spirit of the claims, below. It will be appreciated that the presently disclosed subject matter is susceptible to other modifications, variations, and changes without departing from the spirit thereof.