Primary free detonator

Abstract

A non-primary explosive detonator includes an outer shell having a head portion defining a chamber therein, and a body portion extending distally from the head portion. The body portion of the outer shell defines a longitudinally-extending bore therethrough. The detonator further includes a column of deflagrating and detonating material positioned in the bore of the body portion. The bore and the column of deflagrating and detonating material may taper at a distal section thereof. A distal end of the outer shell may define an opening in fluid communication with the bore to allow for combustion to exit via the opening.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 501,306 filed May 10, 2023 and U.S. Provisional Patent Application No. 63 / 476,780 filed Dec. 22, 2022, the entire contents of each of which are incorporated herein by reference.BACKGROUND OF THE DISCLOSURE

[0002] Most electrically activated detonators employ primary explosives inside the detonator shell due to the material's excellent DDT (Deflagration to Detonation Transfer) characteristics. Primary Explosives such as lead azide or silver azide have the capability to transfer from a burn / ignition, i.e., deflagration, to a high-speed detonation within a few millimeters of compressed material thickness. Deflagration (i.e., “to burn down”) is subsonic combustion propagating through heat transfer; hot burning material heats the next layer of cold material and ignites it. Detonation, in contrast, is propagation of combustion by the explosive shock wave travelling through or into the explosive material.

[0003] Primary explosives, by definition, are extremely sensitive to friction and impact energy as well as being very sensitive to electrostatic discharge. To minimize the risk of an unintentional initiation, there is often a desire or technical requirement to use detonators that do not contain any primary explosives. Most detonators, which do not contain any primary explosives, require a very high voltage (kV) or current level (Amps) to initiate the less sensitive secondary explosive directly from a filament wire or initiating foil by inducing enough energy (e.g., heat) directly to the secondary explosive to cause it to detonate instantaneously.

[0004] Typical high voltage primary-free initiators or detonators include EFI's (Exploding Foil Initiators), EBW's (Exploding Bridge Wires) or SCB Initiators (Semiconductor Bridge Initiators). Other typical primary-free detonators use granulated material, different particles sizes and / or shapes, or crystalline material in the detonator design to achieve initiation sensitivity and also the transformation from a deflagration to detonation without using primary explosives.

[0005] Accordingly, there is a need for a primary-free detonator that provides for a reliable deflagration to detonation process. There is a further need for a primary free detonator that is capable of combustion or deflagration and then detonation when utilizing conventional secondary explosives.BRIEF DESCRIPTION

[0006] In an aspect of the present disclosure, a detonator of a wellbore tool is provided and includes a detonator shell, a column of deflagrating and detonating material, and an initiator head assembly. The detonator shell includes a proximal head portion defining a chamber therein, and a distal body portion extending distally from the proximal head portion. The distal body portion defines a longitudinally-extending bore. The column of deflagrating and detonating material is positioned in the bore of the distal body portion of the detonator shell and the initiator head assembly is positioned in the chamber of the proximal head portion of the detonator shell. The initiator head assembly includes an insulative housing and a circuit board positioned in the insulative housing at the proximal head portion of the detonator shell.

[0007] In another aspect of the present disclosure, a low-voltage, non-primary explosive detonator of a perforating gun assembly is provided and includes an outer shell and a column of deflagrating and detonating material. The outer shell includes a proximal head portion defining a chamber therein, and a distal body portion extending distally from the proximal head portion. The distal body portion defines a longitudinally-extending bore therethrough having a proximal section and a distal section that tapers in a distal direction. The column of deflagrating and detonating material is positioned in the bore.

[0008] In aspects, the column of deflagrating and detonating material may be pressed into the bore with a pressing pressure from about 300 N to about 2500 N.

[0009] In aspects, the column of deflagrating and detonating material may increase in density in a distal direction of the bore.

[0010] In aspects, the outer shell may be fabricated from steel having a high yield strength greater than about 750 MPa, an elastic limit of about 40% elongation, and / or a minimum hardness of about 230 HB.

[0011] In accordance with another aspect of the present disclosure, a detonator of a wellbore tool defining a distal direction in which explosive material exits the detonator and a proximal direction opposite the distal direction includes a detonator shell, a column of explosive material, and an initiator head assembly. The detonator shell has a head portion defining a chamber therein and a body portion extending distally from the head portion. The body portion defines a bore extending therethrough about central longitudinal axis thereof. The body portion terminates at a distal end defining a distal opening in fluid communication with the bore. The column of explosive material in configured to deflagrate and detonate. The explosive material is positioned in bore. The initiator head assembly positioned in the chamber of the head portion. The initiator head assembly includes a housing and a circuit board positioned within the insulative housing.

[0012] In aspects, the initiator head assembly of the detonator further includes a fuse head positioned in the insulative housing adjacent the column of explosive material. The fuse head may be configured to receive an initiation signal from the circuit board.

[0013] In some aspects, the body portion includes a proximal section and a distal section. The distal section may extend distally from the proximal section. The distal section may define a tapering section of the bore. The tapering section of the bore may decrease as the distal section extends distally. The bore may extend through the proximal section such that the bore has a uniform diameter along an entire length thereof. The tapering section of the bore distal section may decrease linearly from a first diameter to a second diameter. The second diameter may be smaller than the first diameter. The second diameter may be positioned at the distal opening.

[0014] In certain aspects, the column of explosive material includes a multilayered pyrotechnical material disposed within the body portion of the detonator shell and a main explosive load disposed within the body portion between the multilayered pyrotechnical material and the distal end of the body portion. The multilayered pyrotechnical material may be configured to deflagrate. The main explosive load may be configured to detonate.

[0015] In particular aspects, the wherein the head portion and the body portion are monolithically formed with one another or coupled to one another. The head portion and the body portion may be monolithically formed with one another and fabricated from a metal. The head portion may protrude radially outward from a proximal end portion of the body portion.

[0016] In aspects, the insulative housing of the initiator head assembly includes a cap positioned in the chamber of the head portion of the detonator shell. The cap may cover an open proximal end of the head portion. The insulative housing of the initiator head assembly may further include a stem extending from the cap of the initiator head assembly and into the bore. The head portion may defines a notch therein and the insulative housing may have a tab configured for snap-fit engagement in the notch.

[0017] In accordance with another aspect of the present disclosure, a non-primary explosive detonator of a perforating gun assembly defines a distal direction in which explosive material exits the detonator and a proximal direction opposite the distal direction. The detonator includes a metal outer shell and column of explosive material. The metal outer shell includes a head portion defining a chamber therein and a body portion extending distally from the head portion. The body portion defines a bore extending therethrough about a central longitudinal axis. The body portion terminates at a distal end thereof. The distal end is configured for the exit of explosive material from the bore. The body portion has a proximal section and a distal section. The distal section defining a tapering section of the bore. A diameter of the tapering section decreases as the distal section extends in the distal direction. The column of explosive material is configured to deflagrate and detonate and is positioned in the bore.

[0018] In aspects, the non-primary explosive detonator includes a circuit board, a line-in terminal, and a fuse head. The circuit board may be supported in the chamber of the head portion. The in-line terminal may be coupled to the circuit board. The fuse head may be positioned within the bore between the circuit board and the column of explosive material. The fuse head may be configured to receive an initiation signal from the circuit board.

[0019] In some aspects, the distal end defines a distal opening. The bore may be in fluid communication within the distal opening. A portion of the column of explosive material may be disposed in the proximal section and may have a diameter from 5 mm to 8 mm. A portion of the column of explosive material may be disposed in the distal opening and may have a diameter from 3 mm to 5 mm.

[0020] In certain aspects, the body portion has a greater wall thickness at the distal section than at the proximal section. The bore may extend through the proximal section of the body such that the bore has uniform diameter along an entire length thereof. The bore may extend through the distal section of the body portion such that a diameter of the tapering section decreases as the distal section extends distally. The tapering section may taper at a taper angle from 20 degrees to 70 degree relative the central longitudinal axis. The column of explosive material may include a plurality of layers whereby the plurality of layers may be combination of pyrotechnical material configured to deflagrate and high explosive material configured to detonate. The metal outer shell may have a wall thickness of at least 1 mm to maintain a gas pressure within the bore during a deflagration to detonation process.

[0021] Further, to the extent consistent, any of the embodiments or aspects described herein may be used in conjunction with any or all of the other embodiments or aspects described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] A more particular description will be rendered by reference to example embodiments that are illustrated in the accompanying figures. Understanding that these drawings depict example embodiments and do not limit the scope of this disclosure, the example embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0023] FIG. 1A is a top perspective view illustrating a primary free detonator according to an example embodiment;

[0024] FIG. 1B is a bottom perspective view illustrating the primary free detonator of FIG. 1A;

[0025] FIG. 2 is a longitudinal cross-sectional view of the primary free detonator of FIGS. 1A and 1B;

[0026] FIG. 3 is a longitudinal cross-sectional view of another example embodiment of a primary free detonator; and

[0027] FIG. 4 is a longitudinal cross-sectional view of yet another example embodiment of a primary free detonator.

[0028] Various features, aspects, and advantages of the example embodiments will become more apparent from the following detailed description, along with the accompanying drawings in which like numerals represent like components throughout the figures and detailed description. The various described features are not necessarily drawn to scale in the drawings but are drawn to emphasize specific features relevant to some embodiments.

[0029] The headings used herein are for organizational purposes only and are not meant to limit the scope of the disclosure or the claims. To facilitate understanding, reference numerals have been used, where possible, to designate like elements common to the figures.DETAILED DESCRIPTION

[0030] As used herein the term “deflagration” is a subsonic combustion propagating through heat transfer whereby hot burning material heats the next layer of cold material and ignites it. “Proximal” as used herein refers to a direction, location, or component opposite or away from the direction of deflagration or detonation of a material within a detonator. “Distal” refers to a direction, location, or component toward or near the direction of deflagration or detonation of a material within a detonator.

[0031] For purposes of illustrating features of the embodiments, an example embodiment will now be introduced and referenced throughout the disclosure. This example is illustrative and not limiting and is provided for illustrating the example features of a primary free detonator as described throughout this disclosure.

[0032] A detonator (primary free detonator assembly / low voltage primary free detonator assembly) to initiate a non-primary explosive is described herein. The detonator combines conventional pyrotechnical materials / compositions, such as black powder (e.g., Pyrodex®), which are capable of combustion or deflagration and then detonation, together with conventional secondary explosives (e.g., cyclotrimethylenetrinitramine or (O2NNCH2)3,), commonly referred to as RDX. The pyrotechnical materials have been tested for friction and impact sensitivity using conventional test methods (that is, test methods for mechanical sensitivity to impact) established by The German Federal Institute for Materials Research and Testing (“BAM”) to confirm that they do not fall into the primary explosives category. The heat energy and pressure produced during the combustion or deflagration process inside the detonator can be increased by using certain additives to the combustible pyrotechnical material such as aluminum or other particles which react exothermically. It has been established that the process is stable without the use of additives.

[0033] The detonator includes a top detonator head integrally formed with or coupled to a generally cylindrical detonator shell (blasting cap / main body / ballistic vessel). The shell includes a single piece of machine or forged metal in which the non-primary explosive is housed.

[0034] FIGS. 1A, 1B, and 2 show an example embodiment of a primary free detonator or detonator assembly 10, which generally includes an initiator head assembly 100, such as a top fire initiator head assembly, a column of deflagrating and detonating material 204, and a detonator shell or outer shell 200 housing the initiator head assembly 100 and the column of deflagrating and detonating material 204.

[0035] The detonator shell 200 of the detonator 10 may be formed from a steel with a high yield strength (e.g., greater than or equal to about 750 MPa) and a high elastic limit (e.g., about 40% elongation). The minimum hardness of the steel may be about 230 HB. The detonator shell 200 includes a proximal head portion 200a, and a distal body portion 200b extending distally from the proximal head portion 200a. The proximal head portion 200a and the distal body portion 200b may be integrally formed with one another such that the proximal head portion 200a and the distal body portion 200b are a single piece monolithic construction (e.g., stainless steel). In embodiments, the detonator shell 200 may be fabricated from two longitudinal sections of stainless steel that are welded together. In some embodiments, the two longitudinal sections of the detonator shell 200 may be secured together via a snap-fit connection or other connection mechanisms. The proximal head portion 200a may assume a disc-shape and extends radially outward from a proximal end 202a of the distal body portion 200b. The proximal head portion 200a defines a chamber 203 therein for housing a portion of the initiator head assembly 100.

[0036] The distal body portion 200b of the detonator shell 200 has the proximal end portion 202a extending from and integrally formed with the proximal head portion 200a of the detonator shell 200, and a distal end portion 202b. In certain embodiments, the proximal end portion 202a of the distal body portion 200b may be connected to the proximal head portion 200a. The distal body portion 200b of the detonator shell 200 may have a cylindrical shape and defines a longitudinally-extending bore 206 in which the column of deflagrating and detonating material 204 is positioned. The bore 206 may be disposed concentrically about a central longitudinal axis A-A. The distal body portion 200b has a wall thickness of at least 1 mm to maintain a gas pressure within the bore 206 during a deflagration to detonation process. In embodiments, the wall thickness of the distal end portion 202b of the distal body portion 200b increases along its length in a distal direction. The wall thickness of the distal end portion 202b is selected to prevent rupture or splitting thereof during the deflagration to detonation process. The wall thickness may be in a range of 1 mm to 8 mm.

[0037] The bore 206 of the distal body portion 200b of the detonator shell 200 has a proximal section 206a and tapering section or a distal section 206b that tapers in a distal direction of the detonator shell 200. The proximal section 206a of the bore 206 may have a uniform diameter along a length thereof, and the distal section 206b of the bore 206 may have a cone-shape or a substantial cone-shape such as a frustoconical shape. The distal section 206b may taper linearly from a first diameter to a second diameter. The distal body portion 200b of the detonator shell 200 has a distal face or end 208 that defines a central opening 210 in fluid communication with the distal section 206b of the bore 206. In certain embodiments, the second diameter of the distal section 206b may be positioned at the central opening 210. The diameter of the proximal section 206a of the bore 206 may be from about 5 mm to about 8 mm, and the diameter of the distal opening 210 may be from about 3 mm to about 5 mm. In embodiments, a taper angle of the distal section 206b of the bore 206 may be from about 20 degrees to about 70 degrees.

[0038] The column of deflagrating and detonating material 204 includes a multilayered pyrotechnical material 204a (e.g., black powder or Pyrodex® RS), and a main explosive load 204b (e.g., RDX, HMX (C4H8N8O8), HNS ([(O2N)3C6H2CH]2), or another suitable high temperature explosive). Within the column of deflagrating and detonating material 204, the multilayered pyrotechnical material 204a may be considered a deflagrating portion and the main explosive load 204b may be considered a detonating portion. The multilayered pyrotechnical material 204a is disposed within the proximal section 206a of the bore 206 of the distal body portion 200b of the detonator shell 200, and the main explosive load 204b is disposed within the distal section 206b of the bore 206 of the distal body portion 200b of the detonator shell 200 between the multilayered pyrotechnical material 204a and the distal end 208 of the distal body portion 200b of the detonator shell 200. A wall thickness of the distal body portion 200b may have a greater wall thickness than the wall thickness of the proximal head portion 200a to confine the column of deflagrating and detonating material 204 and stabilize the initiation process. The tapering or narrowing of the distal section 206b of the bore 206 toward the distal end 208 of the distal body portion 200b of the detonator shell 200 increases the rate of detonation in the main explosive load 204b in a distal direction (e.g., in a direction from the proximal head portion 200a toward the distal end 208 of the distal body portion 200b) and physically prevents any unwanted pushing out or unwanted propelling of the final explosive load-column at the distal end 208 of the distal body portion 200b. Any unwanted pushing out or propelling of the final explosive load could potentially cause a stop-fire or miss-fire to a detonating cord or booster kit.

[0039] The column of deflagrating and detonating material 204 may include a plurality of discrete layers each having a distinct density and material weight. The plurality of layers may be compressed to a different extent in a longitudinal direction of the detonator 10. For example, the column of deflagrating and detonating material 204 may be compressed to a greater extent in a distal direction (e.g., in a direction from the proximal head portion 200a towards the distal end 208 of the distal body portion 200b) such that the deflagrating and detonating material 204 at the proximal section 206a of the bore 206 has a lower density than the deflagrating and detonating material 204 at the distal section 206b of the bore 206. In embodiments, the compression pressures used to form the layers may be in the range from about 300 N to about 2500 N. The propagation of the column of deflagrating and detonating material 204 form layer to layer in the distal direction. The differences in compression between layers of the deflagrating and detonating material may induce an increase of acceleration in the burn speed or gas combustion velocity. For example, as density of the layers of the deflagrating and detonating material 204 increased the burn speed or gas combustion velocity also increased. In other words, the deflagration of the deflagrating and detonating material 204 turns into a high-speed detonation in a very short space within the detonator shell 200.

[0040] The layered arrangement of the main explosive load 204b and the multilayered pyrotechnical material 204a (with one or more layers) may facilitate a delay time of less than about 5 milliseconds (e.g., the time to go from a deflagration or burn to a high-speed detonation). In certain embodiments, the delay time is less than about 1 millisecond from the time a fuse head 118 fires to the time the main explosive load 204b has reached a detonation.

[0041] The multilayered pyrotechnical material 204a can be initiated using a conventional detonator fuse-head 118 that does not require a high voltage impulse or a large current (e.g., less than or equal to about 800 mA) to initiate. In particular embodiments, the primary-free detonator 10 may be electrically initiated just like a conventional 50 Ohm resistorized oilfield detonator. Alternatively, the detonator 10 may also be combined with an internal electronic circuitry by which the fuse head 118 is initiated using a radio frequency safe (“RF-Safe”) digital code sequence through a circuit board 104 of the initiator head assembly 100. The fuse head 118 and the circuit board 104 of the initiator head assembly 100, described below, do not require a high voltage to initiate the multilayered pyrotechnical material 204a. The RF-Safe digital code sequence (digital pulse) will operate with less than 30 volts power supply. The digital pulse signal sequence will charge a capacitor 122 of the initiator head assembly 100, which then discharges onto the fuse-head 118 with the detonator 10.

[0042] The initiator head assembly 100 may include a housing 102, the circuit board 104, a line-in terminal 106, a line-out terminal 108, a ground terminal or contact 110, electrical connections 116, or the fuse head 118. The housing 102 includes a cap or head 112 and a stem 114 extending distally from the head 112. The head 112 is received in the chamber 203 of the proximal head portion 200a of the detonator shell 200 and the stem 114 is received in the proximal end portion 202a of the distal body portion 200b. The housing 102 defines an interior cavity 120 in which the circuit board 104 is supported. The housing 102 may be fabricated from an insulative material (e.g., polyamide) and has a tab 124 (FIG. 1a) configured for snap-fit engagement in a notch 126 defined in the proximal head portion 200a of the detonator shell 200. The stem 114 extends in an axial direction from the head 112 and into the distal body portion 200b. In an example embodiment, the stem 114 may be formed of the same material as the head 112 and may be integrally and / or monolithically formed therewith. The fuse head 118 and the electrical connections 116 may be received in the stem 114.

[0043] The circuit board 104 may be a printed circuit board and / or may include one or more surface mounted components 122, e.g., the capacitor 122. In an example embodiment, the surface mounted component 122 of the circuit board 104 may be an integrated circuit (IC) with a dedicated function, a programmable IC, or a microprocessor IC. The circuit board 104 may be configured to activate the fuse head 118 in response to a control signal received at the line-in terminal 106. For example, a user may send a firing signal via a firing panel. The firing signal may be received at the line-in terminal 106, and the circuit board 104, through ICs provided on the circuit board 104, may process the firing signal and activate the fuse head 118. Additionally, the circuit board 104 may include a switch circuit configured to establish electrical communication between the line-out terminal 108 and the line-in terminal 106 in response to a predetermined switch signal. The line-out terminal 108 may be in electrical communication with subsequent initiator head assemblies 100 provided downstream in a string of connected perforating guns (not explicitly shown), thereby allowing a user to send switch signals to toggle which initiator head is active to receive a firing command.

[0044] In an example embodiment, one of the surface mounted components 122 may be at least one of a temperature sensor, an orientation sensor, a safety circuit, or a capacitor. Readings from one of these surface mounted components 122 may be used by a microprocessor on the circuit board 104 to determine when it is appropriate to activate the fuse head 118. The temperature sensor may be configured to measure temperature of the wellbore environment and provide a signal corresponding to the temperature to the circuit board 104. The orientation sensor may include, but is not limited to, an accelerometer, a gyroscope, and / or a magnetometer. The capacitor 122 may be used to store a voltage to activate the fuse head 118. The size of the interior cavity 120 of the housing 102 may allow for a larger capacity capacitor to be used. This allows a larger discharge voltage for activating the fuse head 118, which may help to ensure more reliable activation of the fuse head 118.

[0045] With reference to FIG. 3, another example embodiment of a primary free detonator 300 is provided. The detonator 300 differs from the detonator 10 in that an initiator head assembly 302 of the detonator 300 has a line-out terminal or freed-through contact 308 that extends from a circuit board 304 of the initiator head assembly 302, through a radial wall 306 of a proximal head portion 320 of a detonator shell 322, to a distally-facing external surface 324 of the proximal head portion 320. The contact 308 may be in electrical communication with subsequent initiator head assemblies 302 provided in a string of connected perforating guns (not shown). The electrical communication between connected perforating guns through the contact 308 may allow a user to activate one or more initiator head assemblies 302 to receive a firing command. In embodiments, an insulative surface or plate 310 may be provided on the distally-facing external surface 324 between the proximal head portion 320 and the contact 308. The plate 310 may electrically insulate the contact 308 from the proximal head portion 320. The plate 310 may also help reduce the risk of unintended activation of the initiator head assembly 302 by insulating the contact 308 from static charge built up on the proximal head portion 320, and thereby reduce the risk of unintended deflagration or detonation of the detonator 300 or any nearby explosive material. Additionally, an electrically insulating material may be provided on the portion of the contact 308 passing through the radial wall 306 so as to electrically insulate the contact 308 from the radial wall 306. Alternatively, an electrically insulating material may be provided on a surface of the passage in the radial wall 306 through which the contact 308 passes.

[0046] With reference to FIG. 4, another example embodiment of a primary free detonator 400 is provided. The detonator 400 differs from the detonator 10 in that an initiator head assembly 402 of the detonator 400 has a line-out terminal or freed-through contact 408 that extends from a circuit board 404 of the initiator head assembly 402 through a longitudinal bore 407 defined by a stem 406 of the initiator head assembly 402. The contact 408 has an end that extends transversely through the stem 406 and contacts an inner-facing surface 412 of a distal body portion 410 of the detonator 400. The contact 408 may be in electrical communication with subsequent initiator head assemblies 402 provided in a string of connected perforating guns (not shown). The electrical communication between connected perforating guns through the contact 408 may allow a user to activate one or more initiator head assemblies 402 to receive a firing command. In some embodiments, the distal body portion 410 may be made of a conductive material and may be configured to carry the electrical communication from the initiator head assembly 402 through the contact 408 to subsequent perforating guns.

[0047] This disclosure, in various embodiments, configurations and aspects, includes components, methods, processes, systems, and / or apparatuses as depicted and described herein, including various embodiments, sub-combinations, and subsets thereof. This disclosure contemplates, in various embodiments, configurations and aspects, the actual or optional use or inclusion of, e.g., components or processes as may be well-known or understood in the art and consistent with this disclosure though not depicted and / or described herein.

[0048] The phrases “at least one,”“one or more,” and “and / or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C,”“at least one of A, B, or C,”“one or more of A, B, and C,”“one or more of A, B, or C,” and “A, B, and / or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together.

[0049] In this specification and the claims that follow, reference will be made to a number of terms that have the following meanings. The terms “a” (or “an”) and “the” refer to one or more of that entity, thereby including plural referents unless the context clearly dictates otherwise. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. Furthermore, references to “one embodiment”, “some embodiments”, “an embodiment” and the like are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to manufacturing or engineering tolerances or the like. Accordingly, a value modified by a term such as “about” is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Terms such as “first,”“second,”“upper,”“lower,” etc. are used to identify one element from another, and unless otherwise specified are not meant to refer to a particular order or number of elements.

[0050] As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and / or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances the modified term may sometimes not be appropriate, capable, or suitable. For example, in some circumstances an event or capacity can be expected, while in other circumstances the event or capacity cannot occur-this distinction is captured by the terms “may” and “may be.”

[0051] As used in the claims, the word “comprises” and its grammatical variants logically also subtend and include phrases of varying and differing extent such as for example, but not limited thereto, “consisting essentially of” and “consisting of.” Where necessary, ranges have been supplied, and those ranges are inclusive of all sub-ranges therebetween. It is to be expected that the appended claims should cover variations in the ranges except where this disclosure makes clear the use of a particular range in certain embodiments.

[0052] The terms “determine,”“calculate,” and “compute,” and variations thereof, as used herein, are used interchangeably and include any type of methodology, process, mathematical operation or technique.

[0053] As used herein, the terms parallel and perpendicular are understood to include relative configurations that are substantially parallel and substantially perpendicular up to about +or −10 degrees from true parallel and true perpendicular.

[0054] This disclosure is presented for purposes of illustration and description. This disclosure is not limited to the form or forms disclosed herein. In the Detailed Description of this disclosure, for example, various features of some example embodiments are grouped together to representatively describe those and other contemplated embodiments, configurations, and aspects, to the extent that including in this disclosure a description of every potential embodiment, variant, and combination of features is not feasible. Thus, the features of the disclosed embodiments, configurations, and aspects may be combined in alternate embodiments, configurations, and aspects not expressly discussed above. For example, the features recited in the following claims lie in less than all features of a single disclosed embodiment, configuration, or aspect. As such, any combination of the above embodiments is also envisioned and is within the scope of the appended claims. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope of the claims appended hereto. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of this disclosure.

[0055] Advances in science and technology may provide variations that are not necessarily express in the terminology of this disclosure although the claims would not necessarily exclude these variations.

Examples

Embodiment Construction

[0030]As used herein the term “deflagration” is a subsonic combustion propagating through heat transfer whereby hot burning material heats the next layer of cold material and ignites it. “Proximal” as used herein refers to a direction, location, or component opposite or away from the direction of deflagration or detonation of a material within a detonator. “Distal” refers to a direction, location, or component toward or near the direction of deflagration or detonation of a material within a detonator.

[0031]For purposes of illustrating features of the embodiments, an example embodiment will now be introduced and referenced throughout the disclosure. This example is illustrative and not limiting and is provided for illustrating the example features of a primary free detonator as described throughout this disclosure.

[0032]A detonator (primary free detonator assembly / low voltage primary free detonator assembly) to initiate a non-primary explosive is described herein. The detonator combi...

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 501,306 filed May 10, 2023 and U.S. Provisional Patent Application No. 63 / 476,780 filed Dec. 22, 2022, the entire contents of each of which are incorporated herein by reference.BACKGROUND OF THE DISCLOSURE

[0002] Most electrically activated detonators employ primary explosives inside the detonator shell due to the material's excellent DDT (Deflagration to Detonation Transfer) characteristics. Primary Explosives such as lead azide or silver azide have the capability to transfer from a burn / ignition, i.e., deflagration, to a high-speed detonation within a few millimeters of compressed material thickness. Deflagration (i.e., “to burn down”) is subsonic combustion propagating through heat transfer; hot burning material heats the next layer of cold material and ignites it. Detonation, in contrast, is propagation of combustion by the explosive shock wave travelling through or into the explosive material.

[0003] Primary explosives, by definition, are extremely sensitive to friction and impact energy as well as being very sensitive to electrostatic discharge. To minimize the risk of an unintentional initiation, there is often a desire or technical requirement to use detonators that do not contain any primary explosives. Most detonators, which do not contain any primary explosives, require a very high voltage (kV) or current level (Amps) to initiate the less sensitive secondary explosive directly from a filament wire or initiating foil by inducing enough energy (e.g., heat) directly to the secondary explosive to cause it to detonate instantaneously.

[0004] Typical high voltage primary-free initiators or detonators include EFI's (Exploding Foil Initiators), EBW's (Exploding Bridge Wires) or SCB Initiators (Semiconductor Bridge Initiators). Other typical primary-free detonators use granulated material, different particles sizes and / or shapes, or crystalline material in the detonator design to achieve initiation sensitivity and also the transformation from a deflagration to detonation without using primary explosives.

[0005] Accordingly, there is a need for a primary-free detonator that provides for a reliable deflagration to detonation process. There is a further need for a primary free detonator that is capable of combustion or deflagration and then detonation when utilizing conventional secondary explosives.BRIEF DESCRIPTION

[0006] In an aspect of the present disclosure, a detonator of a wellbore tool is provided and includes a detonator shell, a column of deflagrating and detonating material, and an initiator head assembly. The detonator shell includes a proximal head portion defining a chamber therein, and a distal body portion extending distally from the proximal head portion. The distal body portion defines a longitudinally-extending bore. The column of deflagrating and detonating material is positioned in the bore of the distal body portion of the detonator shell and the initiator head assembly is positioned in the chamber of the proximal head portion of the detonator shell. The initiator head assembly includes an insulative housing and a circuit board positioned in the insulative housing at the proximal head portion of the detonator shell.

[0007] In another aspect of the present disclosure, a low-voltage, non-primary explosive detonator of a perforating gun assembly is provided and includes an outer shell and a column of deflagrating and detonating material. The outer shell includes a proximal head portion defining a chamber therein, and a distal body portion extending distally from the proximal head portion. The distal body portion defines a longitudinally-extending bore therethrough having a proximal section and a distal section that tapers in a distal direction. The column of deflagrating and detonating material is positioned in the bore.

[0008] In aspects, the column of deflagrating and detonating material may be pressed into the bore with a pressing pressure from about 300 N to about 2500 N.

[0009] In aspects, the column of deflagrating and detonating material may increase in density in a distal direction of the bore.

[0010] In aspects, the outer shell may be fabricated from steel having a high yield strength greater than about 750 MPa, an elastic limit of about 40% elongation, and / or a minimum hardness of about 230 HB.

[0011] In accordance with another aspect of the present disclosure, a detonator of a wellbore tool defining a distal direction in which explosive material exits the detonator and a proximal direction opposite the distal direction includes a detonator shell, a column of explosive material, and an initiator head assembly. The detonator shell has a head portion defining a chamber therein and a body portion extending distally from the head portion. The body portion defines a bore extending therethrough about central longitudinal axis thereof. The body portion terminates at a distal end defining a distal opening in fluid communication with the bore. The column of explosive material in configured to deflagrate and detonate. The explosive material is positioned in bore. The initiator head assembly positioned in the chamber of the head portion. The initiator head assembly includes a housing and a circuit board positioned within the insulative housing.

[0012] In aspects, the initiator head assembly of the detonator further includes a fuse head positioned in the insulative housing adjacent the column of explosive material. The fuse head may be configured to receive an initiation signal from the circuit board.

[0013] In some aspects, the body portion includes a proximal section and a distal section. The distal section may extend distally from the proximal section. The distal section may define a tapering section of the bore. The tapering section of the bore may decrease as the distal section extends distally. The bore may extend through the proximal section such that the bore has a uniform diameter along an entire length thereof. The tapering section of the bore distal section may decrease linearly from a first diameter to a second diameter. The second diameter may be smaller than the first diameter. The second diameter may be positioned at the distal opening.

[0014] In certain aspects, the column of explosive material includes a multilayered pyrotechnical material disposed within the body portion of the detonator shell and a main explosive load disposed within the body portion between the multilayered pyrotechnical material and the distal end of the body portion. The multilayered pyrotechnical material may be configured to deflagrate. The main explosive load may be configured to detonate.

[0015] In particular aspects, the wherein the head portion and the body portion are monolithically formed with one another or coupled to one another. The head portion and the body portion may be monolithically formed with one another and fabricated from a metal. The head portion may protrude radially outward from a proximal end portion of the body portion.

[0016] In aspects, the insulative housing of the initiator head assembly includes a cap positioned in the chamber of the head portion of the detonator shell. The cap may cover an open proximal end of the head portion. The insulative housing of the initiator head assembly may further include a stem extending from the cap of the initiator head assembly and into the bore. The head portion may defines a notch therein and the insulative housing may have a tab configured for snap-fit engagement in the notch.

[0017] In accordance with another aspect of the present disclosure, a non-primary explosive detonator of a perforating gun assembly defines a distal direction in which explosive material exits the detonator and a proximal direction opposite the distal direction. The detonator includes a metal outer shell and column of explosive material. The metal outer shell includes a head portion defining a chamber therein and a body portion extending distally from the head portion. The body portion defines a bore extending therethrough about a central longitudinal axis. The body portion terminates at a distal end thereof. The distal end is configured for the exit of explosive material from the bore. The body portion has a proximal section and a distal section. The distal section defining a tapering section of the bore. A diameter of the tapering section decreases as the distal section extends in the distal direction. The column of explosive material is configured to deflagrate and detonate and is positioned in the bore.

[0018] In aspects, the non-primary explosive detonator includes a circuit board, a line-in terminal, and a fuse head. The circuit board may be supported in the chamber of the head portion. The in-line terminal may be coupled to the circuit board. The fuse head may be positioned within the bore between the circuit board and the column of explosive material. The fuse head may be configured to receive an initiation signal from the circuit board.

[0019] In some aspects, the distal end defines a distal opening. The bore may be in fluid communication within the distal opening. A portion of the column of explosive material may be disposed in the proximal section and may have a diameter from 5 mm to 8 mm. A portion of the column of explosive material may be disposed in the distal opening and may have a diameter from 3 mm to 5 mm.

[0020] In certain aspects, the body portion has a greater wall thickness at the distal section than at the proximal section. The bore may extend through the proximal section of the body such that the bore has uniform diameter along an entire length thereof. The bore may extend through the distal section of the body portion such that a diameter of the tapering section decreases as the distal section extends distally. The tapering section may taper at a taper angle from 20 degrees to 70 degree relative the central longitudinal axis. The column of explosive material may include a plurality of layers whereby the plurality of layers may be combination of pyrotechnical material configured to deflagrate and high explosive material configured to detonate. The metal outer shell may have a wall thickness of at least 1 mm to maintain a gas pressure within the bore during a deflagration to detonation process.

[0021] Further, to the extent consistent, any of the embodiments or aspects described herein may be used in conjunction with any or all of the other embodiments or aspects described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] A more particular description will be rendered by reference to example embodiments that are illustrated in the accompanying figures. Understanding that these drawings depict example embodiments and do not limit the scope of this disclosure, the example embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0023] FIG. 1A is a top perspective view illustrating a primary free detonator according to an example embodiment;

[0024] FIG. 1B is a bottom perspective view illustrating the primary free detonator of FIG. 1A;

[0025] FIG. 2 is a longitudinal cross-sectional view of the primary free detonator of FIGS. 1A and 1B;

[0026] FIG. 3 is a longitudinal cross-sectional view of another example embodiment of a primary free detonator; and

[0027] FIG. 4 is a longitudinal cross-sectional view of yet another example embodiment of a primary free detonator.

[0028] Various features, aspects, and advantages of the example embodiments will become more apparent from the following detailed description, along with the accompanying drawings in which like numerals represent like components throughout the figures and detailed description. The various described features are not necessarily drawn to scale in the drawings but are drawn to emphasize specific features relevant to some embodiments.

[0029] The headings used herein are for organizational purposes only and are not meant to limit the scope of the disclosure or the claims. To facilitate understanding, reference numerals have been used, where possible, to designate like elements common to the figures.DETAILED DESCRIPTION

[0030] As used herein the term “deflagration” is a subsonic combustion propagating through heat transfer whereby hot burning material heats the next layer of cold material and ignites it. “Proximal” as used herein refers to a direction, location, or component opposite or away from the direction of deflagration or detonation of a material within a detonator. “Distal” refers to a direction, location, or component toward or near the direction of deflagration or detonation of a material within a detonator.

[0031] For purposes of illustrating features of the embodiments, an example embodiment will now be introduced and referenced throughout the disclosure. This example is illustrative and not limiting and is provided for illustrating the example features of a primary free detonator as described throughout this disclosure.

[0032] A detonator (primary free detonator assembly / low voltage primary free detonator assembly) to initiate a non-primary explosive is described herein. The detonator combines conventional pyrotechnical materials / compositions, such as black powder (e.g., Pyrodex®), which are capable of combustion or deflagration and then detonation, together with conventional secondary explosives (e.g., cyclotrimethylenetrinitramine or (O2NNCH2)3,), commonly referred to as RDX. The pyrotechnical materials have been tested for friction and impact sensitivity using conventional test methods (that is, test methods for mechanical sensitivity to impact) established by The German Federal Institute for Materials Research and Testing (“BAM”) to confirm that they do not fall into the primary explosives category. The heat energy and pressure produced during the combustion or deflagration process inside the detonator can be increased by using certain additives to the combustible pyrotechnical material such as aluminum or other particles which react exothermically. It has been established that the process is stable without the use of additives.

[0033] The detonator includes a top detonator head integrally formed with or coupled to a generally cylindrical detonator shell (blasting cap / main body / ballistic vessel). The shell includes a single piece of machine or forged metal in which the non-primary explosive is housed.

[0034] FIGS. 1A, 1B, and 2 show an example embodiment of a primary free detonator or detonator assembly 10, which generally includes an initiator head assembly 100, such as a top fire initiator head assembly, a column of deflagrating and detonating material 204, and a detonator shell or outer shell 200 housing the initiator head assembly 100 and the column of deflagrating and detonating material 204.

[0035] The detonator shell 200 of the detonator 10 may be formed from a steel with a high yield strength (e.g., greater than or equal to about 750 MPa) and a high elastic limit (e.g., about 40% elongation). The minimum hardness of the steel may be about 230 HB. The detonator shell 200 includes a proximal head portion 200a, and a distal body portion 200b extending distally from the proximal head portion 200a. The proximal head portion 200a and the distal body portion 200b may be integrally formed with one another such that the proximal head portion 200a and the distal body portion 200b are a single piece monolithic construction (e.g., stainless steel). In embodiments, the detonator shell 200 may be fabricated from two longitudinal sections of stainless steel that are welded together. In some embodiments, the two longitudinal sections of the detonator shell 200 may be secured together via a snap-fit connection or other connection mechanisms. The proximal head portion 200a may assume a disc-shape and extends radially outward from a proximal end 202a of the distal body portion 200b. The proximal head portion 200a defines a chamber 203 therein for housing a portion of the initiator head assembly 100.

[0036] The distal body portion 200b of the detonator shell 200 has the proximal end portion 202a extending from and integrally formed with the proximal head portion 200a of the detonator shell 200, and a distal end portion 202b. In certain embodiments, the proximal end portion 202a of the distal body portion 200b may be connected to the proximal head portion 200a. The distal body portion 200b of the detonator shell 200 may have a cylindrical shape and defines a longitudinally-extending bore 206 in which the column of deflagrating and detonating material 204 is positioned. The bore 206 may be disposed concentrically about a central longitudinal axis A-A. The distal body portion 200b has a wall thickness of at least 1 mm to maintain a gas pressure within the bore 206 during a deflagration to detonation process. In embodiments, the wall thickness of the distal end portion 202b of the distal body portion 200b increases along its length in a distal direction. The wall thickness of the distal end portion 202b is selected to prevent rupture or splitting thereof during the deflagration to detonation process. The wall thickness may be in a range of 1 mm to 8 mm.

[0037] The bore 206 of the distal body portion 200b of the detonator shell 200 has a proximal section 206a and tapering section or a distal section 206b that tapers in a distal direction of the detonator shell 200. The proximal section 206a of the bore 206 may have a uniform diameter along a length thereof, and the distal section 206b of the bore 206 may have a cone-shape or a substantial cone-shape such as a frustoconical shape. The distal section 206b may taper linearly from a first diameter to a second diameter. The distal body portion 200b of the detonator shell 200 has a distal face or end 208 that defines a central opening 210 in fluid communication with the distal section 206b of the bore 206. In certain embodiments, the second diameter of the distal section 206b may be positioned at the central opening 210. The diameter of the proximal section 206a of the bore 206 may be from about 5 mm to about 8 mm, and the diameter of the distal opening 210 may be from about 3 mm to about 5 mm. In embodiments, a taper angle of the distal section 206b of the bore 206 may be from about 20 degrees to about 70 degrees.

[0038] The column of deflagrating and detonating material 204 includes a multilayered pyrotechnical material 204a (e.g., black powder or Pyrodex® RS), and a main explosive load 204b (e.g., RDX, HMX (C4H8N8O8), HNS ([(O2N)3C6H2CH]2), or another suitable high temperature explosive). Within the column of deflagrating and detonating material 204, the multilayered pyrotechnical material 204a may be considered a deflagrating portion and the main explosive load 204b may be considered a detonating portion. The multilayered pyrotechnical material 204a is disposed within the proximal section 206a of the bore 206 of the distal body portion 200b of the detonator shell 200, and the main explosive load 204b is disposed within the distal section 206b of the bore 206 of the distal body portion 200b of the detonator shell 200 between the multilayered pyrotechnical material 204a and the distal end 208 of the distal body portion 200b of the detonator shell 200. A wall thickness of the distal body portion 200b may have a greater wall thickness than the wall thickness of the proximal head portion 200a to confine the column of deflagrating and detonating material 204 and stabilize the initiation process. The tapering or narrowing of the distal section 206b of the bore 206 toward the distal end 208 of the distal body portion 200b of the detonator shell 200 increases the rate of detonation in the main explosive load 204b in a distal direction (e.g., in a direction from the proximal head portion 200a toward the distal end 208 of the distal body portion 200b) and physically prevents any unwanted pushing out or unwanted propelling of the final explosive load-column at the distal end 208 of the distal body portion 200b. Any unwanted pushing out or propelling of the final explosive load could potentially cause a stop-fire or miss-fire to a detonating cord or booster kit.

[0039] The column of deflagrating and detonating material 204 may include a plurality of discrete layers each having a distinct density and material weight. The plurality of layers may be compressed to a different extent in a longitudinal direction of the detonator 10. For example, the column of deflagrating and detonating material 204 may be compressed to a greater extent in a distal direction (e.g., in a direction from the proximal head portion 200a towards the distal end 208 of the distal body portion 200b) such that the deflagrating and detonating material 204 at the proximal section 206a of the bore 206 has a lower density than the deflagrating and detonating material 204 at the distal section 206b of the bore 206. In embodiments, the compression pressures used to form the layers may be in the range from about 300 N to about 2500 N. The propagation of the column of deflagrating and detonating material 204 form layer to layer in the distal direction. The differences in compression between layers of the deflagrating and detonating material may induce an increase of acceleration in the burn speed or gas combustion velocity. For example, as density of the layers of the deflagrating and detonating material 204 increased the burn speed or gas combustion velocity also increased. In other words, the deflagration of the deflagrating and detonating material 204 turns into a high-speed detonation in a very short space within the detonator shell 200.

[0040] The layered arrangement of the main explosive load 204b and the multilayered pyrotechnical material 204a (with one or more layers) may facilitate a delay time of less than about 5 milliseconds (e.g., the time to go from a deflagration or burn to a high-speed detonation). In certain embodiments, the delay time is less than about 1 millisecond from the time a fuse head 118 fires to the time the main explosive load 204b has reached a detonation.

[0041] The multilayered pyrotechnical material 204a can be initiated using a conventional detonator fuse-head 118 that does not require a high voltage impulse or a large current (e.g., less than or equal to about 800 mA) to initiate. In particular embodiments, the primary-free detonator 10 may be electrically initiated just like a conventional 50 Ohm resistorized oilfield detonator. Alternatively, the detonator 10 may also be combined with an internal electronic circuitry by which the fuse head 118 is initiated using a radio frequency safe (“RF-Safe”) digital code sequence through a circuit board 104 of the initiator head assembly 100. The fuse head 118 and the circuit board 104 of the initiator head assembly 100, described below, do not require a high voltage to initiate the multilayered pyrotechnical material 204a. The RF-Safe digital code sequence (digital pulse) will operate with less than 30 volts power supply. The digital pulse signal sequence will charge a capacitor 122 of the initiator head assembly 100, which then discharges onto the fuse-head 118 with the detonator 10.

[0042] The initiator head assembly 100 may include a housing 102, the circuit board 104, a line-in terminal 106, a line-out terminal 108, a ground terminal or contact 110, electrical connections 116, or the fuse head 118. The housing 102 includes a cap or head 112 and a stem 114 extending distally from the head 112. The head 112 is received in the chamber 203 of the proximal head portion 200a of the detonator shell 200 and the stem 114 is received in the proximal end portion 202a of the distal body portion 200b. The housing 102 defines an interior cavity 120 in which the circuit board 104 is supported. The housing 102 may be fabricated from an insulative material (e.g., polyamide) and has a tab 124 (FIG. 1a) configured for snap-fit engagement in a notch 126 defined in the proximal head portion 200a of the detonator shell 200. The stem 114 extends in an axial direction from the head 112 and into the distal body portion 200b. In an example embodiment, the stem 114 may be formed of the same material as the head 112 and may be integrally and / or monolithically formed therewith. The fuse head 118 and the electrical connections 116 may be received in the stem 114.

[0043] The circuit board 104 may be a printed circuit board and / or may include one or more surface mounted components 122, e.g., the capacitor 122. In an example embodiment, the surface mounted component 122 of the circuit board 104 may be an integrated circuit (IC) with a dedicated function, a programmable IC, or a microprocessor IC. The circuit board 104 may be configured to activate the fuse head 118 in response to a control signal received at the line-in terminal 106. For example, a user may send a firing signal via a firing panel. The firing signal may be received at the line-in terminal 106, and the circuit board 104, through ICs provided on the circuit board 104, may process the firing signal and activate the fuse head 118. Additionally, the circuit board 104 may include a switch circuit configured to establish electrical communication between the line-out terminal 108 and the line-in terminal 106 in response to a predetermined switch signal. The line-out terminal 108 may be in electrical communication with subsequent initiator head assemblies 100 provided downstream in a string of connected perforating guns (not explicitly shown), thereby allowing a user to send switch signals to toggle which initiator head is active to receive a firing command.

[0044] In an example embodiment, one of the surface mounted components 122 may be at least one of a temperature sensor, an orientation sensor, a safety circuit, or a capacitor. Readings from one of these surface mounted components 122 may be used by a microprocessor on the circuit board 104 to determine when it is appropriate to activate the fuse head 118. The temperature sensor may be configured to measure temperature of the wellbore environment and provide a signal corresponding to the temperature to the circuit board 104. The orientation sensor may include, but is not limited to, an accelerometer, a gyroscope, and / or a magnetometer. The capacitor 122 may be used to store a voltage to activate the fuse head 118. The size of the interior cavity 120 of the housing 102 may allow for a larger capacity capacitor to be used. This allows a larger discharge voltage for activating the fuse head 118, which may help to ensure more reliable activation of the fuse head 118.

[0045] With reference to FIG. 3, another example embodiment of a primary free detonator 300 is provided. The detonator 300 differs from the detonator 10 in that an initiator head assembly 302 of the detonator 300 has a line-out terminal or freed-through contact 308 that extends from a circuit board 304 of the initiator head assembly 302, through a radial wall 306 of a proximal head portion 320 of a detonator shell 322, to a distally-facing external surface 324 of the proximal head portion 320. The contact 308 may be in electrical communication with subsequent initiator head assemblies 302 provided in a string of connected perforating guns (not shown). The electrical communication between connected perforating guns through the contact 308 may allow a user to activate one or more initiator head assemblies 302 to receive a firing command. In embodiments, an insulative surface or plate 310 may be provided on the distally-facing external surface 324 between the proximal head portion 320 and the contact 308. The plate 310 may electrically insulate the contact 308 from the proximal head portion 320. The plate 310 may also help reduce the risk of unintended activation of the initiator head assembly 302 by insulating the contact 308 from static charge built up on the proximal head portion 320, and thereby reduce the risk of unintended deflagration or detonation of the detonator 300 or any nearby explosive material. Additionally, an electrically insulating material may be provided on the portion of the contact 308 passing through the radial wall 306 so as to electrically insulate the contact 308 from the radial wall 306. Alternatively, an electrically insulating material may be provided on a surface of the passage in the radial wall 306 through which the contact 308 passes.

[0046] With reference to FIG. 4, another example embodiment of a primary free detonator 400 is provided. The detonator 400 differs from the detonator 10 in that an initiator head assembly 402 of the detonator 400 has a line-out terminal or freed-through contact 408 that extends from a circuit board 404 of the initiator head assembly 402 through a longitudinal bore 407 defined by a stem 406 of the initiator head assembly 402. The contact 408 has an end that extends transversely through the stem 406 and contacts an inner-facing surface 412 of a distal body portion 410 of the detonator 400. The contact 408 may be in electrical communication with subsequent initiator head assemblies 402 provided in a string of connected perforating guns (not shown). The electrical communication between connected perforating guns through the contact 408 may allow a user to activate one or more initiator head assemblies 402 to receive a firing command. In some embodiments, the distal body portion 410 may be made of a conductive material and may be configured to carry the electrical communication from the initiator head assembly 402 through the contact 408 to subsequent perforating guns.

[0047] This disclosure, in various embodiments, configurations and aspects, includes components, methods, processes, systems, and / or apparatuses as depicted and described herein, including various embodiments, sub-combinations, and subsets thereof. This disclosure contemplates, in various embodiments, configurations and aspects, the actual or optional use or inclusion of, e.g., components or processes as may be well-known or understood in the art and consistent with this disclosure though not depicted and / or described herein.

[0048] The phrases “at least one,”“one or more,” and “and / or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C,”“at least one of A, B, or C,”“one or more of A, B, and C,”“one or more of A, B, or C,” and “A, B, and / or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together.

[0049] In this specification and the claims that follow, reference will be made to a number of terms that have the following meanings. The terms “a” (or “an”) and “the” refer to one or more of that entity, thereby including plural referents unless the context clearly dictates otherwise. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. Furthermore, references to “one embodiment”, “some embodiments”, “an embodiment” and the like are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to manufacturing or engineering tolerances or the like. Accordingly, a value modified by a term such as “about” is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Terms such as “first,”“second,”“upper,”“lower,” etc. are used to identify one element from another, and unless otherwise specified are not meant to refer to a particular order or number of elements.

[0050] As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and / or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances the modified term may sometimes not be appropriate, capable, or suitable. For example, in some circumstances an event or capacity can be expected, while in other circumstances the event or capacity cannot occur-this distinction is captured by the terms “may” and “may be.”

[0051] As used in the claims, the word “comprises” and its grammatical variants logically also subtend and include phrases of varying and differing extent such as for example, but not limited thereto, “consisting essentially of” and “consisting of.” Where necessary, ranges have been supplied, and those ranges are inclusive of all sub-ranges therebetween. It is to be expected that the appended claims should cover variations in the ranges except where this disclosure makes clear the use of a particular range in certain embodiments.

[0052] The terms “determine,”“calculate,” and “compute,” and variations thereof, as used herein, are used interchangeably and include any type of methodology, process, mathematical operation or technique.

[0053] As used herein, the terms parallel and perpendicular are understood to include relative configurations that are substantially parallel and substantially perpendicular up to about +or −10 degrees from true parallel and true perpendicular.

[0054] This disclosure is presented for purposes of illustration and description. This disclosure is not limited to the form or forms disclosed herein. In the Detailed Description of this disclosure, for example, various features of some example embodiments are grouped together to representatively describe those and other contemplated embodiments, configurations, and aspects, to the extent that including in this disclosure a description of every potential embodiment, variant, and combination of features is not feasible. Thus, the features of the disclosed embodiments, configurations, and aspects may be combined in alternate embodiments, configurations, and aspects not expressly discussed above. For example, the features recited in the following claims lie in less than all features of a single disclosed embodiment, configuration, or aspect. As such, any combination of the above embodiments is also envisioned and is within the scope of the appended claims. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope of the claims appended hereto. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of this disclosure.

[0055] Advances in science and technology may provide variations that are not necessarily express in the terminology of this disclosure although the claims would not necessarily exclude these variations.

Examples

Embodiment Construction

[0030]As used herein the term “deflagration” is a subsonic combustion propagating through heat transfer whereby hot burning material heats the next layer of cold material and ignites it. “Proximal” as used herein refers to a direction, location, or component opposite or away from the direction of deflagration or detonation of a material within a detonator. “Distal” refers to a direction, location, or component toward or near the direction of deflagration or detonation of a material within a detonator.

[0031]For purposes of illustrating features of the embodiments, an example embodiment will now be introduced and referenced throughout the disclosure. This example is illustrative and not limiting and is provided for illustrating the example features of a primary free detonator as described throughout this disclosure.

[0032]A detonator (primary free detonator assembly / low voltage primary free detonator assembly) to initiate a non-primary explosive is described herein. The detonator combi...

Claims

1. A detonator of a wellbore tool defining a distal direction in which a detonation propogates and a proximal direction opposite the distal direction, the detonator comprising:a detonator shell including:a head portion defining a chamber therein; anda body portion extending distally from the head portion and defining a bore extending therethrough about a central longitudinal axis thereof, the body portion terminating at a distal end defining a distal opening in fluid communication with the bore;a column of deflagrating and detonating material positioned in the bore; andan initiator head assembly positioned in the chamber of the proximal head portion of the detonator shell, wherein the initiator head assembly including:an insulative housing; anda circuit board positioned within the insulative housing.

2. The detonator according to claim 1, wherein the initiator head assembly further includes a fuse head positioned in the insulative housing adjacent the column of deflagrating and detonating material, the fuse head being configured to receive an initiation signal from the circuit board.

3. The detonator according to claim 1, wherein the body portion defines a proximal opening such that the bore is in fluid communication with the chamber of the head portion.

4. The detonator according to claim 1, wherein the body portion includes:a proximal section; anda distal section extending distally from the proximal section, the distal section defining a tapering section of the bore, the diameter of the tapering section of the bore decreasing as the distal section extends distally.

5. The detonator according to claim 4, wherein the bore extends through the proximal section such that the bore has a uniform diameter along an entire length thereof.

6. The detonator according to claim 4, wherein the tapering section of the bore decreases linearly from a first diameter to a second diameter, the second diameter smaller than the first diameter, the second diameter positioned at the distal opening.

7. The detonator according to claim 1, wherein the column of deflagrating and detonating material includes:a multilayered pyrotechnical material disposed within the body portion of the detonator shell, the multilayered pyrotechnical material configured to deflagrate; anda main explosive load disposed within the body portion between the multilayered pyrotechnical material and the distal end of the body portion, the main explosive load configured to detonate.

8. The detonator according to claim 1, wherein the head portion and the body portion are monolithically formed with one another or coupled to one another.

9. The detonator according to claim 1, wherein the head portion and the body portion are monolithically formed with one another and fabricated from a metal.

10. The detonator according to claim 9, wherein the head portion protrudes radially outward from a proximal end portion of the body portion.

11. The detonator according to claim 1, wherein the insulative housing of the initiator head assembly includes a cap positioned in the chamber of the head portion of the detonator shell, the cap covering an open proximal end of the head portion.

12. The detonator according to claim 11, wherein the insulative housing of the initiator head assembly further includes a stem extending from the cap of the initiator head assembly and into the bore.

13. The detonator according to claim 1, wherein the head portion defines a notch therein and the insulative housing has a tab configured for snap-fit engagement in the notch.

14. A low-voltage, non-primary explosive detonator of a perforating gun assembly, the detonator defining a distal direction in which a detonation propogates and a proximal direction opposite the distal direction, the detonator comprising:a metal outer shell including:a head portion defining a chamber therein; anda body portion extending distally from the head portion, the body portion defining a bore extending therethrough about a central longitudinal axis, the body portion terminating at a distal end thereof, the distal end configured for the exit of explosive material from the bore, the body portion having a proximal section and a distal section, the distal section defining a tapering section of the bore, a diameter of the tapering section decreasing as the distal section extends in the distal direction; anda column of deflagrating and detonating material positioned in the bore.

15. The low-voltage, non-primary explosive detonator according to claim 14, further comprising:a circuit board supported in the chamber of the head portion;a line-in terminal coupled to the circuit board; anda fuse head positioned within the bore between the circuit board and the column of deflagrating and detonating material, wherein the fuse head is configured to receive an initiation signal from the circuit board.

16. The low-voltage, non-primary explosive detonator according to claim 14, wherein the distal end defines a distal opening, the bore being in fluid communication with the distal opening.

17. The low-voltage, non-primary explosive detonator according to claim 16, wherein a portion of the column of deflagrating and detonating material is disposed in the proximal section and has a diameter from 5 mm to 8 mm, and a portion of the column of deflagrating and detonating material is disposed in the distal opening and has a diameter from 3 mm to 5 mm.

18. The low-voltage, non-primary explosive detonator according to claim 14, wherein the body portion has a greater wall thickness at the distal section than at the proximal section.

19. The low-voltage, non-primary explosive detonator according to claim 14, wherein:the bore extends through the proximal section of the body portion such that the bore has a uniform diameter along an entire length thereof; andthe bore extends through the distal section of the body portion such that the diameter of the tapering section decreases as the distal section extends distally, the diameter of tapering section decreasing along a taper angle from 20 degrees to 70 degrees relative to the central longitudinal axis.

20. The low-voltage, non-primary explosive detonator according to claim 14, wherein the column of deflagrating and detonating material includes a plurality of layers whereby the plurality of layers are a combination of pyrotechnical material configured to deflagrate and high explosives material configured to detonate and the metal outer shell has a wall thickness of at least 1 mm so as to prevent rupture of the outer shell and maintain a gas pressure within the bore during a deflagration to detonation process.

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