DETONATOR OUTPUT INTERRUPTER FOR DOWNHOLE TOOLS

Abstract

An apparatus for selectively activating a downhole tool by using a shockwave generated by a detonator assembly may include an outer housing having a bore and an inner housing disposed in the bore of the outer housing. The inner housing may include a chamber having at least one canted surface, an inlet communicating with the chamber and being positioned between the chamber and the detonator assembly, an outlet communicating with the chamber and being positioned between the chamber and the downhole tool, and an energy blocker disposed in the chamber and being freely movable in the chamber as the inner housing changes orientation relative to a vertical datum. The energy blocker axially aligns with the inlet and the outlet when the inner housing is angularly offset less than a specified amount relative to a vertical datum.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser. No. 61/977,441, filed Apr. 9, 2014, the entire disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to devices and methods for firing one or more downhole tools. More particularly, the present disclosure is in the field of control devices and methods for enhancing the reliability of firing systems used to fire a ballistic downhole tool.

BACKGROUND

One of the activities associated with the completion of an oil or gas well is the perforation of a well casing. During this procedure, perforations, such as passages or holes, are formed in the casing of the well to enable fluid communication between the wellbore and the hydrocarbon producing formation that is intersected by the well. These perforations are usually made with a perforating gun loaded with shaped charges. The gun is lowered into the wellbore on electric wireline, slickline or coiled tubing, or other means until it is at a desired target depth; e.g., adjacent to a hydrocarbon producing formation. Thereafter, a surface signal actuates a firing head associated with the perforating gun, which then detonates the shaped charges. Projectiles or jets formed by the explosion of the shaped charges penetrate the casing to thereby allow formation fluids to flow from the formation through the perforations and into the production string for flowing to the surface.

Many oil well tools incorporate a high-order detonation as part of their operation. When these tools are fired prematurely, it can be costly and time consuming to repair the well and re-attempt the desired wellbore operation. The present disclosure relates to methods and devices for preventing premature high-order detonations from initiating operation of oil well tools.

SUMMARY

In aspects, the present disclosure provides an apparatus for selectively activating a downhole tool by using a shockwave generated by a detonator assembly. The apparatus may include an outer housing having a bore and an inner housing disposed in the bore of the outer housing. The inner housing may include a chamber having at least one canted surface, an inlet communicating with the chamber and being positioned between the chamber and the detonator assembly, an outlet communicating with the chamber and being positioned between the chamber and the downhole tool, and an energy blocker disposed in the chamber and being freely movable in the chamber as the inner housing changes orientation relative to a vertical datum. The energy blocker axially aligns with the inlet and the outlet when the inner housing is angularly offset less than a specified amount relative to a vertical datum.

In aspects, the present disclosure provides a method for selectively activating a downhole tool by using a shockwave generated by a detonator assembly. The method employs detonator output interrupters according to the present disclosure along with one or more well tools that are conveyed to a target depth across a wellbore that has vertical and deviated sections.

It should be understood that examples of the more important features of the disclosure have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the disclosure that will be described hereinafter and which will in some cases form the subject of the claims appended thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

For detailed understanding of the present disclosure, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein:

FIG. 1 schematically illustrates an elevation view of a surface facility adapted to perform one or more pre-defined tasks in a wellbore using one or more downhole tools;

FIG. 2 illustrates a side sectional view of a detonator output interrupter according to one embodiment of the present disclosure;

FIG. 3 illustrates a side sectional view of the FIG. 2 detonator output interrupter in a horizontal orientation; and

FIG. 4 illustrates a side sectional view of the FIG. 2 detonator output interrupter in an inverted orientation.

DETAILED DESCRIPTION

The present disclosure relates to devices and methods for providing a detonator output interrupter to selectively initiate operation of one or more downhole tools. The present disclosure is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the present disclosure with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that illustrated and described herein.

Referring to FIG. 1, there is shown a well construction and/or hydrocarbon recovery facility 10 positioned over a subterranean formation of interest 12. The facility 10 can include known equipment and structures such as a rig 16, a wellhead 18, and cased or uncased pipe/tubing 20. A work string 22 is suspended within the wellbore 14 from the rig 16. The work string 22 can include drill pipe, coiled tubing, wire line, slick line, or any other known conveyance means. The work string 22 can include telemetry lines or other signal/power transmission mediums that establish one-way or two-way telemetric communication. A telemetry system may have a surface controller (e.g., a power source) 24 adapted to transmit electrical signals via a cable or signal transmission line 26 disposed in the work string 22. To perform one or more tasks in the wellbore 14, the work string 22 may include a downhole tool 50 that is activated by a high-order detonation.

Conventionally, the downhole tool 50 is conveyed by the work string 22 along the various sections of the wellbore 14 until a desired target depth is reached. The wellbore 14 may have a complex geometry that includes one or more vertical sections 30 and one or more deviated sections 32. While shown as perfectly vertical and perfectly horizontal, the vertical sections 30 and the deviated sections 32 may vary in actual angular offset from a vertical datum. In some instances, the target depth is in the deviated section 32 of the wellbore 14. As discussed below, detonator output interrupters according to the present disclosure can prevent premature activation while the downhole tool 50 is being conveyed to the target depth.

Referring to FIG. 2, there is sectionally illustrated one non-limiting embodiment of a detonator output interrupter 100 made in accordance with the present disclosure. The detonator output interrupter 100 can selectively prevent an energetic discharge, such as a shockwave, generated by the detonator assembly 110 from energetically activating a downhole tool 120. The detonator assembly 110 may include a firing head 112 and an initiator 114. The downhole tool 50 can be a perforating gun or any other device that uses a high-order detonation and associated shock wave to initiate operation. As shown, the downhole tool 50 may be fired by detonating a bi-directional booster charge 122 that ignites a detonating cord 124.

In one embodiment, the detonator output interrupter 100 may include an outer housing 130, an inner housing 132, and an energy blocker 134.

The outer housing 130 may be formed as a cylindrical structure that acts as a bulkhead and an enclosure for the internal components of the detonator assembly 110 and the detonator output interrupter 100. In one embodiment, the outer housing has a first end 140 that connects via threads 142 to an adjacent tool 144 and a second end 146 that connects via threads 148 to the downhole tool 50. The outer housing also has a bore 150 in which the firing head 112, the initiator 114 and the inner housing 132 are serially disposed. In other embodiments, these components may be disposed in separate enclosures. For example, the firing head 112 and the initiator 114 may be positioned in a separate sub.

In one arrangement, the inner housing 132 may also be a cylindrical structure that is configured to retain the energy blocker 134 and to channel the shockwave generated by the detonator assembly 110 to the downhole tool 50. The inner housing may include an inlet 152 and an outlet 154 that communicate with a chamber 156. The inlet 152 and the outlet 154 are axially aligned with one another and may be concentric within the inner housing 132 as shown or may be offset from the central axis of the inner housing 132.

The chamber 156 includes opposing surfaces 158 that are substantially transverse to the vertical datum 102 and a cylindrical inner surface that is substantially parallel to the vertical datum 102. By substantially, it is meant within 30 degrees. The inlet 152 has one end proximate to the initiator 114 and another end terminating at a first surface of the opposing surfaces 158. The outlet 154 has one end proximate to the downhole tool 50 and another end terminating at a second surface of the opposing surfaces 158. The surfaces are generally canted such that they slope toward the inlet 152 or the outlet 154. That is, the surfaces 158 may be sloped to position an apex at the inlet 152 or the outlet 154. For example, the surfaces 158 may have a conical shape that positions the cone apex at the inlet 152 or the outlet 154. Generally concave shapes may also be used. The shape and amount of slope of the surfaces 158 can control the amount of deviation needed to shift the energy blocker 134. The opposing surfaces 158 are shown as similarly shaped, but they may also be dissimilarly shaped. That is, the surfaces 158 may be canted the same way, canted different ways, or one may have no cant.

The energy blocker 134 deflects, absorbs, or otherwise interrupts an energy train generated by the detonator assembly 110 from initiating the downhole tool 50. The energy blocker 134 is disposed in the chamber 156 and can selectively obstruct the axial path along which a shockwave generated by the initiator 114 traveling to the booster charge 122. The energy blocker 134 may be formed of steel, metal, ceramics, plastics, composites, or any other material that deflects and/or breaks up the shockwave such that the energy is dissipated into the inner housing 132. In one arrangement, the detonator output interrupter 100 blocks the shock wave when the detonator output interrupter 100 is in the vertical position (e.g., aligned with the vertical datum 102). The energy blocker 134 shifts to a position that does not impede the travel of the shockwave after the tool 100 is oriented at or past a selected deviation. In one embodiment, the energy blocker 134 may be a spherical body such as a ball. In the vertical orientation shown in FIG. 2, the energy blocker 134 gravitates to and rests over the outlet 154 because the surface 158 is canted.

In one non-limiting embodiment, the energy blocker 134 may be a metal ball (e.g., a steel ball bearing) that is “freely movable” in the chamber 156. By “freely moveable,” it is meant that the energy blocker 134 is not connected to any other structure and can freely move due to gravity as the detonator output interrupter changes orientation. A ball shape allows the energy blocker 134 to roll due to gravity. However, other shapes may also be used (e.g. disk shapes). Also, actions other than rolling may be used (e.g., sliding, pivoting, rotating, etc.). Thus, the energy blocker 134 may use any configuration that is responsive to gravity and can move out of contact with the inlet 152 or the outlet 154 when the downhole tool 100 is in the appropriate orientation. The shape and weight of the energy blocker 134, as well as the dimensions and shape of the chamber 152, can also control how much deviation will be needed to shift the energy blocker 134.

Referring to FIG. 3, the detonator output interrupter 100 is shown in a horizontal orientation; i.e., the vertical datum 102 (FIG. 2) is transverse to gravity. Because of gravity, the energy blocker 134 has fallen to a region of the chamber 156 that is radially offset from the inlet 152 and the outlet 154. Thus, a shockwave from the initiator 114 travels unimpeded through the chamber 156 to the booster charge 122. It should be noted that a deviated orientation other than a horizontal would also move the energy blocker 134 away in this particular embodiment.

In FIG. 4, the detonator output interrupter 100 is shown in an inverted position; i.e., vertically flipped from the orientation shown in FIG. 2. In this vertical orientation, the energy blocker 134 gravitates to and rests over the inlet 152 because the surface 158 is canted; i.e., sloped. However, the function of the energy blocker 134 remains generally the same in that the shockwave from the initiator 114 is blocked from passing through to the booster charge 122.

One illustrative use of the detonator output interrupter 100 will be discussed in connection with FIGS. 1-3. For clarity, the detonator output interrupter 100 will be discussed with reference to perforating guns. It should be appreciated, however, that the detonator output interrupter 100 is not limited to such use.

In one mode of use, the detonator output interrupter 100 is incorporated into the tool 50. The downhole tool 50 may be any device that is intended to be activated by using by a high-order detonation from the detonator assembly 110. The signal for firing the detonator assembly 110 may be a pressure change, an impact, a time delay, an electrical signal, or any other suitable actuating methodology. When a signal is received, the firing head 112 impacts the initiator 114. Upon impact, the initiator 114 undergoes a high-order detonation that causes a shock wave to enter the inlet 152. Whether or not the shockwave passes successfully through to the booster charge 122 depends on the orientation of the detonator output interrupter 100.

Initially, the downhole tool 50 may be conveyed along the vertical section 30 of the wellbore 14. In this section, the orientation of the detonator output interrupter 100 may be less than the selected minimum value for a deviation. Therefore, if the detonator assembly 110 inadvertently generates a shock wave, then the energy blocker 134 may be in physical contact with one of the opposing surfaces 158 and axially aligned with the inlet 152 and the outlet 154. Thus the energy blocker 134 acts as an energy barrier and/or energy absorber for this inadvertent shock wave. Thus, the downhole tool 50 is not prematurely initiated.

After the downhole tool 50 has reached the target depth at the deviated section 32 of the wellbore, the orientation of the detonator output interrupter 100 may be at or greater than the selected minimum value for a deviation. The selected value for the deviation may be a 15 degree, 30 degree, 45 degree, 60 degree, 75 degree, a 90 degree, or another intervening value. Therefore, the gravity radially shifts the energy blocker 134 out of alignment with the inlet 152 and the outlet 154. Thus, for instance, the energy blocker 134 may be radially displaced from the inlet 152 and the outlet 154 and resting on the opposing surface 158 and/or the cylindrical inner surface. Now, a shockwave generated by the detonator assembly 110 can travel axially unimpeded through the chamber 156, exits at the outlet 154, and ignite the booster charge 122. The booster charge 122 detonates the detonating cord 124 or other device, which then initiates operation of the downhole tool 50.

As used above, a high-order detonation is a detonation that produces high amplitude pressure waves (e.g., shock waves) and thermal energy. Likewise, a high-order explosive is an explosive formulated to generate a high-order detonation when detonated. In firing head assemblies, a high-order detonation occurs when a firing pin percussively impacts and detonates a detonator that includes a high-order explosive. The primary and secondary explosive bodies, as well as the activator, may use one or more high-explosives. Illustrative high-explosives include, but are not limited, to RDX (Hexogen, Cyclotrimethylenetrinitramine), HMX (Octagon, Cyclotetramethylenetetranitramine), HNS, and PYX.

As used above, “selective” means that activation of the downhole tool can occur only when the downhole tool is at a selected orientation relative to a vertical datum 102. The selected orientation can be a range (e.g., at least thirty degrees offset from the vertical datum). As used above, the terms “activation” and “initiation” are used synonymously. As used above, a shockwave is a high amplitude pressure pulse. In some conventions, an orientation less than forty five degrees from vertical is considered a vertical or substantially vertical and an orientation of forty five degrees or greater from vertical is considered deviated or substantially. As used above, a vertical datum is a datum that is substantially parallel with the direction of gravitational pull (e.g., plus or minus ten degrees).

In other embodiments, the detonator output interrupter 100 may be used to block other energy transfer systems. For example, the detonator output interrupter 100 could be used with an igniter and propellant system. In such an embodiment, a flame output from the igniter will be interrupted.

The foregoing description is directed to particular embodiments of the present disclosure for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope of the disclosure. It is intended that the following claims be interpreted to embrace all such modifications and changes.

Claims

1. An apparatus for selectively activating a downhole tool in a wellbore by using a shockwave generated by a detonator assembly, comprising:

an outer housing having a bore;

an inner housing disposed in the bore of the outer housing, the inner housing including: a chamber having at least one canted surface; an inlet communicating with the chamber, the inlet positioned between the chamber and the detonator assembly, an outlet communicating with the chamber, the outlet positioned between the chamber and the downhole tool; and an energy blocker disposed in the chamber, the energy blocker being freely movable in the chamber as the inner housing changes orientation relative to a vertical datum, the energy blocker axially aligning with the inlet and the outlet when the inner housing is angularly offset less than a specified amount relative to the vertical datum.

2. The apparatus of claim 1, wherein the energy blocker is a spherical body.

3. The apparatus of claim 1, wherein the outer housing and the inner housing are cylindrical and the at least one surface has a conical shape.

4. The apparatus of claim 1, wherein the at least one canted surface is canted toward one of: (i) the inlet, and (ii) the outlet.

5. The apparatus of claim 1, wherein the chamber includes opposing surfaces that are substantially transverse to the vertical datum, wherein the at least one canted surface is formed on one of the opposing surfaces.

6. The apparatus of claim 1, wherein the chamber includes canted opposing surfaces that are substantially transverse to the vertical datum.

7. The apparatus of claim 1, wherein the energy blocker is formed of at least one of: (i) steel, (ii) metal, (iii) ceramic, (iv) plastic, and (iv) a composite.

8. An apparatus for use in a wellbore, comprising:

a detonator assembly having a firing head and an initiator, the detonator assembly being configured to generate a shock wave when activated;

detonator output interrupter connectable with the detonator assembly, the detonator output interrupter having: an outer housing having a bore; an inner housing disposed in the bore of the outer housing, the inner housing including: a chamber having a first and a second opposing surface, each opposing surface being substantially transverse to a vertical datum, wherein at least one of the first and the second opposing surfaces is canted; an inlet communicating with the chamber, the inlet positioned between the chamber and the detonator assembly and having an end terminating at the first opposing surface, an outlet communicating with the chamber and having an end terminating at the second opposing face, and an energy blocker disposed in the chamber, the energy blocker being freely movable in the chamber as the inner housing changes orientation relative to a vertical datum, the energy blocker blocking the generated shock wave by axially aligning with the inlet and the outlet when the inner housing is angularly offset less than a specified amount relative to the vertical datum; and a downhole tool connectable with the detonator output interrupter, the downhole tool being activated by a generated shock wave that is not blocked by the energy blocker.

9. The apparatus of claim 8, wherein: the energy blocker is a spherical body, the outer housing and the inner housing are cylindrical, and a conical shape defines at least one of the (i) first opposing surface, and (ii) the second opposing.

10. The apparatus of claim 8, wherein at least one of: (i) the first opposing surface is canted to the inlet, and (ii) the second opposing surface is canted toward the outlet.

11. The apparatus of claim 8, wherein the first opposing surface is canted to the inlet and the second opposing surface is canted toward the outlet.

12. The apparatus of claim 8, wherein the energy blocker is formed of at least one of: (i) steel, (ii) metal, (iii) ceramic, (iv) plastic, and (iv) a composite.

13. The apparatus of claim 8, wherein the downhole tool includes a bi-directional booster charge and a detonating cord.