ALIGNMENT ASSEMBLY FOR DOWNHOLE TOOLS AND RELATED METHODS

Abstract

An apparatus for perforating a subterranean formation comprises a first perforating gun (33b) having a box end (112) having a nose, a second perforating gun (33a) having a pin end (118) having a shoulder (124); and an alignment assembly. The alignment assembly includes internal threads formed on the box end, external threads formed on the pin end, and an alignment member (120) positioned between the box end nose and the pin end shoulder. The internal threads and the external threads are specified to form an angular alignment between the first perforating gun and the second perforating gun within a first specified angular tolerance. The alignment member has at least one characteristic selected to vary the angular alignment within the first specified angular tolerance without degrading a locking force connecting the first perforating gun to the second perforating gun.

Claims

1. An apparatus for perforating a subterranean formation, comprising: a first perforating gun having a box end that includes a first slot; a second perforating gun having a pin end that includes a second slot, wherein the first perforating gun and the second perforating gun are configured to have a specified angular alignment when fired; a threaded connection that includes internal threads formed on the box end and external threads formed on the pin end, the threaded connection having a specified torque value range when the first perforating gun and the second perforating gun have the specified angular alignment, and an alignment assembly having: an alignment member positioned between a first portion of the box end and the pin end, the alignment member configured to deform to maintain the specified torque value range when the box end and the pin end are rotated into the specified angular alignment, and a locking member positioned between a second portion of the box end and the pin end, the locking member including a first tab and a second tab, the first tab being seated in the first slot and the second tab being seated in the second slot after the box end and the pin end are rotated into the specified angular alignment, locking member thereby physically connecting the box end and the pin end.

2. The apparatus of claim 1, wherein the locking member is positioned in a gap between a nose end of the box end and a shoulder of the pin end and the alignment member is positioned in a recess between a face of the pin end and an inner shoulder of the box end.

3. The apparatus of claim 1, wherein the locking member has a body with a first face and an opposing second face, wherein the first tab projects from the first face and the second tab projects from the second face, and wherein the first tab and the second tab are configured to flex axially relative to one another.

4. The apparatus of claim 1, wherein the body includes a slit at least partially physically separating the first tab from the second tab.

5. The apparatus of claim 1, wherein the first perforating gun has at least one shaped charge and the second perforating gun has at least one shaped charge, and wherein the specified angular alignment is selected to cause perforating jets formed by the at least one shaped charge of the first perforating gun and the at least one shaped charge of the second perforating gun to travel in the same angular direction.

6. An apparatus for perforating a subterranean formation, comprising: a first perforating gun having a box end; a second perforating gun having a pin end, wherein the first perforating gun and the second perforating gun are configured to have a specified angular alignment; a threaded connection that includes internal threads formed on the box end and external threads formed on the pin end, the threaded connection having a specified torque value range, and an alignment assembly that includes a deformable alignment member positioned between a portion of the box end and the pin end, the alignment member configured to deform to maintain the specified torque value range when the box end and the pin end are rotated into the specified angular alignment.

7. The apparatus of claim 6, wherein the alignment member is positioned in a gap between a nose end of the box end and a shoulder of the pin end.

8. The apparatus of claim 6, wherein the alignment member is at least partially formed of a material having a modulus of elasticity within 20% of the modulus of elasticity of copper.

9. The apparatus of claim 6, wherein the alignment member has a thickness selected to contact the pin end and the box end before the pin end and the box end can rotate into the specified angular alignment.

10. The apparatus of claim 6, wherein the first perforating gun has at least one shaped charge and the second perforating gun has at least one shaped charge, and wherein the specified angular alignment is selected to cause perforating jets formed by the at least one shaped charge of the first perforating gun and the at least one shaped charge of the second perforating gun to travel in the same angular direction.

10. A method for perforating a subterranean formation, comprising: configuring a perforating tool to include: a first perforating gun having a box end that includes a first slot; a second perforating gun having a pin end that includes a second slot, wherein the first perforating gun and the second perforating gun are configured to have a specified angular alignment when fired; a threaded connection that includes internal threads formed on the box end and external threads formed on the pin end, the threaded connection having a specified torque value range when the first perforating gun and the second perforating gun have the specified angular alignment, and an alignment assembly having: an alignment member positioned between a first portion of the box end and the pin end, the alignment member configured to deform to maintain the specified torque value range when the box end and the pin end are rotated into the specified angular alignment, and a locking member positioned between a second portion of the box end and the pin end, the locking member including a first tab and a second tab, the first tab being seated in the first slot and the second tab being seated in the second slot after the box end and the pin end are rotated into the specified angular alignment, locking member thereby physically connecting the box end and the pin end; conveying the perforating tool into a wellbore; and firing the perforating tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] 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:

[0008] FIG. 1 is a schematic sectional view of one embodiment of a perforating tool of the present disclosure as positioned within a well penetrating a subterranean formation;

[0009] FIG. 2 is a schematic sectional view of a portion of a perforating gun shown in FIG. 1;

[0010] FIG. 3 illustrates a perforating tool in accordance with embodiments of the present disclosure;

[0011] FIG. 3A illustrates the direction of perforating jets formed by perforating guns that are not in angular alignment;

[0012] FIG. 4 illustrates an alignment assembly in accordance with embodiments of the present disclosure;

[0013] FIG. 5 illustrates an alignment assembly in accordance with embodiments of the present disclosure that uses a “pin by pin” sub to connect “box ends” of adjacent guns;

[0014] FIG. 6 illustrates another alignment assembly in accordance with embodiments of the present disclosure;

[0015] FIG. 7 illustrates an “exploded view” of a perforating tool that uses the FIG. 6 alignment assembly;

[0016] FIGS. 8A and 8B illustrates the FIG. 6 alignment assembly in a pre-alignment and aligned conditions;

[0017] FIG. 9 illustrates a locking member in accordance with embodiments of the present disclosure that uses one or more standoffs;

[0018] FIGS. 10A and 10B illustrate a locking member in accordance with embodiments of the present disclosure that uses an undulating body; and

[0019] FIGS. 11A and 11B illustrate a locking member in accordance with embodiments of the present disclosure that uses a coiled body.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0020] Aspects of the present disclosure relate to rotationally aligning two or more portions of a downhole tool. Such rotational alignment may be desirable in order to have devices of adjacent portions have a specified relative angular orientation. For example, the devices may be required to have angular alignment; i.e., all point in the same angular direction. In some situations, it may be desirable to have a specified relative angular offset; e.g., two or more sets of adjacent devices may have a relative angular offset of thirty degrees, forty-five degrees, sixty degrees, ninety degrees, one-hundred twenty degrees, one-hundred eighty degrees, etc. Exemplary devices may include sensors, coring tools, anchors, stabilizers, steering tools, and shaped charges. While the description below is directed to perforating tools having shaped charges, it should be understood that the present disclosure is not limited to such devices.

[0021] Referring now to FIG. 1, there is shown a well construction and/or hydrocarbon production facility 10 positioned over a subterranean formation of interest 12. The facility can be a land-based or offshore rig adapted to convey a tool, such as a perforating tool, in a well bore 16. The wellbore 16 can include open hole sections and/or cased and cemented sections. The facility 10 can include known equipment and structures such as a platform 18 at the earth's surface 20, a derrick 22, a wellhead 24, and casing 26. A work string 28 suspended within the well bore 16 from the derrick 22 is used to convey tooling into the wellbore 16. The work string 28 may include drill pipe, coiled tubing, wire line, slick line, or any other known conveyance means. Further, the work string 28 may be pulled through the wellbore by a device such as a wellbore tractor (not shown), which may be advantageous in extended reach wells or deviated wells. The work string 28 can include telemetry lines or other signal/power transmission mediums that establish one-way or two-way telemetric communication from the surface to a tool connected to an end of the work string 28. A suitable telemetry system (not shown) can use mud pulses, electrical signals, acoustic signals, or other suitable telemetry mediums. For illustrative purposes, there is shown a telemetry system having a surface controller (e.g., a power source and/or firing panel) 30 adapted to transmit signals via a cable or signal transmission line 31 disposed in the work string 28. The signals can be analog or digital signals. In one embodiment of the present invention, a perforating tool 32 is coupled to an end of the work string 28.

[0022] The perforating tool 32 may include a plurality of guns 33a-c, each of which includes detonators (not shown), detonating cords (not shown), and one or more shaped charges 40. When detonated in the wellbore 16, the shaped charges 40 produce perforations 60 through the casing 26, cement (not shown), and the surrounding formation 12. This detonation establishes communication between the formation 12 and wellbore 16 by providing a path for formation fluids and gases to enter the wellbore 16. The process for detonating the shaped charges 70 may be referred to as “firing” the perforating tool 32.

[0023] Referring to FIG. 2, a transverse cross section of a perforating tool 32 is shown. The perforating tool 32 has a tubular carrier 34 in which is disposed a cylindrical charge tube 36. The outside diameter of the charge tube 36 is such that an annular space 38 is created between the charge tube 36 and the carrier 34. An explosive shaped charge 40 has a frusto-conical charge case 42. The charge case 42 is typically formed from steel, die cast aluminum, or zinc alloys and has an interior surface or wall 44 that defines a hollow interior of the charge case 42. The charge case 42 is open at the outer end and tapers inward. Disposed within the interior of the charge case 42 is a liner 48 having a generally conical or frusto-conical configuration. The liner 48 tapers inward from a base 50, located at the outer end, to a nose portion 52. The liner 48 is open at the base 50 and has a hollow interior. Disposed between the liner 48 and interior wall 44 of the charge case 42 is an explosive material 54. The explosive material 54 extends from the interior of the case 42 through channel formed in the innermost end of the case 42. The case 42 receives a detonating cord 56 for detonating the explosive material 54 of the shaped charge 40. The carrier 34 may include one or more scallops 70 that are radially aligned with the shaped charge 40. The scallops 70 includes a wall 71 having reduced thickness as compared to the adjacent wall of the carrier 34.

[0024] When the perforating tool 32 is fired, the thermal energy and shock wave released by the explosive material 54 upon detonation transforms the liner 48 into a molten jet (not shown). The molten jet (not shown) penetrates through the wall 71 of the scallop 70 and eventually tunnels into the surrounding formation to form a perforation.

[0025] Referring now to FIG. 3, there is shown a section of the perforating tool 32 that includes the perforating guns 33a, 33b. Each perforating gun 33a,b has a carrier 34a and 34b, respectively, on which are formed one or more scallops 70a and 70b, respectively. Shaped charges 40 are positioned inside the carriers 34a and 34b and oriented to direct perforating jets through the scallops 70a,b. The shaped charges 40 and associated scallops 70a may be aligned along a plane 90 and the shaped charges 40 and associated scallops 70b may be aligned along a plane 92.

[0026] In embodiments, a threaded connection may be used to interconnect the perforating guns 33a,b. For example, the perforating gun 33a may include internal threads 110 formed on a box end 112 and the perforating gun 33b may include external threads 116 formed on a pin end 118. The internal threads 110 and the external threads 116 are collectively referred to as the “threaded connection.” The threaded connection is susceptible to at least two assembly issues. First, a certain amount of angular misalignment may be present between the planes 90 and 92 after the threaded connection is torqued to the maximum allowed value. Attempting further relative rotation to align the planes 90 and 92 may over-torque and damage the threads 110, 116. Second, the threaded connection may allow the desired alignment between the planes 90 and 92, but there is insufficient locking force to keep the threaded connection made up. Thus, to obtain the desired locking force, additional relative rotation may be required to obtain the desired locking force, which may result in angular misalignment of the planes 90 and 92.

[0027] FIG. 3A illustrates the drawbacks of angular misalignment between the planes 90 and 92 of FIG. 3. FIG. 3A is a simplified schematic end view of the perforating tool 32 having perforating guns 33a,b (FIG. 3). The perforating tool 32 may form perforating jets 81, 83 when fired. Arrow 41a shows the angular direction of the perforating jet 81 formed by the perforating gun 33a (FIG. 3) and arrow 41b shows the angular direction of the perforating jet 83 formed by the perforating gun 33b (FIG. 3). If an angular misalignment 80 is present between the perforating guns 33a,b (FIG. 3) when fired, the perforating jets travel in different angular directions.

[0028] One instance in which angular misalignment is undesirable is if only a specific location 82 in the wellbore is intended to be perforated. This angular misalignment may result in sectors or areas of the formation being unintentionally perforated. Another instance is the presence of one or more objects 84 in the vicinity of the perforation. Illustrative objects 84 include communication lines, hydraulic lines, downhole tooling, etc. Misdirected perforating jets may damage such objects 84.

[0029] Referring to FIG. 3, in accordance with the present disclosure, an alignment assembly 100 may be used to align plane 90 with plane 92 and thereby reduce the angular misalignment 80 of FIG. 3A to below a specified value. By “align,” it is meant that plane 90 and plane 92 are co-planar within a specified tolerance. For example, the tolerance can be specified using an angular value, e.g., within 2 degrees, or within 1 degree. When the angular alignment is within the specified value, the perforating guns 33a,b are considered “clocked.” Therefore, when the perforating guns 33a,b are fired, the perforating jets travel in the same angular direction.

[0030] Referring to FIG. 4, in one embodiment, the alignment assembly 100 may include an alignment member 120 that is interposed between the perforating guns 33a and 33b. In one non-limited arrangement, the alignment member 120 is positioned in a gap 121 between a nose end 122 of the box end 112 and a shoulder 124 of the pin end 118.

[0031] The alignment member 120 may be a deformable member that enables the relative rotational position of the box end 112 and the pin end 118 to be varied while still maintaining the locking force required for the box end 112 and the pin end 118 to remain connected to one another during use.

[0032] First, as noted above, a certain amount of angular misalignment may be present between the planes 90 and 92 after the threaded connection is torqued to the maximum allowed value. However, by deforming, the alignment member 120 allows additional relative rotation to align the planes 90 and 92 without over-torquing and damaging the threads 110, 116. Thus, the alignment member 120 increases the angular range in which a maximum amount of locking force is present to lock the box end 112 and pin end 118.

[0033] Second, as also noted above, the threaded connection may allow the desired alignment between the planes 90 and 92 but insufficient locking force may be present. The alignment member 120 can be dimensioned to contact the box end 122 and the pin end 118 during relative rotation and before alignment of the planes 90 and 92 occurs. The contact deforms the alignment member 120 and introduces a locking force to keep the threaded connection made up before the desired alignment is obtained so that no additional relative rotation is required to obtain the desired locking force.

[0034] In embodiments, the thickness and the modulus of elasticity may be selected to provide the alignment member 120 with the desired elastic characteristics. For example, some or all of the alignment member 120 may be formed of copper or materials having a modulus of elasticity similar to copper (e.g., within 20% of the modulus of elasticity of copper). By thickness, it is meant an axial distance such as the distance separating the box nose end 122 and the pin end shoulder 124.

[0035] In one embodiment, the thickness of the alignment member 120 is selected such that the alignment member 120 contacts and is squeezed between the box end nose 122 and the pin end shoulder 124 at least one full rotation before the internal threads 110 are fully engaged with the external threads 116. By fully engaged, it is meant that no further rotation is possible without damaging either the internal threads 110 or the external threads 116. Further, the material of the alignment member 120 is selected such that the locking force provided by the alignment member 120 is sufficient to maintain a connection over a specified angular range; e.g., 5 degrees.

[0036] The alignment member 120 may have a configuration different from the ring-shape shown. For example, the alignment member 120 may be ring shaped, “C” shaped, have an irregular thicknesses, or be formed of two or more different materials. Generally, any body or structure that provides a desired spring force and elastic behavior to generate the required locking force over a specified angular range may be used.

[0037] In one arrangement, the internal threads 110 and the external threads 116 may be machined to obtain a desired pre-alignment between the planes 90 and 92. The desired pre-alignment may occur after a specified amount of torque has been applied to the mating ends of the guns 33a,b to “make up” the threaded connection. By “make up,” it is meant completing the threaded connection such that the guns 33a,b are ready for deployment in the wellbore 16 (FIG. 1) The applied torque may be the minimum required to ensure that the mating ends after being “made up” do not subsequently degrade while conveyed into or out of a wellbore. By degrade, it is meant become loosen, unthreaded, or otherwise fail to securely connect the guns 33a,b to one another. As used herein, the force that fixes to the perforating guns to one another upon “make up” will be referred to as a locking force. The internal threads 110 and the external threads 116 may be machined such that the angular misalignment between the planes 90 and 92 (FIG. 3) is within a specified value. In some applications, the maximum angular misalignment may be 4 degrees, 3.4 degrees, 3 degrees, 2.5 degrees, 2 degrees, or 1 degree.

[0038] During assembly, the box end 112 and the pin end 118 are made up by relative rotation until the alignment member 120 is compressed between the box end nose 122 and the pin end shoulder 124. To obtain such compression, the alignment member 120 has a thickness selected to contact the pin end 118 and the box end 112 before the pin end 118 and the box end 112 can rotate into the specified angular alignment. Next, additional relative rotation is made until the plane 90 and plane 92 (FIG. 3) are co-planar within the specified value. When the alignment is within the specified value, the guns 33a,b may be said to have been “clocked” relative to one another. Thus, the perforating jets formed by the guns 33a,b all travel in the same angular direction.

[0039] Referring to FIG. 5, there is shown another embodiment of the present disclosure. Similar to previously discussed embodiments, the perforating tool 32 has two or more gun assemblies 33a, 33b. However, both gun assemblies 33a,b have internal threads, or box ends 150a,b, respectively. The box ends 150a,b, each have nose ends 122. Thus, a pin sub 160 is used to connect the gun assemblies 33a,b. The pin sub 160 includes external threads, or pin ends 162a,b at opposing ends. The pin ends 162a,b, each have shoulders 124. For clarity, the charge holder, shaped charges, and scallops of the guns 33a,b are not shown.

[0040] To “clock” the guns 33a,b, the alignment members 120a,b discussed above may be used. Alignment member 120a is positioned at the threaded connection between nose of the box end 150a and shoulder of pin end 162a and alignment member 120b is positioned at the threaded connection between nose of the box end 150b and shoulder of the pin end 162b. The alignment members 120a,b are constructed and function similarly to the alignment members previously discussed.

[0041] Also, markers may be used on the guns 33a,b and the pin sub 160. For example, carrier 34a of the gun 33a may include a marker 170a at or near the box end 150a and carrier 34b of the gun 33b may include a marker 170b at or near the box end 150b. Also, the pin sub 160 may include markers 164a,b at or near the pin ends 162a,b respectively. It should be noted that the markers 164 a,b may be one continuous marker in some embodiments. When all of the markers 170a,b and 164a,b are aligned with one another within a specified tolerance, then gun 33a may be considered “clocked” with gun 33b.

[0042] In use, the threaded connection between box end 150a and pin end 162a is made up until the marker 170a is aligned with the marker 164a. The alignment member 120a deforms as needed to allow the desired alignment. In like manner, the threaded connection between box end 150b and pin end 162b is made up until the marker 170b is aligned with the marker 164b. The alignment member 120b deforms as needed to allow the desired alignment. In some embodiments, the markers 170a,b and 164a,b are visible before, during, and after assembly. The markers 170a,b and 164a,b be a physical deformation such as a scratch or groove or an applied marker such as paint or dye.

[0043] The markers may also be used in embodiments where a pin sub is not used. Referring to FIG. 3, to facilitate “clocking” the gun 33a with the gun 33b, markers with known relative alignment may be used on the guns 33a,b. For example, carrier 34a of the gun 33a may include a marker 170a at or near the box end 112 and carrier 34b of the gun 33b may include a marker 170b at or near the pin end 118. The markers 170a,b may be oriented and positioned such that when aligned with one another within a specified tolerance, then the gun 33a is “clocked” with the gun 33b.

[0044] Referring now to FIG. 6, there is shown a cross-sectional view of another alignment assembly 100 according to the present disclosure. The alignment assembly 100 may include internal threads 110 formed on a box end 112 and external threads 116 formed on a pin end 118. A gap 121 is specified by a nose end 122 of the box end 112 and a shoulder 124 of the pin end 118. A recess 123 is specified by an inner shoulder 125 formed on an inner surface of the box end 112 and an end face 127 of the pin end 118. Thus, the gap 121 and the recess 123 physically separate portions of the box end 112 and the pin end 118 from one another. The threads 110, 116 are disposed between the gap 121 and the recess 123. To obtain and maintain a desired rotational alignment between the guns 33a,b, the alignment assembly 100 includes a locking member 200 disposed in the gap 121 and an alignment member 120 disposed in the recess 123.

[0045] Referring to FIG. 7, the locking member 200 physically connects the perforating guns 33a,b and thereby maintains a desired relative rotational alignment between the perforating guns 33a,b. In one arrangement, the locking member 200 includes a first tab 202 and a second tab 204. The first tab 202 is configured to enter and engage with a complementary slot 94 formed in the shoulder 124 of the pin end 118. The second tab 204 is configured to enter and engage with a complementary slot 96 formed in the nose end 122 of the box end 112. The tabs 202, 204 have a fixed circumferential orientation relative to one another. Thus, when the tabs 202, 204 are engaged with slots 94, 96, respectively, the guns 33a,b have a specified circumferential orientation relative to one another; i.e., the guns 33a,b have been “clocked.”

[0046] In one embodiment, the locking member 200 may be configured to allow the tabs 202, 204 to have move axially to and from one another. For example, tabs 202, 204 may each project from opposing faces 211, 213, respectively, of a body 206. A slit 208 partially physically separates the tabs 202, 204, which provides elasticity in the body 206 in the vicinity of tabs 202, 204. Thus, the tabs 202, 204 can flex in an axial direction relative to one other. The axial direction is shown with the arrows labeled 217. The body 206 may be a continuous ring as shown. In variants not shown, the body 206 may be C-shaped, be composed of two or more structures or materials, or have an irregular shape or other geometry.

[0047] Referring to FIG. 8A, there is shown the alignment assembly 100 in a pre-alignment condition wherein the slots 94 and 96 are rotationally out of alignment. In one method of assembly, the tab 202 of the locking member 200 is first inserted into the slot 94 of the perforating gun 33a. Thus, a face 224 from which the tab 202 projects is flush with and has contiguous contact with the adjacent face 226 of the perforating gun 33a. Before relative rotation, a face 228 of the perforating gun 33b, which may be a part of the nose end 112 of the box end 112, does not contact the tab 204. After relative rotation of the perforating guns 33a,b, the tab 204 eventually contacts the adjacent face 228 of the perforating gun 33b. The adjacent face 228 presses the tab 204 toward the tab 202. As can be seen, the slit 208 reduces in size to accommodate the compression.

[0048] Referring to FIG. 8B, there is shown the alignment assembly 100 in an aligned condition wherein the slots 94 and 96 are rotationally aligned with one another. The tab 202 of the locking member 200 seats in the slot 94 of the perforating gun 33a and the tab 204 seats in the slot 96. Upon aligning with the slot 94, the elasticity of the body 206 allows the tab 204 to flex away from the tab 202. It should be noted that relative rotation between the perforating guns 33a,b is prevented by the tab 202 of the locking member 200 physically residing in the slot 94 of the perforating gun 33a and the tab 204 physically residing in the slot 96 of the perforating gun 33b.

[0049] Referring to FIG. 6, the alignment member 120 provides a locking force for the threads 110, 116 in a manner as previously described. For example, while the perforating guns 33a,b are being connected using the threads 110, 116, the alignment member 120 is compressed between the inner shoulder 125 of the box end 112 and the end face 127 of the pin end 118. The compressed alignment member 120 provides a locking force that helps the mated threaded sections of the perforating guns 33a,b to remain connected while being conveyed into or out of a wellbore. The compression of the alignment member 120 may begin before, during, or after the locking member 200 is compressed in the gap 121.

[0050] It should be appreciated that locking members of the present disclosure are susceptible to numerous variations as discussed below.

[0051] Referring to FIG. 9, the locking member 200 may include one or more retractable stand-offs 220 that extend from a face 222 of the body 206 of the locking member 200. The embodiment of FIG. 9 is configured such that the tab 202 during installation is fitted into the slot 94 (FIG. 6) of the perforating gun 33a (FIG. 6). Thus, a face 224 from which the tab 202 projects is flush with and has contiguous contact with the adjacent face 226 (FIG. 8B) of the perforating gun 33a (FIG. 8B). During relative rotation of the perforating guns 33a,b, the stand-offs 220 and the tab 204 eventually contact the adjacent face 228 (FIG. 8B) of the perforating gun 33b (FIG. 8B). By providing multiple points of physical contact with the adjacent face 228 (FIG. 8B), the stand-offs 220 limit the amount of tilting, pivoting, or other movement of the body 206 that may cause misalignment with respect to the perforating gun 33b (FIG. 8B). The stand-offs 220 retract to allow the tab 204 to seat within the slot 96 once the desired relative rotational alignment has been achieved.

[0052] FIGS. 10A and 11A illustrate additional embodiments of the locking member 200 according to the present disclosure.

[0053] Referring to FIG. 10A, the locking member 200 may have a body 206 that undulates along a circumference. The tabs 202, 204 project from their respective faces 211, 213, respectively. However, the tabs 202, 204 are positioned on undulations that are out of phase; i.e., do not extend in the same axial direction. While the tabs 202, 204 are shown with a one hundred eighty degrees angular offset, other angular offsets may be used. As shown in FIG. 10B, an undulation 240 is out of phase with undulation 242. The undulations enable the body 206 to flex or otherwise elastically deform in a manner similar to a wave spring, which allows the tabs 202, 204 to axially extend and retract relative to one another. Thus, for example, after tab 202 seats in the slot 94 (FIG. 8A), the undulations of the body 206 can flatten to allow the tab 204 to retract upon contact with the face 228 (FIG. 8A) and then later flex outward to enter the slot 96 (FIG. 8A).

[0054] Referring to FIG. 11A, the locking member 200 may have a body 206 that is coiled. The tabs 202, 204 may project from ends 250, 252, respectively, of the coiled body 206. While the tabs 202, 204 are shown with no angular offset, an angular offset may be used. The coils enable the body 206 to behave in a manner similar to a coil spring, which allows the tabs 202, 204 to extend and retract relative to one another. Thus, for example, after tab 202 seats in the slot 94 (FIG. 8A), the coiled shaped body 206 can flatten to allow the tab 204 to retract upon contact with the face 228 (FIG. 8A) and then later flex outward to enter the slot 96 (FIG. 8A).

[0055] As noted previously, the teachings of the present disclosure are not limited to perforating tools. Referring to FIG. 1, any number of drilling, completion, or logging tools may be used place of the perforating tool 32. That is, shaped charges are only illustrative of devices that may require precise relative alignment between two or more sections of a downhole tool.

[0056] From the above, it should be appreciated that the present disclosure includes in part, an apparatus for perforating a subterranean formation that comprises a first perforating gun having a box end having a nose, a second perforating gun having a pin end having a shoulder; and an alignment assembly. The alignment assembly includes internal threads formed on the box end, external threads formed on the pin end, and an alignment member positioned between the box end nose and the pin end shoulder. The internal threads and the external threads are specified to form an angular alignment between the first perforating gun and the second perforating gun within a first specified angular tolerance. The alignment member has at least one characteristic selected to vary the angular alignment within the first specified angular tolerance without degrading a locking force connecting the first perforating gun to the second perforating gun.

[0057] From the above, it should be appreciated that what has been described further includes an apparatus having a first perforating gun having a box end having a nose; a second perforating gun having a box end having a nose; a pin sub having a first pin end with a first shoulder and a second pin end with a second shoulder; and an alignment assembly. The alignment assembly may include internal threads formed on the box ends of the first perforating gun and the second perforating gun, external threads formed on the pin ends of the pin sub, a first alignment member positioned between the first box end nose and the first pin end shoulder, and an second alignment member positioned between the second box end nose and the second pin end shoulder. The internal threads and the external threads may be specified to form an angular alignment between pin sub, the first perforating gun, and the second perforating gun within a first specified angular tolerance. The first and the second alignment member may have at least one characteristic selected to vary the angular alignment within the first specified angular tolerance without degrading a locking force connecting the pin sub to the first perforating gun and to the second perforating gun. Additionally, the first gun may include a first marker, the second gun may include a second marker, and the pin sub may include at least a third marker. The alignment of the first marker, the second marker, and the at least third marker within a specified angular value indicates that the first specified angular tolerance is present.

[0058] As used above, the following terms are used interchangeably: “angular mis/alignment” and “rotational mis/alignment;” “gun” and “perforating gun,” and “axial” and “longitudinal.” The term “specified” means that a value is predetermined using known engineering techniques.

[0059] 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. Thus, it is intended that the following claims be interpreted to embrace all such modifications and changes.