Perforating gun orienting system, and method of aligning shots in a perforating gun

Abstract

A method of avoiding a frac hit in a hydrocarbon producing field. The method comprises locating a parent wellbore in the hydrocarbon producing field, and then locating a child wellbore in the hydrocarbon producing field. The method also includes running a perforating gun assembly into the child wellbore, wherein the perforating gun assembly comprises a first perforating gun and a second perforating gun, with each defining a gun barrel housing having a first end and an opposing second end. The assembly also includes a tandem sub, with the tandem sub having first and second opposing ends defining a threaded connector, and each end having a side port configured to receive an alignment screw. The method also comprises linearly aligning charges of each of the first and second perforating guns, wherein all charges are aligned in a single direction by rotating one or both of the respective perforating guns relative to the tandem sub. The charges are aligned to fire shots into the formation at a horizontal angle and in a direction away from the parent wellbore.

Claims

1. A method of avoiding a frac hit in a hydrocarbon producing field, comprising: locating a parent wellbore in the hydrocarbon producing field; locating a child wellbore in the hydrocarbon producing field; running a perforating gun assembly into the child wellbore, wherein the perforating gun assembly comprises: a first perforating gun, the first perforating gun comprising a tubular gun barrel having a first end and an opposing second end; a second perforating gun, the second perforating gun also comprising a tubular gun barrel having a first end and an opposing second end; a tandem sub, the tandem sub having first and second opposing ends, with each end defining a threaded connector; and a plurality of charges residing within each of the first and second perforating guns; using the tandem sub, threadedly connecting the second end of the tubular gun barrel of the first perforating gun with the first end of the tubular gun barrel of the second perforating gun; linearly aligning the plurality of charges of each of the first and second perforating guns at a surface, wherein all charges are aligned in a single direction by rotating one or both of the respective perforating guns relative to the tandem sub; rotationally locking the first and second perforating guns relative to the tandem sub, at the surface; running the perforating gun assembly into the wellbore at the end of an electric line; and pumping the perforating gun assembly into a horizontal leg of the child wellbore to a selected depth, wherein the charges are aligned to fire shots into a surrounding subsurface formation at a horizontal orientation and in a direction away from the parent wellbore.

2. The method of claim 1, wherein: each of the first and second opposing ends of the tandem sub has a side port configured to receive a threaded alignment screw, and with each threaded alignment screw comprising a head; and the perforating gun assembly further comprises: a first slot placed at the second end of the tubular gun barrel of the first perforating gun; and a second slot placed at the first end of the tubular gun barrel of the second perforating gun; and wherein the step of rotationally locking the first and second perforating guns comprises: running a threaded alignment screw into each side port of the tandem sub such that the head of each threaded alignment screw clears an inner diameter of the tubular gun barrel of each of the first and second perforating guns; rotationally unthreading each of the first and second perforating guns from the opposing ends of the tandem sub until the slots are lined up with the threaded alignment screw in the respective side ports; and backing each threaded alignment screw out of its respective side port until the head of each threaded alignment screw locks into an inner groove of the slot in the corresponding tubular gun barrel, thereby rotationally locking the perforating guns relative to the tandem sub.

3. The method of claim 2, wherein each of the first and second opposing ends of the tandem sub comprises male threads such that the tandem sub serves as a male-by-male threaded connector; each of the first and second ends of each of the first and second perforating guns comprises female threads, forming a female-by-female tubular body; and threadedly connecting the second end of the tubular gun barrel of the first perforating gun with the first end of the tubular gun barrel of the second perforating gun comprises threading each of the first and second perforating guns onto the male threads of the tandem sub until a gun barrel shoulder rests against a corresponding tandem sub shoulder.

4. The method of claim 3, wherein: each slot includes a stepped surface along an inner diameter of the respective gun barrel; and the head of each threaded alignment screw comprises a tapered head that mates with the stepped surface.

5. The method of claim 3, wherein: the perforating gun assembly further comprises at least one weighted, eccentric sub; and the method further comprises: connecting a weighted sub to the perforating gun assembly by means of a bearing connection; and permitting the weighted sub and connected perforating gun assembly to rotate within the horizontal leg of the child wellbore, thereby placing the charges of each of the first and second perforating guns in position to fire at a longitudinal plane of the surrounding subsurface formation.

6. The method of claim 5, wherein: each tubular gun barrel comprises a plurality of charge openings; each of the first and second perforating guns comprises a carrier tube within the tubular gun barrel carrying the plurality of charges, with the carrier tube being rotationally fixed within the corresponding tubular gun barrel so that each of the charges is aligned with a charge opening; and the charges of the first perforating gun and the charges of the second perforating gun are in alignment when the first perforating gun and the second perforating gun are rotationally locked relative to the tandem sub.

7. The method of claim 6, wherein the plurality of charges of each of the first and second perforating guns are each aligned along the respective carrier tube in a single row.

8. The method of claim 6, further comprising: sending an actuation signal down the electric line to initiate charges and to create perforations in a direction that is generally opposite from a direction of the parent wellbore.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) So that the manner in which the present inventions can be better understood, certain illustrations, charts and/or flow charts are appended hereto. It is to be noted, however, that the drawings illustrate only selected embodiments of the inventions and are therefore not to be considered limiting of scope, for the inventions may admit to other equally effective embodiments and applications.

(2) FIG. 1 is a side, cross-sectional view of a wellbore, in one embodiment. The wellbore has been completed with an elongated horizontal section. A perforating gun assembly is shown having been pumped into the horizontal leg.

(3) FIG. 2A is a side view of an illustrative string of gun barrels forming a perforating gun assembly. Tandem subs are shown between gun barrels of the perforating guns, providing threaded connections.

(4) FIG. 2B is a perspective view of a tandem sub as may be used in the string of gun barrels of FIG. 2A.

(5) FIG. 3A is a side, cross-sectional view of a portion of a perforating gun assembly of the present invention, in one embodiment. Two gun barrel housings are seen threadedly connected by means of a novel, orienting tandem sub. Openings are shown in alignment along the gun barrel housings.

(6) FIG. 3B is a perspective view of a bulkhead assembly that may be placed within the bore of the tandem sub. A contact pin is seen extending out of the bulkhead.

(7) FIG. 4 is an enlarged plan view of a portion of the perforating gun assembly of FIG. 3, particularly showing two slots formed in opposing gun barrel housings.

(8) FIG. 5 is an enlarged side view of the perforating gun assembly of FIG. 3. In this view, opposing gun barrel housings are in cross-section while the orienting tandem sub is transparent, revealing an inner bore of the tandem sub.

(9) FIG. 6 is still another enlarged view of the perforating gun assembly of FIG. 3. FIG. 6 offers a perspective view of cap screws (or threaded alignment screws) used to fix a relative position of the two gun barrel housings relative to the tandem sub.

(10) FIG. 7 is a perspective view of a slot as may be placed in the inner diameter at the end of a perforating gun, in one embodiment. This view is taken from inside the gun barrel housing.

(11) FIG. 8 is a perspective view of a carrier tube, holding charges. The carrier tube is designed to reside within a gun barrel housing.

(12) FIG. 9 is a perspective view of a perforating gun assembly of the present invention, in one embodiment. Here, two eccentric weighted subs are provided on opposing sides of perforating guns. Charge openings are shown along the perforating guns, having been rotated into alignment.

(13) FIG. 10 is a cut-away view of two gun barrel housings connected by a tandem sub. FIG. 10 demonstrates the use of cap screws to fix a relative position of the two gun barrel housings along the tandem sub.

(14) FIG. 11 is an enlarged, perspective, cross-sectional view of the cap screws and orienting tandem sub of FIG. 10. Two cap screws are shown different states of insertion through slots. Here, the screws have beveled (or tapered) heads.

(15) FIG. 12 is an enlarged, perspective, cross-sectional view of a cap screw placed along an orienting tandem sub, in an alternate embodiment.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

Definitions

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

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

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

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

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

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

(22) As used herein, the term “sub” generally refers to a cylindrical body. The sub may have opposing threaded ends and is used to connect tubular bodies in series.

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

DESCRIPTION OF SELECTED SPECIFIC EMBODIMENTS

(24) The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements.

(25) The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to attaching two perforating guns to each other through a tandem sub.

(26) In the following, the terms “upstream” and “downstream” are being used to indicate that one gun barrel may be situated above and below, respectively, in relation to a given element in the well. Alternatively, “upstream” and “downstream” may refer to first and second gun barrels along a horizontal wellbore. One skilled in the art would understand that the invention is not limited only to the upstream gun or only to the downstream gun, but in fact can be applied to either gun. In other words, the terms “upstream” and “downstream” or “first” and “second” are not used in a restrictive manner, but only to indicate, in a specific embodiment, the relative positions of gun barrel housings.

(27) FIG. 3A is a side, cross-sectional view of a portion of a perforating gun assembly 300. The perforating gun assembly 300 includes a first perforating gun 310 and a second perforating gun 320. The first perforating gun 310 may be referred to as an upstream gun, while the second perforating gun 320 may be referred to as a downstream gun. During a casing perforating operation, the downstream gun is typically fired before the upstream gun.

(28) Each perforating gun 310, 320 comprises a respective gun barrel 315, 325. Each of the gun barrels 315, 325 defines a tubular housing fabricated from steel (or other metal). The gun barrels 315, 325 are dimensioned to house components of any known perforating gun. Such components include a detonator and a detonator cord. The detonator receives an electrical signal from a firing head.

(29) The detonator cord is a plastic straw packed that runs along an internal bore of the housing, and is packed with an explosive such as RDX. When current is run through the detonator, a small explosion is set off by the electrically heated resistor. This small explosion sets of the detonator cord along the selected perforating gun.

(30) In addition, each gun barrel 315, 325 will house a carrier tube and associated charges. An illustrative carrier tube is shown in FIG. 8, discussed below. The carrier tube secures charges, which are detonated by the detonator cord.

(31) The first perforating gun 310 has a first end 312 and a second end 314. Similarly, the second perforating gun 320 has a first end 322 and a second end 324. When placed in a wellbore, each of the first ends 312, 322 represents an upstream end while each of the second ends 314, 324 represents a downstream end. It is understood that in “oil patch” convention, the left end of a tool indicates the upstream end while the right end of a tool represents the downstream end. In practice, each perforating gun 310, 320 may be between 18 inches and five feet in length.

(32) As shown in FIG. 3A, the second end 314 of the first perforating gun 310 is threadedly connected to the first end 322 of the second perforating gun 320. Each end 314, 322 is a female connector, forming a female-by-female tubular body for the perforating guns 310, 320. Because each of these ends 314, 322 is a female connector, the threaded connection is made by means of a tandem sub 330.

(33) The tandem sub 330 represents a tubular body also fabricated from steel (or other metal). The tandem sub 330 is shown in cross-section, revealing an inner bore 335. The inner bore 335 includes a bulkhead receptacle 337, meaning that a portion of the inner bore 335 is configured to closely receive a bulkhead assembly.

(34) It is also seen that each perforating gun 310, 320 comprises a series of openings 317. The openings 317 are shown in alignment with each other. The openings 317 receive charges from respective carrier tubes. An illustrative carrier tube and charges are again shown in FIG. 8, described below.

(35) FIG. 3B is a perspective view of an illustrative bulkhead assembly 400. The bulkead assembly 400 first comprises bulkhead 410. The bulkhead 410 defines a body having a generally circular profile. The bulkhead 410 is typically fabricated from plastic or polycarbonate or other non-conductive material.

(36) A pair of circular grooves 412 is formed along the body. The grooves 412 are dimensioned and configured to receive respective o-rings (not shown). The o-rings preferably define elastomeric seals that closely fit between an outer diameter of the bulkhead 410 and a surrounding bulkhead receptacle (not shown) within the inner bore 335. The o-rings provide a pressure seal for the bulkhead 410.

(37) The bulkhead assembly 400 also includes a contact pin 420. The contact pin 420 defines an elongated body that is fabricated from brass, or a metal alloying comprised substantially of brass. Thus, the contact pin 420 is electrically conductive.

(38) Opposing ends of the contact pin 420 are seen extending out of the bulkhead 410. The tip 425, 427 of each end serves as a contact head. The contact head 425 extends into an electrical switch assembly (not shown), and delivers an initiation signal from the surface. The contact pin 420 is designed to be in electrical communication with an electrical wire that extends down through the first perforating gun 310. The wire is in electrical communication with an electric line (such as the wire 240 shown in FIG. 2) that extends down from the surface 105. The bulkhead assembly 400 serves to relay an initiation signal to the detonator head within the gun barrel 310.

(39) In operation, the operator will send a signal from the surface 105, down the wireline 240, through the body of the pin 420, to the contact head 425 (sometimes referred to as a firing head) and to the detonator inside of a gun barrel (such as upstream gun barrel 315). The detonator ignites the explosive material within the detonator cord. From there, charges are delivered into the surrounding casing as discussed above. Where a series of gun barrels is used in a gun assembly, the signal from the wireline 240 will be transmitted through a series of bulkheads and pins to the charges to be activated, typically from the downstream end, up.

(40) Returning to FIG. 3A, the tandem sub 330 includes a central shoulder 306. The shoulder 306 serves as a stop, or limit, to how far each end 314, 322 of the respective gun barrel housings 315, 325 can threadedly advance along the tandem sub 330. A pair of cap screws 340 have been run into the tandem sub 330 on opposing sides of the shoulder 306. Each cap screw 340 is advanced into a side port (shown at 345 in FIG. 5) residing within the tandem sub 330. Thus, a side port 345 resides on each end of the tandem sub 330 opposite the shoulder 306.

(41) FIG. 4 is an enlarged plan view of a portion of the perforating gun assembly 300 of FIG. 3. Here, the orienting tandem sub 330 is again shown, with the first 310 and second 320 perforating guns threaded onto the opposing ends of the tandem sub 330. In this view, it can be seen that each alignment screw 340 is aligned with a slot 316. The slots 316 are placed in respective ends (seen at 314 and 322 in FIG. 3) of the perforating guns 310, 320. While not visible, the slots 316 are aligned with side ports 345 in the tandem sub 330.

(42) FIG. 5 is another enlarged view of the perforating gun assembly 300 of FIG. 3. In this view, opposing gun barrel housings 315, 325 are in cross-section while the orienting tandem sub 330 is transparent, revealing the inner bore 335 of the tandem sub 330. Opposing ends 332, 334 of the tandem sub 330 are also visible.

(43) In FIG. 5, it can be seen that the two alignment screws 340 have been fully run into the respective side ports 345. In addition, the opposing gun barrel housings 315, 325 have been advanced over the threaded ends 332, 334 of the tandem sub 330, all the way up to the shoulder 306. Note that the screws 340 are now covered in response to further rotation of the opposing gun barrel housings 315, 325.

(44) FIG. 6 is another enlarged view of the perforating gun assembly 300 of FIG. 3. FIG. 6 offers a perspective view of the alignment screws 340 used to fix a relative position of the two gun barrel housings 315, 325 along the tandem sub 330. Here, threaded shafts 343 of each alignment screw 340 are seen, extending into the side ports 345. In addition, it is observed that each alignment screw 340 includes a tapered head 347, tapering from the bottom up.

(45) Of interest, the alignment screws 340 in FIGS. 5 and 6 have been run all the way into the side ports 345. The result is that the heads 347 reside below the slots 316 and below an inner diameter of the gun barrel housings 315, 325. This allows the female threaded ends 314, 322 of the perforating guns 310, 320 to be rotationally and threadedly placed onto the opposing ends 332, 334 of the tandem sub 330. In the view of FIG. 5, the female threaded ends 314, 322 are tightened all the way down onto opposing sides (identified at 336 of FIG. 5) of the tandem sub shoulder 306. In other words, a gun barrel shoulder 326 hits the tandem shoulder 306.

(46) After the gun barrel housings 315, 325 have been threaded onto the opposing ends 332, 334 of the tandem sub 330, the gun barrel housings 315, 325 are slowly unthreaded (or backed away) from the shoulders 336 until the slots 316 are aligned with the alignment screw heads 347. Ideally, this will not take more than 720° (or two full turns) of rotation. Once the tapered head 347 of each alignment screw 340 is aligned with a slot 316, the alignment screw 340 is backed out into the tapered slot, that is, a stepped surface 319, in each gun barrel housing 315, 325. This serves to rotationally lock each gun barrel housing 315, 325 relative to the tandem sub 330.

(47) FIG. 7 is a perspective view of a slot 316 as placed through an inner diameter 318 of a perforating gun, in one embodiment. In this case, the slot 316 resides at the second end 314 of the first perforating gun 310. It can be seen that the illustrative slot 316 includes a stepped surface 319 along the inner diameter 318. The stepped surface 319 is configured to receive the head 347 of an alignment screw 340 when the alignment screw 340 is backed out of the port 345. Preferably, each head 347 is a socket head cap screw.

(48) As arranged in FIGS. 3-7, backing an alignment screw 340 out of the port 345 fixes a radial position of the perforating guns 310, 320 relative to the tandem sub 330. Ideally, the slot 316 in the gun barrel housing 315 is long enough that the full screw head diameter 347 is engaged by the slot 316 even if the gun barrel housing 315 has to be backed out one full rotation (depending, of course, on thread pitch).

(49) The screw 340 is captured by the gun barrel housing 315 or 325 in case it becomes loose during operation, preventing the screw 340 from falling out in the wellbore. In one aspect, the screw 340 is made with a flange that captures it to simplify the orienting slot design in the gun barrel housing 315 or 325.

(50) As part of the use of the perforating gun orienting system, the operator will align charges associated with the perforating guns 310, 320. Stated another way, the gun charges are linearly aligned between the first perforating gun 310 and the second perforating gun 320. Preferably, the slots 316 and cap screws 340 accommodate a full 360° rotation of the gun barrel housing 315. However, it is anticipated that alignment of the gun barrel slots 316 with respect side portals 345 will automatically align the charge openings 317.

(51) FIG. 8 is a perspective view of an illustrative carrier tube 500. The carrier tube 500 defines an elongated tubular body 510. The tubular body 510 has an upstream end 522 and a downstream end 524. Each of the upstream end 522 and the downstream end 524 may define an end plate used to center the carrier tube 510 within a gun barrel, such as gun barrel 315.

(52) Illustrative insulators 530, 540 are shown extending from the upstream 522 and downstream 524 ends of the body 510, respectively. Power and signal wires 545 may pass through these insulators 530, 540 en route to adjacent perforating guns.

(53) The tubular body 510 also includes a series of charges 520. In the typical carrier tube arrangement, charges 520 are spaced apart radially and longitudinally along the tubular body 510, allowing shots to be fired in all radial directions through the casing 150. However, in the arrangement of FIG. 8, charges 520 are intentionally aligned at nominally 180° relation, allowing the operator to shoot charges horizontally from the wellbore once the perforating guns 310, 320 are in place.

(54) Based on the tandem sub 330, the unique carrier tube 500, the alignment screws 340 and the perforating gun orienting system discussed above, a method of aligning shots in a perforating gun assembly is also provided herein. In one embodiment, the method first comprises providing a first perforating gun. The first perforating gun has a tubular housing having a first end and an opposing second end. The tubular housing serves as a gun barrel housing.

(55) The method also includes providing a second perforating gun. As with the first perforating gun, the second perforating gun also includes a tubular housing having a first end and an opposing second end, and serves as a gun barrel housing.

(56) The second end of the first perforating gun comprises a slot. Similarly, the first end of the second perforating gun also comprises a slot. Each slot may include a stepped surface along an inner diameter of the respective tubular housing. (The stepped surface is shown at 319 in FIG. 7.)

(57) The method further includes providing a tandem sub. The tandem sub has first and second opposing ends, with each end defining a male threaded connector. In other words, a male-by-male tubular body is provided. Each end of the tandem sub includes a side port. The side ports are configured to receive a threaded alignment screw. (An enlarged view of the alignment screws having socket heads is shown in FIG. 6.)

(58) In a preferred embodiment, the tandem sub also includes a circular shoulder. (The circular shoulder is shown at 306 in FIG. 3A, with shoulder ends seen at 336 in FIG. 5.) The circular shoulder serves as a stop when threadedly advancing the gun barrel housings onto the tandem sub.

(59) The method additionally comprises running an alignment screw into each side port of the tandem sub such that a top of each alignment screw resides below an inner diameter of the tubular housing of the connected perforating guns. In one aspect, the operator simply runs the alignment screws all the way into the respective side ports. (Side ports are shown at 345 in FIGS. 3 and 5.)

(60) As a next step, the method includes threadedly connecting the second end of the first perforating gun with the first end of the second perforating gun. This is done using the tandem sub as a threaded connector. Preferably, each of the first and second ends of each of the first and second perforating guns comprises female threads, forming a female-by-female tubular body. This allows the perforating guns to quickly and rotationally connect to the tandem sub. In one aspect, threadedly connecting the second end of the first perforating gun with the first end of the second perforating gun comprises threading each of the first and second perforating guns onto the tandem sub until a gun barrel shoulder is against a corresponding side of the tandem sub shoulder. Thus, the gun barrel housings “shoulder out” against the tandem sub.

(61) The method further comprises rotationally unthreading each of the first and second perforating guns from the opposing ends of the tandem sub until the slots are lined up with an alignment screw in the respective side ports. (FIG. 5 best shows such an alignment.)

(62) Also, the method includes rotationally aligning charges of each of the first and second perforating guns. This is done by further rotating each gun barrel housing relative to the tandem sub until the charges associated with each perforating gun are in linear alignment. Note that this rotational movement may be done without moving the slots out of alignment with the side ports, up to 360° and preferably up to 720° of rotation. (Charges are shown at 520 in FIG. 8.) Then, each alignment screw is backed out of its respective side port until a head of each alignment screw locks into an inner groove of the slot in the corresponding gun barrel housing. (The inner groove is a reference to the stepped inner surface 319 shown in FIG. 7.)

(63) To accommodate this step, it is preferred that the head of each alignment screw comprises a tapered head that mates with the stepped surface. In addition, each slot in the perforating guns will have preferably have an open end. (The open end is shown at 313 in FIG. 7.)

(64) In addition to providing alignment of the charges as between adjoining perforating guns, the charges are preferably oriented in a desired direction within the horizontal portion of a wellbore. In one preferred embodiment, the charges are placed so that they may deliver shots horizontally into the wellbore, either on one side of the casing or on both sides of the casing. To effectuate this, an eccentric weighting sub may be placed along a tool string comprising the perforating guns and the orienting tandem sub. Preferably, a pair of weighting subs are used, with one being placed at each end of the tool string.

(65) Preferably, the charges are offset at 180° from each other, residing on opposing sides of a carrier tube. In one aspect, 3 to 5 charges reside on one side of a carrier tube while 3 to 5 charges reside on an opposing side of the carrier tube, offset by 180°. (Refer again to FIG. 8 showing charges 520 in nominally 180° relation.) In another aspect, the charges may be offset 45° to 60° from the weight of the eccentric weighting sub.

(66) FIG. 9 is a perspective view of a perforating gun assembly 900 of the present invention, in one embodiment. A pair of perforating guns 310, 320 are shown. Charge openings 517 are visible along one side of each of the perforating guns 310, 320. A matching set of charge openings (not shown) is placed on the opposite side of the perforating guns 310, 320 at a 180° offset. It is understood that if the charge openings 517 are aligned, then the charges 520 themselves are also aligned.

(67) The perforating guns 310, 320 are threadedly connected by means of a tandem sub 330. The tandem sub 330 is in accordance with the orienting tandem sub 330 described above in connection with FIGS. 3-7. In this way, the charges 520 of perforating gun 320 are aligned with the charges 520 of perforating gun 310.

(68) At opposing ends of the perforating guns 310, 320 is a pair of tubular subs 350. Each sub 350 is weighted on one side, using weights 357. Each weighted sub 350 is connected to a perforating gun 310 or 320 by means of a threaded connection 355, which may be an end plate such as end plates 322 or 324 shown in FIG. 8.

(69) In the arrangement of FIG. 9, each weighted sub 350 has an eccentric profile to accommodate the weights 357. It is apparent from FIG. 9 that the weights 357 have rotated into a downward position. To accommodate or to permit the rotation, bearing connectors 360 are provided. In FIG. 9, the weights 357 have rotated down, moving the charges 520 into a position where shots emanate directly into the longitudinal plane of the formation 115.

(70) In one aspect, charges 520 are positioned on only one side of the perforating guns 310, 320. This enables the operator to shoot charges into only one side of a string of production casing 150. Then, when a hydraulic fracturing operation is conducted, fracturing fluid is injected in only one direction, such as in a direction away from a pressure sink caused by an existing parent wellbore. This may be beneficial if the operator wishes to avoid a frac hit.

(71) Optionally, the method further comprises pumping the second perforating gun, the tandem sub and the first perforating gun into a wellbore at the end of an electric line. This is done prior to the actual shooting of charges at selected depths along the wellbore. The second perforating gun, the tandem sub, the first perforating gun, the charges and the opposing weighted subs form a perforating gun assembly.

(72) Where one or more weighted, eccentric subs are used, the method may further comprise allowing the eccentric subs to rotate along respective bearings, thereby placing the charges associated with the perforating guns into a horizontal (or other desired) orientation.

(73) FIG. 10 is a cut-away view of the two gun barrel housings 315, 325 connected by the tandem sub 330. This figure demonstrates the use of cap screws 340 to fix a relative position of the two gun barrel housings 315, 325 along the tandem sub 330. The cap screws 340 are driven into respective slots 316 (shown on the same drawing sheet in FIG. 7) from the outside of the gun barrel housings 315, 325.

(74) There are alternate embodiments to the perforating gun orienting system as shown in FIGS. 3A and 5. FIG. 11 is an enlarged, perspective, cut-away view of an orienting system 1100 in such an alternate embodiment. The system 1100 is similar to the perforating gun assembly 300 of FIG. 3. In this respect, the system 1100 also uses a first 310 and a second 320 perforating gun threadedly connected to a tandem sub 330. In addition, alignment screws are again used. However, in the arrangement of FIG. 11, the gun barrel housings 315, 325 are oriented using taper-headed screws 340′ in lieu of cap screws 340. This gives the added benefit of more accurate orientation.

(75) FIG. 12 is an enlarged, perspective, cross-sectional view of a portion of a perforating gun orienting system 1200, in an alternate embodiment. Here, a cap screw 340 is placed along an orienting tandem sub 330′. Of interest, the system 1200 employs a single alignment screw 340 A screw-on key 349 is used for barrel orientation. The key 349 can be designed in such a way that it is also captured by the gun barrels 315, 325 after they are threaded in place.

(76) As can be seen, a method of aligning charge shots in a perforating gun assembly is provided herein. The method employs the perforating gun orienting system as described above, in its various embodiments. In the system, first and second perforating guns are provided, wherein each perforating gun has a gun barrel housing having a slot. Each gun barrel housing provides female threads, which connect to a male-by-male threaded tandem sub. Beneficially, the tandem sub includes side ports at opposing ends.

(77) In operation, a pair of alignment screws is provided. Each alignment screw is run into a side port in the tandem sub. The gun barrel housings are then threaded onto the tandem sub at opposing ends, and the charges of the two perforating guns are placed in alignment. Each gun barrel includes a slot that is rotationally aligned with a respective alignment screw (as residing within a side port). The alignment screw is then unthreaded, or backed out, of the side ports and locked into a respective gun barrel slot. This, in turn, places the charges in the respective perforating guns in fixed alignment.

(78) In some cases, the operator may desire that shots be fired not only horizontally, but also in one direction only. This helps the service company generate and propagate fractures in a particular part of a formation, which may be of benefit in avoiding frac hits. Those of ordinary skill in the art will appreciate that frac hits are generally a by-product of in-fill drilling, meaning that a new wellbore (sometimes referred to as a “child well”) is being completed in proximity to existing wellbores (referred to as “offset” or “parent wells”) within a hydrocarbon-producing field. Frac hits are also, of course, a by-product of tight well spacing. Ultimately, however, frac hits are the result of the operator being unable to control or “direct” the propagation of fractures within the pay zone.

(79) Based on the disclosure provided above, a method of avoiding a frac hit in a hydrocarbon producing field is also provided. In one embodiment, the method first comprises locating a parent wellbore in a hydrocarbon producing field. Similarly, the method also includes locating a child wellbore in the hydrocarbon producing field. The child well is sometimes referred to as an “offset well.”

(80) The method additionally includes running a perforating gun assembly into the child wellbore. The perforating gun assembly is constructed in accordance with the perforating gun assembly described above, in its various embodiment.

(81) The method then includes: running an alignment screw into each side port of the tandem sub such that a top of each alignment screw resides below an inner diameter of the tubular housing of the perforating guns; using the tandem sub, threadedly connecting the second end of the first perforating gun with the first end of the second perforating gun; rotationally unthreading each of the first and second perforating guns from opposing ends of the tandem sub until each slot is lined up with the alignment screw in the respective side port; rotating one or both of the first and second perforating guns relative to the tandem sum, thereby linearly aligning charges of each of the first and second perforating guns such that all charges are aligned in a single direction; backing each alignment screw out of its respective side port until a head of each alignment screw hits an inner groove of the slot in the corresponding perforating gun; running the perforating gun assembly into the wellbore at the end of an electric line; and pumping the perforating gun assembly into a horizontal leg of the wellbore to a selected depth, wherein the charges are aligned to fire shots into the formation at a horizontal azimuth and in a direction away from the parent wellbore.

(82) In connection with avoiding a frac hit, the method may further comprise: connecting a weighted sub to the perforating gun assembly by means of a bearing connection; and permitting the weighted sub and connected perforating gun assembly to rotate within the horizontal leg, thereby placing the charges in position to fire at a longitudinal plane of a surrounding formation.

(83) In order to provide this orientation, current practice is to employ a weight bar. The weight bar is placed along an eccentric sub having bearings at each end. Once the perforating gun assembly is in place, the weight bar will rotate into position at the bottom (relative to vertical) of the wellbore, thereby orienting the perforating guns and placing the charges at a horizontal position.

(84) The method may further include sending an actuation signal down the electric line to initiate charges and to create perforations in a direction that is generally opposite from a direction of the parent wellbore.

(85) Further, variations of the tool and of methods for using the tool within a wellbore may fall within the spirit of the claims, below. It will be appreciated that the inventions are susceptible to other modifications, variations and changes without departing from the spirit thereof.