Orienting Perforating Gun System, and Method of Orienting Shots in a Perforating Gun Assembly

A perforating gun system. The perforating gun system comprises a gun barrel housing, and a pair of tandem subs threadedly connected to the gun barrel housing at opposing ends. The perforating gun system also includes a rail. The rail defines an elongated frame having a plurality of receptacles, wherein each receptacle is configured to receive a shaped charge. A ballast is connected to each of opposing ends of the rail. Each ballast supports a bearing member which interfaces with a central bore of a respective tandem sub. In this manner, relative rotation is provided between the rail and the first and second tandem subs. A method of orienting shots in a perforating gun assembly is also provided.

Not applicable.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present disclosure relates to the field of hydrocarbon recovery operations. More specifically, the disclosure relates to the completion of a well for the production of oil and gas. More specifically still, the inventions herein relate to a perforating gun assembly wherein the shots along the perforating guns may be selectively oriented.

TECHNOLOGY IN THE FIELD OF THE INVENTION

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

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

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

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

FIG.1is a side, cross-sectional view of a wellbore100, in one embodiment. The wellbore100has been completed horizontally, that is, it is completed with a horizontal leg156. The wellbore100defines a bore10that has been drilled from an earth surface105into a subsurface110. The wellbore100is formed using any known drilling mechanism, but preferably using a land-based rig or an offshore drilling rig on a platform.

The wellbore100is completed with a first string of casing120, sometimes referred to as surface casing. The wellbore100is further completed with a second string of casing130, typically referred to as an intermediate casing. In deeper wells, that is wells completed 7,500 feet or more below the earth surface105, at least two intermediate strings of casing will be used. InFIG.1, a second intermediate string of casing is shown at140. Together, casings130,140comprise intermediate casing strings.

The wellbore100is finally completed with a string of production casing150. In the view ofFIG.1, the production casing150extends from the surface105down to a subsurface formation, or “pay-zone”115. As noted, the wellbore100is completed horizontally, meaning that a horizontal portion (indicated by leg156) is provided. The horizontal portion156includes a heel153and a toe154. In this instance, the toe154defines the end (or “TD”) of the wellbore100.

It is observed that the annular region around the surface casing120is filled with cement125. The cement (or cement matrix)125serves to isolate the wellbore from fresh water zones and potentially porous formations around the production casing120.

The annular regions around the intermediate casing strings130,140are also filled with cement135,145. Similarly, the annular region around the production casing150is filled with cement155. However, the cement135,145,155is optionally only placed behind the respective casing strings130,140,150up to the lowest joints of the immediately surrounding casing strings. Thus, a non-cemented annular region132is typically preserved above the cement matrix135; a non-cemented annular region142is typically preserved above the cement matrix145; and a non-cemented annular region152is frequently preserved above the cement matrix155.

In order to facilitate the recovery of hydrocarbons, particularly in low-permeability formations115, the production casing150along the horizontal portion156undergoes a process of perforating and fracturing (or in some cases perforating and acidizing). Due to the very long lengths of new horizontal wells, the perforating and formation treatment process is carried out in multiple stages.

In one method, a perforating gun assembly200is pumped down the wellbore100towards the toe154at the end of a wireline240. The perforating gun assembly200will include a series of perforating guns (shown at210inFIG.2), with each perforating gun210having sets of charges ready for detonation. The charges associated with one of the perforating guns210are detonated, and perforations are “shot” into the casing150. Those of ordinary skill in the art will understand that the perforating guns210have explosive charges, typically shaped charges, which are ignited to create holes in the casing150(and, if present, the surrounding cement) and pass at least a few inches, and possibly several feet, into the formation115. The perforations (not shown) create fluid communication with the surrounding formation115such that hydrocarbon fluids can flow out of the formation115, into the casing150, and up to the surface105.

After perforating, the operator will fracture the formation115through the perforations. This is done by pumping treatment fluids into the formation115at a pressure above a formation parting pressure. After the fracturing operation is complete, the wireline240will be raised and the perforating gun assembly200will be positioned at a new location (or “depth”) along the horizontal portion156. A plug (such as plug112ofFIG.1) is set below the perforating gun assembly200and new shots are fired in order to create a new set of perforations. Thereafter, treatment fluid is again pumped into the wellbore100and into the formation115at a pressure above the formation parting pressure. In this way, a second set of fractures is formed away from the wellbore156.

The process of setting a plug, perforating the casing, and fracturing the formation is repeated in multiple stages until the wellbore100has been completed, that is, the wellbore100is ready for production. The shots create clusters of perforations to create fracture complexity and to enhance fluid communication with the formation115. The result is that multiple plugs112are set along the horizontal wellbore156during the completion process.

In order to provide perforations for the multiple stages without having to pull the perforating gun after each detonation, the perforating gun assembly200employs multiple guns210in series.FIG.2is a side view of an illustrative perforating gun assembly200, or at least a portion of an assembly. The perforating gun assembly200comprises a string of individual perforating guns210.

Each perforating gun210represents various components. These typically include a “gun barrel”212which serves as an outer tubular housing. An uppermost gun barrel housing212is supported by an electric wire (or “e-line”)240that extends from the surface105and that delivers electrical energy down to the perforating gun assembly200. Each perforating gun210also includes an explosive initiator, or “detonator” (shown in phantom at229).

In addition, each perforating gun210comprises a detonating cord (shown at545inFIG.5A). The detonating cord545contains an explosive compound that is ignited by the detonator229. Thus, the detonator229receives electrical energy which in turn initiates the detonator cord545. The detonator cord545propagates an explosion down its length to a series of charges (typically referred to as shaped charges). In some cases, the shaped charges are held in an inner tube, referred to as a charge carrier tube, for security. The charges are discharged through openings215in the selected gun barrel212. An illustrative charge carrier tube is shown at 500 of FIGS. 5 and 6A of co-owned U.S. Pat. No. 11,293,737, which is incorporated herein in its entirety by reference.

The perforating gun assembly200may include short centralizer subs220. In addition, tandem subs225may be used to connect the gun barrel housings212end-to-end. Each tandem sub225comprises a metal threaded connector placed between the gun barrels210. Typically, the gun barrel housings212will have female-by-female threaded ends (such as end412inFIG.5B) while the tandem subs225have opposing male threaded ends.

Further, an insulated connection member230connects the e-line240to the uppermost gun barrel210. The e-line240extends upward to a control interface (not shown) located at the surface105.

The perforating gun assembly200and its long string of gun barrels (the housings212of the perforating guns210) are carefully assembled at the surface105, and then lowered into the wellbore100at the end of the e-line240. After the casing150has been perforated and at least one plug112has been set, the setting tool160and the perforating gun assembly200are taken out of the wellbore100, and a ball (not shown) is dropped into the wellbore100to close the plug112. When the plug112is closed, a frac slurry (e.g., a mixture of water, sand, and surfactant) is pumped by a pumping system down the wellbore100for fracturing purposes. For a formation fracturing operation, the pumping system will create downhole pressure that is above the formation parting pressure.

It is observed that when the operator sends the detonation signals downhole, the directions to which the shots are fired into the formation cannot be controlled; instead, only the depth at which the shots are fired is controllable. In this respect, when the operator releases a perforating gun string into the wellbore100, the perforating gun assembly200may (and likely will) rotate as it gravitationally falls into the wellbore100. As the assembly200is pumped across the heel153and through the horizontal portion156, additional rotational movement may occur. However, the operator may desire that shots be fired not only at selected depths, but also at a selected orientation about the central axis of a generally horizontal wellbore. Specifically, operators may prefer that the perforations be formed vertically upward (a 0° orientation) or downward (a 180° orientation) perpendicular from the central axis of the wellbore. Alternatively, operators may prefer that the perforations be formed laterally outward (90° or 270° orientation) from the central axis of the wellbore. This urges the fractures to propagate outwardly from the wellbore100in the direction of the perforations.

A need exists for an improved perforating gun assembly with orienting capability allowing perforations in any desired orientation from 0° to 360° about the central axis of the wellbore. Further, a need exists for an improved method of aligning charges along a perforating gun assembly for use in a wellbore. Still further, a need exists for a method of avoiding frac hits by shooting aligned perforations in a specific desired direction which may be away from a parent wellbore.

BRIEF SUMMARY OF THE INVENTION

A novel perforating gun assembly is first provided herein. The perforating gun assembly is arranged to enable the operator the ability to select the orientation in which shots may be fired downhole. Shots may be fired in connection with the completion of a well used for the production of hydrocarbon fluids. Alternatively, shots may be fired in connection with the completion of a well used for the production of steam, that is, for a geothermal well.

In one aspect, the perforating gun assembly first includes a gun barrel housing. The gun barrel housing has a first end, a second end, and a bore extending between the first and second ends. Thus, the gun barrel housing defines a tubular body.

The perforating gun assembly also includes a pair of tandem subs. Specifically, a tandem sub is placed at each of the opposing ends of the gun barrel housing. Each tandem sub has a pair of male threaded ends and a bore extending therein. The tandem subs are threadedly connected to the respective ends of adjacent gun barrel housings.

The perforating gun assembly also includes a rail system. The rail system resides within a gun barrel housing. The rail system comprises:a rail defining an elongated frame;a series of receptacles placed along the frame;a charge (such as a shaped charge) residing within each of the series of receptacles;a first ballast secured to a first end of the rail; anda second ballast secured to a second end of the rail.

Uniquely, the perforating gun system provides for a bearing connection. In this respect, a first bearing member resides at a distal end of the first ballast while a second bearing member resides at a distal end of the second ballast. Each ballast member engages and rotates within the bore of a respective tandem sub. Thus, when the perforating gun assembly is pumped into the horizontal leg of a wellbore, the ballasts will rotate into a downward position, placing the shaped charges into desired orientations.

Beneficially, the rail system may be used to support the charges in lieu of using a so-called “charger carrier tube.” The charges may be inserted into the respective receptacles along the rail from either a forward side or a rearward side of the frame. Additionally, the ballasts may be connected to the rail at varying angles relative to the frame. In this way, shots may be fired within the horizontal section of a wellbore in a pre-selected orientation relative to the central axis of the wellbore (or the central axis of the gun barrel Housing).

A perforating gun system is also provided herein. The perforating gun system also includes a gun barrel housing. The gun barrel housing has a first end, a second end opposite the first end, and a bore extending from the first end to the second end of the gun barrel housing. Thus, the gun barrel housing defines a tubular body.

The perforating gun system also comprises a rail. The rail defines an elongated frame having a plurality of receptacles. Each receptacle is configured to receive a charge (such as a shaped charge). Each of the shaped charges may be received within a respective receptacle from either side of the frame. In this way, the charges may face opposite directions relative to each other within the wellbore, or they may all face in the same direction.

In one aspect, the rail comprises one to five receptacles, meaning one to five charges are received. Preferably, the rail is fabricated from aluminum, an aluminum alloy, or a rigid polymeric material. In one aspect, two rails can be connected end-to-end, effectively forming one longer rail with additional receptacles.

A first flange resides at a first end of the rail. Similarly, a second flange resides at a second end of the rail. Each flange includes a plurality of through-openings spaced equi-radially around a perimeter.

The perforating gun system also includes a pair of tandem subs. A first tandem sub is threadedly connected to the first end of the gun barrel housing, while a second tandem sub is threadedly connected to the second end of the gun barrel housing. Each of the first and second tandem subs comprises a first end, a second end opposite the first end, and a bore extending from the first end to the second end.

Preferably, each of the first tandem sub and the second tandem sub comprises male threaded ends. At the same time, the first and second opposing ends of the gun barrel housing each comprises female threads, forming a female-by-female tubular body. In one aspect, each tandem sub houses an addressable switch.

Additionally, the perforating gun system includes a pair of ballasts. These represent a first ballast and a second ballast. Each of the first and second ballasts comprises a weighted body. The first ballast comprises a proximal end connected to the first flange, and a distal end bearingly abutting the first tandem sub. At the same time, the second ballast comprises a proximal end connected to the second flange, and a distal end bearingly abutting the second tandem sub. The weighted bodies reside between the proximal and distal ends of each of the ballasts.

The perforating gun system takes advantage of a pair of bearing connections. In this respect, the system offers a first bearing member supported by the first ballast at the distal end of the first ballast. The system then offers a second bearing member supported by the second ballast at its distal end. The first bearing member interfaces with and rotates within the bore of the first tandem sub, while the second bearing member interfaces with and rotates within the bore of the second tandem sub. The result of these interfaces is that the perforating gun system allows for relative rotation between the ballasts and the first and second tandem subs. This, in turn, allows for relative rotation of the rail and supported shaped charges within the gun barrel housing.

The shaped charges may be placed within respective receptacles along the frame to fire at orientations of any of 0 degrees, 90 degrees, 180 degrees, or 270 degrees within the horizontal wellbore, depending on the direction in which the charges are inserted into the respective receptacles, depending on the angle at which the ballasts are secured to the flanges of the rail. Intermediate angles (such as at 45 degree angles) may be selected at the operator's preference.

In one aspect, a first electrically conductive contact pin resides within the bore of the first tandem sub. Similarly, a second electrically conductive contact pin resides within the bore of the second tandem sub. A detonator resides within the gun barrel housing adjacent the rail and is in electrical communication with the contact pins.

A method of orienting shots in a perforating gun assembly is also provided herein. In one aspect, the method first comprises providing a perforating gun assembly. The perforating gun assembly may be arranged in accordance with any of the embodiments described above. In this respect, the perforating gun assembly includes a gun barrel housing and a pair of tandem subs. Specifically, a tandem sub is placed at each of the opposing ends of the gun barrel housing.

The method also includes providing a rail. The rail defines an elongated frame having a series of receptacles along its length. The receptacles are configured to receive respective charges. Preferably, the receptacles each have a circular profile and are equi-distantly spaced along the frame.

The method further comprises placing a charge within each of the respective receptacles along the frame. Preferably, the rail includes at least three receptacles. Beneficially, the charges may be received within a respective receptacle from either side of the frame.

The method additionally comprises threadedly connecting the first tandem sub to the first end of the gun barrel housing. The method then includes threadedly connecting the second tandem sub to the second end of the gun barrel housing.

The perforating gun system includes a pair of ballasts. These represent a first ballast and a second ballast. Each of the first and second ballasts comprises a weighted body. The first ballast comprises a distal end abutting the first tandem sub. At the same time, the second ballast comprises a distal end abutting the second tandem sub.

The method also comprises providing a first bearing connection between the first ballast and the first tandem sub. Additionally, the method comprises providing a second bearing connection between the second ballast and the second tandem sub. In this way, the first ballast, the second ballast, and the connected rail may rotate together relative to the first and second tandem subs and the connected gun barrel housing.

In one aspect, each of the first and second tandem subs comprises a first end and a second end opposite the first end. Each of the first and second tandem subs further comprises a bore extending from the first end to the second end of the respective tandem sub. The first bearing member interfaces with and rotates within the bore of the first tandem sub, while the second bearing member interfaces with and rotates within the bore of the second tandem sub. This allows for the relative rotation between the rail and the first and second tandem subs.

In one embodiment, the method also includes placing each of the shaped charges into respective charge jackets. Each charge jacket is fabricated from a compliant material, allowing the charges to be removably snapped into place. The rail further comprises slots associated with each of the receptacles. Each of the charge jackets comprises side rails configured to be received within the slots of a respective receptacle along the frame. In this way, the shaped charges are held securely in position along the frame.

The method may also include selecting a direction for each of the shaped charges within its respective receptacle along the frame. The method then includes connecting the proximal end of the first ballast to the first end of the rail, and connecting the proximal end of the second ballast to the second end of the rail.

In one embodiment, the rail comprises a first end defining a first flange, and a second end defining a second flange. The first flange comprises at least four equi-radially spaced through-openings. Similarly, the second flange also comprises at least four equi-radially spaced through-openings. The proximal end of the first ballast comprises a pair of through-openings that may be aligned with a selected pair of the at least four equi-radially spaced through-openings of the first flange. At the same time, the proximal end of the second ballast comprises a pair of through-openings that may be aligned with a selected pair of the at least four equi-radially spaced through-openings of the second flange. In this arrangement, connecting the proximal end of the first ballast to the first end of the rail, and connecting the proximal end of the second ballast to the second end of the rail, comprises:(i) placing first connectors through aligned through-openings between the proximal end of the first ballast and the first end of the rail (or first flange); and(ii) placing second connectors through aligned through-openings between the proximal end of the second ballast and the second end of the rail (or second flange).

In one aspect, the method comprises determining which of the through-openings of the first and second flanges that the connectors are to be placed. This determines the relative angle between the weighted bodies of the ballasts and the rail and supported charges. In this way, when the first and second ballasts and the connected rail rotate within a horizontal portion of a wellbore, the charges can be fired downhole at a desired (or pre-selected) orientation.

In one aspect, the charges may be placed within respective receptacles along the frame to fire at orientations of any of 0 degrees, 90 degrees, 180 degrees, or 270 degrees within a horizontal wellbore, depending on the direction in which the charges are inserted into the respective receptacles and the angle at which the ballasts are secured to the rail.

In one aspect, a first electrically conductive contact pin resides within the bore of the first tandem sub. Similarly, a second electrically conductive contact pin resides within the bore of the second tandem sub. A detonator resides within the gun barrel housing adjacent the rail and is in electrical communication with the first and/or second contact pins.

The method may also include the steps of:running the perforating gun assembly into a wellbore at the end of an electric wireline;pumping the perforating gun assembly into a horizontal portion of the wellbore; andallowing the weighted body of the first ballast and the weighted body of the second body to rotate into a downward position, thereby placing the shaped charges into the pre-selected orientation relative to the wellbore.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

Definitions

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

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

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.

As used herein, the term “surface” refers to a location on the earth's surface. The surface may be a land surface or a water surface.

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

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

As used herein, the term “wellbore” refers to a hole in the subsurface made by drilling or insertion of a conduit into the subsurface. A wellbore may have a substantially circular cross-section, or other cross-sectional shape. The term “well,” when referring to an opening in the formation, may be used interchangeably with the term “wellbore.” A wellbore may be formed for the purpose of producing hydrocarbon fluids. Alternatively, a wellbore may be completed for the purpose of producing steam in connection with a geothermal project.

The terms “upstream” and “downstream” may be used to indicate the relative position of tools or components within a wellbore.

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.

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

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

The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

FIG.3Ais a first perspective view of an illustrative tandem sub225.FIG.3Bis a second perspective view of the same tandem sub225. The tandem sub225will be described with reference toFIGS.3A and3Btogether.

The tandem sub225defines a short tubular body having a first end202and a second opposing end204. The tandem sub225may be, for example, 1.00 inches to 5.5 inches in length, with the two ends202,204being mirror images of one another. Preferably, the tubular body forming the tandem sub225is portless.

The tandem sub225includes externally machined threads206. The threads206are male threads dimensioned to mate with female threaded ends of a gun barrel housing. A gun barrel housing is shown at410inFIG.4B. The tandem sub225is preferably dimensioned in accordance with standard 3⅛″ gun components. This allows the tandem sub225to be threadedly connected in series with perforating guns from any American vendor, e.g., Geo-Dynamics® and Titan®.

Intermediate the length of the tandem sub225and between the threads206is a shoulder216. The shoulder216serves as a stop member as the tandem sub225is screwed into an end412or414of a gun barrel housing410. Stated another way, the shoulder216serves as a limiter to the tightening of the tandem sub225onto the gun barrel housing410. Optionally, grooves217are formed equi-radially around the shoulder216. The grooves217removably engage with a tool (not shown) used for applying a rotational force to the tandem sub225without harming the rugosity of the shoulder216. U.S. Pat. No. 11,559,875 describes a socket driver that may be used to connect the tandem sub225to a gun barrel housing212or410. The '875 patent is titled “Socket Driver, and Method of Connecting Perforating Guns” and is incorporated herein by reference in its entirety.

The tandem sub225includes a central bore235. As will be described in greater detail below, the bore235is dimensioned to receive a bulkhead (seen at475ofFIG.5B). The bulkhead475, in turn, supports a contact pin (shown at550, also inFIG.5B). An upstream end of the contact pin550is seen at552inFIG.3B.

The contact pin550defines an elongated body that is fabricated from brass or a metal alloy comprised at least partially of brass. Thus, the contact pin550is electrically conductive.

Circular grooves212are formed along the tandem sub225. Specifically, a pair of circular grooves212is provided on opposing sides of the shoulder216. The grooves212are 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 tandem sub225and an inner diameter of the surrounding gun barrel housing410. The O-rings provide a pressure seal for the gun barrel housing410when in the wellbore and prior to charges540′,540″ being detonated.

It is noted that the large O-rings on the O.D. of the tandem sub225protect the interior of the barrel (charges, wires, etc.) from wellbore fluid/pressure. Once the charges go off, the interior of the barrel floods. The bulkhead475and O-rings on the bulkhead475protect the upstream gun from flooding when the gun below is flooded from firing.

FIG.4Ais a perspective view of a gun barrel housing410. The gun barrel housing410defines a tubular body420, preferably fabricated from steel. The tubular body420has a first end412, and a second end414opposite the first end412. In the view ofFIG.4A, tandem subs225have been screwed into each of the opposing ends412,414of the gun barrel housing410.

The gun barrel housing410is dimensioned to house components of any known perforating gun. Such components include a detonator and a detonator cord (shown inFIG.5Aat560and545.) In addition, the gun barrel housing410will house a set of explosive charges540′,540″ used to form perforations into the surrounding gun barrel housing410and extending out into the surrounding formation115. Uniquely, and as described further below in connection withFIGS.5A,5B,6A,6B, and6C, the gun barrel housing410does not contain a carrier tube; instead, a novel rail system600is employed to support the individual charges540′,540″. The charges540′,540″ are detonated by the detonator cord545at a pre-determined orientation.

FIG.4Bis a perspective view of the gun barrel housing410ofFIG.4A. Here, the tandem subs225and internal components have been removed for illustrative purposes. It is understood that a series of gun barrel housings410will be threadedly connected together using the tandem subs225ofFIG.4A. Each gun barrel housing410will contain a means for transmitting a detonation signal along with electronics for processing those signals.

It is noted that inFIGS.4A and4B, the gun barrel housing410has both the first end412and the second end414. When placed in a wellbore100, the first end412represents an upstream end, while the second end414represents a downstream end. It is understood that in “oil patch” parlance, a left end of a tool represents the upstream end while a right end of a tool represents the downstream end. In practice, a perforating gun string will include a series of perforating gun assemblies (shown at400inFIG.5A) each of which may be between 8 inches and 3 feet in length.

FIG.5Ais a cut-away view of the gun barrel housing410ofFIG.4A. Tandem subs225are again seen at opposing ends412,414of the gun barrel housing410. In addition, contact pins550are visible within the respective tandem subs225. The tandem subs225are threaded into the bore415of the gun barrel housing410. A distal end552of each contact pin550extends into a first conical opening270of the corresponding tandem sub225. At the same time, a proximal end554of each contact pin550extends through a second conical opening270″ of the tandem sub225, and then into the bore415of the gun barrel housing410. Together, internal components contained within the gun barrel housing410comprise elements of the perforating gun assembly400.

FIG.5Bis an enlarged view of the end412of the gun barrel housing410ofFIG.5A. Here, one of the contact pins550is more visible. Particularly, it can be seen that the distal end552of the contact pin550terminates within the first conical (or angled) openings270′ of the tandem sub225. As shown more fully inFIG.7, the distal end552of the contact pin550may optionally support a banana terminal556. The banana terminal556is configured to provide electrical communication with an upstream signal transmission wire (not shown). It is understood that the signal transmission wire travels down from an upstream gun barrel housing and is itself in electrical communication with the e-line240.

It is believed that the banana terminal556arrangement provides better electrical connectivity than the so-called “pin-on-seat” arrangement used in many perforating gun systems today. The pin-on-seat arrangement relies on a spring-loaded connection that may not always function properly. In the current electrical system, a small brass female banana plug558resides within a connector housing580. A wire585is then crimped or soldered to the banana plug terminal558.

The contact pin550resides within a bulkhead475. The contact pin550includes an enlarged outer diameter portion555. The enlarged outer diameter portion555is arranged with a series of grooves machined into its profile. The grooves (not numbered) cooperate with mating grooves (also not numbered) along an inner diameter of the bulkhead475. Such an arrangement is described in greater detail in co-owned U.S. Pat. No. 10,914,145 which is incorporated herein in its entirety by reference.

Skipping over toFIG.7,FIG.7is a perspective view of the bulkhead475. The bulkhead475houses the elongated contact pin550. The contact pin550can be seen extending out of opposite ends of the bulkhead475. Banana plugs556,558are shown at opposing ends552,554of the contact pin550. Specifically, banana plug556is at the upstream end552while banana plug558is at the downstream end554. It is noted that the bulkhead475ofFIG.7is presented in a reverse orientation from how it is presented inFIG.5B. However, the same bulkhead475is shown in bothFIGS.7and5B.

The bulkhead475includes a portion478having an enlarged inner diameter. This portion478accommodates the corresponding enlarged outer diameter portion555of the contact pin550. O-rings476are shown along the outer diameter of the enlarged inner diameter portion478. The O-rings476and the enlarged inner diameter portion478limit the transmission of fluid and pressure when a downstream perforating gun is detonated.

Returning toFIG.5B, a castle nut275is placed around the contact pin550at the downstream end (this is end554that extends into the bore415of the gun barrel housing410as seen inFIG.5A). The threaded castle nut275holds the bulkhead475in the tandem sub225and in turn holds the contact pin550within the bore of the bulkhead475during assembly of the perforating gun assembly400.

Below the castle nut275is a connector housing580. The connector housing580secures a wire585extending from the female banana plug terminal558and into the gun barrel housing410. The wire585serves as a signal transmission wire, transmitting detonation signals to perforating gun assemblies400downhole, from gun-to-gun. Those of ordinary skill in the art will understand that addressable switches610residing along the gun barrel housings418will watch for a detonation signal addressed to a particular perforating gun assembly400, causing a detonation signal to be sent into a detonator wire.

It is noted that wire585connects to the addressable switch610. The addressable switch610, in turn, connects to a detonator560as well as a wire on the female banana plug at an opposing end of the rail/ballast assembly.

InFIG.5B, a detonator wire is shown at565. The detonator wire565extends into the detonator560. In actuality, the detonator wire565is actually a pair of wires565P,565N shown inFIG.13A. When the detonator560is activated, a controlled explosion takes place that ignites a detonator cord (shown at545inFIG.5A). The detonator cord545, in turn, ignites sets of the shaped charges540′,540″ within the gun barrel housing410.

It is observed that inFIG.5A, three shaped charges540′,540″ are shown. Two outer charges540′ are oriented in a first direction while a middle charge540″ is oriented in a direction that is rotated by 180 degrees relative to the charges540′. Directing charges within a gun barrel housing410in two different orientations allows the operator to shoot charges into the surrounding formation115in opposite directions.

In the typical carrier tube arrangement, charges are spaced apart radially and longitudinally along a tubular body. This allows shots to be fired in all radial directions through the production casing150. However, in the arrangement ofFIGS.5A and6A, charges540′,540″ are intentionally aligned at nominally 180 degree relation. This allows the operator to shoot charges horizontally from the wellbore100once the perforating gun assemblies400are in a horizontal position and the rails (see rail630inFIG.6B) rotate into place.

As noted above, it is also desirable to be able to control the orientation at which the shots are fired from the perforating gun assembly400. To enable the operator to direct the orientation of the shots fired from the charges540′,540″, a novel rail system is provided herein. The rail system is shown at600and described in connection withFIGS.6A and6B. Generally, the rail system600comprises a rail630, and ballast members620which reside at opposing ends of the rail630. As will be discussed further below, the rail system600allows the charges540′,540″ to freely rotate within the horizontal portion156of the wellbore100, placing the charges540′,540″ into a predetermined orientation.

FIG.6Ais a first perspective view of the rail system600. The rail system600is configured to reside within the gun barrel housing410ofFIGS.4B and5A. In this view, each shot540is oriented at 0 degrees. (Note that for illustrative purposes only one of three shots is shown inFIG.6A.)

FIG.8Ais a perspective view of the rail630used in the perforating gun assembly400ofFIG.5A. The rail630defines an elongated frame that is dimensioned to hold a series of charge jackets (shown at670inFIGS.6A and8B). The charge jackets670, in turn, secure respective charges540. Preferably, the rail630is fabricated from either cast aluminum or an aluminum alloy so as to be conductive along a grounding path. Alternatively, the rail630may be fabricated from a rigid polymeric material.

The rail630has a first end632and a second end634opposite the first end632. Each end632,634represents a circular member, or flange, having a plurality of equi-radially positioned through-openings612. Preferably, each end632,634comprises at least four, and more preferably eight, through-openings612.

The through-openings612are dimensioned and configured to receive a bolt or screw or other securing member (shown at629inFIG.9A). The securing members629, in turn, connect the ends632,634to respective ballasts (shown at620inFIG.6A). In this respect, each ballast620contains through-openings (shown at622inFIG.6A) which may be aligned with through-openings612of a respective end632,634of the rail630for connection.

It is understood that the first632and second634flanges may be located on the distal ends of the two ballasts620. In this case, the through-openings622would be positioned on opposing ends of the rail630. Thus, the use of a flange for connecting the rail630to the ballasts620is not limited to the location of the flanges. In lieu of flanges and through-openings622, a clocking mechanism could also be used to adjust the relative rotational positions of the ballasts620and the intermediate rail630.

Each of the ends632,634of the rail630comprises a central opening615. The central openings615are dimensioned to receive the detonator cord545. This allows the detonator cord545to pass from the detonator560, through a central opening615, into the rail630, and on to the respective charges540′,540″.

The rail630further comprises a series of receptacles635. The receptacles635are preferably equi-distantly spaced along the length of the rail630. The receptacles635are uniquely configured to receive respective charge jackets670. In one aspect, each receptacle635has radial edges631to accommodate the typically-circular shaped charges540.

FIG.8Bis a perspective view of an illustrative charge jacket670. The charge jacket670is preferably fabricated from a flexible polymeric material. The charge jacket670is dimensioned to receive and hold any off-the-shelf shaped charge540′ or540″. The flexible polymeric material of the charge jacket670allows the charge jacket670to hold the respective shaped charge540′ or540″ through a snap-fit arrangement.

The charge jacket670comprises a series of side rails672. The side rails672are placed along opposing sides of the charge jacket670. The side rails672help to support the shaped charges540′ or540″. The side rails672are also arranged to slidingly engage into cooperating grooves632adjacent each receptacle635in the rail630. Thus, the side rails672play a role in holding the charges540′,540″ in place along the rail630.

Returning toFIG.6A, it can be seen that the charge jackets670have been slidden into place along each of the three receptacles635along the rail630. Each of the charge jackets670is oriented in the same direction, to wit, 90 degrees from horizontal. This will cause the ensuing shots to be fired in the wellbore vertically.

As noted above, inFIG.6Aa single charge540is shown placed into a charge jacket670. Upper transverse members (shown at674inFIG.8B) hold the charge540in place when the charge540is placed within (or snapped into) the charge jacket670. At the same time, lower transverse members (shown at676in inFIG.8B) hold the charge540in place when the charge jacket670is lowered into a receptacle635of the rail630.

Beneficially, the charge jacket670is fabricated from a compliant (or elastic) material, allowing it to be deformed as it is inserted into respective cooperating grooves632along the rail630, and then return to its original shape to remain within the receptacle635of the rail630. Similarly, the charge jacket670may be stretched to capture the shaped charge540, and then rebound to its original shape to hold the charge540securely in place.

As noted,FIG.6Aalso shows two ballasts620. One ballast620is secured to the first end632of the rail630while the other ballast620is secured to the second end634of the rail630. Each ballast620employs an identical semi-circular profile. Preferably, each ballast620is fabricated from cast zinc and is part of the ground path for the perforating gun assembly.

FIG.9Ais a perspective view of the ballast620, in one embodiment. As the name implies, the ballast620comprises a weighted body624. The weighted body624has a first end621and a second, opposing end623. At the first end621, the weighted body624supports a tubular member625. The tubular member625is dimensioned to receive a bearing member (shown at660inFIGS.6A and6B). Specifically, the tubular member625receives the bearing member660around its outer diameter. Longitudinal movement of the bearing member660along the tubular member625is restricted by a shoulder627above the weighted member624.

The second end623of the weighted body624comprises a pair of wings626. Each wing626contains the through-opening622referenced above. When the through-openings622are aligned with through-openings612of the rail630, a threaded connector629is placed through the aligned through-openings622,612. The threaded connectors629hold the ballast620in place relative to the rail630and supported charges540′,540″.

In an alternative arrangement, a pair of press-fit pins (not shown) are run into the aluminum flanges632,634of the rail630to secure wings626to the opposing flanges632,634.

Intermediate the first621and the second end623of the ballast620is a channel628. Consistent with the semi-circular profile of the ballast620, the channel628is open. The channel628is dimensioned to receive a signal transmission wire, such as wire585ofFIG.5B, extending down from an upstream perforating gun410. Optionally, the channel628may secure the detonator560. The channel628may also be used to contain an addressable switch610as shown inFIG.5B

FIG.11is a perspective view of a threaded connector629, in one arrangement. The connector629comprises a threaded bolt and is dimensioned to extend through the aligned through-openings622,612. The connector629is screwed into the aligned through-openings622,612from the direction of the ballast630.

In a preferred embodiment, eight through-openings622,612are provided on the end flanges632,634to allow the operator to select a desired orientation for the charges540′,540″. A head1129serves as a stop member for the connector629that prevents the connector629from moving completely through the through-openings622,612during assembly. Accordingly, the shoulder1129permits the connector629to thread into the through-openings622,612, secure the ballast members620to the rail630, and prevent over-insertion of the connector629during assembly.

FIG.12Ais an enlarged perspective view of a bearing member660. The bearing member660has a frusto-conical profile, with a central bore665. The central bore665is dimensioned to closely receive the tubular support member625at the first (or distal) end621of the ballast620.FIG.12Bis a second perspective view of the bearing member660ofFIG.12A, seen from an end opposite that ofFIG.12A.

The bearing member660includes a plurality of individual roller bearings662. The roller bearings662are secured within a housing664, forming a race for the bearings662. The bearings662interface with the second conical opening270″ of the tandem sub225, meaning that the roller bearings662permit the bearing member660to rotate within the second conical opening270″. In this way, the bearing member660provides relative rotational movement between the tandem sub225and the ballast620(and its connected rail630and supported shaped charges540′,540″) within the gun barrel housing410.

FIG.12Cis a third perspective view of the bearing member660ofFIG.12A. Here, two opposing bearing members660are shown in exploded apart relation from a tandem sub225. Each bearing member660is dimensioned and configured to slide into the bore235of the tandem sub225and engage a conical surface270′,270″. (The conical surfaces270′,270″ are shown inFIG.10, discussed below.)

Stated another way, each bearing member660is designed to engage with a tandem sub225, wherein the tandem sub225comprises a first end202, a second end204opposite the first end202, connection threads206placed at each of the first202and second204ends, an internal bore235within the tandem sub225extending from the first end202to the second end202. As shown inFIG.10, the tandem sub225includes a pair of tapered shoulders270′,270″ along the inner bore235.

Each bearing member660comprises a first end, or shoulder661, defining a first outer diameter. In addition, each bearing member660comprises a second end, or shoulder663, defining a second outer diameter. The second outer diameter is smaller than the first outer diameter creating the frusto-conical profile. The angle of the frusto-conical profile will match the angle of the tapered shoulder270′ or270″.

A tubular support body668extends between the first shoulder661and the second shoulder663. The support body668is dimensioned to receive the post625of the ballast620while supporting the bearing member660. At the same time, the support body668serves as a race.

A plurality of roller bearings662is disposed around the support body668intermediate the first shoulder661and the second shoulder663. The plurality of roller bearings662is configured to bearingly engage the tapered shoulder270′ along the inner bore235of the tandem sub225. The roller bearings662are contained within the housing664. The housing664serves as a cage for the roller bearings662over the race668. At the same time, the housing664provides windows667through which the respective roller bearings662extend.

The position of the bearing member660is shown inFIG.6B.FIG.6Bis a second perspective view of the rail system600ofFIG.6A. The bearing member660is seen secured over the post625at the first end621of a ballast620. In turn, a flange680at the end of the post625. The flange680is associated with a connector housing (shown at580inFIG.13B). As discussed below, the connector housing580serves multiple purposes including receiving the female banana plug terminal558, holding the bearing660in place on the ballast post625, and supporting the wire585that is crimped or soldered onto the female banana plug terminal558.

Of interest, the bearings662interface with only the ID of the tandem subs225; they do not interface with the ID of the surrounding gun barrel housing410. This allows for the use of smaller bearings662, which in turn allows for reduced cost and lower friction.

The frusto-conical, or tapered, roller bearings662have a high side load rating and better durability. The tapered arrangement for the roller bearings662also provides a better electrical/ground connection with a bigger surface area of contact to improve electrical communication. Those of ordinary skill in the art may understand that the tandem subs225are cleaner and offer more reliable ground surfaces than the ID's of traditional gun barrels.

In one embodiment, roller bearings are integral to the tapered surfaces270′,270″ along the inner bore235of the tandem sub225. In this instance, the housing664, or cage, is built into the inner bore235. Each ballast620would employ a matching angle tapered surface at its first end621. For example, the post625could be modified to include a tapered, or frusto-conical, surface.

In one aspect, the tapered shoulder270′ or270″ represents a short sub, e.g., one to three inches, that is threadedly connected to an end of the tandem sub225. In this instance, the short sub has an outer diameter that is the same as the outer diameter of the tandem sub225, but employs the tapered shoulder270′ or270″ along its inner bore. The bearing member660engages the tapered shoulder of the end cap. For purposes of the claims herein, the end cap essentially becomes a part of the tandem sub225once it is screwed on.

It is observed that inFIG.6B, the rail630and supported charge jackets670have been rotated 90 degrees relative to the view ofFIG.6A. This is because the first end632of the rail630has been rotated 90 degrees before being secured to the second end623of the ballast620. The result is that the shaped charge540is now oriented 90 degrees from vertical. This is a preferred orientation of the charge540as it ensures that shots will be fired parallel to a plane of completion of the horizontal portion156of the wellbore100. This also allows the operator to take advantage of the plane of least resistance, or “least principal stress,” within the formation115to maximizes fracture formation away from the wellbore100and within the stress field.

FIG.6Cis a third perspective view of the rail system600ofFIG.6A. In this view, one shot540′ is oriented at 0 degrees while another shot540″ is oriented at 180 degrees. Thus, the shaped charges540′,540″ may be installed along the rail630in either an “up” or a “down” direction. “Up” may be considered a “0 degree” orientation while down may be considered a “180 degree” orientation. This arrangement may be desirable to help minimize fracture communication with a so-called parent wellbore in the field. In this respect, fractures are led to propagate up and down rather than sideways.

In the arrangement ofFIGS.6A,6B and6C, each weighted ballast620has an eccentric profile. The weight bodies624have rotated into a downward position. Knowing that this will take place when the perforating gun assembly400has been pumped into a horizontal leg156, the operator can pre-select an orientation (reflecting both a direction and an angle relative to the central axis of the wellbore) at which shots will be fired into the formation115.

FIG.9Bis a perspective view of a cover690. The cover690is intended to be fitted over the weighted body624ofFIG.9A. Specifically, the cover690fits over the open channel628to protect wires that extend from the contact pin550, or wires (see inFIG.13Aat565N,565P) that extend from the detonator560, an addressable switch610, and any other components of the perforating gun assembly400. The cover690may be fabricated from a metal or from a durable plastic.

FIG.10is a cross-sectional view of the tandem sub225of the present invention, in one embodiment. As can be seen, the tandem sub225has a bore235that extends from the first end202to the second end204. A first tapered shoulder270′ is provided along the bore235(or inner diameter) at the first end202of the tandem sub225. Similarly, a second tapered shoulder270″ is provided along the bore235at the second end204of the tandem sub225.

FIG.13Ais a perspective view of a detonator560. The detonator560defines a small aluminum housing having a resistor (not seen) inside. The detonator560receives electrical energy from the surface105and through a pair of wires. These represent a positive wire565P and a negative wire565N. Current supplied by the electrical energy from the surface105heats the resistor within the detonator560.

FIG.13Bis a perspective view of the connector housing580referenced above. The connector housing580is designed to secure the bearing member660onto the post625. Specifically, the connector housing580snaps into the bore of the post625. In addition, the connector housing580receives the female banana plug558. The connector housing580is fabricated from a non-conductive composite material.

In operation, the operator will send an electrical signal from the surface105, down the electric wireline240, through the body of the contact pin550, through the female banana plug558, to the addressable switch610, into one of the detonator wires (such as565P), travel into the detonator560inside of the gun barrel housing410, and then return to ground through another one of the detonator wires (such as565N). The detonator560is packed with an explosive such as RDX. When current is run through the detonator560, a small explosion is set off by the electrically heated resistor. This small explosion then sets off the detonator cord545along the selected gun barrel housing410.

Of interest, the second detonator wire is connected to the ballast620, which is fabricated from a conductive material. The ballast620, in turn is connected to the bearing member660. The bearing member660is in electrical communication with the tandem sub225and then the gun body410through thread206. In this way, the bearing member660plays a role in grounding the perforating gun assembly.

In practice, a gun barrel housing410may have a tandem sub225, a bearing member660, a ballast620and a rail630(or explosive charge holder) at each of its first412and second414ends. In this instance, a grounding wire (such as wire565N) is in electrical communication with the gun barrel housing410through the bearing members660at both ends412,414. The benefit is that each end (412may be the upstream end and414may be the downstream end) is part of the same ground circuit. In the unlikely event that one ground fails (such as through dirt on the roller bearings662of one bearing member660or because a ground wire565N becomes disengaged), the perforating gun assembly is still grounded through the other bearing member660. In other words, the ground path is redundantly designed.

In another embodiment, a grounding wire extends through the inner bore415of the gun barrel housing410from bearing member660to bearing member660. More specifically, the wire would travel from connector housing580/banana plug terminal558to connector housing580/banana plug terminal558.

The bearing connection (including bearing members662) provided between the tandem sub225and the ballast620also provides the operator with at least some measure of control concerning the orientation (or altitude) of charges540′,540″ fired into the surrounding formation115. In this respect, once the perforating gun assembly400(that is, the tandem subs225, the gun barrel housing410, and the rail system600within the gun barrel housing410) enters the horizontal leg156of the wellbore110, the weighted bodies624of the ballasts620will roll downward. Because the ballasts620are secured to the ends632,634of the rail630, the rail630and its supported charges540″,540″ will rotate with the ballasts620. The rail630is symmetrically balanced to be “neutral,” allowing the conductive ballasts620to fully dictate the direction the charges540″,540″ will face.

Beneficially, no charge tubes are required for placement within the gun barrel housing410. In this respect, the rail system600supports the charges540′,540″ along the gun barrel housing410rather than a charge tube. In addition, no metal end plates are required at the ends202,204of the tandem subs225. Instead, the ballasts620and rail630provide structural support for the detonator560and associated charges540′,540″.

Based on the tandem subs225, the eccentric ballasts620, and the unique bearing connection between the tandem subs225and the ballasts620within the gun barrel housing410, a method of orienting shots during a formation fracturing operation is provided herein.FIGS.14A and14Btogether present a single flow chart showing steps for a method1400of orienting shots in a perforating gun assembly.

In one embodiment, the method1400first comprises providing a gun barrel housing. This is shown in Box1410ofFIG.14A. The gun barrel housing may be in accordance with the illustrative gun barrel housing410presented inFIG.4B.

The method1400also includes providing a rail. This is seen in Box1415. The rail is configured to support charges (such as shaped charges) along a frame. Specifically, receptacles are provided along the frame in a preferably equi-distantly spaced array in order to receive the shaped charges. The rail may be in accordance with the rail630shown inFIG.8A.

The method1400additionally comprises connecting ballasts to ends of the rail. This is offered in Box1420. The ballasts are connected using threaded cutting screws that are run into aligned through-openings. In an alternate embodiment, the ballasts may be connected via screws (such as connector629ofFIG.11), that are run through the aligned through-openings. Each of the ballasts may be in accordance with the ballast620ofFIG.9A.

In operation, the ballasts are connected to opposing ends of the rail. The ballasts are connected such that when the gun barrel housing is pumped into a horizontal leg of a wellbore, the ballasts will be gravitionally rotated into a downward position. This downward rotation of the ballasts will turn the receptacles along the rail within the wellbore at desired orientations.

The method1400also includes the optional step of providing charge jackets for the shaped charges. This is provided in Box1425. Each charge jacket is dimensioned to receive and hold any “off-the-shelf” shaped charge. The charge jackets may be in accordance with charge jacket670ofFIG.8B.

The method1400also comprises the optional step of determining a location of adjacent wellbores in a hydrocarbon producing field. This is shown at Box1430. Those of ordinary skill in the art will understand that the hydrocarbon field may, and likely will, comprise numerous wells. In connection with so-called in-fill drilling, new wells are drilled in relative proximity to existing wells. The new well is sometimes referred to as a “child wellbore” or an “offset well,” while an existing adjacent well may be referred to as a “parent wellbore.”

In this instance, the operator may desire that shots be fired not only horizontally, but also in one direction only, that is, away from a parent wellbore. This assists the service company in generating and propagating fractures in a particular part of the formation to avoid frac hits. Those of ordinary skill in the art will appreciate that frac hits are generally a by-product of in-fill drilling. Frac hits are also, of course, a by-product of tight well spacing, that is, wells spaced in close proximity to one another in the same field. Ultimately, however, frac hits are the result of the operator being unable to control or “direct” the propagation of fractures within the pay-zone. By firing shots away from a direction of a parent well, the likelihood of a frac hit occurring is reduced.

The method1400further includes the step of placing the shaped charges into the charge jackets. This is provided at Box1435. Thereafter, the charge jackets are inserted into receptacles (such as receptacles635) provided along the rail. This is shown at Box1440.

It is noted that in lieu of charge jackets, the operator may simply clip the shaped charges onto the receptacles. What is important is that the charge jackets are inserted in select directions. Depending on the placement of the charges along the rail and the angle at which the ballasts are secured to the rail, charges may be shot at a variety of orientations. Examples may be 90-90-90, 270-270-90, 0-90-180, etc.

Beneficially, this allows the operator to orient charges away from a known pressure sink in the formation, such as a pressure sink caused by a parent wellbore in the same field. To facilitate this, the charge jackets are run into the rail from only one direction, e.g., 0-0-0, 90-90-90, 180-180-180, or 270-270-270. This minimizes the chances of a frac hit occurring during formation fracturing.

Optionally, charge jackets may be placed along the rail in a way that charges will fire vertically, e.g., 0-180-0. This too may minimize the chances of a frac hit occurring during formation fracturing. Of course, the rail may be connected to the ballasts at any angle and the charges may be inserted into the rail receptacles from either direction, providing a high degree of pre-selection for the orientation of the charges.

The method1400additionally includes connecting the charges to a detonator cord. This is offered in Box1445. The operator then positions the rail and the supported charges within the gun barrel housing. This is seen in Box1450ofFIG.14B.

As discussed above, the novel perforating gun assembly described herein offers a bearing connection within the gun barrel housing. Thus, in Box1455the method includes the step of providing a bearing member at an end of each ballast. Each of the bearing members may be in accordance with the bearing member660ofFIG.12. In this respect, the bearing members form a frusto-conical profile, mating with a conical inner diameter section along a tandem sub.

The method1400next includes threadedly connecting each end of the gun barrel housing to a tandem sub. This is seen in Box1460. Upon connection, the bearing members engage an inner diameter of the respective tandem subs. Together, the tandem subs, the gun barrel housing, the roller bearings (or bearing members), the ballasts, the rail, and the charges form a novel perforating gun assembly.

As an alternative, at least one bearing member is connected to an end plate, which in turn is connected to a gun barrel housing. The end plate comprises a short sub, such as one to three inches, that screws onto the second end of the gun barrel housing. In this case, an opposite end of the end plate may screw into the first end of an adjoining gun barrel housing, or onto a setting tool for a plug, as the case may be.

The method1400may also include running the perforating gun assembly into a wellbore. This is provided at Box1465. This step is typically done by running the perforating gun assembly into the wellbore at the end of an electric wireline (such as wireline240ofFIG.1). The perforating gun assembly is then pumped into a horizontal portion of the wellbore (such as horizontal leg156ofFIG.1). This is shown at Box1470.

Once the perforating gun assembly is positioned within the horizontal wellbore, the ballasts are allowed to rotate into a downward position. This occurs automatically in response to the gravitational force acting on the weighted bodies. This step is shown in Box1475. This rotation takes place through the bearing members. The result is that the shaped charges are oriented at a desired angle or direction within a surrounding formation.

It will be appreciated by the petroleum engineer that the size and orientation of a fracture, and the amount of hydraulic pressure needed to part the rock along a fracture plane, are dictated by the formation's in situ stress field. This stress field can be defined by three principal compressive stresses which are oriented perpendicular to one another. These represent a vertical stress, a minimum horizontal stress, and a maximum horizontal stress. The magnitudes and orientations of these three principal stresses are determined by the geomechanics in the region and by the pore pressure, depth, and rock properties.

According to principles of geomechanics, fracture planes will generally form in a direction that is perpendicular to the plane of least principal stress in a rock matrix. Stated more simply, in most wellbores, the rock matrix will part along vertical lines when the horizontal section of a wellbore resides below 3,000 feet, and sometimes as shallow as 2,000 feet, below the surface. In this instance, hydraulic fractures will tend to propagate from the wellbore's perforations in a vertical, elliptical plane perpendicular to the plane of least principal stress. If the orientation of the least principal stress plane is known, the longitudinal axis of the horizontal leg156is ideally oriented parallel to it such that the multiple fracture planes will intersect the wellbore100at, or near, orthogonal to the horizontal leg156of the wellbore100.

The method1400may finally 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, thus avoiding a frac hit in the hydrocarbon producing field while optimizing the creation of a fracture network within the formation. This may be a part of the step of Box1475.

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.