Patent Publication Number: US-10329851-B2

Title: Sub for accommodating large devices

Description:
PRIORITY 
     The present application is a U.S. National Stage patent application of International Patent Application No. PCT/US2014/069818, filed on Dec. 11, 2014, the benefit of which is claimed and the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates generally to oilfield equipment, and in particular to downhole tools, drilling and related systems and techniques for drilling, completing, servicing, and evaluating wellbores in the earth. 
     BACKGROUND 
     During the drilling, completion, servicing, or evaluation of an oil or gas wellbore or the like, situations are encountered it which it may be desirable to provide measurement data or perform other operations. A logging tool, which may have one or more devices, which may include instruments, detectors, circuits, and the like, may be carried along a drill string or a bottom hole assembly and lowered into a wellbore for taking and communicating measurements at various wellbore depths and/or performing other functions. 
     For example, measurements may be taken in real time during drilling operations. Such techniques may be referred to as measurement while drilling (“MWD”) or logging while drilling (“LWD”). Measurement data and other information may be communicated through fluid within the drill string or annulus using various telemetry techniques and converted to electrical signals at the surface. 
     MWD or LWD tools must also generally provide drilling fluid flow paths to support drilling operations. Because of inherent size restrictions, MWD or LWD tools may have limited cross-sectional area to provide optimal drilling fluid flow while accommodating larger devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments are described in detail hereinafter with reference to the accompanying figures, in which: 
         FIG. 1  is an elevation view in partial cross section of a drilling system that employs a drill string with drill pipe, and a sub according to an embodiment; 
         FIG. 2  is a perspective view of a sub having a collar with longitudinal grooves, covered by individual strip-shaped flow channel covers according to an embodiment, which may be used in the drilling system of  FIG. 1  and which is shown oriented to reveal a lower end and the flow channel side of the collar; 
         FIG. 3  is a perspective view of the sub of  FIG. 2 , with an upper end and the flow channel side of the collar being visible; 
         FIG. 4  is an exploded perspective view of the sub of  FIG. 2 , showing longitudinal grooves forming flow channels along the flow channel side of the collar and covers for separating the flow channels from the exterior; 
         FIG. 5  is a perspective view in axial cross section of the collar of  FIG. 4 , oriented 180 degrees about its longitudinal axis to show a housing side of the collar, showing upper, lower, and medial bores and upper and lower angled bores formed therein; 
         FIG. 6  is a perspective view in axial cross section of the sub of  FIG. 4 , oriented 180 degrees about its longitudinal axis to show the housing side of the collar, showing a flow channel cover disposed over a longitudinal groove; 
         FIG. 7  is a transverse cross section taken along line  7 - 7  of  FIG. 6 , showing a medial bore, three flow channels, and a detector flat; 
         FIG. 8  is a perspective view of a collar with a circumferential arrangement of longitudinal grooves according to an embodiment, which may be used in the drilling system of  FIG. 1 ; 
         FIG. 9  is a perspective view in axial cross section of the collar of  FIG. 8 ; 
         FIG. 10  is a transverse cross section taken along line  10 - 10  of  FIG. 9 , showing a medial bore and eight longitudinal grooves; 
         FIG. 11  is a perspective view in axial cross section of a sub according to an embodiment using the collar of  FIGS. 8 and 9  with a sleeve-shaped cover; 
         FIG. 12  is a transverse cross section taken along line  12 - 12  of  FIG. 11 , showing a medial bore and eight flow channels; 
         FIG. 13  is a perspective view in axial cross section of the sub of  FIG. 11  with flow-diverting plug according to an embodiment; 
         FIG. 14  is a detailed axial cross section of a portion of the sub of  FIG. 13  denoted by lines  14 - 14 ; 
         FIG. 15  is an enlarged perspective view of a flow-diverting plug of  FIG. 13 ; 
         FIG. 16  is an axial cross section taken along lines  16 - 16  of  FIG. 15 ; 
         FIG. 17  is a flowchart of a method for manufacturing a downhole tool within a sub according to an embodiment; and 
         FIG. 18  is a flowchart of a method for manufacturing a collar of the sub of  FIG. 17 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” “uphole,” “downhole,” “upstream,” “downstream,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the apparatus in use or operation in addition to the orientation depicted in the figures. 
       FIG. 1  is an elevation view in partial cross-section of a drilling system  20  which may include a bottom hole assembly  90  according to an embodiment. Drilling system  20  may include a drilling rig  22 , such as the land drilling rig shown in  FIG. 1 . However, drilling system  20  may be deployed on offshore platforms, semi-submersibles, drill ships, and the like. 
     Drilling rig  22  may be located proximate to or spaced apart from well head  24 , such as in the case of an offshore arrangement. Drilling rig  22  may include rotary table  38 , rotary drive motor  40 , and other equipment associated with rotation and translation of drill string  32  within wellbore  60 . Annulus  66  is formed between the exterior of drill string  32  and the inside wall of wellbore  60 . For some applications, drilling rig  22  may also include a top drive unit  42 . Pressure control devices  43 , such as blowout preventers and other equipment associated with drilling a wellbore may also be provided at well head  24 . 
     The lower end of drill string  32  may include bottom hole assembly  90 , which may carry at a distal end a rotary drill bit  80 . Drilling fluid  46  may be pumped to the upper end of drill string  32  and flow through the longitudinal interior  33  of drill string  32 , through bottom hole assembly  90 , and exit from nozzles formed in rotary drill bit  80 . At bottom end  62  of wellbore  60 , drilling fluid  46  may mix with formation cuttings and other downhole fluids and debris. The drilling fluid mixture may then flow upwardly through annulus  66  to return formation cuttings and other downhole debris to the surface. 
     Bottom hole assembly  90  may include a downhole mud motor. Bottom hole assembly  90  and/or drill string  32  may also include various other tools that provide information about wellbore  13 , such as logging or measurement data from the bottom  62  of wellbore  60 . Measurement data and other information may be communicated using measurement while drilling techniques using electrical signals or other telemetry that can be converted to electrical signals at the well surface to, among other things, monitor the performance of drilling string  32 , bottom hole assembly  90 , and associated rotary drill bit  80 . 
     In particular, devices, including MWD, LWD instruments, detectors, circuits, or other tools may be provided within a sub  100 , according to one or more embodiments described in greater detail below. Sub  100  may be located as part of bottom hole assembly  90  or elsewhere along drill string  32 . Moreover, multiple subs  100  may be provided. Although described in conjunction with drilling system  20 , sub  100  may be used in any appropriate system and carried along any type of string. Sub  100  may be used to house an instrument, tool, detector, circuitry, or any other suitable device. 
       FIGS. 2 and 3  are perspective views of sub  100  according to an embodiment. Sub  100  may include a collar  110 , having a generally cylindrical body  106  of outer diameter  112  and defining an upper end  102  and a lower end  104 . The centerline of collar  110  may define a longitudinal sub axis  107 . Collar  110  may be unitary, machined from a single bar for example. As used herein, a multi-faceted collar, for example, having a hexagonal or octagonal cross section, is generally cylindrical. 
     Upper end  102  of collar  110  may include an upper blind bore  124  ( FIG. 3 ) formed therein, which may be but need not necessarily be centered about sub axis  107 . Similarly, lower end  126  ( FIG. 2 ) of collar  110  may include a lower blind bore  126  formed therein, which may also be but need not necessarily be centered about sub axis  107 . As used herein, a blind bore refers to hole that is reamed, drilled, milled or otherwise formed to a specified depth without breaking through to the other side of the work piece, i.e., collar  110 . 
     Upper and lower ends  102 ,  104  may have upper and lower connectors  120 ,  122 , respectively. In an embodiment, upper and lower connectors  120 ,  122  may be integrally formed as part of collar  110 . Connectors  120 ,  122  may be threaded pin and/or box connectors, for example. However pin/pin or box/box combinations, or other types of connectors may be used as appropriate. Connectors  120 ,  122  may allow sub  100  to be assembled as part of drill string  32  or bottom hole assembly  90  ( FIG. 1 ), for example. 
     Body  106  of collar  110  may include a number of longitudinal stabilizer protrusions  130  extending beyond outer diameter  112 . In the embodiment of  FIGS. 2 and 3 , three stabilizer protrusions  130  are provided (only two are visible) at 120 degree angular positions. However, four or more stabilizer protrusions  130  may be provided and spaced about collar body  106 . Stabilizer protrusions  130  may function to keep sub  100  centered within wellbore  60  ( FIG. 1 ). In an embodiment, stabilizer protrusions  130  may be integrally formed as part of collar  110 . More specifically, collar  110 , with stabilizer protrusions  130 , may be machined from a cylindrical bar, by milling or otherwise cutting away the regions between and at the ends of stabilizer protrusions  130  to form outer diameter  112  of collar  110 . Stabilizer protrusions may be straight, as illustrated, or they may spiral around outer diameter  112 . 
       FIG. 4  is an exploded perspective view of sub  100  according to the embodiment of  FIGS. 2 and 3 . Referring to  FIGS. 2-4 , body  106  of collar  110  may generally be considered to define two sides—a flow channel side  140  and a housing side  142 . Flow channel side  140  is visible in  FIGS. 2-4 . Flow channel side  140  may include one or more flow channels  150  ( FIGS. 6 and 7 ), each of which may be defined in part by a longitudinal groove  152  formed along an exterior of collar  110  and a flow channel cover  190  connected to collar  110 . Flow channel  110  may form a seal with collar  110 . In an embodiment, as illustrated, flow channel cover  190  may generally have the shape of a strip. One or more longitudinal grooves  152  may be formed along one or more stabilizer protrusions  130 , thereby positioning flow channels  150  further outward with the advantage of providing more volume within collar  110  that may be used for housing one or more instruments, tools, detectors, circuits, and/or other suitable devices. One or more longitudinal grooves  152  may also be formed along the outer diameter  112  of collar  110 , between stabilizer protrusions  130  if provided. Although not expressly illustrated, longitudinal grooves  152  need not be straight. For example, longitudinal grooves  152  may be spiral or helical grooves. 
       FIGS. 5 and 6  are axial cross sections of collar  110 , shown without and with flow channel covers  190  installed, respectively.  FIG. 7  is a transverse cross section of sub  100  taken along line  7 - 7  of  FIG. 6 . As compared to  FIG. 2-4 , collar  110  is shown in  FIGS. 5-7  rotated 180 degrees about sub axis  107  to reveal housing side  142 . Collar  110  may include upper and lower blind bores  124 ,  126  formed at upper and lower ends  102 ,  104 , respectively. Upper and lower blind bores  124 ,  126  may be formed centered at sub axis  107 . 
     A medial bore  128  may be formed within collar  110 , opening into upper blind bore  124  or lower blind bore  126 . Medial bore  128  may be a blind bore (illustrated in  FIGS. 5 and 6 ), or it may be a through bore that is formed through collar  110  opening between upper and lower blind bores  124 ,  126  (see  FIG. 9  hereinafter). 
     In an embodiment, medial bore  128  may, but need not necessarily, be formed on a centerline  127  that is offset from sub axis  107  a distance d towards housing side  142 . An instrument, tool, detector, circuit and/or other device (not illustrated) may be loaded into sub  100  through upper blind bore  124 , into medial bore  128 , and sealed to avoid effects of hydrostatic pressure. Tapered female threads  129  may optionally be provided within medial bore  128  for receiving a threaded plug (not illustrated) to seal medial bore  128 . However, other sealing methods, such as O-rings or potting, may be used as appropriate. 
     Referring now to  FIGS. 4-7 , flow channels  150  may be formed within sub  100  so as to bypass medial bore  128  by diverting drilling fluid flow to the circumferential extremities of flow channel side  140  while maintaining adequate flow area, thereby facilitating the positioning of medial bore  128  toward housing side  142  of sub  100  and maximizing the available diameter of medial bore  128 . In an embodiment, one or more flow channels  150  are defined in part by longitudinal grooves  152  formed along the exterior of collar  110 . Three such flow channels  150  are illustrated, but any suitable number of flow channels  150  may be provided. 
     An upper angled through bore  160  may be formed between the upper end of each longitudinal groove  152  and upper blind bore  124 . Similarly, a lower angled through bore  162  may be formed between the lower end of each longitudinal groove  152  and lower blind bore  126 , thereby fluidly coupling upper blind bore  124  with lower blind bore  126 . As used herein, a through bore refers to hole that is reamed, drilled, milled or otherwise formed so as to break through at least a portion of the work piece. Any suitable angle for upper and lower through bores may be used, up to and including 90 degrees with respect to sub axis  107 . 
     Referring to  FIGS. 5-7 , a conduit  180  may be formed through collar  110  from a blind end of medial bore  128  to the blind end of lower blind bore  126 . Conduit  180  may allow for communication from a device housed within medial bore  128  to a device mounted below sub  100 . Conduit  180  may be stuffed, packed, or a gland seal may be provided (not illustrated), to maintain fluid-tight integrity of medial bore  128 . A similar arrangement (not illustrated) may be provided at the upper end of medial bore  128  for communication to a device mounted above sub  100 . 
     In an embodiment, a flat  194  may optionally be formed on housing side  142  of body  106 . Flat  194  may reduce adverse shielding effects of collar  110  on a gamma ray detector housed within medial bore  128 . Thus, increased gamma detection rates may be provided by maximizing the size of a gamma detector housed within sub  100 , by positioning medial bore  128  closer to housing side  142  of collar  110 , and by providing flat  194  to reduce adverse shielding. 
     As illustrated in  FIGS. 4 and 7 , each longitudinal groove  152  may be a compound groove, which may include a wider and shallower seating surface  170  and a narrower and deeper trough  172 . Seating surface  170  may be flat, and trough  172  may be arcuate, although other profiles may be used as appropriate. Seating surface  170  may provide a receptacle into which a strip-shaped flow channel cover  190  may be positioned and affixed to collar  110 . Trough  172  may provide at least a portion of flow channel  150 . Additionally, the inner side of flow channel cover  190  may include a trough  174  which may also form at least a portion of flow channel  150 . 
     Each flow channel cover  190  may be attached to collar  110  within seating surface  170 , thereby completing flow channels  150  and preventing fluid flow from exiting sub  100  at longitudinal grooves  152 . Although not expressly illustrated, flow channel cover  190  may be attached using fasteners, such as bolts. A gasket may be provided between flow channel cover  190  and seating surface  170  to effect a seal. However, a complete seal may not be required. Flow channel cover  190  may also be both attached to and sealed against collar  110  by welding or brazing, for example. Other suitable attachment and sealing methods may also be used. 
     Referring now to  FIG. 7 , stabilizer protrusions  130  may be rounded and be characterized by radii r p  that are smaller than the radius r c  of outer diameter  112  of collar  110 . Flow channel cover  190  may similarly have an outer radius r p  for covering a longitudinal groove  152  formed along a stabilizer protrusion  130  or an outer radius r c  for covering a longitudinal groove  152  formed along outer diameter  112  of collar  110  between stabilizer protrusions  130 , if provided. 
       FIG. 8  is a perspective view of collar  110 , according an embodiment, having longitudinal grooves  152  intervaled about the circumference of collar  110 .  FIGS. 9 and 10  are axial and transverse cross sections, respectively, of collar  110  of  FIG. 8 . Referring to  FIGS. 8-10 , collar  110  may have a generally cylindrical body  106  of outer diameter  112  and defining an upper end  102  and a lower end  104 . The centerline of collar  110  may define a longitudinal sub axis  107 . Collar  110  may be unitary, machined from a single bar for example. 
     Upper end  102  of collar  110  may include an upper blind bore  124  formed therein, which may be centered at sub axis  107 . Similarly, lower end  126  of collar  110  may include a lower blind bore  126  formed therein, which may also be centered at sub axis  107 . 
     Upper and lower ends  102 ,  104  may have upper and lower connectors  120 ,  122 , respectively. In an embodiment, upper and lower connectors  120 ,  122  may be integrally formed as part of collar  110 . Connectors  120 ,  122  may be threaded box connectors, for example. However pin connectors, or other types of connectors may be used as appropriate. Connectors  120 ,  122  may allow sub  100  to be assembled as part of drill string  32  or bottom hole assembly  90  ( FIG. 1 ), for example. 
     A medial bore  128  may be formed within collar  110 , opening into upper blind bore  124  and/or lower blind bore  126 . Medial bore  128  may be a blind bore (illustrated in  FIGS. 5 and 6 ), or it may be a through bore that is formed through collar  110  opening between upper and lower blind bores  124 ,  126 , as illustrated in  FIG. 9 . 
     An upper angled through bore  160  may be formed between the upper end of each longitudinal groove  152  and upper blind bore  124 . Similarly, a lower angled through bore  162  may be formed between the lower end of each longitudinal groove  152  and lower blind bore  126 , thereby fluidly coupling upper blind bore  124  with lower blind bore  126  via longitudinal groove  152 . As used herein, a through bore refers to hole that is reamed, drilled, milled or otherwise formed so as to break through at least a portion of the work piece. Any suitable angle for upper and lower through bores may be used, up to and including 90 degrees with respect to sub axis  107 . 
       FIG. 11  is a perspective view in axial cross-section of sub  100  according an embodiment, using collar  110  of  FIGS. 8-10 .  FIG. 12  is a transverse cross section of sub  100  of  FIG. 11 . Flow channels  150  may be formed within sub  100  so as to bypass medial bore  128  by diverting drilling fluid flow to the circumferential extremities while maintaining adequate flow area, thereby maximizing the available diameter of medial bore  128 . In an embodiment, one or more flow channels  150  are defined in part by longitudinal grooves  152  formed along the exterior of collar  110  and sleeve-shaped cover  190 . Eight such flow channels  150  are illustrated, but any suitable number of flow channels  150  may be provided. Although not expressly illustrated, longitudinal grooves  152  need not be straight. For example, longitudinal grooves  152  may be spiral or helical grooves. 
     Flow channel cover  190  may be attached to collar  110 , thereby preventing fluid flow from exiting sub  100  at longitudinal grooves  152 . Although not expressly illustrated, flow channel cover  190  may be attached using fasteners, such as bolts. Gaskets, O-rings, or other seals may be provided between flow channel cover  190  and collar  110  to effect a seal. Flow channel cover  190  may also be both attached to and sealed against collar  110  by welding or brazing, for example. Other suitable attachment and sealing methods may also be used. However, sealing may not be required. 
     An instrument, tool, detector, circuit and/or other device (not illustrated) may be loaded into medial bore  128 , and sealed to avoid effects of hydrostatic pressure.  FIGS. 13-16  illustrate an arrangement for sealing a device within medial bore  128  according to an embodiment.  FIG. 13  is a perspective view in axial cross section of sub  100  into which each open end of medial bore  128  is sealed from the interior  33  of drill string  32  ( FIG. 1 ) by a flow-diverting plug  165 . Depending on the arrangement, the upper end, the lower end, or both, of medial bore  128  may be open to adjacent blind bores  124 ,  126 , respectively.  FIG. 14  is an enlarged cross section of a flow-diverting plug  165  installed into the downhole end of medial bore  128  via lower blind bore  126 .  FIGS. 15 and 16  are a perspective view and a perspective axial cross section, respectively, of flow-diverting plug  165  according to an embodiment. 
     Referring to  FIGS. 13-16 , flow-diverting plug  165  may have a generally cylindrical body  300  having a medial portion  302  and a distal portion  304 . Medial portion  302  may be dimensioned for being fitted within medial bore  128 , and distal portion  302  may be dimensioned for being fitted within either upper blind bore  124  or lower blind bore  126 . Medial portion  302  may include an O-ring or similar sealing element  310  for sealing against the inner wall of medial bore  128 . 
     Flow-diverting plug  165  may include a nozzle  320  formed therethrough. Nozzle  320  may be arranged to divert axial flow at distal portion  304  to radial flow at medial portion  302  and vice versa. Nozzle may have a singular opening  324  at a medial end which may be in fluid communication with a number of radial ports  322  at medial portion  302 . The number and position of radial ports  322  may be such as to align with angled through bores  160 ,  162 . Nozzle may have a profile designed to minimize pressure drop therethrough. 
     When flow-diverting plugs  165  are positioned as shown in  FIGS. 13-16 , medial blind bore  128  forms a cavity into which one or more devices  101  ( FIG. 13 ), such as instruments, detectors, sensors, circuits, and the like, may be inserted. 
       FIG. 17  is a flowchart of a method  200  for manufacturing a downhole tool using sub  100  according to an embodiment. As set forth in  FIG. 17 , with periodic reference to the previous figures, at step  204 , collar  110  may be formed, for example as set forth hereinafter with respect to  FIG. 18 . Collar  110  may include upper and lower connectors  120 ,  122 , upper and lower blind bores  124 ,  126 , a medial bore  128 , stabilizer projections  130 , longitudinal groove  152  formed along an exterior of the collar, and upper and lower angled through bores  160   162  formed between longitudinal groove  152  and upper and lower blind bores  124 ,  126 , respectively. In an embodiment, collar  110  may be unitary, formed from a solid cylindrical bar using conventional machining and manufacturing processes. 
     At step  208 , flow channel cover  190  may be formed using conventional machining and manufacturing processes. Flow channel cover  190  may be manufactured from the same or similar material as channel  110 , which may include steel, stainless steel, or nickel alloys for example. In some embodiments, as illustrated in  FIGS. 11 and 12 , flow channel cover  190  may be a sleeve that fits about collar  106 , which may cover a number of longitudinal grooves  152 . 
     In some embodiments, flow channel cover  190  may have the shape of a strip dimensioned to be received within longitudinal groove  152 . In such embodiments, depending on the particular location of longitudinal groove  152  for which flow channel cover  190  is to cover, the outer surface of flow channel cover  190  may be rounded at radius r c  to match outer diameter  112  of collar  110  or at radius r p  to match the curvature of projection  130 . A trough  174  may be formed along the inner surface of flow channel cover  190  to provide a portion of fluid flow path  150 . 
     At step  212 , flow channel cover  190  is disposed over longitudinal groove  152 , and at step  216 , collar  110  and flow channel cover  190  are joined together to isolate flow channel(s)  150  from the exterior of collar  110 . Flow channel cover  190  may be attached using fasteners, such as bolts. A gasket may be provided between flow channel cover  190  and collar  110 , such as at seating surface  170 , to effect a seal. Flow channel cover  190  may also be both attached to and sealed against collar  110  by welding or brazing, for example. Other suitable attachment and sealing methods may also be used. However, sealing may not be required. 
     At step  220 , an instrument, tool, detector, circuit, and/or other device  101  ( FIG. 13 ) may be loaded into sub  100  into medial bore  128 , and sealed to avoid effects of hydrostatic pressure. Tapered female threads  129  may optionally be provided within medial bore  128  for receiving a threaded plug to seal medial bore  128 . However, other sealing methods, such as O-rings or potting, may be used as appropriate. 
       FIG. 18  is a flowchart of a method  204 , according to an embodiment, for manufacturing a unitary collar  110  by turning, boring, drilling, reaming, milling, grinding and/or other machining and manufacturing techniques. Although  FIG. 18  shows steps occurring in a particular sequence, the order of the steps may be varied to facilitate manufacturing. 
     As set forth in  FIG. 18 , with periodic reference to the previous figures, at step  230 , a solid cylindrical bar may be provided. The bar may be formed of a steel, stainless steel, or nickel alloy, for example, although other suitable materials may be used. The bar may have an outer diameter that is sufficiently large to produce the finished collar  110 , with stabilizer protrusions  130  if desired. 
     At step  234 , stabilizer protrusions  130  may optionally be formed by removing material from the cylindrical work piece between and at the ends of stabilizer protrusions  130 , thereby defining outer diameter  112  of collar  110 . Three or more stabilizer protrusions  130  may be provided and equally spaced about outer diameter  112  to keep sub  100  centered within wellbore  60  ( FIG. 1 ). Stabilizer protrusions  130  may have rounded outer surfaces. 
     In embodiments using a sleeve-shaped flow cover  190 , stabilizer protrusions may optionally be formed on the exterior surface of flow cover  190  at step  208  rather than on collar  110 . 
     Upper and lower blind bores  124 ,  126  may be formed at upper and lower ends  102 ,  104  of the work piece. Upper and lower blind bores  124 ,  126  may be formed centered at sub axis  107  defined by the cylindrical bar. The depths and diameters of upper and lower blind bores  124 ,  126  may be varied to any suitable dimensions. 
     At step  242 , medial bore  128  may be formed in the work piece from upper end  102  or from lower end  104 . Medial bore  128  may be a blind bore or may be through bore opening into both upper and lower blind bores  124 ,  126 . 
     At step  246 , longitudinal groove  152  may be formed along a portion of an outer surface of said bar. In an embodiment, multiple longitudinal grooves  152  may be provided and may be evenly circumferentially spaced about collar  110  or may be located in proximity to one another so as to define a flow channel side  140  of collar  110 . Each longitudinal groove  152  may be formed along a stabilizer protrusion  130  and/or along outer diameter  112  of collar  110  between stabilizer protrusions  130 , if provided. Each longitudinal groove  152  may be formed as a compound groove, which may include a wider and shallower seating surface  170  and a narrower and deeper trough  172 . Seating surface  170  may be flat, and trough  172  may be arcuate, although other profiles may be used as appropriate. Seating surface  170  may provide a receptacle into which a strip-shaped flow channel cover  190  may be positioned and affixed to collar  110 . Trough  172  may provide at least a portion of flow channel  150 . The dimensions and number of longitudinal grooves  152  may be selected to reduce flow velocity and resultant erosion, increasing reliability and life of sub  100 . 
     At step  250 , for each longitudinal groove  152 , upper and lower angled through bores  160 ,  162  may be formed between an upper and lower ends, respectively, of longitudinal groove  152 , and upper and lower blind bores  124 ,  126 , respectively. Any suitable angle for upper and lower through bores may be used, up to and including 90 degrees with respect to sub axis  107 . The diameter of angles of upper and lower angled through bores  160 ,  162  may be selected to reduce flow velocity, turbulence, and resultant erosion, increasing reliability and life of sub  100 . 
     In summary, a sub, a downhole tool, and a method for manufacturing a sub have been described. Embodiments of the sub may generally have: A cylindrical unitary collar, the collar defining a longitudinal sub axis; an upper blind bore formed along the sub axis at the upper end of the collar; a lower blind bore formed along the sub axis at the lower end of the collar; a medial bore formed within the collar; a longitudinal first groove formed along an exterior of the collar; a first upper angled through bore formed between an upper end of the first groove and the upper blind bore; a first lower angled through bore formed between a lower end of the first groove and the lower blind bore; and a first cover disposed over the first groove and connected to the collar; whereby the upper blind bore is in fluid communication with the lower blind bore via the first upper angled through bore, the first groove, and the first lower angled through bore. Embodiments of the downhole tool may generally have: A cylindrical unitary collar, the collar defining a longitudinal sub axis; an upper blind bore formed along the sub axis at the upper end of the collar; a lower blind bore formed along the sub axis at the lower end of the collar; a medial bore formed within the collar; a longitudinal first groove formed along an exterior of the collar; a first upper angled through bore formed between an upper end of the first groove and the upper blind bore; a first lower angled through bore formed between a lower end of the first groove and the lower blind bore; a first cover disposed over the first groove and connected to the collar; and a device disposed within the medial bore; wherein the upper blind bore is in fluid communication with the lower blind bore via the first upper angled bore, the first groove, and the first lower angled bore; and the medial bore is fluidly isolated from the upper and lower blind bores. Embodiments of the method may generally include: Forming a collar by providing a cylindrical bar, the bar defining a sub axis, forming an upper blind bore along the sub axis at an upper end of the bar, forming a lower blind bore along the sub axis at a lower end of the bar, forming a medial bore within the bar, forming a longitudinal first groove along an exterior of the bar, forming a first upper angled through bore between an upper end of the first groove and the upper blind bore, and forming a first lower angled through bore between a lower end of the first groove and the lower blind bore; covering the first groove with a first cover; and connecting the first cover to the collar. 
     Any of the foregoing embodiments may include any one of the following elements or characteristics, alone or in combination with each other: A plurality of stabilizer protrusions intervaled about the exterior; a first of the plurality of stabilizer protrusions is integrally formed as part of the collar; the first groove is formed along the first stabilizer protrusion; the medial bore has an opening formed in one of the upper blind bore and the lower blind bore; a plug dimensioned to be at least partially received within the medial bore for sealing the medial bore from the one of the upper blind bore and the lower blind bore; a nozzle formed in the plug between a medial portion of the plug and a distal portion of the plug, the nozzle having a radial port formed in the medial portion and a longitudinal opening formed in the distal portion; the medial bore is characterized by a centerline that is offset from the sub axis; a longitudinal second groove formed along the exterior in proximity to the first groove; a second upper angled through bore formed between an upper end of the second groove and the upper blind bore; a second lower angled through bore formed between a lower end of the second groove and the lower blind bore; a second cover disposed over the second groove and connected to the collar; a longitudinal third groove formed along the exterior in proximity to the first groove; a third upper angled through bore formed between an upper end of the third groove and the upper blind bore; a third lower angled through bore formed between a lower end of the third groove and the lower blind bore; a third cover disposed over the third groove and connected to the collar; first, second, and third stabilizer protrusions are integrally formed as part of the collar equally distributed about the exterior; the second groove is formed along the second stabilizer protrusion; the third groove is formed along the third stabilizer protrusion; the first, second and third covers are generally strip-shaped; the first cover is generally sleeve-shaped and covers both the first and the second grooves; the first groove is a compound groove including a seating surface and a trough; the first cover is dimensioned to be received at the seating surface; forming a plurality of stabilizer protrusions intervaled about the exterior; forming the first groove along a first of the plurality of stabilizer protrusions; fluidly isolating the medial bore from the upper and lower blind bores; forming the medial bore on a centerline that is offset from the sub axis; forming a longitudinal second groove along the exterior in proximity to the first groove; forming a second upper angled through bore between an upper end of the second groove and the upper blind bore; forming a second lower angled through bore between a lower end of the second groove and the lower blind bore; covering the second groove with a second cover; connecting the second cover to the collar; forming a longitudinal third groove along the exterior in proximity to the first groove; forming a third upper angled through bore between an upper end of the third groove and the upper blind bore; forming a third lower angled through bore between a lower end of the third groove and the lower blind bore; covering the third groove with a third cover; connecting the third cover to the collar; forming first, second, and third stabilizer protrusions about the exterior; forming the second groove along the second stabilizer protrusion; forming the third groove along the third stabilizer protrusion; and covering both the first and second grooves by the first cover. 
     The Abstract of the disclosure is solely for providing the reader a way to determine quickly from a cursory reading the nature and gist of technical disclosure, and it represents solely one or more embodiments. 
     While various embodiments have been illustrated in detail, the disclosure is not limited to the embodiments shown. Modifications and adaptations of the above embodiments may occur to those skilled in the art. Such modifications and adaptations are in the spirit and scope of the disclosure.