Patent Publication Number: US-7900720-B2

Title: Downhole drive shaft connection

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in-part of U.S. patent application Ser. No. 11/306,976, filed Jan. 18, 2006, now U.S. Pat. No. 7,360,610. This application in herein incorporated by reference for all that it contains. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to drill bits, specifically drill bit assemblies for use in oil, gas and geothermal drilling. Drill bits are continuously exposed to harsh conditions during drilling operations in the earth&#39;s strata. Bit whirl in hard formations for example may result in damage to the drill bit and reduce penetration rates. Further loading too much weight on the drill bit when drilling through a hard formation may exceed the bit&#39;s capabilities and also result in damage. Too often unexpected hard formations are encountered suddenly; and damage to the drill bit occurs before the weight on the drill bit may be adjusted. When a bit fails, it reduces productivity resulting in diminished returns to a point where it may become uneconomical to continue drilling. The cost of the bit is not considered so much as the associated down time required to maintain or replace a worn or expired bit. To replace a bit requires removal of the drill string from the bore in order to service the bit which translates into significant economic losses until drilling can be resumed. 
     The prior art has addressed bit whirl and weight on bit issues. Such issues have been addressed in the U.S. Pat. No. 6,443,249 to Beuershausen, which is herein incorporated by reference for all that it contains. The &#39;249 patent discloses a PDC-equipped rotary drag bit especially suitable for directional drilling. Cutter chamfer size and backrake angle, as well as cutter backrake, may be varied along the bit profile between the center of the bit and the gage to provide a less aggressive center and more aggressive outer region on the bit face, to enhance stability while maintaining side cutting capability, as well as providing a high rate of penetration under relatively high weight on bit. 
     U.S. Pat. No. 6,298,930 to Sinor which is herein incorporated by reference for all that it contains, discloses a rotary drag bit including exterior features to control the depth of cut by cutters mounted thereon. Sinor seeks to control the volume of formation material cut per bit rotation as well as the torque experienced by the bit and an associated bottomhole assembly. The exterior features preferably precede, taken in the direction of bit rotation, cutters with which they are associated, and provide sufficient bearing area so as to support the bit against the bottom of the borehole under weight on bit without exceeding the compressive strength of the formation rock. 
     U.S. Pat. No. 6,363,780 to Rey-Fabret which is herein incorporated by reference for all that it contains, discloses a system and method for generating an alarm relative to effective longitudinal behavior of a drill bit fastened to the end of a tool string driven in rotation in a well by a driving device situated at the surface, using a physical model of the drilling process based on general mechanics equations. The model is reduced to retain only pertinent modes. At least two values, Rf and Rwob, are calculated. Rf a function of the principal oscillation frequency of weight on hook (who) divided by the average instantaneous rotating speed at the surface. Rwob is a function of the standard deviation of the signal of the weight on bit (WOB) estimated by the reduced longitudinal model from measurement of the signal of the weight on hook (WOH), divided by the average weight on bit defined from the weight of the string and the average weight on hook. Any danger from the longitudinal behavior of the drill bit is determined from the values of Rf and Rwob. 
     U.S. Pat. No. 5,806,611 to Van Den Steen which is herein incorporated by reference for all that it contains, discloses a device for controlling weight on bit of a drilling assembly for drilling a borehole in an earth formation. The device includes a fluid passage for the drilling fluid flowing through the drilling assembly, and control means for controlling the flow resistance of drilling fluid in the passage in a manner that the flow resistance increases when the fluid pressure in the passage decreases and that the flow resistance decreases when the fluid pressure in the passage increases. 
     U.S. Pat. No. 5,864,058 to Chen which is herein incorporated by reference for all that is contains, discloses a down hole sensor sub in the lower end of a drillstring. The sub has three orthogonally positioned accelerometers for measuring vibration of a drilling component. The lateral acceleration is measured along either the X or Y axis and then analyzed in the frequency domain as to peak frequency and magnitude at such peak frequency. Backward whirling of the drilling component is indicated when the magnitude at the peak frequency exceeds a predetermined value. A low whirling frequency accompanied by a high acceleration magnitude based on empirically established values is associated with destructive vibration of the drilling component. One or more drilling parameters (weight on bit, rotary speed, etc.) is then altered to reduce or eliminate such destructive vibration. 
     BRIEF SUMMARY OF THE INVENTION 
     A section of a drill string has a drill bit with a body intermediate a shank and a working face. The working face at least one cutting element. A jack element is disposed within the drill bit body and has a distal end substantially protruding from the working face. A drive shaft is in communication with the jack element and a source of rotational power. The drive shaft has a first portion secured within a bore of a tool string component in the tool string and a second portion secured within a bore of the drill bit. The first and second portions of the drive shaft are connected at a pin and box connection wherein the first and second portions are automatically connected as the tool string component is mechanically coupled to the drill bit. 
     The connection of the first and second portions may a sleeve that has an internal shape with an at least one external feature to interlock either the first or second portion, or both. The at least one feature may be selected from the group consisting of splines, threads, keys, polygonal (in section) surfaces, elliptical (in section) surfaces, or combinations thereof. 
     The connection may be a threaded connection. The connection may comprise a guide. The connection may comprise a bore adapted to receive the guide. The guide may comprise a geometry selected from the group consisting of splines, keys, polygonal surfaces or combinations thereof. 
     The drive shaft and jack element may advance the drill string further into a formation by rotating. The drive shaft and jack element assist in advancing the drill string further into the formation by oscillating back and forth with respect to the formation. 
     The pin and box connection may comprise a press-fit. The first portion may be press-fit into the sleeve. The second portion may be press-fit into the sleeve. The first portion may comprise a material selected from the group consisting of cemented metal carbide, steel, manganese, nickel, chromium, titanium, or combinations thereof. The second portion may comprise a material selected from the group consisting of cemented metal carbide, steel, manganese, nickel, chromium, titanium, or combinations thereof. 
     The second portion may comprise a generally conical region The at least one feature may have a length of 2.5 inches to 3.75 inches. The at least one feature may have a length of 3 inches. 
     The first portion and the second portion may comprise at least one coating. The at least one coating may comprise a material selected from the group consisting of a material selected from the group consisting of gold, silver, a refractory metal, carbide, tungsten carbide, cemented metal carbide, niobium, titanium, platinum, molybdenum, diamond, cobalt, nickel, iron, cubic boron nitride, and combinations thereof. The first portion and the second portion may comprise a cemented metal carbide distal end. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective diagram of an embodiment of a drill string suspended in a bore hole. 
         FIG. 2  is a cross-sectional diagram of an embodiment of a drill string. 
         FIG. 3  is a cross-sectional diagram of an embodiment of a section of a drill string. 
         FIG. 4  is a cross-sectional diagram of another embodiment of a section of a drill string. 
         FIG. 5  is a perspective diagram of another embodiment of a section of a drill string. 
         FIG. 6  is a perspective diagram of an embodiment of a drive shaft portion 
         FIG. 7  is a perspective diagram of another embodiment of a drive shaft portion. 
         FIG. 8  is a perspective diagram of another embodiment of a drive shaft portion 
         FIG. 9  is a perspective diagram of another embodiment of a drive shaft portion. 
         FIG. 10  is a perspective diagram of another embodiment of a drive shaft portion 
         FIG. 11  is a perspective diagram of another embodiment of a drive shaft portion. 
         FIG. 12  is a perspective diagram of another embodiment of a drive shaft portion 
         FIG. 13  is a perspective diagram of another embodiment of a section of a drill string. 
         FIG. 14  is a perspective diagram of another embodiment of a drive shaft portion 
         FIG. 15  is a perspective diagram of another embodiment of a drive shaft portion. 
         FIG. 16  is a perspective diagram of another embodiment of a drive shaft portion 
         FIG. 17  is a perspective diagram of another embodiment of a drive shaft portion. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT 
       FIG. 1  is a perspective diagram of an embodiment of a drill string  100  suspended by a derrick  101 . A bottom-hole assembly  102  is located at the bottom of a wellbore  103  and includes a drill bit  104 . As the drill bit  104  rotates downhole, the drill string  100  advances farther into the subterranean formations. The drill string  100  may penetrate soft or hard subterranean formations  105 . The drill bit  104  may be adapted to steer the drill string  100  in a desired trajectory. Steering may be controlled by rotating a jack element (see  FIG. 2 ) that is disposed at least partially within the drill bit  104  around a central axis of the jack element. The bottom-hole assembly  102  and/or downhole components may comprise data acquisition devices which may gather data. The data may be sent to the surface via a transmission system to a data swivel  106 . The data swivel  106  may send the data to the surface equipment. Further, the surface equipment may send data and/or power to downhole tools and/or the bottom-hole assembly  102 . U.S. Pat. No. 6,670,880 which is herein incorporated by reference for all that it contains, discloses a telemetry system that may be compatible with the present invention; however, other forms of telemetry may also be compatible such as systems that include mud pulse systems, electromagnetic waves, radio waves, and/or short hop. In some embodiments, no telemetry system is incorporated into the drill string  100 . 
     Referring now to  FIG. 2 , a cross-sectional diagram of a portion of the drill string  100  shows a bottom-hole assembly (BRA)  102 . The drill bit  104  may be part of the BRA  102  and which includes a jack element  201 . The jack element  201  may oscillate towards and away from the formation  105  and/or the jack element  201  may rotate with respect to the drill bit body  304 . The drill string  100  may comprise at least one position feedback sensor  202  that is adapted to detect a position and/or orientation of the jack element  201 . Monitoring the position and/or orientation of the jack element  201  may aid in steering the drill string  100 . Rotation of the jack element  201  may be powered by a rotary source, such as a downhole motor  203 . The downhole motor  203  may be an electric motor, a mud motor, or combinations thereof. In some embodiments, drill string  100  includes an upper generator  204  and a lower generator  205 . Both generators  204 ,  205  are powered by the flow of drilling mud (not shown) past one or more turbines  206  disposed intermediate the two generators  204 ,  205 . In some embodiments only one generator may be used, and in other embodiments another method of powering the motor  203  may be employed. 
     The upper generator  204  may provide electricity to a direction and inclination (D&amp;I) package  207 . D&amp;I package  207  may monitor the orientation of the BHA  102  with respect to some object, such as the center of the planet, the moon, the surface of the planet, a satellite, or combinations thereof. The lower generator  205  may provide electrical power to a computational board  208  and to the motor  203 . The computational board  208  may control steering and/or motor functions. The computational board  208  may receive drill string orientation information from the D&amp;I package  207  and may alter the speed or direction of the motor  203 . 
     In some embodiments a tool string component  301  is disposed in a terminal section  210  of the drill string  100  and may be adapted to rotate with respect to the drill string  100  while the motor  203  may be rotationally fixed to the drill string  100 . In some embodiments one or more motor like motor  203 , generators  204 ,  205 , computational boards  208 , D&amp;I package  207 , or some other electrical component, may be rotationally isolated from the drill string  100 . 
     In some embodiments, the motor  203  connects to the jack element  201  via a gear train  209 . The gear train  209  may couple rotation of the motor  203  to rotation of the jack element  201  at a ratio of 25 rotations to 1 rotation and may itself be rotationally fixed to the drill string  100 . In some embodiments a different ratio may be used, such as, but not limited to 15-30 rotations to 1 rotation. The gear train  209  and the jack element  201  may be part of the tool string component  301 . 
       FIGS. 3 through 4  are cross-sectional diagrams of embodiments of portions of the tool string component  301 . The tool string component  301  is part of the drill string  100  ( FIG. 1 ) and may be disposed within the BRA  102 . The tool string component  301  has a bore  324  adapted to house at least one component of the tool string component  301 . The jack element  201  is disposed on a distal end  302  of tool string component  301 ; and the jack element  201  substantially protrudes from a working face  303  of the drill bit  104 , and is adapted to move with respect to the bit body  304  of the bit  104 . The bit body  304  is disposed intermediate a shank  305  and the working face  303 . The bit body  304  has a bore  325  formed in it. The working face  303  has at least one cutting element  306 . In some embodiments the working face comprises a plurality of cutting elements like element  306 A-C. The drill bit  104  may advance the drill string  100  further into the formation  105  ( FIG. 1 ) by rotating, thereby allowing the cutting elements  306  to dig into and degrade the formation  105 . The jack element  201  may assist in advancing the drill string  100  further into the formation  105  by oscillating back and forth with respect to the formation  105 . 
     In some embodiments the jack element  201  has a primary deflecting surface  1001  disposed on a distal end  330  of the jack element  201 . The deflecting surface  1001  may form an angle  332  relative to a central axis  307  of the jack element  201  of 3 to 75 degrees. The primary deflecting surface may cause the distal end to be asymmetric. The angle  332  may create a directional bias in the jack element  201 . The deflecting surface  1001  of the jack element  201  may cause the drill bit  104  to drill substantially in a direction indicated by the directional bias of the jack element  201 . By controlling the orientation of the deflecting surface  1001  in relation to the drill bit  104 , the direction of drilling may be controlled. In some drilling applications, the drill bit  104 , when desired, may drill 3 to 20 degrees per 100 feet drilled. In some embodiments, the jack element  201  may be used to steer the drill string  104  in a straight trajectory if the formation  105  comprises characteristics that tend to steer the drill string  104  in an opposing direction. 
     The primary deflecting surface  1001  of the jack element  201  has a surface area of 0.5 to 4 square inches. The primary surface  1001  may have a radius of curvature of 0.75 to 1.25 inches. The jack element  201  may have a diameter of 0.5 to 1 inch, and may be made of carbide. The distal end  330  of the jack element  201  may have rounded edges so that stresses exerted on the distal end  330  may be efficiently distributed rather than being concentrated on corners and edges. 
     The jack element  201  may be supported by a bushing  314  and/or bearing and may be in communication with another bearing  334 . The bushing  314  may be placed between the jack element  201  and the drill bit body  304  in order to allow for low-friction rotation of the jack element  201  with respect to the drill string  100 . The bushing  314  may be beneficial in allowing the jack element  201  to be rotationally isolated from the drill bit body  304 . Thus, during a drilling operation, the jack element  201  may steer the drill string  100  as the drill bit body  304  rotates around the jack element  201 . The jack element  201  may be driven by the motor  203  ( FIG. 2 ) to rotate in a direction opposite to the rotation of the drill string  100 . 
     In some embodiments two position feedback sensors  308  and  313  are disposed proximate the tool string component  301 . A first sensor  308  is disposed proximate a coupler  310  on a gear train side  311  of the coupler  310 . A drive shaft  309  may rotationally couple the jack element  201  to the coupler  310  and may be disposed intermediate the motor  203  and the jack element  201 . The coupler  310  may connect the gear train  209  that is disposed intermediate the motor  203  and the drive shaft  309  to the drive shaft  309 . A bearing  312  facilitates rotation of the coupler  310  with respect to the drill string  100 . 
     A second sensor  313  may be disposed proximate the jack element  201  in the drive shaft  309 . Both the first sensor  308  and the second sensor  313  may be embodiments of a position feedback sensors. In some embodiments a plurality of position feedback sensors disposed proximate the tool string component  301  may all be first sensors  308 , or they may all be second sensors  313 . In other embodiments a drill string  100  may comprise no more than one position feedback sensor like sensor  308  or sensor  313 . 
     The drive shaft  309  has a first portion  401  secured within the bore  324  of the tool string component  301 . A second portion  402  of the drive shaft  309  is secured within the bore  325  of the drill bit  104 . The first and second portions  401 ,  402  may be made of material selected from the group consisting of cemented metal carbide, steel, manganese, nickel, chromium, titanium, or combinations thereof. 
     The first and second portions  401 ,  402  of the drive shaft  309  are connected by box  404  and pin connection  403 . The box and pin connection  403  may be adapted such that the first and second portions  401  and  402  respectively are automatically connected as the tool string component  301  is mechanically coupled to the drill bit  104 . The first portion  401  may include the box  404 ; and the second portion  402  may included the pin  405  or vise versa. A sleeve  406  may be used to form the box  404  in the box and pin connection  403 . 
     Referring now to  FIGS. 5 through 6 , the first and second portions  401 A, and  402 A have at least one external torque transferring feature  501 , such as a spline. The box  404  ( FIG. 3 ) or sleeve  406 A of the pin connection  403 A of  FIG. 5  may have an internal opening  502  adapted to interlock with the at least one external torque transferring feature  405 A and  405 B of the first and second portions  401 A and  402 A. As the first portion  401 A of the drive shaft  309  is rotated, it is believed that the at least one external feature like external feature  50 A and  501 B will allow torque to be transferred from the first portion  401 A to the second portion  402 A of the shaft  309 . 
     The at least one feature  501  may include shapes with surfaces to be polygonal  601  in section. In some embodiments, the first and second portions  401 A and  402 A have may be shaped to have surfaces  601  to be a Reuleaux triangle in cross-section. The sleeve  406 A of  FIG. 5  has an internal opening  502  formed to mate with the surface  601  of the first and second portions  401 A and  402 B. The at least one feature  501  may have a length of 2.5 to 3.75 inches. In some embodiments the at least one feature  501  has a length of 3 inches. 
     The second portion  402 B of the shaft  309  in  FIG. 6  may include a generally conical region  602 . The generally conical region  602  may be formed such that the at least one feature  501  of the second portion  402 B may converge into a point  603  of the conical region  602 . It is believed that the generally conical region  602  will assist in guiding the second portion  402 B of the drive shaft  309  as it is inserted into a sleeve like sleeve  406 A or box  404  ( FIG. 3 ) of the pin connection  403 . 
     The first portion  401 A in  FIG. 5  may be press-fit to the inside of the sleeve  406 A; and the second portion  402 A may rest in the sleeve  406 A. The second portion  402  A may be press-fit to the inside or opening  502  of the sleeve  406 A; and the first portion  401 A may rest in the sleeve  406 B. Both the first and second portions  401 A and  402 A may be press-fit to the inside of the sleeve  406 A. Both the first and second portions  401 A and  402 B may rest in the sleeve  406 A. A hole  410  may be formed in the side of the sleeve  406 A to allow air to exit the sleeve  406 A as the first portion  401 A and the second portion  402 A are inserted into the sleeve  406 A. 
     In some embodiments some or all of the features of the first portion  401 A may be applied to the second portion  402 A and in some embodiments, some or all of the features of the second  402 A portion may be applied to the first portion  401 A. 
       FIG. 7  discloses a connection wherein the first and second portions  401 C and  402 C have threads  700 A and  700 B as the at least one feature  501 C. The sleeve  406 C is internally threaded. The threads  700 A of the first portion  401 C may be right-handed; and the threads  700 B of the second portion  402 C may be left-handed, or vise versa. The inside of the sleeve  406 C may have corresponding both right-handed and left-handed threads  700 A and  700 B. The threads  700 A and  700 B may cause the first and second portions  401 C and  402 C to have a reduced diameter portion  701 A and  701 B at the connection. It is believed that the reduced diameter  701 A and  701 B of the first and second portions  401 A,  402 B at the pin connection  403 C may prevent the sleeve  406 C from wandering away from the connection  403 . 
       FIGS. 8 through 9  disclose more embodiments for connecting portions of shaft  309  like portion  402 D and  402 E to a sleeve like sleeves  406 D and  406 E. The portions  402 D and  402 E have the at least one feature  501 D and  501 E which here are surfaces  601 D and  601 E that are polygonal in section. The surface  601 D may be star-shaped in section; and the surface  601 E is square shaped in section and sized to register with opening  502 E. The surfaces  601 D and  601 E may also be shaped to be in section one of but not limited to, triangles, rectangles, pentagons, hexagons, heptagons, octagons, or combinations thereof. The edges  801 D and  801 E of the surfaces  601 D and  601 E may be rounded so as to reduce wear and stress buildup in the connection  403 D and  403 E. The surface  601 E has a pyramid formation  602  at its end with a tip  603 . 
     The at least one feature  501 F may be an to be elliptical surface  1002  in section extending from the portion  402 F of shaft  309  as seen in the embodiment of  FIG. 10 . The elliptical surface  1002  has a conical end  602 F with a truncated tip  603 F for insertion into the opening  502 F in sleeve  406 F. 
     The at least one feature  501 G of  FIG. 11  shows the portion  402 G of the shaft  309  having an end  1101  with a key  1102  sized to register with a slot  1110  in the opening  502 G of the sleeve  406 G. The key  1102  may also a bead, groove, notch, teeth, or combinations thereof with similar. The key  1102  is shaped to effectively lock the second portion  402 G to the sleeve  406 G. 
     Referring now to  FIG. 12 , the at least one feature  501 H may comprise at least one spline  1201  formed at the end of portion  402 H. The at least one spline  1201  may be selected from a group consisting of helical splines, straight splines or a combination thereof. The opening  1202  of the sleeve  406 H may be internally splined to mate with the at least one spline  1201  of the second portion  402 H. 
       FIGS. 13  though  14  disclose a pin connection  403 J and  403 K wherein the second portion  402 J and  402 K of the shaft  309  includes a guide  1301 J and  1301 K respectively. The guides  1301 J and  1301 K may be formed to have a shape of one of the group consisting of splines, keys, polygonal surfaces, elliptical surfaces, or combinations thereof. The first portions  401 J and  401 K may include a recess  1303 J and  1303 K adapted to receive their guides  1301 J and  1301 K. The recesses  1303 J and  1303 K have a tapered opening  1304 J and  1304 K that tapers into the recess  1303 J and  1303 K, respectively. The recesses  1303 J and  1303 K may be adapted to accommodate the shape of the guides  1301 J and  1301 K, respectively. It is believed that as the drill bit  104 J is connected to the tool string component  301 J, the tapered opening  1304 J will direct the guide  1301 J into the recess  1303 J which will in turn guide the second portion  402 J into the sleeve  406 J causing the external features to align. Similarly for the embodiment of  FIG. 14 , it is believed that as the drill bit, like drill bit  104 J, is connected to the tool string component, like component  301 J, the tapered opening  1304 K will direct the guide  1301 K into the recess  1303 K which will in turn guide the second portion  402 K into the sleeve  406 K causing the portions  401 K and  402 K to align. Also shown in  FIG. 13  is at least one centering element  5000 A and  5000 B may be used to help keep one or both of the portions of the drive shaft  309  centered within the bore  324  and  325  of the downhole components. 
       FIGS. 15 through 16  disclose an embodiment wherein the second portions  402 L and  402 M have a cemented metal carbide distal ends  1501 L and  1501 M. The carbide distal ends  1501 L and  1501 M may include the at least one external torque transferring feature like feature  501 M. The carbide distal ends  1501 L may have a cavity  1502 L. The cavity  1502 L may be formed to receive a shank  1520  of the second portion  402 L. The second portion  402 L may be brazed or press-fitted within the cavity  1502 L. The cavity  1502 L may have a rectangular, elliptical, or polygonal geometry. It is believed that a rectangular, elliptical or polygonal geometry will help prevent the braze or press-fit between the cavity  1502 L and the second portion  402 L from failing in torque. 
     The cavity  1502 M in  FIG. 16  may be disposed in second portion  402 M. The carbide distal end  1501 M may include a shank  1602 M. The shank  1602 M may be shaped to fit within the cavity  1502 M. The shank  1602 M may be brazed or press-fitted within the cavity  1502  M. Both the shank  1602  M and the cavity  1502  M may be formed to be rectangular, elliptical, or in some other polygonal geometry to help prevent the braze or press-fit between the cavity  1502 M and the shank  1602 M from failing in torque. 
     Referring now to  FIG. 17 , the second portions  402 N may have a section  1702  formed for connection to a sleeve like sleeve  406 . The portion  1702  has at least one coating  1701 . The at least one coating  1701  may be made from a material selected from the group consisting of gold, silver, a refractory metal, carbide, tungsten carbide, cemented metal carbide, niobium, titanium, platinum, molybdenum, diamond, cobalt, nickel, Iron, cubic boron nitride, and combinations thereof. 
     Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.