Patent Publication Number: US-2010126773-A1

Title: Drilling apparatus and system for drilling wells

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application, claiming priority to the U.S. patent application having Ser. No. 11/904,136, filed Sep. 26, 2007, which claims priority to the U.S. patent application having Ser. No. 11/713,942, filed Mar. 5, 2007, now U.S. Pat. No. 7,607,496. The present application also claims priority to the U.S. patent application having Ser. No. 12/584,100, filed Aug. 31, 2009. The above-referenced patents and patent applications are incorporated herein by reference, in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Conventionally, in the search for oil and gas, operators have utilized a specifically designed drill string to drill wells, the drill string being attached to a drill bit. To drill the well, the drill string is rotated, which in turn causes the bit to rotate, forming a hole in the earth, thus drilling the well. Various types of drill strings have been developed to drill directional, or inclined, well bores. 
     Different types of bottom hole assemblies have also been developed to drill wells. A typical drilling string for use drilling directional well bores may contain a bottom hole assembly having a bit, a bent sub, a drilling motor, and one or more measurement-while-drilling surveying and logging tools. When using a conventional bottom hole assembly, the drill string ideally is retained in a stationary orientation with respect to down hole rotation. The drilling motor generates rotation of the bit via circulation of the drilling fluid through the drilling motor, as known in the art. With the drill string retained in a stationary orientation with respect to the rotation, the well is drilled in the desired, controlled direction of the bend in the bent sub. 
     A common problem when using this type of drilling assembly is the torque generated by the bit. The torque from the bit generates an equal and opposite reactive torque that is transferred from the motor into the bottom hole assembly and drill string, causing counter-rotation relative to the bit. Further, the reactive torque, and hence the drill sting counter-rotation, can vary due to drilling conditions, such as the weight applied to the bit, properties of the rock being drilled, and the hole condition, which all vary independently of each other. As the bent sub is part of the bottom hole assembly being counter-rotated, the direction in which the well is being drilled changes responsive to changes in the reactive torque. 
     As a result, the directional driller is required to make numerous surface adjustments of the drill string, and hence the bent sub, to maintain drilling in a desired direction. These numerous adjustments reduce the efficiency of the drilling operation and require substantial time and cost. By eliminating, or greatly reducing, the reactive torque in the bottom hole assembly and drill string, drilling can proceed unabated in the desired direction, saving valuable rig time. Other benefits of eliminating, or reducing, reactive torque include the ability to use more powerful motors and more weight on bit to increase drilling rates, and the ability to drill a smoother, less tortuous borehole for running logging tools and setting casing. A non-reactive bit apparatus and method were disclosed in U.S. Pat. No. 5,845,721 entitled “Drilling Device And Method Of Drilling Wells”, which is incorporated herein by reference. 
     After a well is drilled, the well is prepared for running and cementing a casing string into the well. Hence, any time saved cleaning, running and cementing the casing can result in significant cost savings. Conventional tools have not allowed an operator to effectively drill with a casing string forming a part of the work string due to structural limitations of the casing string and the casing string thread connections. Generally, casing strings and casing string connections are not structurally designed to handle the stress and strain applied by the numerous torquing requirements for a drill string. Use of a non-reactive torque drilling device can enable drilling with an attached casing string. 
     Therefore, a need exists for a drilling device that will allow the drilling of a well with a casing string attached thereto, with the casing string able to be left within the well after cessation of drilling operations such that additional remedial operations, such as perforation of the casing, can be performed. There is also a need for a non-reactive drilling tool with dual bits. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention relate, generally, to devices for boring a well that include a motor with a power shaft for imparting rotational movement responsive to fluid flow. A driver can be operatively connected to the power shaft, the driver having a tubular body with an internal bore for accommodating the fluid flow. A first bit is attached to the driver such that rotational movement of the driver is imparted to the first bit. A second bit is attached to or otherwise formed on a housing disposed about the driver. A nozzle communicates fluid between the internal bore of the tubular body to an outer portion of the tubular body, the nozzle being oriented to deliver at least a portion of the fluid flow to the second bit. Directing of the fluid flow directly to the second bit can maximize the removal of cuttings. Additionally, the upward flow direction of the nozzles can provide a Venturi affect that reduces bottomhole pressure below the nozzles, which can improve hydraulic performance and drilling performance of the bits. 
     In an embodiment of the invention, the nozzles can be provided in a cross-over sub, or similar element, between the drive shaft and the first bit. In a further embodiment of the invention, a flow directing skirt can be provided to the cross-over sub and/or to the housing of the driver to direct fluid flow toward the second bit, the junk slot area, and into the annulus, which can further facilitate removal of cuttings generated by the first bit and cleaning of the second bit. In another further embodiment of the invention, the nozzles can include three or more nozzles angled in an upward direction, such as at an approximate 45 degree angle, oriented to provide fluid to the cutters of the second bit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of a drilling apparatus usable within the scope of the present disclosure. 
         FIGS. 2A ,  2 B and  2 C depict a side cross-sectional view of the drilling apparatus of  FIG. 1 . 
         FIG. 3  depicts a cross-sectional view of the drilling apparatus of  FIG. 2A  taken from the line  3 - 3 . 
         FIG. 4  depicts a cross-sectional view of the drilling apparatus of  FIG. 2A  taken from the line  4 - 4 . 
         FIG. 5  is a schematic drawing of an embodiment of a drilling apparatus system of usable within the scope of the present disclosure disposed within a well. 
         FIG. 6  is a schematic drawing of the drilling apparatus system of  FIG. 5  cemented within the well with perforations to a hydrocarbon reservoir. 
         FIG. 7  is a schematic drawing of the drilling apparatus system of  FIG. 6  with the inner bit removed. 
         FIG. 8  is a schematic drawing of the drilling apparatus system of  FIG. 5  drilling a well from a rig. 
         FIG. 9  is a cross-sectional view of an embodiment of a drilling apparatus usable within the scope of the present disclosure. 
         FIG. 10  is a disassembled perspective view of the drilling apparatus of  FIG. 9 . 
         FIG. 11  is a schematic drawing of the drilling apparatus of  FIG. 9  disposed within a well. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to  FIG. 1 , a perspective view of an embodiment of a drilling apparatus  2  is shown. The drilling apparatus  2  includes a power shaft  4  having a first end with external threads  6  disposed thereon, and a second end with internal threads  8  disposed therein. A driver  10  can be threaded to the power shaft through use of complementary external threads  12  that will engage the internal threads  8  of the power shaft  4 . The driver  10  also includes a second end having external threads  14 . The depicted driver  10  has a cylindrical body having a plurality of cogs  16  and/or splines disposed thereon, proximate to a raised shoulder  18 . A sleeve  20  is also shown, the sleeve having internal threads  22  on a first end for engagement with complementary external threads  14  of the driver  10 , and a plurality of openings  24  at a second end. Also, on the radial end of the driver  10 , a plurality of indentations  26  are shown. 
       FIG. 1  also depicts pinions  28 ,  30 ,  32 , disposed through openings  24  of the driver  10  for rotation, through use of pins. For example, a pin  34   a  is shown, which can be disposed through a corresponding pinion  32  and retained with bushings  36 ,  38 . The pins can cooperate to engage with a radial shoulder located within the openings of the sleeve  20 .  FIG. 1  also illustrates a housing  40 , which is shown having a first end  42  that will abut a ledge  44  of the sleeve  20 . The depicted housing  40  also includes external threads  46  disposed on the opposing end. 
       FIG. 1  also depicts the thrust pack cylindrical assembly  48  which can include a plurality of ball bearings (not visible in  FIG. 1 ), or other types of bearings or similar elements, as known in the art. The thrust pack assembly  48  can be disposed about the thrust mandrel  50 .  FIG. 1  depicts a thrust mandrel  50  with a first end having external threads  52  and a second end having a lip  54 . A trim spacer  56  is also shown, the depicted trim spacer  56  being a ring member that cooperates with the thrust mandrel  50  and the thrust pack assembly  48 , as shown in  FIG. 2A .  FIG. 1  also depicts an outer bit  58 , having internal threads  60  at a first end, and a bit face  62  at a second end. The bit face  62  contains indentations for allowing fluid and debris circulation. A cross-over  64  is shown for facilitating assembly of the drilling apparatus  2 , the cross-over  64  having a generally cylindrical body with internal threads  66  that will engage the external threads  14  of the driver  10 . The cross-over  64  is also shown having internal threads  68 , which engage external threads  72  of an inner bit  70 . The opposing end of the inner bit  70  includes a cutting face  74 , for boring of a well, as known in the art. 
     Referring now to  FIGS. 2A ,  2 B and  2 C, a cross-sectional view of the drilling apparatus  2  of  FIG. 1  is shown. It should be noted that like numbers appearing in the various figures refer to like components. The outer bit  58  is shown disposed about the cross-over  64 , with the inner bit  70  is threadably connected to the cross-over  64 . The outer bit  58  is shown threadably connected to the housing  40  using the external threads  46  of the housing  40  and the internal threads  60  of the outer bit  58 . The driver  10  is threadably connected to the cross-over  64  on one end, and to the power shaft  4  at the opposing end. The sleeve  20  is shown having a radial shoulder  80  within the previously described openings, wherein pins  34   a  and  34   b  are connected to the radial shoulders of the openings, such that the pins  34   a,    34   b  are held in place as the pinions rotate, as described previously. Additionally, an indented bottom portion  82  of the sleeve  20  is shown, which includes the indentation  26  shown in  FIG. 1 . The indented bottom portion  82  is shown threadably attached to the thrust mandrel  50 . The pins  34   a  and  34   b  are attached to the indented bottom portion  82  to fix the pins  34   a  and  34   b  in place during operation of the down hole motor. 
     The power shaft  4  is shown connected to a down hole motor  84 , which can include a mud motor, such as a positive displacement motor available from Robbins and Meyers Inc. As seen in  FIGS. 2A ,  2 B and  2 C, the power shaft  4  is connected to the rotor  86  of the motor  84 . The rotor  86  cooperates with a stator of the motor  84  and the fluid flow to impart a rotational movement to the power shaft  4 , as understood by those of ordinary skill in the art. As seen specifically in  FIG. 2C , the motor  84  is connected to a cross-over  88 , and the cross-over  88  is connected to a casing string  90 . 
       FIG. 3  depicts a cross-sectional view of the drilling apparatus  2  of  FIG. 2A  taken along the line  3 - 3 .  FIG. 3  shows the external cogs  16  of the driver  10 . The pinion  32  is shown with the pin  34   a  disposed therethrough; the pinion  30  is shown with the pin  34   b  disposed there though; the pinion  91  is shown with the pin  34   c  disposed there through; the pinion  92  is shown with the pin  34   d  disposed there through; the pinion  94  is shown with the pin  34   e  disposed there through; the pinion  96  is shown with the pin  34   f  disposed there through. In operation, as the driver  10  rotates through connection to the rotor, the pinions  28 ,  30 ,  32 ,  91 ,  92 ,  94  and  96  rotate due to the engagement of the cogs, which in turn imparts a counter rotation movement to the housing  40  via the engagement of the pinion cogs with internal cogs  98  located on the housing  40 . 
     Referring now to  FIG. 4 , a cross-sectional view of the drilling apparatus  2  of  FIG. 2A  is shown, taken along the line  4 - 4 . In this view, the ends of pins  34   a,    34   b,    34   c ,  34   d,    34   e,    34   f  are shown configured to engage with the indented bottom portion  82  of sleeve  20 , and in particular, with a slot within the indented bottom portion  82 . A set screw or a similar fastener can be used to attach the pin ends to the indented bottom portion  82 . Specifically, a set screw  102  is shown configured to be inserted into the slot  104 , such that the end of pin  34   a  is engaged with the set screw  102  so that the pin  34   a  is attached to the indented bottom portion  82 . The other set screws  106 ,  108 ,  110 ,  112 ,  114  can be similarly engaged with the respective pin ends of the other pins. 
     Referring now to  FIG. 5 , a schematic drawing of an embodiment of a drilling apparatus system disposed within a well  120  is shown. A down hole motor  84  is threadably attached to a cross-over sub  88 , as described previously. Fluid flow through the inner bore of the casing string  90 , and into the down hole motor  84 , through the rotor-stator of the motor  84 , causes rotation of the inner bit  70  in a first direction, which in turn will impart a counter rotational movement to the outer bit  58 , such that the of the two bits in counter directions will produce a non-reactive force.  FIG. 5  depicts the bits  70 ,  58  boring through subterranean reservoirs with the casing string  90  attached. Thus, the described non-reactive force facilitates the drilling of the well  120  with the attached casing string  90 , which heretofore has not been possible due to the extreme torque applied to the casing string thread connections during conventional drilling operations. 
     Under many circumstances, a well is drilled in a series of sections, which are provided with progressively smaller hole sizes. Casings are run to consolidate the current progress, to protect some zones from contamination and to provide the well with the ability to hold higher pressures.  FIG. 6  is a schematic drawing of an embodiment of a drilling apparatus system cemented within a well  120  with perforations  122  to a hydrocarbon reservoir  124 . The cement, denoted by the numeral  126 , can be applied to the annulus between the outer portion of the drilling apparatus  2  and casing  90  and the inner portion of the well  120  using various known techniques. 
     Referring now to  FIG. 7 , a schematic drawing of the drilling apparatus system of  FIG. 6  is shown, with the inner bit  70  removed.  FIG. 7  depicts the casing string  90  cemented in place. Once the casing string  90  is cemented, a second drilling apparatus system can be run into the hole, down the casing string  90  and through the open end so that drilling may continue. This second drilling apparatus system can also utilize a casing string as the work string.  FIG. 8  depicts a schematic drawing of the drilling apparatus  2  drilling a well  127  from a rig  128 . The rig is showed positioned on a drilling platform  130 , located in water.  FIG. 8  shows an intermediate casing string  132  within the well  127 , while a second casing string  134  is used as a work string during drilling. The second casing string  134  can subsequently cemented in place after drilling a second portion of the well  127 , as described previously. It should be noted that in various embodiments of the invention, a coiled tubing string or other types of tubular conductors can be used as the work string in place of the casing string. Due to the continuous nature of a coiled tubing string, use of a non-reactive torque system herein disclosed, allows use of coiled tubing as a work string. 
     Referring now to  FIG. 9 , a cross-sectional view an embodiment of a drilling apparatus is shown.  FIG. 9  depicts the driver  10  being threadably connected to the cross-over sub  64 , and the cross-over sub  64  threadably connected to the inner bit  70 . It should be noted that in an embodiment of the invention, the driver  10 , cross-over sub  64 , and/or inner bit  70  may be integrally formed as a single member. The housing  40  is shown threadably connected to the outer bit  58 , however in an embodiment of the invention, the housing  40  and outer bit  58  can be an integral member. During operation, the inner bit  70  rotates in a first direction, and the outer bit  58  rotates in an opposite direction, as described previously.  FIG. 9  depicts a first passage  140  and a second passage  142  extending through the drilling apparatus. 
     Disposed within the first passage is a first nozzle  144 , and disposed within the second passage is a second nozzle  146 . The nozzles  144 ,  146  are shown oriented relative to the axial center line  148 , in an upward direction, such as an approximate forty-five (45) degree angle of inclination. In various embodiments of the invention, the angle of inclination can range from 30 degrees to 75 degrees in an upward direction. While  FIG. 9  depicts two nozzles  144 ,  146 , in an embodiment of the invention, three or more nozzles can be provided. The size of the nozzle may be selected based on the desired flow rate, as understood by those of ordinary skill in the art.  FIG. 9  also depicts a flow skirt  150  disposed about the cross-over sub  64 . The flow skirt  150  can include a ring member formed integrally on the outer portion of the cross-over sub  64 . As shown, the flow skirt  150  has an angled surface  152  that extends to a radially flat surface  154 . The flow skirt  150  directs drilling fluid flow toward the outer bit and the junk slot area, and into the annulus. 
       FIG. 10  depicts a disassembled perspective view of the drilling apparatus of  FIG. 9 . The cross-over sub  64  is shown along with the passages  140 ,  142  disposed therethrough, adjacent the nozzles  144 ,  146 . A third nozzle  156  is also shown. The flow skirt  150  is depicted having the radially flat surface  154 . As noted earlier, the inner bit  70  can be threadably connects with the cross-over sub  64 , and the cross-over sub  64  can in turn be threadably connected to the driver  10  (not visible in  FIG. 10 ). 
     Referring now to  FIG. 11 , a schematic drawing of the drilling apparatus system  2  of  FIG. 9  is shown disposed within a well  127 . The inner bit  70  is shown drilling a bore hole  158  using cutters on the bit face  74 , while the outer bit  58  is shown boring a larger hole within the well  127 . In use, drilling fluid is pumped down the drill string, as readily appreciated by those of ordinary skill in the art. A portion of the drilling fluid will exit nozzles within the inner bit  70  (nozzles in inner bit  70  not shown), with the fluid flow being represented by the flow arrows “A” through the annular area  160  about the inner bit  70 . The flow “A” flows in a generally upward direction toward the surface. The remaining portion of the drilling fluid will exit the nozzles  144  and  146 , shown within the cross-over sub  64 , with the fluid flow exiting the nozzles  144  and  146  represented by the flow arrows “B” within the annular area  162  about the outer bit  58 . 
     In an embodiment of the invention, the nozzles can be machined for threaded placement into the cross-over sub  64  to allow different sizes of nozzles to be used. The nozzles can be supplied with drilling fluid flow from inside the cross-over sub  64 . Because the inner bit  70  is drilling only part of the bore hole, a larger quantity of drilling fluid is pumped through the drill string than the quantity is required to adequately clean the inner bit. The nozzles which provide flow “A” on the inner bit can be sized and positioned such that the inner bit will receive the required flow to be effectively cleaned during the drilling. The remainder of the flow (i.e. flow “B”) can ext from the nozzles exiting the cross-over sub  64 . 
     In an embodiment of the invention, the flow skirt  150  can be provided as an integral part of the cross-over sub  64  that extends about the circumference of the cross-over sub  64 . The flow skirt  150  can direct drilling fluid flow toward the cutters of the outer bit  58  and into the annulus  162 . The flow being directed can be continuous flow from the inner bit and from the nozzles, while the continuous flow from the nozzle will strike the bit face intermittently due to the counter rotation. The flow skirt  150  can also prevent drilling fluid and cuttings from becoming lodged in the bearing area between the cross-over sub  64  and the outer bit  58 . Additionally, the flow skirt  150  can be used as simply a deflector sleeve without the use of the nozzles, to deflect fluid flow from the bearing area. 
     In an embodiment of the invention, the upward direction of the nozzles can provide a Venturi effect that will reduce the bottom-hole pressure below the nozzles. The resulting reduction of bottom-hole pressure can improve both the hydraulic performance and drilling performance of the inner bit  70 . 
     Changes and modifications in the specifically described embodiments can be carried out without departing from the scope of the invention which is intended to be limited only by the scope of the appended claims and any equivalents thereof.