Patent Publication Number: US-10316595-B2

Title: Method and apparatus for reaming and/or stabilizing boreholes in drilling operations

Description:
FIELD OF ART 
     The disclosed method and system relate generally to well bore reamers for reaming ledges and cleaning loose cuttings from a drilled hole, and more specifically to a drilling device which rotates while it slides in a wellbore, and which rotates in conjunction with the drilling pipe in a wellbore when the device is positioned in a locked position with the drill pipe. 
     BACKGROUND 
     In the oil and gas industry, wellbores have been drilled by tools such as reamers, stabilizers and combination reamer and stabilizer units which are connected to a tubular drill stem or a string of drill piper at one end of the tool and a drill bit at an opposite end of the tool. These tools are used to enlarge a wellbore to a specific diameter, smooth the wall of a wellbore, help stabilize a bit, and straighten the wellbore if kinks or doglegs are encountered. Such devices can reduce lateral deviation, vibration and wobble of the drill bit, thereby improving the penetration rate of the bit in the wellbore. Additionally, the unit has the purpose of stiffening the drill collar to reduce collar deflection and the tendency of the collars in the wellbore to tilt, which may cause a drill bit to also tilt and thereby produce an oversized hole which has deviated from the desired drilling direction. 
     The disclosed device provides for an improved device that can be used in drilling applications which require a high degree of accuracy in drilling. The device is adapted to a string of drill pipe for use in a wellbore to center, guide and stabilize the pipe in the bore and which is capable of reaming excess subsurface materials and achieve a uniform wellbore diameter. When the disclosed device is situated in a fixed position in the drill string, a clutch system can lock the device in place—forcing the disclosed device to rotate with the drill string, thus ensuring that the disclosed device rotates with the maximum rotational torque to more effectively ream excess subsurface materials. When sliding, the drag force allows the device to disengage the clutch to allow rotation of the sleeve section to minimize torque and drag on the drill string. 
     SUMMARY OF THE DISCLOSURE 
     The disclosed device provides for a drilling tool intended to clean a wellbore, wherein the body is roughly cylindrical and comprises a top end and a bottom end, each of the ends further comprising a portion having helical blades formed of a chromoly (SAE 41xx) steel alloy, and a middle segment comprising a plurality of polycrystalline diamond compact (PDC) cutters. 
     The disclosed device provides for a drilling tool which is run through a wellbore and is attachable to a string of drill pipe by means of connecting the pin end of one joint into the box end of another. 
     The disclosed device provides for a tool comprising helical blades and an internal clutch system which cause the tool to freely rotate about its own axis in a clockwise direction (or while sliding) in a wellbore along the pipe axis. 
     The disclosed device provides for a clutch system that locks the device in place—forcing the disclosed device to rotate with the drill string, thus ensuring that the disclosed device rotates with the maximum rotational torque. 
     The helical blades of the disclosed device are bi-directional and utilize axial (lateral) drag forces in one or more directions to induce a clockwise rotation. 
     The disclosed device provides for a tool that when sliding, the clockwise torque of the blade geometry compresses the springs, allowing the middle reamer section to rotate about an axle of the device. 
     The disclosed device provides for a blade geometry that gradually increases with the outside diameter of the device, which results in a low torque response during pipe rotation and acts to minimize the forces encountered by one or more clutch pins. 
     The disclosed device provides for a pair of bearings located on ends of the reamer section to enable rotation of the reamer section in a sealed environment. 
     Although the disclosed device is not used specifically to enlarge a wellbore, it is capable of enlarging a wellbore diameter slightly, for example, if there are bends in a horizontal wellbore and gravity forces the tool to cut on the device&#39;s bottom edge. Also, it is contemplated that some embodiments could comprise eccentric reamer devices which actually enlarge a wellbore. It should be recognized that while the disclosed apparatus and method can be used as a wellbore reamer, it is also capable of being used as a stabilizer to stabilize a wellbore, 
     These and other advantages of the disclosed device will appear from the following description and/or appended claims, reference being made to the accompanying drawings that form a part of this specification wherein like reference characters designate corresponding parts in the several views. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of the wellbore reamer/stabilizer tool disclosed herein.  FIG. 2  is a cross-sectional view of the disclosed device taken along line  3 - 3 .  FIG. 3  depicts an axle cap in one embodiment of the disclosed device.  FIG. 4  is a perspective view of a reamer section of one embodiment of the disclosed device. 
         FIGS. 5, 6, 7  depict the pin and spring mechanisms on the reaming section of the disclosed device. 
     
    
    
     Before explaining the disclosed embodiments of the disclosed device in detail, it is to be understood that the device is not limited in its application to the details of the particular arrangements shown, since the device is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation. 
     DESCRIPTION OF THE DRAWINGS 
     As shown in FIG. 1 , tool  100  comprises an axle  10  or a central shaft on which a reaming section  20  rotates. Axle  10  comprises a one-piece unit which may be machined from  4140  steel, for example. Axle  10  comprises a box end connection  11 , a pin end connection  12 , and a stop  14  for receiving bearing assembly  15  and an end of reamer section  20 . An axle cap  19  can be connected to axle  10  by means of threads  18  when reaming section  20  is positioned thereon. See also FIG. 3 . O-rings (gaskets)  13  can be used to provide a seat between threads  18  and shoulder  17  and to provide a seal from fluid infiltration. If desired, axle cap  19  can be tightened to a specific torque value. For example, axle cap  19  may be tightened so as to obtain a certain compression on each O-ring  13 . Threaded Allen screws (not shown) may be used to lock axle cap  19  in place so as to create a failsafe from the device being uncoupled. 
     As seen in FIG. 2 , axle  10  comprises one or more clutch relief grooves  16  which can be milled at any configuration of set positions as desired. In one embodiment, relief grooves  16  were machined with a ½″ flat end mill (5-Axis). It is contemplated that once machining is begun, all the tool paths could be completed before un-chucking the steel from the mill. Each tool path is elliptical in shape. One groove is completed perpendicular to the pipe axis. The other at an angled path. 
     As shown in  FIGS. 4 , reaming section  20  features a hollow cylindrical body or mandrel  22  having two ends. Reaming section  20  may be machined as a unitary piece of metal from, for example  4140  steel. When assembled, reaming section  20  slides over axle  10  and is positioned between a pair of O-rings  13  and thrust bearings  15 . The inner diameter of the reamer section can be set to be at about 0.05″ greater than the outer diameter of axle  10 , thereby allowing for a gap of about 0.025″ to facilitation rotation. It should be understood that although thrust bearings were used, other bearing types could be employed. 
     Thrust bearings  15  allow an end of reamer section  20  to rotate against the stationary stop  14  of axle  10 . O-rings  13  placed on each side of bearings  15  can be used to provide a seal between flange  24 , bearing  15  and stop  14  and between box end  11 , bearing  15  and flange  25  so as to keep drilling fluid from making contact with other internal systems, thereby allowing reaming section  20  to rotate in a sealed environment. Reaming section  20  rotates clockwise on axle  10  while tool  100  slides in and out of a wellbore (not shown), or during travel. When tool  100  is rotating pipe, on the other hand, reaming section  20  remains fixed on axle  10 . 
     It should be understood that final bearing designs will be depend of engineering and safety considerations. In one embodiment, for example, bearing  15  was about 1″ wide with about a 3.57″ inner diameter and a 4.57″ outer diameter. Regarding the O-rings, it may be helpful that the inner and outer diameters are about the same as the bearing. 
     Reaming section  20  comprises bi-directional helical blades  26  which utilize axial drag or lateral forces in either direction to induce clockwise rotation during operation. A material such as “Cut-Rite” (not shown) may be applied to an external surface of blades  26  to harness axial drag forces. It can extend about 0.100″ above the top surface of the blades; the thickness could be in the range of about ⅜″ to about ½″ . In one example, a thickness of about ⅛″- about 3/16″ of hard facing was used. Hardfacing could be done with a brazing rod. 
     As shown in  FIGS. 1, 4 , each blade  26  comprises seven ( 7 ) polycrystalline diamond compact (PDC) cutters (or pockets)  28 . It should be recognized however that any number of cutters (or none) could be employed. If three blades  26  are used, an embodiment would comprise  21  pockets. In one embodiment, each pocket  28  was machined with a ½″ flat end mill and sized to be approximately 0.536″ in diameter. While each blade  26  comprising cutters  28  can be located on the same 45° plane on the blade front and are linearly aligned with each other, other cutter configurations may be more suitable or desired. 
     As shown in  FIGS. 5, 6, 7 , reaming section  20  comprises an internal clutch system  30  having a plurality of pin and spring access points  34 . In one embodiment, the clutch system  30  comprises six pin and spring mechanisms that are equally positioned on each side of cutting blades  26 . Clutch system  30  allows reaming section  20  to rotate clockwise while pipe is being pushed or pulled (while sliding). 
     In one embodiment, each access point  34  provides access to a pin and spring mechanism comprising a pin  31 , a spring  32  and a cap  33 . Access points  34  were machined with a ½″ flat end mill and configured to be perpendicular to the pipe axis. In one embodiment, coil springs were selected for their ability to provide enough force to press clutch pins  31  into clutch reliefs  18 . It was observed that springs  32  can be a max ¼″ compressed and ½″ uncompressed. Although coil springs were are used, other spring types could also be suitable. 
     In one embodiment, clutch pin  31  comprises a ½″ diameter tungsten carbide insert about ½″ in length that can be positioned so that shear forces apply zero or little torque to reamer section  20 . It may be desirable to use the softest tungsten available to minimize steel body wear and decrease brittleness. Although the clutch pin may be set to only travel ¼41  when transitioning between the locked to rotating positions, it is contemplated that other travel distances may be more suitable. The clutch pin cap  33  may contain a cavity that allows spring  32  to fully compress. It may be threaded to a stopping point and held in place by a lock tight so as to keep the clutch pin in position. It should be understood that although pin and spring—based clutch system is described, other clutch mechanisms could be employed depending on sizing requirements. 
     The clockwise torque provided by the blade geometry compresses springs  32 , thereby allowing the reamer section  20  to rotate on axle  10 . When pipe is being rotated, springs  32  of clutch system  30  expand and thus create a torsional lock thereby allowing one or more surfaces to make contact with the outer diameter of the wellbore. 
     In one embodiment, tool  100  was approximately 80″ in length and weighed about 300 pounds after assembly. The blade geometry presented by the disclosed device provides for a gradual increase in the tool&#39;s outer diameter until it reaches a cutter value of approximately 5.875″ and a low torque response during pipe rotation. This low torque response also minimizes the forces on the clutch pins. 
     To assemble the device, a user should begin with a box end  11  of axle  10  and fasten an O-ring  13  and bearing  15  thereto before attaching reamer section  30  followed by an O-ring  13  and bearing  15  followed by an O-ring  13  and axle cap  19 . Before assembly it would be good practice to ensure both the outer surface of axle  10  and the inner surface of reamer section  20  are cleaned and lubricated with a grease such as “Pedros”. It is also contemplated that each side of the bearings  15  and O-rings  13  are lubricated. 
     After axle cap  19  has been threaded into position and torqued to the desired specifications, the pin and spring system  34  can be assembled. One could rotate reamer section  20  on axle  10  until pins  31  are at the lowest point. This allows for ease in threading caps  33  into place. It is contemplated that caps  33  be coated with Loctite™ before being threaded to their stop points. 
     It is contemplated that the disclosed device or rotate-while-sliding (RWS) device, as assembled, is approximately 80 inches (2.032 m) in length. It is also contemplated that the device could be designed to rotate in a counter-clockwise direction, if desired. 
     Although the disclosed device and method have been described with reference to disclosed embodiments, numerous modifications and variations can be made and still the result will come within the scope of the disclosure. No limitation with respect to the specific embodiments disclosed herein is intended or should be inferred.