Patent Publication Number: US-2018051520-A1

Title: Method of forming a hole in a hard ground structure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 15/446,599, filed Mar. 1, 2017, which is a continuation of U.S. patent application Ser. No. 14/333,746 filed Jul. 17, 2014, now issued as U.S. Pat. No. 9,624,732. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The subject matter disclosed generally relates to hole openers. In particular, the subject matter relates to drill-bits. 
     Background Art 
     Hole openers have long been used in the HDD (Horizontal Directional Drilling) industry as well as in any geological well drilling applications. Traditional hole openers consist of roller cones (built in varying configurations) designed to pound, cut and penetrate rock formations. These “roller-cone” rock bits have been in use since the first design was patented by Baker Hughes in 1909. Since then, the roller cone rock bit has evolved through numerous iterations. The concept, in its most basic of terms, consists of one or more metal toothed, cone shaped, bearing driven cutters that literally roll over the rock continuously while a drilling rig applies pressure or weight from above. As these cone cutters roll over the rock, the metal teeth pound, cut and chew up the rock, allowing the bit to slowly penetrate the formation. An example of a traditional roller-cone rock bit is shown in  FIG. 1A . 
     Another example of a traditional hole opener is shown in  FIGS. 1B and 1C . These hole openers are typically referred to as split bits or cone cutter reamers. Generally these hole openers define a rotation shaft around which there are provided two or more drilling cones. 
     Although such hole-openers/reamers have achieved considerable popularity and commercial success in the HDD application, they frequently experience failures and cause increasing job costs (which are a significant burden to drilling companies). For example, it is a common occurrence for drillers to lose cones from their split bit reamers. This happens for a variety of reasons—whether it is poor construction of the tool, overuse, or other extenuating circumstances. Cone loss is a constant and looming threat. Having this happen in a bore can be catastrophic. This causes the need for the drilling Company to either fish out the lost cone, and in some cases start the bore again from scratch. All of this is done at the cost of the drilling company. 
     There is therefore an ongoing need for an improved drilling bit which is durable and at the same time achieves a higher drilling speed and less failure. 
     SUMMARY OF THE INVENTION 
     In one form, the invention is directed to a method of forming a hole in a hard ground structure. The method includes the steps of: a) obtaining a drill-bit with a longitudinal axis and first and second axially spaced ends, the drill-bit having a central portion and a plurality of blades protruding radially from the central portion; and b) turning the drill-bit around the longitudinal axis in a first direction so that the blades each advances in a circumferential direction, with a circumferentially facing leading portion on each blade first, while pulling the drill-bit axially, with the first drill-bit end in a leading direction, through the hard ground structure to thereby cause discrete cutters to cut the hard ground structure as the drill-bit is pulled to form the hole in the hard ground structure. Each blade has a first blade end, a second blade end, a first end portion, a second end portion, and a middle portion. The first end portion extends from the first blade end to the middle portion. The middle portion is disposed between the first end portion and the second end portion. The second end portion includes the second blade end and extends from the middle portion towards the second end of the drill-bit. The circumferentially facing leading portion of each blade has at least one of the discrete hard cutters placed thereat. 
     In one form, the discrete hard cutters are polycrystalline diamond cutters. 
     In one form, the at least one discrete hard cutter on each blade is on the first end portion of each blade. 
     In one form, there are a plurality of the discrete hard cutters on the first end portion of each blade. 
     In one form, the circumferentially facing leading portion of each blade has a curved shape between the first and second blade ends. 
     In one form, the discrete hard cutters each has a cutting edge. The cutting edges on each blade are arranged to cooperatively extend in a curved shape. 
     In one form, the middle portion of each blade has a radially outwardly facing surface that is substantially parallel to the longitudinal axis. 
     In one form, a discrete hard element is fixed at the radially outwardly facing surface of each blade to provide wear resistance. 
     In one form, the drill-bit has at least a one nozzle between adjacent blades. The method further includes the step of directing a fluid under pressure through the at least one nozzle to clear foreign matter from between the adjacent blades. 
     In one form, the step of turning the drill-bit while pulling the drill-bit consists of turning the drill-bit while pulling the drill-bit with a component that is threadably engaged with the drill-bit at one of the axially spaced ends of the drill-bit. 
     In one form, the other of the axially spaced ends of the drill-bit is threaded to engage a component usable to advance the drill-bit axially. 
     In one form, the at least one discrete hard cutter on each blade is on the second end portion of each blade. 
     In one form, each blade defines an edge at the circumferentially facing leading portion. At least one discrete hard cutter extends radially outwardly beyond the edge. 
     In one form, the at least one discrete hard cutter has a rounded cutting corner. 
     In one form, the at least one discrete hard cutter has a cylindrical shape. 
     In one form, the drill-bit has a radial dimension and an axial dimension. The axial dimension is greater than the radial dimension. 
     In one form, the axial dimension is not greater than 1.5 times the radial dimension, 
     In one form, the axial dimension is on the order of 1.2 times the radial dimension. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A to 1C  illustrate examples of traditional drill bits; 
         FIG. 2A  is a side view of a drill-bit in accordance with an embodiment; 
         FIG. 2B  is side view image of an exemplary drill-bit; 
         FIG. 3A  is a top view of the drill-bit of  FIG. 2A  showing an upper connection; 
         FIG. 3B  is a top view image of an exemplary drill-bit in accordance with an embodiment; 
         FIG. 3C  is a view of a bottom connection of the drill-bit opposite to the upper connection; 
         FIG. 3D  is a side view of the drill-bit of  FIG. 2A  showing inner connection threads; 
         FIG. 4  illustrates an example of a PDC cutter in accordance with an embodiment; 
         FIG. 5  illustrates an example of a nozzle in accordance with an embodiment; 
         FIGS. 6A and 6B  illustrate different views of a drill-bit including two rows of PDC cutters in accordance with an embodiment; and 
         FIGS. 6C and 6D  illustrate different views of a drill-bit including three rows of PDC cutters in accordance with another embodiment. 
     
    
    
     It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The embodiments are drill-bits for making holes in a hard structure such as a rock. The drill-bit preferably has no moving parts and achieves both rigidity and a fast rate of penetration into rocks. In an embodiment, the drill-bit has a cone-shaped central portion with a plurality of blades/ribs (hereinafter, “blades”) protruding from the central portion. The blades are curved along a direction of a longitudinal axis of the cone to facilitate insertion into a hole when turned in a first direction, and exit from the hole when turned in a second direction opposite the first direction. Each blade has a plurality of discrete polycrystalline diamond cutters (PDC) provided in a first position for cutting the hard structure as the drilling-bit rotates in the first direction, and a plurality of updrill PDC cutters provided in a second position for cleaning the hole. Discrete hard cutters other than PDC cutters are usable in place of, or together with, PDC cutters. For example, discrete tungsten carbide cutters might be used. This is but one example. 
       FIG. 2A  is a side view of a drill-bit in accordance with an embodiment, and FIG,  2 B is side view image of an exemplary drill-bit, Likewise,  FIG. 3A  is a top view of the drill-bit of  FIG. 2A  showing an upper connection, and  FIG. 3B  is a top view image of an exemplary drill-bit in accordance with an embodiment. 
     As shown in  FIGS. 2A and 2B , the drill-bit  100  has a central portion defining a cone  101  and top and bottom connections  102  and  103  with inner threads  105   a,    105   b  (as shown in  FIG. 3D ) at axial opposite ends AE 1 , AE 2  of the drill-bit  100  for connecting to a drilling rig (DR). The drilling rig may be connected to either the top connection  102  or to the bottom connection  103 .  FIG. 3C  is a view of the bottom connection  103  of the drill-bit opposite to the upper connection  102 , and  FIG. 3D  is a three dimensional view of the drill-bit of  FIG. 2A  showing the inner threads  105   a,    105   b.    
     One or more up-drill PDC cutters  116  may be positioned for reverse drilling only to allow the drill to drill its way of the hole. In the example of  FIG. 2A , the up-drill cutter  116  is provided between the gage pad  108  and the lower portion  112 . The up-drill PDC cutters  116  serve to clean the hole as the drill-bit rotates in the opposite direction of the drilling rotation e.g. clockwise, to exit the hole because the reverse rotation makes the location of the up-drill cutter  116  as the main surface with the debris in the hole. The up-drill PDC cutters  116  are designed to assist in the swabbing of the hole. If there is any residual rock formation, the up drills will cut the rock as the bit is pushed or pulled in the swabbing process. 
     Referring back to FIGS,  2 A and  2 B, it is shown that the drill-bit has a plurality of blades/ribs  104  (3-9 blades or and preferably 5-6 blades for a regular hole) provided co-centrally around the connection  102  and projecting radially from the cone  101 . In an embodiment, the blades are shaped and dimensioned to open the hole and advance upon being rotated from the hole. In the embodiment in  FIG. 2A , the blades are slightly curved along the direction of the rotation axis RA so as to ensure a smooth penetration into the rock to open the hole when the rotation is clockwise, as viewed from above, and a smooth/easy exit from the hole when the drill-bit is pulled axially oppositely. Accordingly, the blades are shaped and dimensioned to facilitate penetration into the hole of the drill-bit as a result of the rotation of the drill-bit. 
     The blades may define a middle portion  108 , an upper portion  110  adjacent the connection  102  and a lower portion  112  defining a ski slope and provided at the lower half of the cone  101  as shown in  FIGS. 2A and 2B . In an embodiment, the ski slopes  112  end at the bottom  103  of the drill-bit  100  and do not extend past the latter as shown in  FIGS. 2A and 2B . 
     In an embodiment, the blades  104  may also be curved along the Z axis and have different thicknesses along the Y axis and different widths along the X axis, In an embodiment, the width of the blades may increase as the thickness decreases and vice versa to maintain the rigidity of the blades beyond a certain level. 
     In an embodiment, the upper portion  110  of the blades  104  may include a plurality of discrete hard/Polycrystalline Diamond Cutters (aka PDC cutters)  114  for cutting the rock as the drill-bit  100  rotates to make the hole. For purposes of simplicity, the hard cutters  114  will be identified as PDC cutters, though the cutter construction is not limited to Polycrystalline Diamond, as noted above. The PDC cutters may be provided in a row at the leading edge/corner E of each blade which is the main point of contact between the drill-bit and the rock formation. The PDC cutters are shown as disc/cylindrical/tapered cylindrical shapes that have portions that project radially to beyond the edge E of each blade. The projecting portion has a rounded cutting corner RC. The blades may be dimensioned to have holes/pockets therein to receive the PDC cutters. The number of PDC cutters is generally determined based on the hardness of the rock that is being cut.  FIG. 4  illustrates an example of a PDC cutter in accordance with an embodiment. As shown in  FIG. 4 , the PDC cutter  114  comprises a polycrystalline diamond (PCD) top layer  116  integrally sintered onto a tungsten carbide substrate using a high-pressure, high-temperature process. This layer combination allows consistent high drilling performance to be maintained. The polycrystalline diamond layer offers controlled wear and the retention of a sharp cutting edge. The tungsten carbide substrate provides a strong and tough support for the polycrystalline diamond layer while facilitating attachment to the drill-bit body. 
     The middle portion  108  (aka gage pad  108 ) of the blade may be substantially parallel to the Y axis for stabilizing the drill-bit while in the hole and also for defining and refining the inner surface of the hole. The different gage pads  108  of the different blades are concentrically provided around the rotation axis of the drill-bit to avoid deviation of the drill-bit to the left or the right or up or down while rotating within the hole. 
     The lower portion (aka ski-slope)  112  of the blade is designed for easier pushing of the bit as while swabbing the hole. Swabbing is necessary to make sure the bore is clean and free of rock debris left behind during the cutting process. The shape of the lower portion  112  helps the bit  100  not to get hung up on any debris left behind in the bore. 
     Referring back to  FIGS. 2A and 2B , there is shown a plurality of nozzles  118  provided between adjacent blades. Accordingly, the cone  101  may be hollow at the center thereof to fluidly connect a drilling pipe DP connected to the top connection  102  or the bottom connection  103  for providing the nozzles with a stream of fluid/water from a pressurized fluid/water source S outside the hole. A plug P may be provided at the bottom portion  103  or top portion  102  of the drill-bit  100  (depending on which end of the drill-bit the pipe is connected to) for preventing the water/fluid from running there through, thereby forcing the water flowing through the pipe to exit from the nozzles  118 . 
       FIG. 5  illustrates an example of a nozzle in accordance with an embodiment. The nozzles  118  are located between the blades and positioned to clean the PDC cutters and/or the blades using a water stream injected under pressure out of the nozzles  118 . For instance as shown in FIGS,  2 A and  2 B, the nozzles may be provided in proximity of at least the upper portion  110  and the gage pad  108  since these portions have a higher thicknesses when compared to the lower portion  112  and therefore, debris is more likely to accumulate at these portions rather than the lower portion  112 . 
     In operation, as the drill-bit  100  is rotated by the drive component DC in the direction indicated by the arrow A (in a right-handed clockwise direction as viewed axially from above), the drive component DC is controlled to apply the appropriate amount of pull pressure to the bit  100  in the direction of the arrow D 1 , substantially parallel to the axis RA. The PDC cutters scrape the formation, and drilling fluid may then carry the cuttings through the bore hole back to the surface, and into a pit. There the cuttings are collected, run through a shaker, and drilling fluid may be pumped back through the drilling rig and back through the drilling rods and back through the bit. This recirculation may continue throughout the boring process. 
     An appropriate component C 1  may be engaged with the threads  105   b  and operated to draw the drill-bit axially oppositely to the direction D 1  as to set the drill-bit  100  preparatory to being pulled and turned for hole formation, 
     Accordingly, the embodiments describe a drilling bit which has no moving parts, and thus, it is less prone to failure and breaking in the hole. Testing has shown that the present drill-bit can achieve a rate of penetration (ROP) of at least 40%-60% higher than existing bits due in large part to the shape and structure of its blades. In some cases the increase in ROP was 5-7 times. A comparison was done in Hamilton, Tex. where a driller was penetrating the rock at 3-4 inches per minute with their cone cutter reamer. When they tested the drill-bit of the present invention (known as the DDI Volcano PDC Hole Opener/Reamer), their ROP increased to 3½ feet per minute. With respect to rigidity and failure rate, testing has shown that the present drill-bit has reduced the failure rate by 85%. 
     The higher rate of penetration is attributable to the fact that traditional “split bit” or cone cutter reamers pound and cut the formation using moving parts, while the present drill-bit scrapes and cuts the formation as the entire bit rotates within the hole. The higher rate of penetration generally translates to savings in fuel and labor for the drilling companies and faster deliveries for the clients. 
     Another problem associated with the traditional hole openers is that each cone cutter is designed to cut different types of rock, and this becomes a problem when the bit transitions from one layer of rock formation to another i.e. from limestone to shale to clay to dirt. Since there does not exist a single cone cutter that is designed to cut rock formations of varying hardness, the driller is forced to choose the cutter type for the rock he/she thinks he/she will be in more than the others. This is a very difficult guessing game, because it is rare to have accurate geological data. In fact, it is more common to have incorrect data than to have correct data, if any at all. The ideal scenario for any driller is to have a bit that is capable of cutting all ground formations with equal effectiveness. 
     To address this problem, the drill-bit  100  may be coated with a layer of Tungsten Carbide to allow the drill-bit  100  to drill in formations with different hardness and without breaking and/or wearing quickly. In an embodiment, the thickness of the Tungsten Carbide may vary depending on the area on which it is being applied. For example, areas of the blade which are in higher contact with the debris during forward and backward drilling may have a thicker layer to improve their rigidity, 
     In an embodiment, to improve the rigidity of the drill-bit and decrease interruptions during the drilling process, one or more additional rows (or partial rows) of PDC cutters may be provided in the drill-bit parallel to or adjacent the main row of PDC cutters shown in  FIGS. 2A and 2B . The additional rows may be provided in areas that sustain the most pressure and friction with the rock formation. In an embodiment, the additional rows of PDC cutters may be provided on the upper section of the blade adjacent the gage pad as exemplified in  FIGS. 6A to 6D .  FIGS. 6A and 6B  illustrate different views of a drill-bit including two rows of PDC cutters in accordance with an embodiment, and  FIGS. 6C and 6D  illustrate different views of a drill-bit including three rows of PDC cutters in accordance with another embodiment. 
     As shown in  FIGS. 6A and 6B , the drill-bit  140  has a plurality of blades. One or more of these blades comprise primary row of PDC cutters  142  provided at the edge of the blade, and a secondary row  144  of back-up PDC cutters provided parallel to and adjacent the primary row  142 . The blade may include a first row of pockets for receiving the first row  142  of PDC cutters and a secondary row of pockets provided behind the first row of pockets. Similarly,  FIGS. 6C and 6D  illustrate a similar drill-bit  150  with three rows of PDC cutters: a main row  152 , a second row  154  and a third row  154 . Needless to say, four or more rows of PDC cutters may be included all depending on the thickness of the blade at the portion of the blade where the additional rows of PDC cutters are added. 
     Drilling equipment is manufactured worldwide with right-handed threads. Thus, cooperating threads on a drill-bit are made so that as the drive component DC ( FIG. 2A ) turns in its driving direction, as indicated by the arrow A, the connection between the drive component DC and drill-bit is tightened. This avoids inadvertent separation between the drive component DC and drill-bit in operation. 
     The drill-bit  100  depicted is actually configured specifically effectively for only pull-reaming, with the threads  105   a  engaged by the threads T on the drive component DC, by turning the drill-bit  100  around the rotational/longitudinal axis RA in the direction A while pulling the drill-bit  100  axially in the direction of the arrow D 1 . The turning of the drive component DC in this manner tightens the threaded connection of the drive component DC and drill-bit. Turning of the drive component DC in the driving direction causes the PDC cutters  114  at circumferentially facing leading portions LP of each blade to cut the hard ground structure to thereby form a hole/bore. 
     The PDC cutters  114  at each circumferentially leading portion LP cooperatively extend in a curved shape that preferably at least nominally matches the curvature of the leading portion LP. The curved shape of each blade  104  at the leading portion, and preferably the nominally matching curved shape of a trailing portion TP of each blade  104  is chosen to facilitate advancement through hard ground structure as the drill-bit is turned around the axis RA and an advancing axial force is applied. 
     As depicted, the axial dimension AD of the drill-bit  100  is greater than the radial dimension RD thereof. AD in one form is not greater than 1.5 RD. AD may be on the order of 1.2 times RD. 
     While preferred embodiments have been described above and illustrated in the accompanying drawings, it will be evident to those skilled in the art that modifications may be made without departing from this disclosure. Such modifications are considered as possible variants comprised in the scope of the disclosure.