Abstract:
The present disclosure provides a drilling machine configuration and related method that avoids drilling mud from contaminating hydraulic fluid that flows through the drive system of the machine. The disclosed system and method provides a drilling mud anti-contamination system that requires infrequent service and a system wherein the service can be quickly and easily performed.

Description:
[0001]    This application is being filed on 3 Oct. 2012, as a PCT International patent application, and claims priority to U.S. Provisional Patent Application No. 61/542,577, filed Oct. 3, 2011, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD  
       [0002]    The present disclosure provides an apparatus and method for directional drilling. 
       BACKGROUND 
       [0003]    Directional boring machines and methods for making underground holes are known. A typical directional boring machine is generally configured to drive into the ground a series of drill rods joined end-to-end to form a drill string. At the end of the drill string is a rotating drilling tool. Typically, the rotation of the drill tool is driven by a mud motor or by axially rotating the drill string itself. Various techniques and configurations can be used to provide steering of the drill string during boring operations. Improvements in directional boring machines, drill strings for use with such machines, and methods of directional drilling are needed. 
       SUMMARY 
       [0004]    The present disclosure provides a drilling machine configuration and related method that avoids drilling mud from contaminating hydraulic fluid that flows through the drive system of the machine. The disclosed system and method provides a drilling mud anti-contamination system that requires infrequent service and a system wherein the service can be quickly and easily performed. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0005]      FIG. 1  is a cross-sectional view of a portion of the drilling machine according to the present disclosure; 
           [0006]      FIG. 2  is an enlarged view of the drive assembly of the drilling machine of  FIG. 1  with schematic illustrations of a hydraulic circuit and drilling mud; 
           [0007]      FIG. 3  is an enlarged view of a portion of  FIG. 2 ; 
           [0008]      FIG. 4  illustrates a drilling machine that embodies the features of the present disclosure; 
           [0009]      FIG. 5A  is a first alternative embodiment of the present disclosure; 
           [0010]      FIG. 5B  is an enlarged view of a portion of  FIG. 5A ; 
           [0011]      FIG. 6A  is a second alternative embodiment of the present disclosure; 
           [0012]      FIG. 6B  is an enlarged view of a portion of  FIG. 6A ; 
           [0013]      FIG. 7A  is a third alternative embodiment of the present disclosure; and 
           [0014]      FIG. 7B  is an enlarged view of a portion of  FIG. 7A . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    A machine which can utilize various aspects of the present invention can be, for example, a machine shown in  FIG. 4  that is primarily used for horizontal surface boring, wherein the bore will enter the ground at an angle typically between 10 degrees and 30 degrees, as measured from the horizontal. However, it should be appreciated that the current invention is not limited to this configuration, and could be applied to drill machines configured for vertical boring, which typically include the same basic machine elements. 
         [0016]    The basic elements of the drilling machine include a chassis which in some embodiments is movably supported on wheels or tracks. The chassis supports a drill string drive assembly  10  and a break out mechanism  12 . 
         [0017]    The drill string drive assembly  10  is configured to rotate the drill string  14  about a drill axis, and to push and pull drill string  14  by moving longitudinally along the rack  16 . The drill string  14  is comprised of any number of individual drill rods that have been connected end-to-end. The angle of the drill string drive assembly  10  relative to the ground surface can be adjusted via controlling a tilt mechanism (e.g., hydraulic cylinder). In other words, the tilt control mechanism can be used to control the vertical orientation of the drill string  14  as it is introduced into the ground. The drill rod loading assembly  300  is configured to transport drill rods between the drill string drive assembly and the drill rod storage unit. 
         [0018]    In the depicted embodiment, the drill string drive unit  10  is configured to be driven towards the break out mechanism  12  to push a section of the drill string  14  into the ground, and be driven away from the break out mechanism  12  to pull a section of the drill string  14  from the ground. During the pushing and the pulling, the drive unit  10  can also rotate the drill string  14  about its longitudinal axis. In the depicted embodiment, the drill string drive assembly  10  includes a carriage  18  that engages the rack  16 . The carriage  18  supports the drive unit  10  and moves the drive unit  10  in an axial direction relative to the frame  18 . In the depicted embodiment the carriage  18  includes two hydraulic motors  20 ,  22  that drive the movement of the carriage  18  along the rack  16 . 
         [0019]    The break out mechanism  12  is configured to hold the drill string  14  in place while sections of the drill string (drill rods) are added or removed. In the drill rod adding process, the break out mechanism  12  secures the upper end of the drill string  14  while the drill rod loading assembly aligns the drill rod that is to be added to the drill string  14  with the upper end of the drill string  14  and drive unit  10 . For machines without rod loading mechanisms, the drill rod is held in alignment in an alternate method. Once the lower end of the newly added rod is secured to the upper end of the drill string, the break out mechanism  12  releases the drill string  14 , allowing the drive unit  10  to rotate and push the drill string  14  further into the ground. 
         [0020]    In the drill rod removal process, the break out mechanism  12  secures the upper end of the drill string  14  while the drill rod that is to be removed is broken free from the drill string  14  and transported out of alignment from the drill string  14  by the drill rod loading assembly. For machines without rod loading mechanisms, the drill rod is held in alignment in an alternate method. Once the rod is removed, the drive unit  10  moves down to the upper end of the drill string  14  and is connected thereto. The break out mechanism  12  then releases the end of the drill string  14 , allowing the drive unit to rotate and pull the drill string  14  further out of the ground. 
         [0021]    The present disclosure incorporates features of a drilling machine that are particularly beneficial for drilling systems wherein the drill string is a dual tube, pipe or rod configuration, wherein there is an outer member, and an inner member. The outer member is referred to as a casing or the outer rod or outer pipe, while the inner member is referred to as an inner rod or inner pipe. In this document the drilling system will be referred to as a dual rod system. However, it should be appreciated that features of the present disclosure can be used with single rod machines as well. 
         [0022]    Referring to  FIG. 2 , the drill rod drive unit  10  of the present invention includes both an inner rod drive assembly with an inner rod drive spindle  24  (inner rod drive shaft) for rotating inner rods of a dual rod drill string, and an outer rod drive assembly with an outer rod drive spindle  26  (outer rod drive shaft) for rotating outer rods of a dual rod drill string. The rod drive unit  10  further includes a compensator assembly  28  for extending the inner rod drive spindle relative to the outer rod drive spindle a distance adequate to assure proper operation of the overall system, as will be explained in more detail below. 
         [0023]    The drive unit  10  includes an outer rod driver gearbox  30  that supports two hydraulic motors  32  and  34 , outer rod drive shaft  26 , outer rod head shaft  36  and a set of gears  38  and  40 . These components are configured to provide rotational drive torque to the outer rod drive spindle  26  through an arrangement that includes the head shaft  36  that is connected to an adapter  42  and includes the outer rod drive spindle  26  that is configured to thread onto the end of an outer member of a drill rod of a drill string. 
         [0024]    The drill rod drive unit  10  further includes an inner rod driver motor  44  coupled to inner head shaft  46  that is coupled to the inner drive shaft  24  in a manner that inner drive shaft  24  can slide using components as illustrated in more detail in  FIG. 3 . The inner head shaft includes an inner drive tube  48  that has a non-circular inner profile that cooperates with a non-circular portion  23  of the inner drive shaft  24 . This configuration allows the inner drive tube  25  to provide rotational drive torque to the inner drive shaft, while at the same time allowing the inner drive shaft to slide in a longitudinal direction. In the depicted embodiment the inner head shaft  46  is constructed from three separate components that are welded together. Drive sleeve  47  is welded to the inner drive tube  48  on one end. The drive sleeve  47  includes a drive coupling configured to mate with the drive shaft  80  of inner rod driver motor  44 . Seal adaptor sleeve  49 , welded to the inner drive tube  48  on the opposite end, includes a threaded inner diameter configured to mate with a replaceable seal adaptor  59 . With this configuration the inner drive shaft  24  can slide in a longitudinal direction relative to the outer drive shaft  26 . In the depicted embodiment the inner drive shaft  24  is housed partially within the head shaft  36 , which is configured to rotate. Drilling mud is supplied to the drill string via the drilling mud delivery interface  50 , which is mounted to the down hole end of the outer shaft  26 . 
         [0025]    Is should be appreciated that sealing the drilling mud to prevent contamination of the drilling machine components is challenging, and is particularly challenging for a dual rod system as described above wherein an inner drive shaft moves longitudinally relative to an outer drive shaft. The seals that are in contact with the abrasive drilling mud will be subjected to significant wear. The present invention incorporates several related aspects of the mechanical configuration which have been found to reduce the rate of seal wear, to extend the expected service life of the seals, to provide a convenient method for replacing the seals, and to minimize the impact of failed seals. 
         [0026]      FIG. 3  illustrates the location of the primary seal system  91  where pressurized drilling mud is expected to be in cavity  54  and oil is expected to be in cavity  60 . 
         [0027]    Referring to  FIG. 2 , a hydraulic circuit  28 , used for affecting the longitudinal movement of the inner drive shaft, is shown. In the depicted embodiment, this circuit includes a hydraulic motor  79  that is mechanically coupled to a hydraulic pump  78 . The hydraulic motor  79  is in fluid coupling with a hydraulic circuit  77  of the rest of the machine, including a pump  75  and fluid reservoir  73 , while the hydraulic pump  78  is in fluid coupling only with the gearbox, due to the fact that reservoir  29  is the gearbox itself. 
         [0028]    During both the drill rod adding process and the drill rod removal process, the inner rod drive shaft  24  is moved longitudinally relative to the outer rod drive shaft, to expose the joint between the individual sections of the inner rod. This movement occurs when the motor  79  is caused to rotate, by the hydraulic circuit  77  of the main machine. This control can be accomplished in a number of ways, in the depicted embodiment a directional control valve (not shown) directs oil from pump  75  to motor  79 . When motor  79  is caused to rotate, it will power hydraulic pump  78  which will draw oil from the gearbox or sump  29 , directing it to cavity  45  on the inside of the inner head shaft  46 , causing the inner rod drive shaft  24  to move longitudinally. This hydraulic circuit is configured to prevent widespread contamination of the hydraulic system of the drilling machine, that could result if mud in cavity  54  leaked past the primary seal system  91  and into cavity  60 . Contamination of the hydraulic system of the drilling machine is avoided by the utilization of separate hydraulic reservoirs, and by the mechanical drive connection between the motor  79  and the pump  78 . In other words, the power is transferred with a mechanical drive connection, wherein there is no transfer of fluid from hydraulic circuit  28  to the hydraulic circuit  77  of the rest of the machine. 
         [0029]    In addition to creating the pressure to extend the inner drive shaft, hydraulic circuit  28  also provides oil to ensure consistent charging of a pressure intensifier assembly  68 . This system is designed to provide a source of pressurized oil routed to a cavity adjacent each seal that is both in fluid contact with drilling mud and that can experience a high rate of relative movement. The system is designed such that the hydraulic pressure in those cavities is equal to or greater than the mud pressure. 
         [0030]    The seals that are in fluid contact with the drilling fluid are illustrated in  FIG. 3 , including  90   b ,  90   c , and  90   e . The cavities adjacent those seals, that are provided to contain pressurized oil include  66   c ,  66   b  and  66   a . The pressurized oil is contained in these cavities that are defined by the seals noted above, on one side, and by seals  90   a ,  90   d , and  90   f  on the opposite side. Thus, cavity  66   c  is defined on one side by seal  90   a , and on the opposite side by seal  90   b . These two seals can be the identical part, or they could be different types of seals. In the preferred embodiment the paired seals are identical parts, to reduce the number of different service parts. Seal  90   a  contacts drilling fluid on one side, while it is in contact with pressurized oil in the other side. Seal designs have been developed specifically to optimize seal performance and are described in U.S. Pat. No. 6,382,634 and published application US 2011/0127725 both of which are incorporated by reference. The other two cavities,  66   b  and  66   a  are likewise defined by the seals. 
         [0031]    In operation the pressure in the mud can change very unpredictably and quickly. The present system provides a configuration that maintains the hydraulic pressure in the cavity adjacent the seals at a level greater than the mud pressure, even when the mud pressure spikes abruptly. 
         [0032]    In the depicted embodiment this pressure intensifier is passive in that it does not rely on an active control system (e.g., measuring the pressure in the mud and controlling valves or pumps to maintain a certain pressure differential). In the depicted embodiment, the system is instantaneous in that an increase in mud pressure causes a direct increase in hydraulic fluid pressure. In the depicted embodiment a pressure intensifier assembly  68  includes a first line  70  in fluid communication with the space  72  that contains mud, and a second line  74  in fluid communication with space  76  that contains hydraulic fluid. 
         [0033]    In the depicted embodiment the second line  74  is in fluid communication with a control valve  94  and pump  78  that are used to increase the volume of fluid in the space  45  to extend the inner drive assembly relative to the outer drive assembly during the process of building a drill string or breaking down a drill string. In the depicted embodiment, the passive pressure intensifier assembly  68  is configured to function regardless of whether this active fluid control component is shut off as during typically drilling (e.g., thrusting and rotating of the drill rod), or turned on as when extending or retracting the inner rod drive assembly during make up and break up of a drill string. 
         [0034]    The first line  70  is directed to a first portion  72  of the cylinder assembly with a piston face having a first area, and the second line  74  is directed to a second portion  76  of the cylinder assembly having a second area. The first line  70  is also in fluid communication with a mud pump  82 , which supplies mud to the drill string via spaces in the drilling mud interface  50 . The area of the piston adjacent the first portion  72  is greater than the area of the piston adjacent the second area  76 , which results in a greater pressure in the second portion  76  than the first portion  72 . The ratio of the first area to the second area of the piston is proportional to the difference in pressure between the two portions of the cylinder assembly. Accordingly, a pressure increase (spike) in the mud in space  54  will result in a corresponding hydraulic pressure increase (spike) in the spaces  66   a ,  66   b  and  66   c.    
         [0035]    In one embodiment the drilling machine includes: a hydraulic drive system; an outer drive shaft driven by the hydraulic drive system, the outer drive shaft configured to rotate an outer drill rod of a drill string, an inner drive shaft driven by the hydraulic drive system, the inner drive shaft configured to rotate an inner drill rod of a drill string, a drilling mud delivery interface unit mounted to the outer drive shaft configured to direct drill mud into the drill string, a seal assembly configured to prevent drilling mud from contaminating hydraulic fluid in the hydraulic drive system, the seal assembly including: a seal  66   a  that includes a mud interface (left surface of the seal) and a pressure compensated interface (right surface of the seal); a hydraulic fluid port  84  extending from the mud delivery interface through a portion of the outer drive shaft to the pressure compensated interface. 
         [0036]    In some embodiments the drilling machine further includes a pressure compensator  68  in fluid communication with the hydraulic fluid port  84  configured to control the hydraulic pressure at the pressure compensated interface, wherein the pressure compensator is configured to vary the hydraulic pressure based on the mud pressure and is configured to maintain the hydraulic pressure at a level that is greater than the mud pressure. In some embodiments the pressure compensator comprises a chamber having mud on a first side  72  of a piston  86  and hydraulic fluid on a second side  76  of the piston. Some of these embodiments further include a position sensor that monitors the position of the piston. Also, in some of the embodiments with pistons  86 , the pistons include a leak path  88  therein. The leak path is configured to drain any fluid that would otherwise leak past the annular seals on the piston  86 . 
         [0037]    In the depicted embodiment of the mud delivery interface, the swivel  50  includes two spaced apart radial mud delivery interface seal assemblies, with the first assembly comprising seals  90   a  and  90   b  and the second assembly comprising  90   c  and  90   d , on either side of a mud delivery port. Each radial mud delivery interface seal assembly includes a mud interface (surface facing the mud) and a pressure compensated interface (surface opposite the mud facing surface). The hydraulic fluid port  84  extending from the mud delivery interface through a portion of the outer drive shaft also provides hydraulic pressure to the pressure compensated interface of the two spaced apart radial mud delivery interface seals. 
         [0038]    The present disclosure also provides a method of drilling. In the depicted embodiment the method includes the steps of: employing a hydraulic drive system to drive a dual rod drill string into the ground; employing a mud delivery system to deliver drilling mud down hole through the drill string; providing a first radial seal to block drilling mud from exiting the mud delivery system and a second radial seal adjacent the first radial seal to block hydraulic fluid from exiting the hydraulic drive system; pressurizing a cavity between the first radial seal and the second radial seal to a pressure that is greater than, or equal to, the pressure of the drilling mud. 
         [0039]    In some embodiments the step of pressuring the cavity includes providing pressure compensating hydraulic fluid to the cavity. In addition, some methods involve monitoring the flow of pressure compensating hydraulic fluid to determine whether either of the first or second radial seal has failed. The seals are intended to prevent flow, so if flow occurs the seal may have failed. In such embodiments the flow can be monitored by monitoring the position of a piston  86  that interfaces between drill mud and hydraulic fluid, wherein the piston is part of a pressure intensifier  68 . 
         [0040]    The system described above can be easily and quickly serviced. Seals  90   e  and  90   f  are consistently exposed to a significant speed differential as the speed of the inner rod is significantly higher than the speed of the outer rod. Wherever the boring operation is advancing along a deviated path, the inner rod will be rotated at full speed, while the outer rod will be held in a fixed position, oriented to control the direction of the deviated bore. During this operation the relative rotation seen by seals  90   e  and  90   f  is at the maximum, wherein the wear rate of these seals will likewise be at the maximum, while there will be no relative motion at seals  90   a ,  90   b ,  90   c , and  90   d.    
         [0041]    Whenever the boring operation is advancing along a straight path, the inner rod will be rotated at full speed, while the outer rod is rotated slowly. During this operation the relative rotation seen at seals  90   e  and  90   f  is less than maximum, but still significant, while the relative rotation at seals  90   a ,  90   b ,  90   c , and  90   d  is minimal. 
         [0042]    Seals  90   a ,  90   b ,  90   c , and  90   d  will experience the highest relative rotation during the backreaming process wherein the outer rod can be rotated at full speed, as the outer rod is used to transfer power to the backreamer. 
         [0043]    As a result of these operating characteristics, seals  90   e  and  90   f  are expected to require the most frequent replacement as they interface between structures that rotate relative to each other (e.g., the head shaft  36  and the seal adapter sleeve  49 ). Seals  90   e  and  90   f  are also referred to herein as main seals. Seals  90   a ,  90   b ,  90   c  and  90   d  are also expected to require replacement. One of the advantages of the current invention is the accessibility of these seals. 
         [0044]    To access seals  90   e  and  90   f , the adaptor  42  can be removed from the head shaft  36 . The replaceable seal adaptor  59  will then be accessible. It can be removed from the inner drive head shaft  46  by unthreading the threaded connection with the seal adaptor sleeve  49 . Once the replaceable seal adaptor  59  has been removed, the seals  90   e  and  90   f  can be serviced. The replaceable seal adaptor  59  includes seals on its inner diameter, that have not been described in the previous description. These seal against the inner drive shaft  24  as it slides longitudinally. These seals do not experience any relative rotational movement, and only see sliding movement (axial movement), so they do not experience as significant wear. These seals can, however, be replaced. Once the appropriate parts have been serviced the assembly can conveniently be put back together. 
         [0045]    To access the seals  90   a ,  90   b ,  90   c  and  90   d , the swivel  50  can slide off of the adaptor  42  to expose the seals. 
         [0046]    Another aspect of the present invention is useful in its impact on logistics for servicing the machine. The seals  90   a ,  90   b ,  90   c ,  90   d ,  90   e , and  90   f  are all configured in the illustrated embodiment as identical parts. From the aspect of keeping a supply of repair parts, it is an advantage to utilize the same part for all these different seal locations. It should be appreciated that the main seals  90   e  and  90   f  could be radial seals or seals of another variety, for example, a mechanical face seal could act as a main seal to prevent mud from contaminating the hydraulic fluid. 
         [0047]    Referring to  FIGS. 5A-7B  alternative embodiments are shown. In these embodiments the mud delivery interface (swivel) is shown attached to the inner rod on the up hole side of the outer tube drive motor. In these embodiments the inner rod includes a hydraulic oil port that provides the pressure compensated hydraulic fluids to the seal assemblies. These embodiments are generally similar. 
         [0048]      FIG. 5A  shows an embodiment wherein the mud delivery interface  100  is attached around the inner shaft and an oil port end through the inner shaft in the down hole direction. 
         [0049]      FIG. 6A  is generally similar to  FIG. 5A , but it shows an embodiment where the mud delivery interface  102  is attached at the end of the inner drive shaft and includes fewer radial seals than in the embodiment shown in  FIG. 2 . In the depicted embodiment drilling mud would be delivered axially through the motor that drives the rotation of the inner rod. 
         [0050]      FIG. 7A  shows an embodiment with seals that allow longitudinal movement of the inner rod which are separated from the main seal that only sees rotation. The main seals (similar to seals  90   e  and  90   f  of  FIG. 3 ) seal against a replaceable seal adaptor. In the depicted embodiment the replaceable seal adapter includes: a portion of its inner diameter being non-circular, to mate with a non-circular section outer diameter portion of the inner drive member so that the seal adaptor will rotate with the inner drive member; an inner bore that has grooves to support the seals that see longitudinal movement; and an outer sealing diameter for the main mud seals. 
         [0051]    The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.