Patent Publication Number: US-6702040-B1

Title: Telescopic drilling method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 60/286,498, filed Apr. 26, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to drilling methods, and, in particular, to telescopic drilling methods for use in connection with overburden drilling operations. 
     2. Description of Related Art 
     In order to collect and transfer water, wells are used and created by drilling a well hole or bore into the ground to an aquifer or water layer. As these bores are being drilled, often an overburden layer or rock layer is encountered and must be breached prior to reaching the water layer. In addition, the water layer often is far underground and requires special machinery and drilling equipment to reach. 
     Prior art drilling systems use long conduits, referred to as casings, welded together and gradually moved down the bore as it is drilled. However, the drilling operation creates stress on the casings and weld joints and may cause these casings to fracture. Such drilling impact and vibration stress is sustained by the rigid one-piece drill casing and its weld joints, causing cracks and fractures, which typically require the hole or bore to be cleared and the drilling process recommenced only after time and material expenditures. 
     Further, the present drilling methods are slow, as the drill is required to pull the entire casing length along with it as it penetrates further into the earth. This process is further slowed since the casing being pulled by the drill may be experiencing friction, pressure and contortions as a result of the outer walls of the bore collapsing and overburdened filling in against the casing. These deficiencies, exhibited by the prior art drills and the prior art drilling methods, decrease the drilling process efficiency and increases the “wear and tear” on the drilling machinery. 
     As the bores are often deep, the prior art drilling methods also require large and extended lengths of casings to be attached together, which causes the casing segments to stand high over the work area, and the drill rod segment must be loaded within the next casing section before it is transported and erected above the bore for welding to the preceding section. Such transport of the next casing segment containing the next drill rod segment is often precarious and results in human injury. 
     Present drilling methods require that the drilling by product and debris be expelled and managed high above ground level, with the use of a converter system which caps the top of the next casing section as it moves toward ground level during each drilling segment. Typically, a long overhead hose carries the debris from this converter system. However, this converter system must be removed and replaced for each drilling segment. Further, this converter system also stands high over the work site and poses an overhead hazard. In addition, there remains the possibility that the hose may entangle a person or machinery, and this overall converter system is complex and causes unnecessary delays in the drilling process. 
     Accordingly, it is an object of the present invention to provide a telescopic drilling method that overcomes these and other deficiencies in prior art drilling methods. 
     SUMMARY OF THE INVENTION 
     The present invention is a telescopic drilling method, and includes the steps of: (a) drilling an outer bore through a surface, the outer bore defined by an outer bore wall and an outer bore base and having an outer bore diameter and a first outer bore depth; (b) inserting a hollow outer conduit into the outer bore, the outer conduit having a drill end with a ring drill bit rotatably attached thereto; (c) at least partially inserting a first hollow inner conduit through the outer conduit; (d) preventing the first inner conduit from moving longitudinally with respect to the outer conduit; (e) engaging a rotatable inner drill bit with the ring drill bit, thereby creating a unitary drill bit head; (f) further drilling the outer bore using the unitary drill bit head to a successive outer bore depth; and (g) disengaging the inner drill bit from the ring drill bit, such that the outer conduit is capable of moving freely within the outer bore. 
     In the preferred embodiment, a second end of a successive hollow inner conduit is attached to a first end of an immediately preceding inner conduit, thereby creating an extended inner conduit, which is able to reach greater depths under the surface. The telescopic drilling method of the present invention is particularly useful in connection with overburden or rock drilling. 
    
    
     The present invention, both as to its construction and its method of operation, together with the additional objects and advantages thereof, will best be understood from the following description of exemplary embodiments when read in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side schematic sectional view of a drilling method and apparatus according to the prior art; 
     FIG. 2 is a side schematic sectional view of a drilling apparatus performing a step of a preferred embodiment of the telescopic drilling method according to the present invention; 
     FIG. 3 is a side schematic view of the drilling apparatus of FIG. 2 performing a further step of a preferred embodiment of the telescopic drilling method according to the present invention; 
     FIG. 4 is a side schematic sectional view of the drilling apparatus of FIG. 2 performing a further step of a preferred embodiment of the telescopic drilling method according to the present invention; 
     FIG.  5 ( a ) is a side schematic sectional view of the drilling apparatus of FIG. 2 performing a further step of a preferred embodiment of the telescopic drilling method according to the present invention; 
     FIG.  5 ( b ) is a front view of a unitary drill bit head of the drilling apparatus of FIG. 2 according to the present invention; 
     FIG. 6 is a side schematic sectional view of the drilling apparatus of FIG. 2 performing a further step of a preferred embodiment of the telescopic drilling method according to the present invention; 
     FIG. 7 is a side schematic sectional view of the drilling apparatus of FIG. 2 performing a further step of a preferred embodiment of the telescopic drilling method according to the present invention; 
     FIG. 8 is a side schematic sectional view of the drilling apparatus of FIG. 2 performing a further step of a preferred embodiment of the telescopic drilling method according to the present invention; 
     FIG. 9 is a side schematic sectional view with certain portions removed of the drilling apparatus of FIG. 2 performing a further step of a preferred embodiment of the telescopic drilling method according to the present invention; 
     FIG. 10 is side schematic sectional view of the drilling apparatus of FIG. 2 performing a further step of a preferred embodiment of the telescopic drilling method according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a drilling apparatus  10  and method according to the prior art. A typical drilling apparatus includes a drilling machine  12 , which rotates a drill rod  14  having a drill hammer  16  attached thereto. The drill rod  14  and drill hammer  16  extend through a casing section  18 . A ring drill bit  20  is attached to the casing section  18  and has a tubular construction. A pilot drill bit  22  is engaged with the ring drill bit  20 , thereby creating a unitary drill bit head  24 . It is this unitary drill bit head  24  that the drilling machine  12  uses to drill a bore  26  through a surface  28 , typically the surface of the earth. 
     As the unitary drill bit head  24  penetrates further below the surface  28  and increases the depth of the bore  26 , byproduct and debris (not shown), typically referred to as shavings, are expelled from the bore  26  through the casing section  18 . The shavings move up the casing section  18  and encounter a cap  30 , which directs the shavings through a tube  32  to a pile on the surface  28 . 
     As the drilling machine  12  drills the bore  26  deeper, the unitary drill bit head  24  pulls the casing section  18  further below the surface  28 . This prior art drilling method uses successive lengths of equal-diameter casing sections  18  routed directly to the upper end of the immediately preceding casing  18  section. This creates a unitary drill casing  34 . It is this unitary drill casing  34  that is pulled further into the bore  26 , as the drilling process continues, and, further, it is this drill casing  34  that sustains and absorbs substantial drilling impact and vibration stress. The prior art drilling method also requires that each successive welded casing section  18  remain above the surface  28  during the drilling process. Therefore, the next casing section  18  must be welded or attached to the lower or previous casing section  18  prior to its entry into the bore  26 . In addition, each successive casing section  18  must be “loaded” with another section of the drill rod  14  before it is transported and erected over the bore  26  and before the casing section  18  is welded to the preceding casing section  18 . Further, the cap  30  must be reinstalled at the top of each new casing section  18 . 
     The present invention is directed to a telescopic drilling method, and a drilling apparatus  50  engaged in a preferred embodiment of this method is illustrated in FIGS. 2-11. First, as seen in FIG. 2, an outer bore  52  is drilled through a surface  54 , and the outer bore  52  extends below the surface  54 . The outer bore  52  is defined by an outer bore wall  110  and an outer bore base  112 . In order to drill this outer bore  52 , the drilling apparatus  50  includes a drill rod  56  with a drill hammer  58  attached thereto. A rotatable drill bit  60  is attached to the drill hammer  58 , and all of the drill rod  56 , drill hammer  58  and drill bit  60  are rotated by a drilling machine  62 . See FIG.  2 . The drill rod  56 , drill hammer  58  and drill bit  60  are removed from the outer bore  52 . Next, a hollow outer conduit  64  is inserted into the outer bore  52 , and the outer conduit  64  has an outer conduit drill end  66  with a ring drill bit  68  attached thereto. This ring drill bit  68  is able to rotate independently of the outer conduit  64 . See FIG.  3 . 
     A first hollow inner conduit  70  is inserted into the outer conduit  64  and extends a portion of the length of the outer conduit  64 . As seen in FIG. 4, a clamping mechanism  72  clamps the first inner conduit  70  at or near the surface  54 , such that the first inner conduit  70  cannot move longitudinally within the outer conduit  64 . The first inner conduit  70  has a first inner conduit first end  74  and a first inner conduit second end  76 , and the clamping mechanism  72  holds the first inner conduit  70 , such that the first inner conduit first end  74  is in an exposed and accessible position. Further, the first inner conduit  70  is sized such that it is slidable within the outer conduit  64 . 
     Next, the drilling machine  62  lowers the drill rod  56  and drill hammer  58  through the first inner conduit first end  74 . Since the drill bit  60  is attached to the end of the drill hammer  58 , the drill bit  60  is also lowered through the first inner conduit  70  and towards the outer conduit drill end  66 . When the drill bit  60  reaches the ring drill bit  68 , it is engaged therewith, thereby creating a unitary drill bit head  78 . See FIG.  5 ( a ). FIG.  5 ( b ) shows a preferred engagement arrangement between the drill bit  60  and the ring drill bit  68 . In this preferred arrangement, the drill bit  60  has a tubular shape, with two locking recesses  80  circumferentially and oppositely spaced from each other. The ring drill bit  68  has two locking tabs  82  extending from an inner surface of the ring drill bit  68  and configured to mate with the locking recesses  80 . Once the locking tabs  82  are engaged with the locking recesses  80 , the drill bit  60  and the ring drill bit  68  are able to rotate simultaneously using the driving force that the drilling machine  62  imparts on the drill bit  60 . The ring drill bit  68  typically includes a carbide insert for cutting. In addition, the drill bit  60  typically includes at least one air flow orifice  83  for forcing air through the drill bit  60  to the cutting area, and a cuttings flow orifice  84  for receiving and passing cuttings up to the surface  54 . The cuttings flow orifice  84  may be in the form of a gap between the ring drill bit  68  and the drill bit  60 . The drilling cuttings or shavings would flow up through the cuttings flow orifice  84 , further through the first inner conduit  70  and up to the surface  54 . 
     The drill bit  60  can be any size and shape, and constructed from any material, as long as it is able to be appropriately engaged with the ring drill bit  68 , if required. For example, the drill bit  60  may be a pilot bit. The drill bit  60  used to drill the initial outer bore  52  section is typically sized and shaped differently than the drill bit  60  that engages the ring drill bit  68 . 
     As seen in FIG. 6, as the unitary drill bit head  78  continues drilling a deeper outer bore  52 , the outer conduit  64  is pulled downward with the unitary drill bit head  78 . After the outer bore  52  has been drilled to an appropriate depth using the unitary drill bit head  78 , the drill bit  60  is disengaged from the ring drill bit  68 , and the outer conduit  64  is capable of moving freely and longitudinally within the outer bore  52 . See FIG. 7 
     Next, in a preferred embodiment, a second inner conduit  86  having a second inner conduit first end  88  and a second inner conduit second end  90 , is attached to the first inner conduit  70 . Specifically, the second inner conduit second end  90  is attached to the first inner conduit first end  74 , thereby creating an extended inner conduit  92 . Typical methods of attachment are envisioned, such as welding the second inner conduit  86  to the first inner conduit  70 . 
     After attachment, the first inner conduit  70  is released by the clamping mechanism  72 , and the extended inner conduit  92  is extended further through the outer bore  52  and through the outer conduit  64 . Preferably the drill rod  56 , drill hammer  58  and drill bit  60  are removed from the first inner conduit  70  prior to attaching the first inner conduit  70  and the second inner conduit  86 . 
     As with the first inner conduit  70 , the extended inner conduit  92 , having an extended inner conduit first end  94  and an extended inner conduit second end  96 , is partially exposed at or near the surface  54 . Specifically, the extended inner conduit first end  94  is clamped, using the clamping mechanism  72 , in a workable position above the surface  54 , while the extended inner conduit second end  96  extends to within the outer conduit  64 , near the outer conduit drill end  66 . The relative placement of the extended inner conduit  92 , with respect to the outer bore  52  and the outer conduit  64  is illustrated in FIG.  8 . 
     Next, the drill rod  56 , drill hammer  58  and drill bit  60  are lowered through the extended inner conduit  92 , and the drill bit  60  is engaged with the ring drill bit  68 . As the outer bore  52  continues to deepen, additional drill rods  56  are attached or mated together using techniques and apparatus that are well known in the art. Drilling continues and the extended inner conduit  92  is lengthened using the above-described method until an underground layer  98  is encountered. This underground layer  98  may be bedrock, shale, clay or some other overburden material. At this point, drilling operations are terminated. 
     After this underground layer  98  is encountered, again the drill rod  56 , drill hammer  58  and drill bit  60  (as disengaged from the ring drill bit  68 ) are removed from the extended inner conduit  92 . An inner bore drill bit  100  is attached to the drill hammer  58 , and this inner bore drill bit  100  has an outside diameter, which is smaller than the inside diameter of the ring drill bit  68 . Therefore, the inner bore drill bit  100  is able to pass through the ring drill bit  68 . 
     As shown in FIG. 9, the drill rod  56  and drill hammer  58 , with the inner bore drill bit  100  attached, are lowered through the extended inner conduit  92 , pass through the ring drill bit  68  and are utilized to drill an inner bore  102 . While the inner bore drill bit  100  penetrates the underground layer  98 , creating the inner bore  102 , the outer conduit drill end  66  rests on an upper surface of the underground layer  98 . In addition, the extended inner conduit  92  is sized such that the extended inner conduit second end  96  rests on the ring drill bit  68 . 
     Drilling operations continue, and the inner bore  102  deepens until a second underground layer  104  is encountered. This second underground layer  104  is typically an underground aquifer or a water layer. At this point, the drill rod  56 , drill hammer  58  and inner bore drill bit  100  are removed from the inner bore  102  and the outer bore  52 . The inner bore  102  now provides access to the aquifer layer or successive underground layer  104 , and the water is able to pass up through the inner bore  102 , through the ring drill bit  68 , and further up through the extended inner conduit  92  to the surface  54 . When the successive underground layer  104  is encountered, the extended inner conduit first end  94  is sealed with a cap  106 . This arrangement is shown in FIG.  10 . 
     Typically, the first inner conduit  70 , second inner conduit  86 , and any other successive sections which form the extended inner conduit  92  all have a uniform inside diameter and are provided with an appropriate seal such that water can flow up through the extended inner conduit  92  to the surface  54 . 
     EXAMPLE 
     In a specific example of the telescopic drilling method of the present invention, the outer bore  52  has a ten inch diameter, and an initial depth of twenty-five feet. The drill bit is a ten and one-eigth inch diameter bit. The outer conduit  64 , with the ring drill bit  68  attached, has a length of twenty-five feet four inches. The ring drill bit  68  has a seven and one-half inch diameter. 
     The first inner conduit  70 , second inner conduit  86  and, therefore, the extended inner conduit  92 , have a six and five-eighths inch diameter. As the outer bore  52  deepens to a depth of about forty feet four inches, the outer conduit  64  overlaps the first inner conduit  70  by at least four feet. This ensures that the first inner conduit  70  does not exit and misalign with the outer conduit  64 . The clamping mechanism  72  holds the second inner conduit first end  88  and/or the extended inner conduit first end  94  approximately one foot above the surface  54 . After the first inner conduit  70  and second inner conduit  86  have been attached, there is approximately twenty-four feet of overlap between the extended inner conduit  92  and the outer conduit  64 . As the unitary drill bit head  78  continues drilling, the outer conduit  64  may have a diameter of seven and one-fourth inch. 
     The unitary drill bit head  78  continues drilling and when the extended inner conduit first end  94  is approximately one foot above the surface  54 , the outer bore  52  is now at a depth of approximately sixty feet four inches. This method continues until bedrock is encountered, which, in this example, is at eighty feet four inches. In order to drill through the first underground layer  98 , namely bedrock, the drill hammer  58  is fitted with a five and one-eighth inch drill bit  60 , and drilling continues until the second underground layer  104  is encountered. 
     The telescopic drilling method of the present invention utilizes a free or floating telescoping bit in the form of the outer conduit  64  attached to the ring drill bit  68 . This relieves fracture-causing stress from the extended inner conduit  92  and its weld joints, which is typically experienced in known drilling methods. The outer conduit  64 , with the ring drill bit  68  attached, absorbs substantial drilling impact and vibration stress, thereby alleviating stress cracks or fractures in the extended inner conduit  92 , which eventually becomes the water well. Since a cracked or fractured casing or weld joint requires that the outer bore  52  be cleared and the drilling process halted for reparations, the telescopic drilling method of the present invention increases efficiencies and decreases material expense. 
     In addition to relieving impact and vibration stress from the extended inner conduit  92 , the use of the telescopic drilling method of the present invention and free or floating outer conduit  64  and ring drill bit  68 , the overall drilling system and process may continue at a more rapid pace. This increased speed is achieved since the unitary drill bit head  78  is not required to pull the extended inner conduit  92  along with it as it penetrates further into the earth. Instead, the unitary drill bit head  78  of the present invention must only pull, and in effect works with, the telescoping portion (outer conduit  64  and ring drill bit  68 ), and not with the extended inner conduit  92 , which may be experiencing friction, pressure and contortions, as a result of the outer bore  52  walls collapsing and overburden filling-in against the extended inner conduit  92 . With the present invention, successive inner conduit may simply be pushed along behind the unitary drill bit head  78  from above by the drilling machine  62 . This, in turn, makes the telescopic drilling method of the present invention a more efficient drilling process and reduces “wear and tear” effects on the drilling apparatus  50 . 
     The prior art drilling methods require that each successive, welded inner conduit or casing section remain above the surface  54  during the drilling process, whereas the telescopic drilling method of the present invention permits each successive inner conduit to be fully lowered into the outer bore  52  prior to recommencing drilling. The present invention is safer than the prior art drilling methods, as the next or successive inner conduit section does not need to be positioned unsafely overhead over the work site during the drilling process, and, further, the next segment of the drill rod  56  does not need to be loaded within the next drill rod  56  section before it is transported and directed above the outer bore  54  for welding to the preceding section. The transport of the next inner conduit section or segment containing the next segment of the drill rod  56  to a position above the outer bore  52  is both precarious and has resulted in human injury. The method of the present invention permits the next segment of the drill rod  56  to be positioned only after the next inner conduit section is lowered into the outer bore  52 . 
     Known current drilling methods also require that the drilling byproduct or shavings be expelled and managed high above the surface  54 , and these methods require the use of a cap  30  or converter system, which caps the top of the next casing section  18  as it moves toward surface  54  level during the drilling process. Both the cap  30  and the tube  32  must be removed and replaced for each drilling segment. The method of the present invention allows drilling byproduct to be expelled, managed and collected immediately above the outer bore  52  at the surface  54  and negates the use of an unwieldy converter system towering above. Therefore, the method of the present invention alleviates an overhead hazard, the possibility that the tube  32  may entangle a person or machinery, and eliminates certain steps, thereby reducing complexity, the opportunity for further harm and unnecessary delays in the drilling process. 
     This invention has been described with reference to the preferred embodiments. Obvious modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be constructed as including all such modifications and alterations.