Abstract:
An apparatus for shaping boreholes used in seismic operations. A drill body is attached to a drill bit and is movable in axial and rotational directions. Selective operation of the drill body causes a moveable sleeve to operate a reaming bit to extend through a drill body port and into contact with the borehole wall. A cover seals the portion of the port not covered by the reaming bit to prevent loss of a transport fluid within the drill body and to prevent drill cuttings from entering the drill body interior. The cover can be integrated within the movable sleeve or can comprise a separate component. The force exerted by the drill body against the drill bit can be proportional to the force exerted by the reaming bit against the borehole wall. The reaming bit can be operated separately or simultaneously with operation of the drill bit, and can be retracted and reset to perform another shaping operation at a different position within the borehole.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to the field of geophysical exploration. More particularly, the invention relates to an improved, portable apparatus for drilling and underreaming boreholes for containing explosives in land based seismic operations.  
           [0002]    Conventional drill equipment uses flow controlled actuators or bias springs within a drill string to drill and to underream a borehole. Large diameter drill stems manage hydraulic actuators and springs together with associated bearings, gears, cams and guides. Conventional equipment using actuators and springs is illustrated in U.S. Pat. No. 5,351,758 to Henderson et al. (1994), which described a hydraulically actuated mandrel for operating expandable reaming dogs. U.S. Pat. No. 4,893,675 to Skipper (1990) disclosed a section milling tool using pump pressure and a coil spring to operate cutters. U.S. Pat. No. 4,614,242 to Rives (1986) disclosed a mechanical connection between an outer pipe and cutter arms for expanding the cutter arms outwardly to enlarge a borehole. U.S. Pat. No. 4,431,065 to Andrews (1984) disclosed an underreamer having a hydraulic plunger for deploying cuffing arms.  
           [0003]    Seismic shot holes in land based geophysical operations have different requirements unattainable with conventional drilling equipment. Shallow seismic shot holes are slender (less than four inches in diameter) and typically extend less than twenty meters deep. Light duty water or air systems provide a fluid for clearing drill cuttings from the borehole. The narrow cross-section of such boreholes and the associated drilling equipment limits the effectiveness of conventional drill equipment because conventional equipment restricts air flow through the narrow drill pipe diameter. Additionally, seismic shotholes preferably have enlarged sections suitable for installation of explosive material. By enlarging one or more portions downhole in a borehole, extra explosive power can be positioned below the surface to enhance the energy coupling of such explosive power to the geologic formations.  
           [0004]    A significant limitation of seismic borehole drill equipment is the need for portability and deployment by a single person. Seismic surveys cross extreme terrain sometimes inaccessible to trucks and other vehicles, and environmental and economic issues further limit the potential use of conventional drill operations. Seismic boreholes are typically positioned every fifty meters and are carried by hand from one location to the next. The portability of manheld portable drill equipment is limited by the weight and volume of the drill equipment. The time required to setup, drill, break down, and move such equipment determines the overall operating efficiency of the drill system.  
           [0005]    Various slide rail systems offer an alternate method for reaming a drill hole. Slide or guide rail systems have a rail embedded within the borehole diameter to steer the cutting equipment through openings in the main drill stem. Representative reaming bits using guide rails or slide rails are illustrated in U.S. Pat. No. 4,604,818 to Hachiro (1986) which disclosed a pile bore underreaming bucket, and in U.S. Pat. No. 4,407,376 to Inoue (1983) which disclosed an under-reaming pile bore excavator using guide rails to cross the drill pipe axis. Rail type systems are undesirable in slender seismic boreholes because the rails increase fluid or air turbulence within the borehole and thereby lessen the flow available to flush debris from the borehole.  
           [0006]    A need exists for an improved, portable drilling apparatus suitable for drilling and underreaming slender boreholes for seismic operations. The apparatus should be highly portable for use in locations difficult to access and should efficiently create boreholes having the desired shape.  
         SUMMARY OF THE INVENTION  
         [0007]    The invention provides a portable apparatus for engagement with a drill bit and with a drill mechanism for shaping a seismic borehole wall drilled by the drill bit. The apparatus comprises a drill body having an exterior surface and having a lower end connected to the drill bit, wherein the drill body is selectively moveable by the rotating mechanism. A port extends through the drill body exterior surface, and a reaming bit is movably engaged with the drill body and selectively extendible through the port to contact the borehole wall. A switch is operable by movement of the drill body, and a sleeve is activatable by operation of the switch to move within the drill body and to selectively extend the reaming bit through the port. A cover selectively blocks the port. In various embodiments of the invention, the cover can be integrated within the sleeve, the reaming bit can be retractable within the drill body for operation at another position along the borehole wall, and the force exerted by the reaming bit against the borehole wall can be proportional to a force exerted by the drill body against the drill bit.  
           [0008]    In another embodiment, the invention provides a portable apparatus for drilling a seismic borehole wall in soil which comprises a movable drill body having an exterior surface and a lower end, a drill bit attached to the drill body lower end for forming a borehole wall in the soil, a port through the drill body exterior surface, a reaming bit movably engaged with the drill body and selectively extendible through the port to contact the borehole wall, a switch operable by movement of the drill body, a sleeve activatable by operation of the switch to move within the drill body and to selectively extend the reaming bit through the port, and a cover for selectively blocking the port. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 illustrates a drill body and drill bit operable with a drill mechanism for forming a seismic borehole.  
         [0010]    [0010]FIG. 2 illustrates an initial position of a sleeve and reaming bits relative to a drill body.  
         [0011]    [0011]FIG. 3 illustrates operation of a movable sleeve to initiate reaming bit operation.  
         [0012]    [0012]FIG. 4 illustrates a dish shaped borehole expansion.  
         [0013]    [0013]FIG. 5 illustrates a cylindrical borehole expansion.  
         [0014]    [0014]FIG. 6 illustrates a borehole expansion having a shape controlled by movement of the reaming bits relative to the drill body.  
         [0015]    [0015]FIG. 7 illustrates one configuration for a movable sleeve.  
         [0016]    [0016]FIG. 8 illustrates one configuration of rotatable reaming bits operable with a movable sleeve.  
         [0017]    [0017]FIGS. 9 and 10 illustrate one combination of a switch for selectively operating the movable sleeve.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    The invention illustrates a highly portable, efficient apparatus for drilling and shaping boreholes used in seismic operations. Referring to FIG. 1, borehole  10  is illustrated in geologic formations  12  and is formed with drill bit  14  rotated or otherwise moved by drive mechanism  16  to form a substantially cylindrical wall defining borehole  10 . Pump  18  injects compressed air or a liquid or other fluid into the interior of drill body  20  to provide a transport mechanism for removing drill cuttings from borehole  10 .  
         [0019]    As shown in FIG. 2, drill body  20  comprises a substantially hollow tubular having exterior surface  22  and interior surface  24 . Although drill body  20  is shown as cylindrical in shape, other configurations can provide the function of transferring steerage and motive forces between drive mechanism  16  and drill bit  14 , and of providing the transport mechanism for conveying the compressed fluid into borehole  10 . Drill body  20  supports one or more reaming bits  26  suspended on axles  28  and movable sleeve  30  positioned within the hollow interior of drill body  20 . FIG. 2 illustrates reaming bits  26  in an initial position during trip time into borehole  10  or while vertical drilling of borehole  10  is conducted. In such initial position, reaming bits  26  are axially and radially aligned with vertical ports  32  through drill body  20  having an alignment dictated by the orientation of axles  28  and the shape of sleeve  30  and of reaming bits  26 . Vertical ports  32  are initially sealed by the upper shutter portion  34  of movable sleeve  30  as shown in FIG. 2. Upper shutter portion  34  provides a cover which prevents leakage of the compressed fluid from within drill body  20  and which prevents intrusion of drill cuttings or other debris contacting exterior surface  22  from entering through vertical ports  32  into the hollow interior of drill body  20 .  
         [0020]    Referring to FIG. 3, as drill body  20  is rotated counterclockwise, lifted and rotated further counterclockwise, a switch (identified below) facilitates movement of sleeve  30  relative to drill body  20  and permits operation of reaming bits  26  relative to drill body  20  and to geologic formations  12 . Upper shutter portion  34  of sleeve  30  opens vertical ports  32  through drill body  20  and permits extension of reaming bits  26  radially outwardly into contact with geologic formations  12 . Such radial extension cuts geologic formations  12  and creates an enlarged portion of borehole  10 .  
         [0021]    As shown in FIG. 4, one representative shape of the borehole  10  enlarged portion can be dish shaped as reaming bits  26  are rotated outwardly. Translation of drill body  20  relative to borehole  10  will cause such dish shapes to be modified to a cylindrical shape as shown in FIG. 5. Various combinations and more complicated shapes for the wall of borehole  10  can be formed with combinations of selective variations of these basic movements, or with different shapes or combinations of reaming bits as shown in FIG. 6.  
         [0022]    The form, configuration and operation of reaming bits  26  can be accomplished in many different ways. One type of reaming bits  26  is illustrated in FIGS. 7 and 8, wherein movable sleeve  30  has upper shutter portion  34  for selectively sealing vertical ports  32  through drill body  20 . Openings  35  through sleeve  30  permit rotatable movement of reaming bits  26  therethrough. Sleeve  30  also has protrusions  36  for contacting cam surfaces  38  of axles  28 . As such contact progresses, reaming bits  26  are rotated outwardly through sleeve openings  35  and ports  32  and into contact with the wall of borehole  10  through geologic formations  12 . Additional movement outwardly and movement of drill body  20  causes reaming bits  26  to cut into the wall of borehole  10  to provide a selected shape.  
         [0023]    [0023]FIGS. 9 and 10 illustrate one combination of a switch for selectively engaging or disengaging movable sleeve  30  relative to drill body  20 . Protruding key or keys  40  can be attached to or formed in drill bit  14  or in a sub such as adapter  42  connected between drill bit  14  and drill body  20 . Keys  40  can be disposed within grooves, channels or slots  44  formed within interior surface  24  of drill body  20  for operation in different directions and sequences suitable for engaging or disengaging operable components such as moveable sleeve  30 . In one embodiment of the invention as illustrated, keys  40  located on an outer wall of adapter  42  are routed such that keys  40  follow slot  44  allowing drill body  20  to slide down the length of adapter  42  toward the bottom of borehole.  
         [0024]    In a preferred embodiment of the invention, drill body  20  slides down adapter  42  a selected distance such as six inches further than the position which was held during the vertical drilling effort. As drill body  20  slides down along adapter  42 , the upper end of adapter  42  makes contact with the lower end of movable sleeve  30 . Movable sleeve  30  then begins to move upward through drill body  20 . As the upper shutter  34  rises past reaming bits  26  each protrusion  36  contacts each reaming bit  26  at the edged portion identified as cam surface  38  causing each reaming bit  26  to rotate outward through the now open vertical ports  32 . As the lower end of each reaming bit  26  clears the bottom of the respective vertical port  32 , the upper end of lower shutter  46  begins to close vertical ports  32  from the bottom end. The axial forces now placed on reaming bits  26  are applied by the upper end of lower shutter  46  and these forces cause reaming bits  26  to extend outward such that each reaming bit  26  bit contacts the wall of borehole  10 . When the reaming bits  26  make contact with the borehole  10  wall the downward sliding of drill body  20  stops as the entire drill string is suspended in borehole  10  by reaming bits  26 . The downward sliding motion of drill body  20  for a selected distance such as the six inches identified above serves as an indicator to the drilling crew that reaming bits  26  are successfully deployed. Axial and radial forces now applied to the drill body  20  will cause reaming bits  26  to cut outwardly and upward. When fully extended, reaming bits  26  can excavate downward.  
         [0025]    For the embodiment of reaming bits  26  identified in FIGS. 7 and 8, a pair of rectangular or cylindrical metal reaming bits  26  are each suspended vertically from a pair of axles  28  which span the diameter of drill body  20 . Cutting edges on each bit  26  are configured to enable each reaming bit  26  to excavate upward, outward, and downward along the borehole  10  wall. Vertical openings such as ports  32  in drill body  20  allow reaming bits  26  to pivot outward beyond exterior surface  22  and into contact with the borehole  10  wall. Moveable sleeve  30  located inside drill body  20  provides integral shutters which position and retain reaming bits  26  inside drill body  20 , and further seals vertical ports  32  from the loss of flushing air or fluid and prevents intrusion of drilling debris until the reaming process is initiated.  
         [0026]    As described above, the reaming process is started with a mechanical matrix or “switch” integral to drill body  20  and to adapter  42 . The switch can comprise a series of slots or grooves machined into the inner wall comprising the base of drill body  20 . A set of protruding keys  40  are fitted or machined into the outer wall of adapter  42  so that drill body  20  is routed to a specified position within the slot-and-key selector matrix relative to the vertical drill bit adapter or sub. For instance, rotating the drill body  20  one quarter turn counterclockwise, then lifting drill body  20  four inches, then rotating another quarter turn counterclockwise, then lowering drill body  20  eight inches would allow the lower end of movable sleeve to contact the upper end of vertical drill bit adapter  42 . After adapter  42  contacts the lower end of movable sleeve  30  and presses upward against moveable sleeve  30 , the reaming process is initiated. When the reaming process is initiated, the upper sleeve shutter  34  rises to open vertical ports  32  and simultaneously actuates cam surface  38  integral to the upper end of each reaming bit  26 . This camming function is executed by cam surface  38  protrusion similar to the shape of a single gear tooth located on the inner wall at the bottom edge of upper shutter  34 , as it contacts and passes by the upper portion of each reaming bit  26 .  
         [0027]    Each cam surface  38  pivots the respective reaming bit  26  outward and upward through the corresponding vertical ports  32 . As the upper shutter  34  moves upward to allow reaming bits  26  to pivot outward and upward, a portion of sleeve  30  identified in FIG. 7 as lower shutter  46  simultaneously rises to block reentry of each reaming bit  26 , to prevent the escape of flushing fluid or air, and to seal against drilling debris intrusion.  
         [0028]    Lower shutter  46  also redirects the downward forces applied to the drill body  20  upward into reaming bits  26  such that either all of the drilling effort is directed to reaming bits  26  of the drilling effort is distributed to reaming bits  26  and vertical drill bit  14 . The force, and consequently the excavation rate applied to reaming bits  26  is controlled by the amount of downward force applied to drill body  20 . The mechanical selector matrix or switch is controlled by the amount of downward force applied to the drill body  20 . The mechanical selector matrix or switch can be configured to allow vertical drilling simultaneously with the reaming process or can disable vertical drilling during the reaming process. As reaming bits  26  expand outward and upward, a bowl or dish shaped cavity can be formed as shown in FIG. 4. Once the reaming bits reach their maximum hole diameter, further drilling can transform the cavity shape from a dish to a cylinder. Reaming bits  26  can be retracted, guided and locked to their original rest position with upper shutter  34  closed by means of the mechanical switching function of the selector matrix or switch. Once reaming bits  26  are retracted and secured, the vertical drilling effort alone can resume if desired, and the expansion process can be restarted at any time to create a series of cavities with a variety of controlled volumes and shapes.  
         [0029]    The length, diameter, shape and cutting edge arrangement of reaming bit or bits  26  can vary depending on the size of the desired cavity, rate of excavation and the general quality of the cavity wall within borehole  10 . A single bit or a plurality of bits  26  can be deployed from the same drill body  20  and more than one reaming bit  26  can be located on a single axle  28  with drill body  20 . Bit axles  28  can be located inline, adjacent the other, or in different combinations to vary the cutting angle and shape of bits  26 . Various functions can be activated directly by the drilling crew to raise, lower and rotate the drill body  20  so that drill body  20  and reaming bit  26  cooperate to provide various cavity shapes.  
         [0030]    The seismic borehole reaming process described in the present invention suspends reaming bits  26  on axles  28  inside drill body  20  which provides a conduit to reaming bits  26  for the drilling forces to be applied to the primary drill stem. Reaming bits  26  are capable of reaming outward from a location within the confines of borehole  10  and are capable of reaming in both upward and downward directions. Moveable sleeve  30  is shaped so that multiple functions are integral to the one-piece sleeve  30 . Such functions include the ability to retain reaming bits  26  in a specific position inside drill body  20  such that bits  26  are always aligned with vertical ports  32  located in drill body  20 . Sleeve  30  releases reaming bits  26  and projects them along a specific path such that they pass through vertical ports  32  of drill body  20 . Sleeve  30  minimizes flushing fluid or air loss through vertical ports  32  during all stages of drilling. Sleeve  32  also retrieves reaming bits  26  in a manner such that reaming bits  26  are returned along a specific path to their original resting position and locked into place and aligned with vertical posts ready to deploy on multiple occasions within the same borehole. Sleeve  30  provides the conduit for all available reaming force from drill body  20  to reaming bits  26  during the outward reaming process and the upward reaming process. Force acting on reaming bits  26  is applied directly from drill body  20  during the downward drilling process.  
         [0031]    The invention is capable of functioning without hydraulic, pneumatic, or electrical power, or without stored energy techniques such as spring functions for actuating any phase of the reaming process. One or more selector matrixes or switches can be deployed to control various processes along the entire drill string. Flow restrictions are minimized because moving sleeve  30  and pivoted reaming bits  26  within the drill body  20  comprise the only impediments to fluid flow. Drill body  20 , sleeve  30  and pivoted bits  26  are integrally shaped to provide direct remote manual control of multiple cycles of guided bit deployment, guided bit retrieval, bit parking and securing, preservation of flushing fluid or flushing air flow, continuous seal against drilling debris intrusion, and direct control of the drilling force applied to reaming bits  26  and drill bit  14 . The invention uniquely provides a system for drilling a vertical borehole and for expanding the borehole diameter at one or more locations along the drilled borehole while maintaining direct control over the radial and axial excavating forces applied and over the size, shape and location of each expanded cavity.  
         [0032]    Although the invention has been described in terms of certain preferred embodiments, it will become apparent to those of ordinary skill in the art that modifications and improvements can be made to the inventive concepts herein without departing from the scope of the invention. The embodiments shown herein are merely illustrative of the inventive concepts and should not be interpreted as limiting the scope of the invention.