Abstract:
A device for preserving the orientation of a core is described. A core barrel is attached to a rotatable orienting rod. A plurality of projections are located on an inner surface of the core barrel. Three projections are grouped together and opposite from a fourth projection. A ratchet assembly is included at an end of the rotatable orienting rod opposite from the core barrel. The ratchet assembly includes a first body, to which the rotatable orienting rod is attached, a plate, a second body, and a biasing mechanism. A turning rod is mounted on the plate, which is located between the two bodies. The plate and the second body each have teeth which intermesh, but which slip if a clog in the core barrel inhibits rotation of the rotatable orienting rod.

Description:
BACKGROUND  
         [0001]    It is desirous in obtaining sample cores from bore holes to know the direction that certain parts of the core bear with relation to the surface of the ground where the bore has been made. To accomplish this, complicated mechanisms have heretofore been used. An example is a mechanism including, for instance, a compass and photographic equipment. One disadvantage in such a mechanism is that the drilling operation sends vibrations through the coring equipment and drilling fluid. The vibrations tend to blur the photographs, making it necessary to completely halt the drilling and fluid pumping operations and allow the vibrations to subside, which consumes time, to obtain a clear photograph.  
           [0002]    Further, with the use of a compass, the apparatus and the ground material must be non-magnetic so that the compass will not be affected. One such mechanism is shown in U.S. Pat. No. 3,450,216 dated Jun. 17, 1969. It is also known for core taking apparatus to include a core barrel attached to the bottom end of the drill string and isolated from the rotation by bearings. In such an arrangement, friction between the core and core barrel provides the only force holding the core barrel from rotating. Such an apparatus is shown in U.S. Pat. No. 3,004,614. If, however, the core should break, the core barrel will rotate, and all orientation will be lost. In fact, many prior core sampling apparatus rely on the integrity of the core.  
           [0003]    It is also known to score the core with internally extending projections, such as, for example, as shown in U.S. Pat. No. 1,701,784. One disadvantage with such projections is that they have been evenly spaced around the core barrel, and thus the orientation of the core may not be accurately ascertained. A further disadvantage is that sometimes the projections fail to adequately score the core.  
           [0004]    Another disadvantage of conventional coring device is that such devices are prone to inner rod failure due to clogging at the bottom of the coring device. Conventional coring devices, such as the coring device  100  shown in FIG. 3, are double tube core barrels, with outer tubes  110  and inner tubes  111  mounted on separate bearing assemblies. The inner and outer tubes  110 ,  111  do not rotate together. Through this arrangement, the amount of water contacting the core is minimized. Blockages sometimes occur during coring operations. A consequence of such blockages is that the inner orienting tubes  111  are prevented from rotating. The continued force of the motor used to rotate the inner orienting tubes  111  eventually leads to the breakage of the tubes  111 , thus destroying the orientation of the core.  
         SUMMARY  
         [0005]    The invention provides a device for orienting a core cut in a bore hole. The device includes a plurality of orienting rod sections connected one to another into a rotatable orienting rod, and a core barrel attached to one end of the rotatable orienting rod. The core barrel is configured to receive the core and the core barrel includes a plurality of projections extending from an inward surface of the core barrel. At least three projections are grouped together on the inward surface opposite from a fourth projection.  
           [0006]    The invention further provides a system for cutting a core in a bore hole. The system includes a driving means, a plurality of orienting rod sections connected together as an orienting rod, the orienting rod being rotatable by the driving means, a core barrel attached to one end of the orienting rod, and a ratchet assembly for protecting the orienting rod from breakage caused by a clog in said core barrel.  
           [0007]    The invention also provides a method for obtaining a cut core from a bore hole. The method includes the steps of extending a rotatable orienting rod, with a core barrel attached thereto, into the bore hole, cutting the core, depositing the core in the core barrel, and scribing the core with a plurality of grouped projections and one opposing projection located on an inner surface of the core barrel.  
           [0008]    The foregoing and other advantages and features of the invention will be more readily understood from the following detailed description of the invention, which is provided in connection with the accompanying drawings.  
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a cross-sectional view of a coring device constructed in accordance with an embodiment of the invention.  
         [0010]    [0010]FIG. 2 is an enlarged cross-sectional view of a portion of the device of FIG. 1.  
         [0011]    [0011]FIG. 3 is an enlarged cross-sectional view of another portion of the coring device of FIG. 1.  
         [0012]    [0012]FIG. 4 is an enlarged view of the portion of the device within circle IV of FIG. 1.  
         [0013]    [0013]FIG. 5 is an enlarged view of the portion of the device within circle V of FIG. 1.  
         [0014]    [0014]FIG. 6 is a cross-sectional view along line VI-VI of FIG. 4.  
         [0015]    [0015]FIG. 7 is an elevation view partly in cross-section showing the entire coring device in use downhole. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0016]    Referring to FIG. 7, a drill pipe assembly  9  formed in several sections and suitably secured together, includes drill rods, outer barrels and an inner core taking means. As shown, the drill rods are rotated by a suitably powered rotary spindle  10 . The remainder of the operating rig is completed with a suitable support structure, such as a derrick D, and a source of drilling fluid directed by a drilling fluid swivel  76 , together with an engine, a water pump and a drum hoist (not illustrated).  
         [0017]    With specific reference to FIGS.  1 - 6 , an inner core taking means is shown including a plurality of sections  11   a  (FIGS.  1 - 3 ) which are keyed together to form an orienting rod  11 . At the working end of the orienting rod  11 , a core receiving barrel  12  is rotationally and axially secured (FIGS. 1, 2 and  4 ). The core receiving barrel  12  carries scribing means  13   a ,  13   b ,  13   c  (FIGS. 4, 6), and  13   d  (FIG. 6) on an inner surface thereof. The scribing means  13   a - d  may be projections which are configured to scribe marks in a core section, or the scribing means  13   a - d  may be another suitable configuration. As the core is cut and moves into a center area  15  of the core receiving barrel  12 , marks or grooves are scribed into the outer surface of the core which are intended to extend generally axially of the core. As shown in FIG. 6, the scribing means  13   a  is opposite (180 degrees) from the scribing means  13   d  and the scribing means  13   b  and  13   c  are grouped together and flank the scribing means  13   a . Through this arrangement, determining the orientation of a core is rendered more accurate. In practice, scribing means do not always produce scribe marks on cores, and so the presence of three such scribing means  13   a - c  on one side and another scribing means  13   d  on an opposing side of the core receiving barrel  12  allows one examining the core to piece together partial scribe marks from all of the scribing means  13   a - d  to ascertain the proper orientation of the core.  
         [0018]    The core receiving barrel  12  has a generally closed upper end and through this end there is an axially drilled, keyed bore  17 . The lower end of the orienting rod  11  as shown in FIG. 2 is threaded, and this threaded portion  16  passes through the bore  17  with a key  18  securing the core receiving barrel  12  against rotation. A pair of nuts  21  and  22  secure the barrel  12  in an axially adjustable position. The head of the core barrel  12  is provided with a plurality of small conduits  27  that extend upwardly and radially outwardly into a groove  28  which is closed by means of an O-ring  29 . Thus, if any drilling fluid is trapped in the core barrel  12 , it may pass by virtue of its pressure through these conduits  27  and  28 , and out past the O-ring  29 .  
         [0019]    As has been mentioned, the orienting rod  11  is made up of a plurality of sections  11   a  as necessary. For example, a first rod section  11   a  is keyed to a second rod section  11   a  by providing a socket  30  which receives a reduced end  31  of the second rod section  11   a , which is held in position by a holding screw  32  and keyed by a key  33 .  
         [0020]    Surrounding the orienting rod  11  is a drill rod designated  40  which is illustrated as composed of several sections, each threadingly coupled together throughout the length as necessary. At one end of the drill rod section  40 , there is threadingly secured thereto an outer barrel head  50   a  and an outer barrel  50 . At an end of the outer barrel  50  are cutting blades  51  (FIG. 4). The outer barrel  50  rotates, which allows the cutting blades  51  to cut the core which is received in the non-rotating core barrel  12 .  
         [0021]    The outer barrel head  50   a  is provided with threads  55  that threadingly engage the outer barrel  50 . The outer barrel head  50   a  is provided with a central bore therethrough, and the central bore is counter-bored at counter-bore areas  56  and  57 . The counter-bore areas  56 ,  57  receive, respectively, bearing units  58  and  59 . The orienting rod  11  is rotationally supported by these bearings  58  and  59  and is provided with means for stabilizing its axial position with an enlarged boss  60  having a seal  60   a  and a nut  61 . The nut  61  also has a seal  61   a  and is threadingly received on the threaded portions  16  of the orienting rod section  11   a . In addition, the outer barrel head  50   a  includes means for allowing drilling fluid to pass therethrough and is provided with a plurality of axially extending bores  62  that connect via a groove  62   a  to the open central portion of the drill rod assembly  9 . Lubrication of the bearings is readily provided by means of an axially extending bore  64  and a lateral passageway  65  which is fed through a grease fitting  66  in a fashion well known to those skilled in the art.  
         [0022]    The outer barrel head  50   a  is coupled to a portion of the drill rod section  40  by means of a connector  68  which has threads  69  and  69   a  at either end thereof for engaging corresponding threads in the drill rod section  40  and the outer barrel head  50   a . The connector  68  is provided with a central bore therethrough which allows the passage of the orienting rod  11  as well as sufficient area for the passage of drilling fluid through the drill rod section  40  as will be explained in greater detail below. Each additional drill rod section  40  needed to provide the proper length may be coupled onto the drill rod section  40  and to each other by means of the same connector  68 , or by a different connector, as required.  
         [0023]    In use, a driving means, namely the rotary spindle  10  (FIG. 7) at the upper end of the drill pipe assembly  9 , rotates the drill pipe assembly  9  as it is passed downhole into the ground to cut a core which passes into the center area  15  (FIGS. 1, 2). The core is scribed by the scribing means  13   a - d , one of which is oriented with a pointing device  38  having an arm  39  (FIGS. 1, 5). The pointing device  38  may be oriented in such a fashion that it will point to some certain predetermined position either fixed on the ground or to a certain compass bearing, such as to north or the like. For example, a pair of vertical posts  90 ,  91  (FIG. 1) driven in the ground may maintain alignment. Thus, the core will be marked by reason of the alignment with one of the scribing means  13   a - d  which may be differentiated from the other scribing means  13   a - 13   d  so that it may be known how the core lines up with a certain location above ground. The arm  39  may extend outwardly between, for example, the vertical posts  90 ,  91  so that it will maintain its position unless manually changed to orient the device in a different position. It should be appreciated that the device may be started at any point of orientation which is desirable. Further, if desired, the pointing device  38  and arm  39  may simply be left free and unrestrained with notations made of its compass bearing at various intervals during the coring operation. From the above, it will be apparent that the position of the scribes as received on the core is unaffected by interruptions in the coring operation or by breaks, seams, voids or any other faults that may exist in the material being cored.  
         [0024]    With specific reference to FIG. 5, next will be described a ratchet assembly useful to suppress the breaking of the orienting rod  11  when a blockage is encountered at the working end of the drilling rod assembly  9 . As shown, a ratchet assembly  150  includes a first body  152  and a second body  162 . The first and second bodies  152 ,  162  are retained to one another with a retaining pin  170 . The orienting rod  11  extends into the first body  152 . A turning rod  167 , which is rotated by the rotary spindle  10 , extends through the pointing device  38  through an opening  168  in the second body  162 . As will be described in greater detail below, the turning rod  167  rotates the first and second bodies  152 ,  162  and thereby rotates the orienting rod  11 .  
         [0025]    The first body  152  is cup-shaped having an open area  153 . A plate  160  is positioned within the open area  153 . The turning rod  167  extends through and is mounted to the plate  160 . The plate  160  includes a plurality of teeth  161 . The second body  162  also has a plurality of teeth  164  which mesh with the teeth  161  of the plate  160 . An O-ring  166  encircles the turning rod  167  within a cavity of the second body  162 .  
         [0026]    A biasing mechanism is positioned in the first body  152 . Specifically, as shown in FIG. 5, a spring  154  is positioned within the open area  153  and extends toward the plate  160 . At one end of the spring  154  is a sphere  158  which contacts the plate  160 . At the other end of the spring  154  is a spring biasing member  156 . The spring biasing member  156  is tightened down to put a certain amount of force on the plate  160  such that the teeth  161  mesh with the teeth  164  during normal use but slip against each other when a clog at the working end of the drilling rod assembly  9  causes torsional forces on the orienting rod  11 . The rotary spindle  10  (FIG. 7) rotates the turning rod  167 , which in turn rotates the plate  160 . Under normal loading, the teeth  161  of the plate  160  mesh with the teeth  164  of the second body  162 , thereby causing rotation of the first and second bodies  152 ,  162  and the orienting rod  11 . When torsional forces act upon the orienting rod  11 , the orienting rod  11  ceases to rotate or rotates at a lower rotational speed than the turning rod  167 . Prior to the inclusion of the ratchet assembly, these torsional forces would act severely enough on the drilling rod assembly  9  to shear the orienting rod  11 , thus destroying the ability to ascertain the true orientation of a cut core sample. With the ratchet assembly, the torsional forces act on the plate  160 , causing the plate teeth  161  to slip relative to the teeth  164  of the second body  162 . This allows for a differential in the turning speeds of the orienting rod  11  and the turning rod  167 , thus suppressing the breakage of the orienting rod  11 .  
         [0027]    While the foregoing has described in detail preferred embodiments known at the time, it should be readily understood that the invention is not limited to the disclosed embodiments. The invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. For example, while three scribing means  13   a - c  are shown and described, it should be appreciated that two or more than three such scribing means can be grouped closely together on one side and opposite from another such scribing means within a core taking apparatus. Accordingly, the invention is not limited to the embodiment specifically described but is only limited by the scope of the appended claims.