Abstract:
Window reaming and coring apparatus has a reamer connected in the middle of the tool by mechanical joints which permit the reamer to be displaced substantially parallel to the rest, of the tool body. The apparatus is lowered adjacent a pre-determined zone of interest and mills a parallel window along the edge of an existing wellbore into which the reamer is displaced. Once the reamer is fully displaced laterally into the window, the reamer and coring head can be rotated parallel to the wellbore, in the zone of interest for obtaining and retrieving a crescent-shaped core which has a significant cross section and length, enabling improved analysis of the wellbore lithography.

Description:
FIELD OF INVENTION  
       [0001]     Embodiments of the invention relate to drilling operations and a tubular workstring for reaming of parallel windows along the side of a wellbore. More particularly, the window can be used to place and position drilling tools in order to: start entry to a lateral section of the well and to harvest a long core along the wellbore sidewall.  
       BACKGROUND OF THE INVENTION  
       [0002]     It is known to cut windows in a sidewall of a main wellbore to drill offset or lateral wellbores from the main wellbore and for creating a pocket or window from which a core sample may be obtained.  
         [0003]     The best-known and most widely used method for redirecting a drill bit off-center of a wellbore is by first setting a wedge-type device, known as a whipstock, by means of retaining it to the walls of the wellbore using slips and friction. A drill bit is then lowered and pushed to the side of the wellbore at the angle of the whipstock to start a sidetrack hole. Typically, windows cut using a whipstock may be rough and may present some difficulties when tying back the offset wellbore to the main wellbore&#39;s casing or liner. Typically, reaming a window using a whipstock requires multiple trips into the wellbore. Further, the full width and depth of the window can only be achieved at the bottom end of the whipstock.  
         [0004]     During drilling of wellbores, conventional core samples are often taken to obtain information relative to the formations. Typically, coring occurs at the bottom of the wellbore during the process of deepening the hole. Typically, the process requires that the drill string be tripped out and a coring tool be run in for obtaining the core sample, after which the coring tool is removed and the drill string is run in to further deepen the borehole to total depth. The need for multiple trips into and out of the wellbore makes conventional coring time consuming and relatively expensive. Further, as the location for obtaining core samples is selected before drilling through a zone of interest, the formation cannot be assessed using well logging techniques and the like and therefore the core samples often have little or no value in assessing the wellbore.  
         [0005]     Further, conventional wireline coring tools and technologies have imposed limitations regarding the retrieval of a useful length of continuous core, or can retrieve only very small samples of rock by means of trepan drilling or impacting perpendicularly into the wellbore wall.  
         [0006]     Sidetrack coring tools form independent offset boreholes by projecting below a reaming collar or deflection tool. The coring tube may become trapped in the offset borehole and may not be retrievable therefrom. Further, other problems occur as a result of penetration of zonal interfaces without means for sealing the offset borehole and formation of short boreholes formed along a curved trajectory which compromise the ability to harvest a long, continuous, undisrupted core sample therefrom.  
         [0007]     One form of coring assembly, set forth by Applicant in U.S. Pat. No. 5,103,921, suffers from some of the disadvantages of the prior art systems. A deflection crank at a lower end of a reaming and coring tube, contained within a reaming collar, and a universal ball joint at a top end of the reaming tube permit displacement of a lower end of the reaming tube for reaming a window into the main wellbore wall, after which the reaming tube projects below the reaming collar for cutting an angled offset borehole from which a core sample is obtained.  
         [0008]     An improved, cost effective and reliable window reaming and coring apparatus, which is capable of cutting and retrieving long cores having a sizeable cross-section and which are substantially continuous and representative of the lithography of the main wellbore, is required. Further, the apparatus should be readily tripped in and out of the wellbore without risk of the apparatus becoming stuck during reaming or coring. Preferably, cutting of the core samples should occur after the wellbore has been drilled and logged to ensure that the samples taken represent zones of interest along the wellbore.  
       SUMMARY OF THE INVENTION  
       [0009]     Apparatus and method are provided for milling a substantially parallel window or windows into the sidewall of an existing wellbore that is cased or uncased, using a single round trip of the apparatus. A reamer, connected between and upper and lower section of the apparatus by upper and lower lateral displacement means, receives lateral displacement force therefrom and is displaced laterally against the sidewall for milling the substantially parallel window. The laterally displaced, substantially parallel reamer may then be used to cut and retrieve a core or cores at zones of interest along the sidewall of the wellbore. The cores are crescent shaped, being scalloped or cut from the sidewall of the existing wellbore, are substantially continuous in length and have a sizable cross section for improved analysis. The length of the core is significant, being limited only by the length of a core retaining passage within the reamer. The core having been taken along the sidewall of the wellbore accurately reflects the lithography of the wellbore at the zones of interest. Further, as coring can now be performed after drilling the wellbore, the cores can be cut at zones of interest in the wellbore, identified previously by well logging and the like.  
         [0010]     In a broad aspect of embodiments of the invention apparatus for mounting on the end of a drill string having a rotatable distal end in a wellbore, the apparatus comprises: a reamer, at least a portion of which has a rotatable abrasive reaming tube thereon; a non-rotating lower lateral displacement means connected to a lower end of the reamer and operable to displace the reamer between a non-displaced position and a laterally displaced position; and an upper lateral displacement means adapted for connection to the rotatable distal end of the drill string and connected to an upper end of the reamer for driveably rotating the abrasive reaming tube and for displacing the reamer between a non-displaced position and a laterally displaced position; and a fluid passage through the upper lateral displacement means and the reamer for supplying drilling fluids from the drill string a downhole end of the abrasive reaming tube, and wherein when the lower and upper lateral displacement means are in the non-displaced position the reamer and abrasive reaming tube are aligned with the wellbore; and when the lower and upper lateral displacement means are actuated to the laterally displaced position, the reamer and abrasive reaming tube are positioned substantially parallel to the wellbore for milling a window in a sidewall of the wellbore.  
         [0011]     One embodiment of the apparatus is a tubular workstring or tool comprising three sections: an upper section adapted for connection to a rotatable distal end of a drill string, coiled tubing or the like from surface, a middle section comprising the reamer for milling the window and cutting and retaining a core sample therein and a lower section at the bottom of the workstring. The sections are interconnected by the upper and lower lateral displacement means, which, when actuated, laterally displace and maintain the parallel arrangement of the reamer against the side of the wellbore. The reamer is equipped with an outer reaming tube clad with an abrasive or abrasive protrusions, such as PDC cutters or the like. The reaming tube is rotatable relative to a non-rotataing inner section or mandrel which is connected to the non-rotatable upper and lower sections of the apparatus. Rotary motion is transferred to the reaming tube through drive means, located in the upper section. The reaming tube is rotatably supported and retained on the mandrel by bushings or bearings.  
         [0012]     The lower lateral displacement means, laterally displaces the reaming tube via a displacement crank or link which provides lateral force to a bottom end of the reaming tube in a particular direction. The lower section of the apparatus contains actuation means to actuate the lateral displacement means. Actuation may be by power generation means, such as by a hydraulic power unit generating hydraulic pressure via an accumulator, an electric motor, spring pressure or force from a motor-driven linear actuator. Preferably, the link is actuated through linear motion from a hydraulic ram powered by a hydraulic unit in the lower section of the apparatus.  
         [0013]     The upper section comprises a driveshaft having U-joints so as to enable parallel offset of the reaming tube. The bottom U-joint accommodates transferring of the drill string&#39;s torque to the rotatable reaming tube, provides drilling fluid flow to the reaming tube, and exerts push or pull to the reaming tube and lower section of the apparatus in the particular direction.  
         [0014]     The upper lateral displacement means comprises a spindle, extending from the drive means to engage the mandrel. Preferably, the spindle engages a biased socket in an axially shiftable housing to permit lateral displacement of the upper end of the reamer in the same direction as the lower end of the reamer. The axis of the socket is shifted similarly with the lower link action so as to direct the top of the biasing section in the direction of the lower link action.  
         [0015]     To achieve the parallel orientation of the reamer and to avoid a jack-knife effect, the lower and upper lateral displacement means straddling the reaming tube are connected through the mandrel. Preferably, the mandrel is a mechanical member running inside the apparatus along the entire length of the reamer and forms the fluid bypass conduit in the reaming tube for providing drill fluid to be circulated through the bottom of the reamer for removing cuttings and cleaning the hole.  
         [0016]     In a broad embodiment of a method of use, a method for milling a window in a wellbore comprises: providing a tool having a non-rotating lower section and an upper section and a reamer connected therebetween, the tool being positionable in the wellbore and each of the upper and lower sections being actuable between a non-displaced position aligned in the wellbore and a laterally displaced position parallel and offset from the wellbore; and positioning the tool in the wellbore; actuating at least the lower section to displace a lower end of the reamer; rotating an abrasive outer surface of the reamer to form a window in a sidewall of the wellbore; manipulating the tool uphole and downhole, as necessary, to lengthen the window and forming a parallel window substantially parallel to the wellbore; and actuating an upper section to displace an upper end of the reamer into the parallel window so that the reamer is positioned substantially parallel to the wellbore.  
         [0017]     In another broad aspect of the method for obtaining a core sample, wherein the reamer has a non-rotating mandrel extending therealong and having a core-receiving passage therein and wherein the rotating abrasive outer surface further comprises a coring head, the method further comprises: rotating the abrasive reaming tube about the mandrel; lowering the tool downhole from the window and into a zone of interest below the window to cut a crescent-shaped core from the sidewall of the wellbore; and receiving and retaining the crescent-shaped core into the mandrel&#39;s core-receiving passage. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is a partial longitudinal section view of a window reamer and coring apparatus according to an embodiment of the invention, shown having an abrasive reaming tube in an aligned position for tripping in or out of a wellbore;  
         [0019]      FIG. 2  is a partial longitudinal sectional view according to  FIG. 1  and shown having the abrasive reaming tube in a displaced position parallel to an axis of the wellbore;  
         [0020]      FIGS. 3   a  and  3   b  are partial sectional views of an upper section of the reaming and coring apparatus according to  FIG. 1  illustrating an upper lateral displacement means, particularly,  
         [0021]      FIG. 3   a  is shown in the aligned position; and  
         [0022]      FIG. 3   b  is shown in the displaced position;  
         [0023]      FIGS. 4   a  and  4   b  are partial sectional views of the abrasive reaming tube according to  FIG. 1 , connected to the upper section and to a lower section by lateral displacement means, more particularly,  
         [0024]      FIG. 4   a  is shown in the aligned position; and  
         [0025]      FIG. 4   b  is shown in the displaced position positioned substantially parallel to the wellbore;  
         [0026]      FIGS. 5   a  and  5   b  are partial sectional views of a lower section of the reaming and coring apparatus according to  FIG. 1  illustrating a lower lateral displacement means, more particularly,  
         [0027]      FIG. 5   a  is shown in the aligned position; and  
         [0028]      FIG. 5   b  is shown in the displaced position;  
         [0029]      FIG. 6  is a perspective view of a lower U-Joint of a drive assembly according to  FIGS. 1-4   b , illustrating lodging of a ball in a fluid passage for fluid actuation of a piston to shift the piston within a housing to permit lateral displacement of the abrasive reaming tube (the reaming tube omitted for clarity);  
         [0030]      FIG. 7   a  is a cross sectional view of the abrasive reaming tube according to  FIG. 4 , along section lines A-A, illustrating a core receiving passage and a fluid bypass passage, the fluid bypass passage being a manufactured conduit;  
         [0031]      FIG. 7   b  is a cross sectional view of the abrasive reaming tube according to  FIG. 4 , along section lines A-A, illustrating a core receiving passage and a fluid bypass passage, the fluid bypass passage being a solid structural element having a bore formed therethrough,  
         [0032]      FIGS. 8   a  and  8   b  are cross sectional views of the upper lateral displacement means according to  FIGS. 3   a - b , illustrating shifting of the piston within the socket for displacing the abrasive reaming tube laterally, more particularly,  
         [0033]      FIG. 8   a  is shown in the aligned position; and  
         [0034]      FIG. 8   b  is shown in the displaced position;  
         [0035]      FIGS. 9   a - b  are cross sectional views of the lower lateral displacement means according to  FIGS. 5   a - b , illustrating a link for lateral displacement of the abrasive reaming tube, more particularly,  
         [0036]      FIG. 9   a  is shown in the aligned position; and  
         [0037]      FIG. 9   b  is shown in the displaced position;  
         [0038]      FIGS. 10   a - e  are schematic views of a reaming operation wherein the reaming and coring apparatus is lowered into the wellbore while rotating a portion of the abrasive reaming tube, more particularly,  
         [0039]      FIG. 10   a  illustrates lowering the apparatus into the wellbore, the abrasive reaming tube in the aligned position;  
         [0040]      FIG. 10   b  illustrates lateral deflection of the abrasive reaming tube against a sidewall of the wellbore adjacent a zone of interest;  
         [0041]      FIG. 10   c  illustrates reaming of a parallel window in the wall of the wellbore by continuing to rotate the abrasive reaming tube;  
         [0042]      FIG. 10   d  illustrates a core cut from a bottom of the window and retained in a core retaining passage in the apparatus; and  
         [0043]      FIG. 10   e  illustrates the apparatus having the abrasive reaming tube aligned in the wellbore, the core retained therein, for removal from the wellbore;  
         [0044]      FIGS. 11   a - d  are schematic views of a reaming operation according to  FIGS. 10   a - c  and wherein the window is elongated by raising the reaming and coring apparatus while rotating the abrasive reaming tube, more particularly,  
         [0045]      FIG. 11   a  illustrates lowering the apparatus into the wellbore, the abrasive reaming tube in the aligned position adjacent a zone of interest;  
         [0046]      FIG. 11   b  illustrates lateral deflection of the abrasive reaming tube;  
         [0047]      FIG. 11   c  illustrates reaming of a parallel window in a wall of the wellbore by continuing to rotate the abrasive reaming tube while raising and lowering the apparatus; and  
         [0048]      FIG. 11   d  illustrates positioning the reaming and coring apparatus at a bottom of the parallel window to commence coring;  
         [0049]      FIGS. 12   a  and  12   b  are longitudinal cross sectional views of an alternate embodiment of the upper displacement means, more particularly,  
         [0050]      FIG. 12   a  is shown in the aligned position; and  
         [0051]      FIG. 12   b  is shown in the displaced position;  
         [0052]      FIG. 13  is a cross-sectional view of the apparatus in the wellbore having had a parallel window reamed therein and a crescent-shaped core retained in the apparatus; and  
         [0053]      FIGS. 14   a  and  14   b  are longitudinal cross sectional views of a lower end of the abrasive reaming tube illustrating core retaining means, more particularly,  
         [0054]      FIG. 14   a  illustrates a finger biased into the core receiving passage prior to receiving a core; and  
         [0055]      FIG. 14   b  illustrates the finger biting into or applying force to a core in the core receiving passage for retaining the core therein. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0056]     Having reference to  FIGS. 1-11   d , a window reaming and coring apparatus  1  is shown for mounting on the end of a drill string having a rotatable distal end  4 . One embodiment is shown schematically in  FIGS. 11   a - 11   d , wherein the apparatus  1  cuts along a sidewall of a wellbore in a formation for forming a window therein, at least a portion of the window being substantially parallel to the axis of the wellbore and along the sidewall of the wellbore, into which a portion of the apparatus  1  can be laterally displaced and subsequently used for cutting a core sample adjacent the sidewall of the wellbore.  
         [0057]     As shown in  FIGS. 1 and 2 , the apparatus  1  comprises a reamer  10  comprising a rotatable and abrasive reaming tube  11 , the reaming tube  11  having a bore  2  and a non-rotatable mandrel  12 , extending along the bore  2 . The rotatable reaming tube  11  is clad with cutting elements  13 , such as PDC buttons or the like, over at least a portion of an outer surface  3  of the rotatable reaming tube  11 .  
         [0058]     An upper section  20  of the apparatus  1  comprises upper lateral displacement means  21  which are adapted for connection to the drill string&#39;s rotatable distal end  4  through drive means  30  for driveably rotating the abrasive reaming tube  11  and to the non-rotatable mandrel  12  of the reamer  10  for urging at least an upper end  14  of the reamer  10  laterally, between an aligned, non-displaced position and a laterally displaced position.  
         [0059]     A lower section  40  of the apparatus  1  comprises non-rotating lower lateral displacement means  41  connected to a lower end  15  of the non-rotatable mandrel  12  and operable to laterally displace at least a bottom end  16  of the reamer  10 .  
         [0060]     Before the upper and lower displacement means  21 , 41  are actuated, and as shown in  FIGS. 3   a ,  4   a  and  5   a , the apparatus  1  is substantially linear and lies within a wellbore  100 ; After the upper and lower displacement means  21 , 41  are actuated, the reamer  10  is laterally displaced from the wellbore  100 , including up to the extent shown in  FIGS. 3   b ,  4   b  and  5   b.    
         [0061]     More particularly, the reamer  10  is actuable between a non-displaced position aligned with the wellbore ( FIGS. 1 and 4   a ) and a laterally displaced position offset from the wellbore ( FIGS. 2 and 4   b ). In the non-displaced position, the reamer  10  is aligned with the upper and lower sections  20 , 40  of the apparatus  1 , for running the apparatus  1  into an existing wellbore  100 . In the laterally displaced position, a least a portion of the reamer  10  is laterally displaced from the upper and lower sections  20 , 40 , and preferably the entire reamer  10  is laterally displaced to a position aligned substantially parallel to a common axis of the upper and lower sections  20 , 40 .  
         [0062]     In operation, as shown in  FIGS. 10   a - e  and  11   a - d , the apparatus  1  is lowered into the wellbore  100  to a position adjacent a zone of interest ( FIGS. 10   a ,  11   a ), such as immediately above the zone of interest. At least the lower displacement means  41  is actuated to cause the abrasive reaming tube  10  to be displaced laterally against a sidewall  101  of the wellbore  100  ( FIGS. 10   b , 11   b ). Displacement force, such as hydraulic or mechanically biased force, results at the upper lateral displacement means  21  and with compressive force applied through the drill string acts to urge the upper displacement means  21  to the laterally displaced position. The upper displacement means  21  orients the reamer  10  to the displaced position. The rotatable reaming tube  11 , supported and retained by bushings or bearings on the mandrel  12 , is rotated by the drive means  30  to cause the abrasive reaming tube  11  to ream a pocket or window  102  in the sidewall. Fluid, such as drilling mud, is conducted through a main fluid passage  55  extending through the upper lateral displacement means  21  of the apparatus  1  and exits through fluid ports  17  at the bottom end  16  of the reamer  10  to remove cuttings (not shown) generated from the reaming process and clean the wellbore  100 . For some operations, a short angular window ( FIGS. 10   b  and  11   b ) is sufficient such as to enable re-entry and drilling which is deviated from the original wellbore.  
         [0063]     In an operational embodiment to form parallel window  202 , as shown in  FIGS. 10   a - 10   c , the apparatus  1  can be positioned, displaced, and rotated to ream and extend the length of the window  102 . The window  102  is extended in length to form parallel window  202  which is sufficiently long and deep enough to permit maximum displacement of the upper and lower displacement means  21 , 41  and the reamer  10 .  
         [0064]     Optionally, to lengthen the Window  102 , and as shown in  FIG. 11   c , the apparatus  1  can be positioned, displaced and then lifted and lowered, as necessary during reaming to backream the side wall  101  for extending the length of the window  102 . Preferably, the window  102  is lengthened to form a parallel window  202  which is sufficiently long and deep enough to permit maximum displacement of the upper and lower displacement means  21 , 41 . In the parallel window  202 , the reamer  10  can be displaced so as to align substantially parallel to the axis of the wellbore  100 .  
         [0065]     As shown in both  FIGS. 10   c  and  11   d , once the reamer  10  is positioned parallel to the axis of the wellbore  100 , a coring operation may begin by advancing the apparatus  1  for cutting and receiving a core therein.  
         [0066]     In a preferred embodiment of the invention, as shown in  FIGS. 3   a  and  3   b , the upper section  20  of the apparatus  1  further comprises an uphole portion  22 , which remains aligned in a wellbore  100  pivotally connected through the drill string&#39;s distal end  4  to a driveshaft  23 , which is pivotally and driveably connected to the rotatable abrasive reaming tube  11  of the reamer  10 .  
         [0067]     The driveshaft  23  comprises an upper U-joint  31  being driveably connected to the uphole portion  22  and a bottom U-joint  32  being driveably connected to the rotatable outer surface  11 .  
         [0068]     The bottom U-joint  32  enables the reamer  10  to be operable between the aligned position and the displaced position relative to the uphole portion  22 . Axial compressive forces and rotation from the uphole portion  22  are transferred to the rotatable abrasive reaming tube  11  through the driveshaft  23  such as those imposed by the drill string (not shown) connected to the uphole portion  22 .  
         [0069]     As shown in  FIGS. 1, 2 ,  6  and in greater detail in  FIGS. 8   a - b , the upper displacement means  21  comprises a non-rotating housing  50  connected to an upper end of the mandrel  12  adjacent the driveshaft  23  for aligning the driveshaft  23  in the non-aligned position and misaligning the mandrel  12  from the driveshaft  23  in the laterally displaced position.  
         [0070]     In a preferred embodiment, the non-rotatable housing  50  is axially moveable within the reaming tube  10  between an uphole position and a downhole position. The abrasive reaming tube  11  is rotatable relative to the housing  50 . The housing  50  is operable to vary lateral force onto a spindle  33  extending downwards from the bottom U-joint  32  and thereby laterally displace the upper end  14  of the reamer  10 .  
         [0071]     The housing  50  further comprises a biased ramp or socket  51  for engaging and displacing the spindle  33 , the socket  51  being angled to achieve a desired direction of lateral displacement to enable lateral movement of the spindle  33  thereon as the housing  50  is actuated to shift from the uphole position to the downhole position. The spindle  33  remains freely rotatable in the socket  51  so as to permit rotation of the rotatable abrasive reaming tube  11  by the drive means  30 .  
         [0072]     In one embodiment, for shifting the housing  50  from the uphole position to the downhole position, a passage  52  is formed through the bottom U-joint  32  and spindle  33 . Further, a restricted fluid passage  53  is connected between the housing  50  and a fluid bypass conduit  60  formed in the mandrel  12  of the reamer  10 . In operation, and to aid in shifting the housing  50  from the uphole to the downhole position, a plug or small ball  54  is dropped from surface into the fluid flowing through the apparatus  1 . The small ball  54  passes through the passage  52  in the U-joint and spindle  32 , 33  and lodges in the main fluid passage  55  between the housing  50  and the reamer  10 , the blockage creating a pressure differential which acts on the housing  50 , like a piston, to shift the housing  50  to the downhole position and to divert the flow of fluids to the restricted fluid passage  53  and into the fluid bypass conduit  60 .  
         [0073]     Further, as shown in  FIGS. 5   a  and  5   b , the lower section  40  of the apparatus  1  comprises a downhole portion  42  which remains aligned in the wellbore  100  and an uphole portion  43  which is operable between the aligned position and the displaced position. In the preferred embodiment, as shown in  FIGS. 1, 2 ,  5   a - 5   b  and in greater detail in  FIGS. 9   a  and  9   b , the lower lateral displacement means  41  comprises a link  42  connected to the lower end  16  of the reamer  10  and more particularly to the mandrel  12  of the reamer  10 .  
         [0074]     The fluid bypass conduit  60 , shown in  FIGS. 7   a  and  7   b , extends from the top end  14  adjacent the housing  50  to the bottom end  16  of the reamer  10  and is non-rotating. The conduit  60  acts as a structural member to connect the non-rotating upper lateral displacement means  21  generally to the non-rotating lower lateral displacement means  41  and to assist in achieving parallel orientation of reamer  10  and to assist in avoiding a “Z” jack-knife effect. The fluid bypass conduit  60  may be a manufactured conduit as shown in  FIG. 7   a  or a solid structural member having a bore formed therethrough as shown in  FIG. 7   b . The rotatable reaming tube  11  is supported and retained thereon by bushings and bearings.  
         [0075]     The link  43  is connected at a first point  44  to actuation means  45  positioned in the uphole portion  42  of the lower section  40  of the apparatus  1 . More particularly, the link is connected to a ram  46  which may be actuated by hydraulics, an electric motor, an accumulator or a linear actuator or the like. Further, the link  43  is connected at a second point  47  to the bottom end  15  of the mandrel  12  of the reamer  10  and pivotally at a third point  48  to the uphole portion  42  of the lower section  40  of the apparatus. The link  43  is manipulated by the ram  46 , when actuated, to rotate about the third point  48  to displace the bottom end  16  of the reamer  10 , laterally.  
         [0076]     In the preferred embodiment, when hydraulic pressure is applied to the ram  46 , the linear motion of the ram  46  pivots the link  43  resulting in radial displacement of the bottom  16  of the reamer  10 , thus anchoring the apparatus  1  inside of wellbore  100  and exerting perpendicular force against the sidewall  101 .  
         [0077]     Having reference to  FIG. 13 , the extent of the maximal displacement of the reamer  10  is limited by the extent of motion of the upper and lower displacement means  21 , 41  and is preferably sized to obtain the maximum thickness of the core sample while still maintaining the fluid bypass conduit  60  therein. More preferably, the maximum displacement is about or greater than one half the diameter of the reamer  10  resulting in an oblong shaped wellbore  100  at the window  102 . Alternately, in an embodiment of the invention as shown in  FIGS. 12   a - b , the upper lateral displacement means  21  may comprise a splined housing  56  formed about the bottom U-joint  32  which is axially shiftable from an uphole position to a downhole position on a splined inner surface  57  of an upper portion of the reaming tube  10 . A wedge  58  is positioned below the bottom U-joint  32  and the spindle  33  extending therefrom. As load is applied to the drill string (not shown), the splined housing  56  and bottom U-joint and spindle  32 , 33  are shifted to the downhole position and the spindle  33  is driven down the wedge  58  to displace the upper end  14  of the reamer  10 , laterally.  
         [0078]     Optionally, the upper and lower lateral displacement means  21 , 41  can be actuated by applying weight onto the drill string (not shown). In order to actuate in this manner, the lower section  40  of the apparatus  1  must be first temporarily anchored in the wellbore  100  using anchors or packers and the like. Alternately, a tailpipe piece may be added to the lower section  40  of the apparatus  1  for bottoming in the wellbore  100 . Once anchored, weight applied to the apparatus  1  will cause the displacement means  21 ,  41  to be actuated and initiate the process of forming a window  102 . In order to continue to core, once the reamer  10  has been displaced, the anchors must be released to permit uphole or downhole reaming or coring movement of the apparatus  1 .  
         [0079]     Further, in certain circumstances reactive torque may be produced. The drill string (not shown) can be set on the bottom of the wellbore  100  to resist downhole and rotary forces. Otherwise, in order to initiate and maintain the displacement of the reaming tube and hold reactive torque-generated forces induced by rotary motion, the lower section can be equipped with apparatus such as anchors or packers for retaining the bottom section in relation to the wellbore.  
         [0080]     As shown in  FIGS. 10   d  and  10   e  and in a preferred operation, once the parallel window  202  has been reamed and the reamer  10  is fully displaced laterally relative to the remainder of the apparatus  1  and the wellbore  100 , a core sample  110  may be cut and retained therein.  
         [0081]     As shown in  FIGS. 4   a - b ,  7   a - b ,  9   a - b  and  13 , the rotatable abrasive reaming tube  11  of the reamer  10  comprises the mandrel  12 , containing the fluid bypass conduit  60  and a core receiving passage  61  formed therein. The core receiving passage  61  is crescent-shaped to correspond with a crescent-shaped core  110  cut from the sidewall  101  of the wellbore  100  as the reamer  10  advances therealong ( FIG. 13 ). Force applied to the apparatus  1  through the drill string and rotation of the rotatable abrasive reaming tube  11  cuts the crescent shaped core  110  which is received into the core receiving passage  61  as a continuous core  110 . The length of the core  110  is limited only by the length of the core receiving passage  61  and therefore the core  110  can be of significant length. During the coring process, fluid which has been diverted from the housing  50  into the fluid bypass conduit  60  exits through fluid ports  62  at the bottom end  15  of the reamer  10  into the wellbore  100  for cleaning debris resulting from the coring and for cooling the coring head  63 .  
         [0082]     Preferably, a diamond core-head  63 , is fitted to a bottom face  17  of the reaming tube  10  for cutting the core  110 . The coring proceeds at a bottom  103  of the window  102  by pushing the apparatus  1 , rotating the abrasive reaming tube  11  and circulating fluid therethrough.  
         [0083]     With reference to  FIGS. 14   a  and  14   b , core retaining means  70  are positioned adjacent a bottom end  64  of the core-receiving passage  61  for retaining the core  110  therein. In a preferred embodiment, the core retaining means  70  is a finger  71  biased outwardly by a spring  72  into the core receiving passage  61 . The core  110 , as it enters the passage  61 , forces the finger  70  to rotate uphole against a wall  65  of the core receiving passage  61 . Once the core  110  is fully received into the core receiving passage  61 , the biased finger  70  bites or otherwise exerts force onto the core  110 , retaining the core  110  in the core receiving passage  61 .  
         [0084]     Alternately, the core retaining means  70  may be a slip or dog (not shown) set in the wall  65  of the core receiving passage  61  and biased outwardly into the core receiving passage  61 .  
         [0085]     Once the core  110  has been cut, received and retained in the core receiving passage  61 , the lower displacement means  41  are actuated to retract the reamer  10 , containing the core  110 , into alignment with the axis of the wellbore  100 . Tension applied to the drill string causes the upper displacement means  21  to realign. Once aligned, the apparatus  1  is lifted to surface where the core  110  can be retrieved therefrom for analysis.