Abstract:
A method and apparatus for allowing a downhole drill string to be stuck at one location and continue to rotate above the stuck section. The apparatus provides a method for collapsing the stuck subassembly by reducing its outside diameter. Simultaneous with the subassembly collapse, a jarring action is initiated from within the drill string to further loosen the stuck sections. At the same time drilling fluid inside the string is allowed to circulate outside the string through a circulation sub. The fluid is forced around the stuck subassembly further increasing the likelihood that the subassembly will be freed.

Description:
[0001]     This application claims priority to pending U.S. Provisional Patent Application No. 60/395,739 filed Jul. 10, 2002. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to an apparatus and method for loosening a stuck section of a downhole drill string within a well borehole. More particularly, but not by way of limitation, the present invention relates to collapsing a subassembly along a section of a rotatable drill string to reduce the subassembly&#39;s outside diameter while at the same time initiating within the string a jarring action or force that resonates along the entire drill string and simultaneously allowing drilling fluid inside the drill string to circulate to the outside of the string within the well borehole. All of the structural features and actions of the present invention cooperate to collapse a sub-section of the drill string allowing upstream sections to continue to rotate within the borehole. The collapsing subassembly may be a drilling stablizer, a reamer, or even a casing scraper. In some applications, the collapsing subassembly need not be stuck to activate the natural jarring actions and the circulating features of the present invention.  
         [0003]     A drill string is used to drill a subterranean well bore. The drill string typically consists of multiple joints of drill pipe, drill collars, and a drill bit. To facilitate completion of the well, it is important that deviation from vertical be controlled. In the past, deviation of the well bore has been controlled by the manipulation of the string weight on the drill bit or directional control tools, such as mud motors and monel collars. The length, weight, and outside diameter of the drill collars help maintain stabilization while applying a sufficient amount of weight on the bit to affect bit penetration. However, too much weight on the bit may result in hole deviation problems.  
         [0004]     Additional equipment has been used to stabilize the drill string. These devices are commonly known as stabilizers. These tools have a larger outside diameter than the drill collars and are in constant rotational contact with the sidewall of the well bore during the drilling process. The problem with stabilizers is that the contact between the stabilizer and the well bore can be the source of many problems. For example, penetrated, soft formations may collapse or swell inwardly after penetration of the bit which may in turn cause the stabilizer to become stuck. In addition, water loss in some formations may cause excessive mud cake buildup on the wall of the well bore which can also cause sticking to occur.  
         [0005]     There are times when other subassemblies other than stabilizers get stuck, slowing or stopping the drilling process. Sometimes reamers which are cutting a larger bore above the drill bit bore become lodged in the walls of the formation. Occasionally, a casing scraper used to clean an in place casing run also becomes stuck within the casing. These problems are tremendously costly to correct with current technology. Often the drill string must be left downhole and the well bore redrilled.  
         [0006]     Further, if a subassembly does become stuck, this can lead to the drill string becoming stuck in several additional locations along the string if rotation of the drill string and circulation of drilling fluid is not maintained. The present invention allows the stuck subassembly to cease rotating while the sections above the stuck one continue to rotate. Further, it may be difficult to free the drill string from being stuck if the point of sticking is not known, and the process of determining the sticking point is expensive and time consuming.  
         [0007]     To this end, a need exists for a subassembly that is capable of being selectively collapsed to reduce its outside diameter if the sub becomes stuck thereby possibly eliminating the point of sticking. A need further exists for a drill string that is capable of maintaining circulation and rotation above the point of sticking to prevent further sticking of the drill string. Further, there is a need to be able to jar the string internally when stuck, and to be able to locate where along the string the subassembly is stuck. It is to such an apparatus that the present invention is directed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1A  is an elevational view, partly in cross section, showing a drill string constructed in accordance with the present invention installed in a well bore in a drilling position with an upstream pipe section attached to the subassembly and showing a bit.  
         [0009]      FIG. 1B  shows a lower portion of the subassembly of the present invention in the drilling mode from the bit crossover section to above the spacer mandrel without showing a bit or the well bore.  
         [0010]      FIG. 1C  shows an upper portion of the subassembly of the present invention in the drilling mode from the leaf barrel to the mandrel top sub without showing the upstream drill string section on the well bore.  
         [0011]      FIG. 2A  illustrates an elevational view, partly in cross section, showing the drill string in the released position with the drill string left off the bottom of the well bore.  
         [0012]      FIG. 2B  shows a position of the subassembly of the present invention in the released mode from the bit crossover section to leaf barrel.  
         [0013]      FIG. 2C  shows a portion of the subassembly of the present invention in the released mode from the leaf barrel to the mandrel top sub.  
         [0014]      FIG. 3A  is a partial, cutaway, isometric view of a bit crossover.  
         [0015]      FIG. 3B  is an elevational view, partially in cross section, of the bit crossover.  
         [0016]      FIG. 4A  is a cutaway, isometric view of a circulating sub.  
         [0017]      FIG. 4B  is an elevational view, partially in cross section, of the circulating sub.  
         [0018]      FIG. 5  is an isometric view of a spline housing.  
         [0019]      FIG. 6  is an isometric view of another embodiment of a spline hosuing.  
         [0020]      FIG. 7  is a cutaway, isometric view of a spacer housing.  
         [0021]      FIG. 8A  is an isometric view of a leaf barrel.  
         [0022]      FIG. 8B  is a cutaway, isometric view of the leaf barrel.  
         [0023]      FIG. 8C  is a cross-sectional view taken along line  8 C- 8 C of  FIG. 8A .  
         [0024]      FIG. 9A  is an isometric view of a centralizing leaf.  
         [0025]      FIG. 9B  is a side elevation view of one of the centralizing leaves.  
         [0026]      FIG. 10  is an isometric view of a trip ring.  
         [0027]      FIG. 10B  is an elevational view, partially in cross section, of the trip ring.  
         [0028]      FIG. 11  is a cutaway, isometric view of a trip ring retainer.  
         [0029]      FIG. 12A  is a cutaway, isometric view of a mandrel.  
         [0030]      FIG. 12B  is an elevational view, partially in cross section, of the mandrel.  
         [0031]      FIG. 12C  is a detail view of the trip ring and anvil taken from A in  FIG. 12A .  
         [0032]      FIG. 13A  is an isometric view of a spacer mandrel.  
         [0033]      FIG. 14A  is a cutaway, isometric view of a spline mandrel.  
         [0034]      FIG. 14B  is an elevational view, partially in cross section, of the spline mandrel.  
         [0035]      FIG. 14C  is an end view of the spline mandrel taken along line  14 C- 14 C of  FIG. 14 .  
         [0036]      FIG. 15A  is a cutaway, isometric view of a stinger.  
         [0037]      FIG. 15B  is a split, elevational view, partially in cross section, of the stinger.  
         [0038]      FIG. 16  is an elevational view of another embodiment of a drill string containing a plurality of stabilizers constructed in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]     Referring to  FIGS. 1A and 2A , a portion of a drill string  10  constructed in accordance with the present invention, is shown incorporated in an overall drill string  12  located downhole within a well bore hole  14 . Although a single section  10  is illustrated as being attached to the string  12  between drill collar  16  and drill bit  18 , it should be understood that single or multiple sections may be attached to the string  12  as discussed below.  
         [0040]      FIG. 1A  illustrates the string  12  in a drilling mode with the weight of the drill string  12  applied to the bit  18  and the entire string  12  being rotated by a drilling rig (not shown) or the bit  18  may be independently rotated by a mud motor. In the drilling mode, a collapsing subassembly  11  engages the side wall of the well bore  14  to maintain a substantially vertical orientation. In  FIG. 1A , the subassembly  11  is a stabilizer wherein leaves  34  are extended against the sidewall. As previously stated, the leaves  34  may be replaced by a reamer or scraper mechanism.  
         [0041]      FIG. 2A  shows the string  12  in a non-drilling mode wherein the subassembly  11  has been tripped, the leaves  34  have collapsed to a release position away from the sidewalls, and the subassembly longitudinal extended initiating an internal jarring action within the drill string and circulation of drilling fluid via holes  72  from inside the subassembly  11  to outside the subassembly and into the well bore hole, and allowing for continued rotation of the drill string sections above the tripped subassembly.  
         [0042]     The subassembly  11  includes a housing assembly  20  and a mandrel assembly  22  that is adapted for telescopic movement relative to the housing assembly  20 . The housing assembly  20  includes a bit crossover  24 , a circulating sub  26 , a spline housing  28 , a spacer housing  30 , a leaf barrel  32 , a plurality of centralizing leaves  34 , and a trip ring retainer  36 . The mandrel assembly  22  includes a mandrel top sub  23 , centralizing mandrel  82 , a spacer mandrel  84 , a spline mandrel  86 , and a stinger  88 .  
         [0043]     Turning to  FIGS. 1B and 1C , the bit crossover  24  has an external threaded portion  38  for connection with the drill bit  18  or another member of the drill string  12 , such as a drill collar. The crossover  24  is provided with an annular recess  40  for receiving the stinger  88  portion of the mandrel assembly  22 , as discussed below, and a second threaded portion  39  for connection with the circulating sub  26 . Additionally, it should be understood that the bit crossover  24  may be provided with a plurality of circulating parts (not shown) and a sliding sleeve activated by a drop bar to facilitate circulation of drilling fluid without the need to move the subassembly  11  to the released position.  
         [0044]     The circulating sub ( FIGS. 4A and 4B ) is provided with a plurality of holes  42  to permit the release of drilling fluid when the subassembly  11  is in the released condition. The holes  42  may be provided with accessories, such as check valves or tungsten inserts. The circulating sub  26  is further provided with a plurality of annular grooves  44  for receiving an O-ring and a pair of grooves  46   a  for receiving seal members, such as a polypak type seal. The upper end of the circulating sub  26  is provided with an internal shoulder  47  for supporting a jarring wear ring  49 . The upper end of the circulating sub  26  is connected to the spline housing  28 .  
         [0045]     The spline housing  28  is provided with a plurality of involute splines or teeth  48  extending longitudinally along the interior surface of the spline housing  28 .  FIG. 6  illustrates another embodiment of a spline housing  28   a  having a plurality of equi-spaced splines or teeth  48   a . The upper end  23  of the spline housing is connected to the spacer housing  30 .  
         [0046]     As shown in  FIG. 7 , the spacer housing  30  is an elongated tubular member having a bore  50 . Each end of the spacer housing  30  is provided with an annular groove  52   a  and  52   b  for receiving an O-ring. The upper end of the spacer housing  30  is connected to the leaf barrel  32 .  
         [0047]     As shown in  FIGS. 8A through 8C , the leaf barrel  32  is provided with an internal shoulder  56  for supporting another wear ring  49  (see  FIG. 4B ). The upper end of the leaf barrel  32  is provided with an annular recess  80  for receiving a trip ring  81  ( FIG. 10A ). The leaf barrel  32  further includes a plurality of elongated slots  58  spaced circumferentially about the leaf barrel  32 . The slots  58  are adapted to receive one of the centralizing leafs  34  so that the centralizing leaves  34  are moveable through the slots  58  in a radial outward and inward direction, as will be discussed in greater detail below. The slots  58  are interrupted at medial locations by one or more bridges  77 .  
         [0048]     As shown in  FIGS. 9A and 9B , each of the centralizing leaves  34  has a first end portion  60  and a second end portion  62  which are adapted to be disposed in corresponding recesses  64  and  66  of the leaf barrel  32  ( FIG. 8B ). Each centralizing leaf  34  is provided with a wall engaging portion  68  which is formed at a medial portion of the leaf  34 . The external side of the wall engaging portion  68  is provided with a plurality of arcuate shaped grooves  70  to facilitate sliding engagement with the sidewall of the well bore  14  and permit fluid passage. It will be understood that the size and shape of the wall engaging portion  68  of the leaf  34  may be formed in a variety of shapes depending on the functional requirements. For example, the wall engaging portion  68  can be configured to function as a reamer or a casing scraper.  
         [0049]     The interior side of each centralizing leaves  34  is provided with a cam surface  72 . The centralizing leaves  34   b  are provided with medial grooves  78  adapted to receive the bridges  77  of the leaf barrel  32   a  to stabilize the centralizing leaves  34   b  in the expanded condition.  
         [0050]     The trip ring  81  ( FIG. 10A ) is retained in the annular recess  80  of the leaf barrel  32  ( FIG. 8B ) by the trip ring retainer  36 , best shown in  FIG. 11 .  
         [0051]     Referring again to  FIGS. 1-1B  and  2 - 2 B, the housing assembly  20  forms a housing for the mandrel assembly  22  which is adapted for telescoping movement relative to the housing assembly  20  between a drilling position and a released position. In the drilling position, the mandrel assembly  22  is positioned to force the centralizing leaves  34  of the subassembly  11  to move to the expanded position and to transfer torque applied to the mandrel assembly  22  by a drilling rig (not shown) to the housing assembly  20  and in turn to the drill bit  18 . In the released position, the mandrel assembly  22  allows the centralizing leaves  34  to move to the collapsed position, creates a jarring action (within the drill string portion  10 ) to the housing assembly  20  upon being released from the drilling position, is capable of rotating freely relative to the housing assembly  20 , and permits fluid circulation through the drill string  12  to be uninterrupted. To facilitate these functions, the mandrel assembly  22  includes a mandrel  82 , a spacer mandrel  84 , a spline mandrel  86 , and a stinger  88 .  
         [0052]     As shown in  FIGS. 12A and 12B , the mandrel  82  has an internal bore  90  extending therethrough from an upper end  83  to a lower end  89 . The upper end  83  of the mandrel  82  is provided with internal threads  91  for connection with a drill collar or drill pipe. Telescopic movement of the mandrel  82  relative to the centralizing leaves  34  causes the centralizing leaves  34  to move between the expanded position and the collapsed position. To affect the movement of the centralizing leaves  34  to the expanded position, the mandrel  82  is provided with a cam surface  94  near the lower end  89  thereof. The cam surface  94  cooperates with the cam surface  72  of the centralizing leaves  34  to force the centralizing leaves  34  radially outward to the expanded position upon telescopic contraction of the mandrel  82  into the housing assembly  20 . Upon telescopic expansion of the mandrel  82  from the housing assembly  20 , the elasticity of the centralizing leaves  34  causes the centralizing leaves  34  to return to the collapsed position. Contact of the centralizing leaves  34  with the sidewall of the well bore  14  may assist in returning the centralizing leaves  34  to the collapsed position.  
         [0053]     The mandrel  82  is further provided with an annular recess  96  sized to hold the trip ring  81  ( FIG. 10A ) so as to restrain longitudinal movement of the mandrel assembly  22  relative to the housing assembly  20  in the drilling position. The trip ring  81  is fabricated to be released from the annular recess  96  upon the application of a longitudinal pulling force on the drilling string  12  which translates into a predetermined axial force in the ring. The axial forces created in the trip ring  81  are determined by the length of the ring L; the thickness of the ring T; and, most significantly, the angle A of the trip ring edges and the angle of the shoulder  97  of the annular recess  96  of mandrel  82 . As will be described in more detail below, the pulling force required to overcome the predetermined axial force to “open” the trip ring  81  may be varied to provide an indication of where the drill string  12  is stuck in the well bore hole. It should further be appreciated that other retaining members can be used in place of a trip ring. For example, the housing assembly  20  may be provided with a friction grip collet quick release device which is adapted to mate with a corresponding recess in the mandrel  82 . Other friction trips or shear pins may be used, but one time trips have the disadvantage of requirement the drill string  12  to be withdrawn from the well hole.  FIG. 12C  illustrates the details of the trip ring operation.  
         [0054]     The lower end  89  of the mandrel  82  is connected to the upper end  93  of the spacer mandrel  84  ( FIGS. 13 ). The upper end of the spacer mandrel  84  is provided with a groove  98  to receive an O-ring so as to provide a fluid tight seal between the spacer mandrel  84  and the mandrel  82 . The lower end  101  is also provided with an annular groove  100  or receiving an O-ring. The spacer mandrel  84  has an internal bore  102  extending from the upper end  93  to the lower end  101 .  
         [0055]     The lower end  101  of the spacer mandrel  84  is connected to an upper end  103  of the spline mandrel  86  ( FIGS. 14A-14C ). The spline mandrel  86  is provided with an internal bore  104  extending from the upper end  103  to the lower end  107  thereof. The external surface of the spline mandrel  86  is provided with a plurality of splines or teeth  105  extending longitudinally along the external surface thereof. The splines  105  are sized and shaped to mate with the splines  48  of the spline housing  28  when the subassembly  11  is in the drilling position and thereby transmit rotational torque applied to the mandrel assembly  22  to the housing assembly  20 . When the subassembly  11  is moved to the released position, the spline mandrel  86  is in a non-engaging position relative to the spline housing as shown in  FIGS. 2A-2B . As such, the mandrel assembly  22  is capable of being rotated relative to the housing assembly  20 . If the housing assembly  20  is stuck, that portion of the drill string  12  extending above the housing assembly  20  may be rotated and hereby prevent additional portions of the drill string  12  from becoming stuck. To further facilitate rotation of the mandrel assembly  22  relative to the housing assembly  20 , the housing assembly  20  may be provided with load bearings (not shown) at the upper and lower ends of the leaf barrel  32  to centralize rotation of the mandrel assembly  22  and reduce friction.  
         [0056]     The ends  120  of the splines  105  are beveled to facilitate engagement with the spline housing  28  when the mandrel assembly  22  is moved from the released position to the drilling position. The beveled ends of the splines  105  additional prevent damage to the splines  105  upont he mandrel assembly  22  being released from the drilling position. That is, upon the release of the mandrel assembly  22  from the drilling position as a result of a pulling force being applied sufficient to overcome the tripping force of the trip ring  81 , the mandrel assembly  22  travels upwardly until the upper end  103  of the spline mandrel  86  impacts the wear ring  49  thereby producing a hammer type action within the subassembly  11  that may loosen or free the stuck drill string. The beveled ends  120  of the splines  105  also prevent damage to the splines  104  when the mandrel assembly  22  is moved to the drilling position. Upon initial engagement of the spline mandrel  86  with the spline housing  28 , the drill string  12  may be lowered to cause the lower end of the spline mandrel  86  to impact the adjacent wear ring  49  and produce a downward hammer type action that may loosen or free the stuck drill string.  
         [0057]     To further prevent damage to the spline mandrel  86 , the wear rings  49  are preferably fabricated of a material that is softer than the material from which the spline mandrel  86  is fabricated. Consequently, only the wear rings  49  need be replaced after each use of the subassembly  11 , rather than the spline mandrel  86 .  
         [0058]     The lower end  107  of the spline mandrel  86  is connected to an upper end  122  of the stinger  88 . The stinger  88  ( FIGS. 15A and 15B ) is an elongated pipe with an internal bore  106  extending from the upper end  122  to the lower end  124  thereof. The upper end  122  of the stinger  88  is provided with an annular groove  108  for receiving an O-ring so as to form a fluid tight seal between the upper end of the stinger  88  and the lower end of the spline mandrel  86 . The lower end of the stinger is provided with a pair of annular grooves  110  for receiving seal members  111  ( FIGS. 1 and 2 ) which are preferably pressure activated and which are capable of rotational sealing. The stinger  88  has a length such that the lower end  124  of the stinger  88  is positioned in the annular recess  40  of the bit crossover  24  when the subassembly  11  is in the drilling position. With the lower end of the stinger  88  positioned in the annular recess  40  of the bit crossover  24 , the seal members  111  form a fluid tight seal between the stinger  88  and the bit crossover  24  thereby providing a fluid conduit extending through the mandrel assembly  22  and through the bit crossover  24  to permit circulation to the drill bit  18 .  
         [0059]     When the mandrel assembly  22  is moved to the released position, the lower end of the stinger  88  is positioned above the holes  42  of the circulating sub  26 . As such, if the drill bit  18  is plugged or if a plug is inserted into the upper end of the bit crossover  24 , drilling fluid is capable of being circulated through the mandrel assembly  22  and out through the holes  42  of the circulating sub  26 . It should be noted that the internal diameter of the circulating sub  26  is greater than the outer diameter of the seal members  111  of the stinger  88  such that the seal members are in a non-compressed state which the mandrel assembly  22  is traveling between the drilling position and the released position. However, substantial circulation of drilling fluid to the drill bit  18  is again initiated upon the lower end of the stinger  88  being lowered below the holes  42  of the circulating sub  26 .  
         [0060]     Referring now to  FIG. 16 , a drill string  12  that includes stabilizers  10   a ,  10   b , and  10   c  is illustrated. As previously stated, the subassembly  11  maybe stabilizers  10   a ,  10   b , and  10   c ; or, alternatively, a reamer or casing scraper. In  FIG. 16 , the stabilizer  10   a  is located adjacent to a drill bit  18   a  with the stabilizers  10   b  and  10   c  shown to be spaced at approximately thirty to sixty foot intervals. The stabilizers  10   a - 10   c  are each provided with a trip ring  81  which is designed to release at different preset pulling forces. For example, the stabilizer  10   a  may be provided with a trip ring designed to release upon the application of a pulling force of 20,000 pounds above drill string weight, while the trip ring of the stabilizer  10   b  is designed to release at 40,000 pounds above drill string weight, and the trip ring of the stabilizer  10   c  is designed to release at 60,000 pounds above drill string weight.  
         [0061]     By utilizing stabilizers or any collapsing subassembly in the drill string with different trip settings, the approximate location that the drill string  12  is stuck maybe determined. If the drill string  12  becomes stuck and upon applying a pulling force of at least 20,000 pounds above drill string weight, and the stabilizer  10   a  releases, then it can be concluded that the drill string  12  is stuck at the housing assembly of the stabilizer  10   a  or lower. Likewise, if a pulling force greater than 40,000 pounds above drill string weight is required to release one of the stabilizers, then it can be concluded that the drill string  12  is stuck below the stabilizer  10   a  and the stabilizer  10   b . Finally, if a pulling force of 60,000 pounds above drill string weight is required to release one of the stabilizers, then it can be concluded that the drill string  12  is stuck between the bit  18   a  and the stabilizer  10   c . With the location of the sticking point identified, an appropriate treatment can be more easily designed and implemented.  
         [0062]     Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the inventions will become apparent to persons skilled in the art upon the reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention.