Abstract:
A packer and method and apparatus for releasing pressure within a pressurized annulus around the packer. The apparatus comprises a central tubular member having a central bore therethrough extending between first and second ends, an outer plug slidably locatable within a first end of the tubular member and having a central bore therethrough and an inner plug slidably locatable within the central bore of the outer plug. The method comprises longitudinally retracting the inner plug from sealed engagement within the central bore of the outer plug member so as to permit fluid to flow therethrough and engaging the outer plug with a retraction body operably connected to the inner plug extending adapted to engage the inner plug after a predetermined length of travel so as to draw the outer plug out of the central tubular member thereafter.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The present disclosure relates to methods and apparatus for isolating zones in a subterranean formation in general and in particular to methods and apparatus for releasing the pressure around sealing elements. 
         [0003]    2. Description of Related Art 
         [0004]    In hydrocarbon production, it is frequently desired to seal or isolate one or more zones of an oil well from adjacent zones. In such situations, a sealing element is frequently used to seal and isolate the production string to the main bore or to seal adjacent zones from each other. Such sealing elements may be components of a production packer, an open hole production packer, seal adapter, pressure chamber seal adapter (with charged high pressure chamber on board), a liner hanger packer, a full bore liner top packer, a straddle type stimulation tool, a hybrid type stimulation tools (hydroelement and mechanical packer), a hydroelement made from swellable rubber compounds, an open hole seal or a cased hole seal all of which may be mechanically, hydraulically, hydrostatically or pressure chamber operated. 
         [0005]    Production packers are designed to be located between the casing or liner and a working or production tubing in a well. In such conventional production packers, one difficulty that exists is that the packer may be difficult to remove or retrieve after they are set. One of the reasons for this is that such packers are designed to isolate one zone from another and will therefore in practice include a pressure differential across the packer. Such pressure differential is known to impair the ability of the packer to be removed. 
       SUMMARY 
       [0006]    According to embodiments there is disclosed an apparatus for releasing pressure within a pressurized annulus around a tool string of a well bore comprising a central tubular member having a central bore therethrough extending between first and second ends. The apparatus further comprises an outer plug slidably locatable within a first end of the tubular member and having a central bore therethrough and an inner plug slidably locatable within the central bore of the outer plug. 
         [0007]    The first end cap may be operably connected to the second plug such that axial movement of the end cap retracts the second plug from the central bore of the fist plug. 
         [0008]    The apparatus may further comprise a retraction member operably connected to and movable with the inner plug, the retracting member being adapted to engage the inner plug after a predetermined length of travel so as to draw the outer plug out of the central tubular member thereafter. The retraction member may comprise a retraction sleeve surrounding the inner plug along a parallel axis therewith. The retraction sleeve may include fluid flow passages therethrough. 
         [0009]    The retraction sleeve may surround the outer plug and includes an inwardly oriented lip positioned to engage a corresponding outwardly oriented lip on the outer plug. The outer plug may include a centralizer body extending therefrom adapted to maintain the outer plug in axial alignment with the central bore of the tubular member after the removal of the outer plug therefrom. 
         [0010]    According to embodiments there is disclosed a packer comprising a central tubular member having a central bore therethrough extending between first and second ends and a sealing element extending around the central tubular member adapted to be longitudinally compressed so as to axially expand the sealing element into contact with a surface of a well bore. The packer further comprises an outer plug slidably locatable within a first end of the tubular member and having a central bore therethrough and an inner plug slidably locatable within the central bore of the outer plug. 
         [0011]    The packer may further comprise a first end cap operably connected to the second plug such that axial movement of the end cap retracts the second plug from the central bore of the fist plug. The packer may further comprise a retraction member operably connected to and movable with the inner plug, the retracting member being adapted to engage the inner plug after a predetermined length of travel so as to draw the outer plug out of the central tubular member thereafter. 
         [0012]    The retraction member may comprise a retraction sleeve surrounding the inner plug along a parallel axis therewith. The retraction sleeve may include fluid flow passages therethrough. The retraction sleeve may surround the outer plug and includes an inwardly oriented lip positioned to engage a corresponding outwardly oriented lip on the outer plug. The outer plug may include a centralizer body extending therefrom adapted to maintain the outer plug in axial alignment with the central bore of the tubular member after the removal of the outer plug therefrom. 
         [0013]    The sealing elements may comprise a plurality of tubular elements disposed annularly around the central member. The tubular elements may include annular springs encased therein. 
         [0014]    The packer may further include top and bottom extrusion blocks disposed annularly around the tubular member to opposed sides of the sealing element. The top extrusion block may include an extended portion lip to engage a corresponding lip extending radially outwardly from a body secured to the inner plug after a predetermined length of travel so as to draw the top extrusion block upwards thereby releasing the sealing element. 
         [0015]    According to embodiments there are disclosed methods for releasing pressure within a pressurized annulus of a well bore comprising providing an outer plug slidably locatable within a first end of the tubular member and having a central bore therethrough and providing a inner plug slidably locatable within the central bore of the first plug. The methods further comprise longitudinally retracting the inner plug from sealed engagement within the central bore of the outer plug member so as to permit fluid to flow therethrough and engaging the outer plug with a retraction body operably connected to the inner plug extending adapted to engage the inner plug after a predetermined length of travel so as to draw the outer plug out of the central tubular member thereafter. 
         [0016]    The method may further comprise engaging a top extrusion block of surrounding the tubular member with the retraction body after a predetermined length of travel so as to draw the top extrusion block back thereafter. 
         [0017]    Other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    In drawings which illustrate embodiments wherein similar characters of reference denote corresponding parts in each view, 
           [0019]      FIG. 1  is a cross-sectional view of a wellbore having a liner hanger according to a first embodiment located therealong. 
           [0020]      FIG. 2  is a perspective view of the packer according to a first embodiment. 
           [0021]      FIG. 3  is a cross sectional view of the packer of  FIG. 2 . 
           [0022]      FIG. 4  is a detailed cross view of the extending arms of the packer of  FIG. 2  at a first position. 
           [0023]      FIG. 5  is a detailed exploded view of arms of the packer of  FIG. 2  at a second position. 
           [0024]      FIG. 6  is a detailed plan view of the indexing slots of  FIG. 2 . 
           [0025]      FIG. 7  is a detailed layout of the indexing slots of  FIG. 2 . 
           [0026]      FIG. 8  is a detailed cross view of the extending arms of the packer of  FIG. 2  at a second position. 
           [0027]      FIG. 9  is a detailed perspective view of first end of the packer of  FIG. 2  at a first position. 
           [0028]      FIG. 10  is a detailed perspective view of first end of the packer of  FIG. 2  at a second position. 
           [0029]      FIG. 11  is a detailed perspective view of first end of the packer of  FIG. 2  at a third position. 
           [0030]      FIG. 12  is a side view of the packer of  FIG. 2  located within a well at an expanded position. 
           [0031]      FIG. 13  is a detailed cross sectional view of the first and second unloader stage according to a further embodiment of the present disclosure. 
           [0032]      FIG. 14  is a detailed perspective view of the collet arms according to a further embodiment of the present disclosure. 
           [0033]      FIG. 15  is a detailed perspective view of the sealing elements of the packer of  FIG. 2  according to a further embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Referring to  FIG. 1 , a wellbore  10  is drilled into the ground  8  to a production zone  6  by known methods. The production zone  6  may contain a horizontally extending hydrocarbon bearing rock formation or may span a plurality of hydrocarbon bearing rock formations such that the wellbore  10  has a path designed to cross or intersect each formation. As illustrated in  FIG. 1 , the wellbore includes a vertical section  12  having a valve assembly or Christmas tree  14  at a top end thereof and a bottom or production section  16  which may be horizontal or angularly oriented relative to the horizontal located within the production zone  6 . After the wellbore  10  is drilled a production string  18  is located therein with at a packer  20  to isolate a zone  19  within the well. 
         [0035]    With reference to  FIGS. 2 and 3 , a packer according to a first embodiment is illustrated generally at  20 . The packer  20  extends between first and second ends,  22  and  24 , respectively, and is formed around a central tubular member or mandrel  26 . The central mandrel  26  includes the second end  24  which is operable to have a production string  18  connected thereto according to known methods such as threading and the like. As illustrated the packer  20  includes gripping arm slips  40  proximate to the second end  24 , a release section  100  proximate to the first end  22  and at least one seal element  90  between top and bottom extrusion blocks,  92  and  94 . 
         [0036]    Turning now to  FIG. 3 , a cross sectional view of the packer  20  is illustrated. The packer  20  includes an elongate central mandrel  26  extending between first and second ends,  28  and  30 , respectively. The second end  30  of the mandrel forms the second end  24  of the packer. The mandrel  26  rotatably supports a collet arms  72  and the gripping arm slips  40  therearound as will be more fully described below. 
         [0037]    Turning now to  FIG. 4 , a detailed cross sectional view of the slip  40  is illustrated. The slip  40  comprises a plurality of longitudinally extending arms  42  extending in a direction generally towards the first end  22  of the packer. The arms  42  have proximate  43  and distal ends  44  wherein the distal ends have outwardly oriented bore engaging surfaces  48  as are commonly known and an inner angled surface  46 . The arms  42  include a notch  41  on the outside surface thereof for receiving a portion of the cage therein as will be more fully described below. As illustrated, the arms  42  extend substantially parallel to the mandrel  26 . With reference to  FIG. 5 , the arms  42  may be located within slots  50  of a slip cage  52  so as maintain a relative position and alignment of the arms  42  around the mandrel  26 . The arms  42  may be retained within the slip cage  54  by locating a portion  56  of the slip cage between the slots  50  and the top end of the slip cage. As illustrated. The arms  42  are also maintained proximate to the slip cage  54  with a slip housing  58  extending therearound. The slip housing  58  includes bores therethrough to permit the removal of debris from between the arms and the mandrel. 
         [0038]    As illustrated in  FIG. 4 , each arm includes at least one bore  64  in a bottom thereof sized to receive a biasing pin  66  with a corresponding spring  68 . The bores  64  are located with the inwardly oriented surface of the arms between the notch  41  and the proximate ends  43 . The biasing pins  66  extend from the bores  64  to engage upon the slip housing so as to bias the arms to a retraced position. 
         [0039]    The slip  40  includes a cone  60  associated therewith comprising a tubular body slidably located around the mandrel  26 . The cone  60  includes an angled trailing surface  62  corresponding to the bottom surface  46  of the arms  42 . 
         [0040]    The slip  40  further includes a drive housing  70  located towards the second end  24  of the packer  20 . The drive housing  70  comprises a tubular body engaging with and abutting against the slip housing  58  and the slip cage  52  so as to be operable to move the slip housing, slip cage and arms longitudinally along the mandrel. The drive housing further includes a plurality of longitudinally extending collet arms  72  extending in a direction towards the second end  24  of the packer. The collet arms include a radially extended contact surface  74  and are radially flared from the packer as illustrated in  FIGS. 2 and 3  so as to cause the contact surface  74  to engage upon the liner of the wellbore and cause drag therewith. The contact surfaces  74  may be substantially the same width as the collet arms  72  or may optionally have tapered edges as illustrated in  FIG. 14  to provide additional space for fluid flow therepast. 
         [0041]    As illustrated in  FIG. 4 , the drive housing includes a plurality of pins  76  extending radially inwardly therefrom which are received with in a profiled groove  78  on the outside surface of the mandrel. With reference to  FIG. 6  a perspective view of the mandrel  26  is illustrated. The profiled groove  78  extends around the mandrel  26  and includes a plurality of indexing notches  80  located along the edge towards the second end  24  of the packer. The profiled groove  78  further includes alternating long and short slots,  82  and  84 , respectively along the edge towards the first end  22  of the packer. The indexing notches  80  are arranged to be located intermediate the long and short  82  and  84  slots with angled walls  86  and  88  on one side thereof each so as to cause the pins  76  to be alternatingly advanced between the long and short slots as the mandrel is cycled forwards and backwards relative to the drive housing as illustrated in  FIG. 7 . When the pins  76  are located within the short slots, the drive housing will be prevented from moving towards the first end  22  of the packer thereby preventing the arms  42  from being extended. When the pins  76  are located within the long slots  84 , the drive housing  70  will be permitted to move towards the first end  22  thereby extending the arms  42 . 
         [0042]    With reference to  FIG. 3 , the packer  20  includes seal elements  90  located around the mandrel  26  at a position towards the first end  22  from the arms  42  between the top and bottom extrusion blocks  92  and  94 . The bottom extrusion block is secured to the cone  60  and the top extrusion block is secured to the mandrel  26 . As illustrated in  FIG. 8 , when the pins  76  are located within the long slots  84  and the mandrel pressed toward the second end  24 , the arms  42  will extend engaging the well bore wall. Further pressure applied to the mandrel  26  toward the second end  24  will press compress the mandrel  26 , seal elements  90  and top extrusion block towards the second end  24  of the packer so as to compress the seal elements  90  between the top and bottom extrusion blocks  92  and  94  thereby expanding the seal into contact with the well bore wall as illustrated in  FIG. 12 . As illustrated in  FIG. 15 , the seal elements may include at least one annular spring element  95  therein providing a radially non-compressible core in each seal element so as to prevent the seal element  90  from extruding past the top or bottom extrusion block. The seal elements  90  may also include a spacer therebetween  93 . As illustrated in  FIGS. 3 , the packer may include 3 seal elements  90  however it will be appreciated that more or less than 3 may also be utilized. 
         [0043]    Turning now to  FIG. 9 , the release section  100  located proximate to the first end  22  of the packer  20  is illustrated. The release section includes a top collar  102  forming the first end  22  of the packer. The top collar  102  may include a threaded bore  104  into the end thereof for connection to the production string as is commonly known. The release section  100  includes a bypass mandrel  106  secured to the top collar  102  with first and second bypass plugs,  108  and  110  respectively. The first and second bypass plugs  108  and  110  are adapted to sequentially permit an increasing amount of material past the packer as will be more fully described below. 
         [0044]    As illustrated in  FIGS. 9 through 11 , the bypass mandrel  106  is secured to the top collar  102  at a first end  112  of thereof. The first bypass plug  108  is secured with within a bore  114  at a second end  116  of the bypass mandrel by fasteners  118  or the like. The first bypass plug  108  comprises a body having a cylindrical seal section  120  with at least one seal  122  extending therearound which is sized to be sealably received within a corresponding bore  130  of the second bypass plug  110 . As illustrated in  FIG. 9 , the first bypass plug  108  may include two seals, however it will be appreciated that one or three or more seals  122  may also be utilized as illustrated in  FIG. 13 . 
         [0045]    The second bypass plug  110  comprises a tubular body extending between first and second ends,  132  and  134  respectively and having a central bore  130  extending therethrough. The second bypass plug  110  includes a cylindrical seal section  136  extending from the second end  134  with at least one seal  138  extending therearound. As illustrated in  FIG. 9 , the second bypass plug  110  may include two seals, however it will be appreciated that one or three or more seals may also be utilized. The central mandrel  26  includes a central bore  140  sized to sealably receive the seal section  136  of the second bypass plug  110  therein. The second bypass plug  110  may include a centralizing extension  142  extending therefrom for maintaining the second bypass plug  110  in axial alignment with the central mandrel  26  when the second bypass plug  110  is removed therefrom as illustrated in  FIG. 11 . As illustrated in  FIG. 13 , the first bypass plug  108  may also include a radiued annular flange  115  sized and shaped to be sealably received against a corresponding filleted recession  117  in the first end  132  of the second bypass plug  110  around the central bore  130  thereof. When the first bypass plug  108  is engaged within the central bore  130  of the second bypass plug  110 , it will be appreciated that the annular flange  115  will bear against the recession to provide an additional seal therebetween. 
         [0046]    With reference to  FIG. 10 , when a user wishes to release the packer, the top collar  102  is drawn in a direction generally indicated at  160  away from the second end  24  of the packer. The top collar  102  pulls the bypass mandrel  106  with it drawing the first bypass plug  108  so as to disengage it from the central bore  130  of the second bypass plug  110  thereby permitting full flow of material therethrough in a direction generally indicated at  170 . The bypass mandrel  106  includes an extension sleeve  144  with a distal interior ridge  146 . The interior ridge  146  is adapted to engage a corresponding exterior ridge  148  on the first end  132  of the second bypass plug  110 . When the travel of the top collar  102  and bypass mandrel  106  engages the interior ridge  146  upon the exterior ridge  148 . As illustrated in  FIG. 11 , subsequent movement of the top collar  102  and bypass mandrel  106  will also draw the second bypass plug  110  so as to disengage it from the central bore  140  of the central mandrel  26  thereby permitting full flow of material therethrough in a direction generally indicated at  172 . 
         [0047]    As illustrated in  FIG. 11 , the central mandrel  26  includes and extension sheath  150  extending from the first end  28  thereof. The extension sheath includes an interior ridge  152  at a distal end  156  thereof adapted to engage an exterior ridge  154  on the bypass mandrel  106 . When the top cap  102  and bypass mandrel  106  reaches a sufficient distance for the interior and exterior ridges  152  and  154  to engage each other, the extension sheath  150  and thereby the central mandrel  26  will be drawn in the retraction direction as well. It will be appreciated that movement of the central mandrel  26  will cause the cone  60  to be pulled away from the arms  42  thereby permitting the arms to disengage from the well bore wall as well as decompressing the sealing elements. Thereafter the entire packer  20  may be removed or repositioned as desired. If the packer  20  is desired to be repositioned, it may be positioned at the desired location in the well and a downward force applied 
         [0048]    While specific embodiments have been described and illustrated, such embodiments should be considered illustrative only and not as limiting the disclosure as construed in accordance with the accompanying claims.