Abstract:
A casing patch includes a deformable seal configurable to a deformed and undeformed position for sealing and unsealing respectively with a target stub and a pressure based subsystem in operable communication with the deformable seal. The patch may also contain a stop ring to prevent overcompression of the seal.

Description:
BACKGROUND 
       [0001]    Casing patches have long been used in the hydrocarbon recovery industry in conjunction with a repair to a tubing or casing segment in a wellbore. It will be understood that the term “casing patch” as used herein is intended to relate to both patches actually in the casing of a wellbore and patches that are in a tubing string for a wellbore. 
         [0002]    It is to be assumed for purposes of this disclosure that a faulty section of casing or tubing has already been cut out of the well and the “stub”, i.e., the piece left downhole, and to which the casing patch will be connected, has been dressed. 
         [0003]    Prior art casing patches have included Chevron seals and lead based seals but these have drawbacks such as damage to the Chevron type seals during engagement with the stub as they are exposed to the sharp edge thereof and such as the one time operation of the lead seal type, among other things. 
       SUMMARY 
       [0004]    A casing patch includes a deformable seal configurable to a deformed and undeformed position for sealing and unsealing respectively with a target stub and a pressure based subsystem in operable communication with the deformable seal. 
         [0005]    A casing patch includes a body, at least one slip system at the body, at least one seal actuatable in response to actuation of the slip system and a stop ring located at the seal to prevent overcompression thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
           [0007]      FIG. 1  is a schematic quarter section view of a casing patch in an unactuated position; 
           [0008]      FIG. 2  is a schematic quarter section view of the embodiment of  FIG. 1  a casing patch in an actuated position; 
           [0009]      FIG. 3  is a schematic quarter section view of another embodiment of a casing patch in an unactuated position; 
           [0010]      FIG. 4  is a schematic quarter section view of the embodiment of  FIG. 3  in an actuated position; and 
           [0011]      FIG. 5  is a view of an alternate bottom sub with dressing features. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    In order to enhance understanding of the invention applicants have elected to describe briefly the components of the tool followed by a discussion of its operation. 
         [0013]    Referring to  FIG. 1 , a casing patch  10  as disclosed herein is illustrated in an unactuated position. It is in this position that the device is stored and run in the hole prior to engagement with a stub (introduced and numbered hereunder) in a wellbore. 
         [0014]    The patch  10  comprises a housing  12  that includes several features. One of the features is an anchor system comprising slip ramp  14  extending from housing  12 . The ramp  14  is in one embodiment a unitary structure of the housing and includes two ramp faces  16  and  18 . These, in the illustrated embodiment are generally frustoconically shaped and are configured to complementarily guide and support a plurality of slips. It is to be understood that at least one of the plurality of slips will hold in an uphole direction (uphole slips  20 ), and at least one of the plurality of slips will hold in the downhole direction (downhole slips  22 ), when actuated. The slips may be cut with a left hand thread if desired to promote removal of the patch from the well if desired. In some embodiments of the patch several slips will hold in each direction, when actuated. 
         [0015]    In the illustrated embodiment, a biasing member  24 , which may be a spring, gas charged member, or another member which itself is driven to extend, urges slips  20  to climb ramp  16  thereby causing slip(s)  20  to move in a direction to bite into a stub  26  with which the patch  10  is to engage. Slips  20  therefore are automatically engaged with the stub  26  when the patch  10  comes in engaging contact therewith. 
         [0016]    Another feature of housing  12  is a pressure channel  28  that is formed within the housing  12  as illustrated or may be attached thereto as a separate structure, if desired. The channel  28  has the function of providing a pressure passageway to a volume changeable chamber  70 (seen only in  FIG. 2 ) through port  30 , which is connected by channel  28  to inlet port  32 . 
         [0017]    The housing further includes, as illustrated, a pressure relief port  36  and a toothed section  38  complementary to a body lock ring  40  mounted at an end housing  42  of a seal  44 . The body lock ring functions to maintain a compression load on the seal  44  that is created by application of pressure to port  30 . Simultaneously as the compression load is applied to the seal, the fluid supplied through port  30  to chamber  70  exerts a driving force on a drive piston  46  to actuate slips  22 . Thus it will be appreciated that although the slips  20  are actuated automatically upon engagement with the stub  26 , the slips  22  require input from a remote pressure source to actuate. 
         [0018]    Additionally connected to the housing  12  a top sub  50  at an uphole end of the housing  12  and a bottom sub  52  at a downhole end of the housing  12 . 
         [0019]    Further included in the illustrated embodiment of the casing patch  10  is a piston  54  that is moveable from (1) a position in which it inhibits application of pressure to pressure inlet  32  to (2) a position where application of pressure to port  32  is permitted. A release arrangement  56 , which may be a shear member, such as for example a shear ring, is installed to restrain movement of the piston  54  until the opportune time. That time comes when the stub  26  is fully engaged by the patch  10  when set down weight of the patch on the stub  26  (taken up by the piston  54 ) causes the release member  56  to release. 
         [0020]    Referring now to  FIGS. 1 and 2  together, illustrating both a run in and actuated position, respectively, operation of the patch  10  is addressed. Upon running the patch in the hole, the patch encounters stub  26 . It is noted that the illustration hereof presents the stub  26  at the inside dimension of the patch  10 . It is to be appreciated however that the patch could be constructed inside out and then would engage a stub  26  located at an outside dimension of the patch. The components and general principle of operation are identical for the two concepts. In the illustrated embodiment, a leading edge  60  of stub  26  is enveloped by the advancing patch  10  in a more or less clearance fit until the stub  26  encounters slips  20 . Slips  20  are driven somewhat uphole (left in figure) and radially outwardly on ramp  16  by contact with the stub  26  but against the urging of biasing member  24 , which as noted above may be of any type including a coil spring as illustrated. Because of the biasing action of the member  24 , the slips  20  bite into stub  26  and tend to bite more deeply as well as climb ramp  16  radially inwardly upon a pull uphole on patch  10 . Slips  20  thus effectively prevent movement uphole by patch  10 , once engaged. 
         [0021]    Further downhole movement of patch  10  brings edge  60  into contact with a contact face  62  of piston  54 . Contact plus further movement downhole of patch  10  causes a growing load to be placed upon piston  54  and release member  56 . Since piston  54  is releasably retained by release member  56 , piston  54  will not move until a predetermined load is reached. Upon the predetermined load being reached however the release member  56  releases. In the illustrated embodiment, since the release member is a shear ring, the ring shears allowing piston  54  to move to the position illustrated in  FIG. 2 . It should be noted that because biasing member  24  bears against piston  54 , consideration must be given to the length of displacement of piston  54  in a given tool to ensure that a sufficient biasing force remains on slips  20  after release of the release member and consequent movement of piston  54 . 
         [0022]    Upon movement of piston  54 , port  32  is newly exposed to hydrostatic pressure having been protected therefrom by piston  54  and seals  64  prior to movement of piston  54 . Since hydrostatic pressure (or pressure-up pressure) is calculable or otherwise known for the target depth, the differential pressure needed at the volume changeable chamber  70  illustrated in  FIG. 2  is calculable. It is to be appreciated that what is necessary is that the applied fluid pressure through channel  28  be higher than the environmental pressure surrounding chamber  70  so two movements occur. The movements are simultaneous in an uphole direction for the drive piston  46  (moving uphole) and in a downhole direction for the seal end housing  42  (moving downhole). These movements, in turn, cause certain desirable functions of the patch to occur. The driver piston  46  urges downhole slip(s)  22  to climb ramp  18  moving thus radially inwardly of the housing  12  and uphole to engage the stub  26  and prevent or significantly retard downhole movement of the patch  10  relative to the stub  26 . Simultaneously, end-housing  42  loads the seal  44  to cause engagement with the stub  26  due to an opposite end of the seal  44  being blocked from movement downhole by bottom sub  52 . A seal is also maintained at an inside surface  72  of housing  12 . It is to be noted that because seal  44  is a clearance fit while initially engaging the stub  26 , it is not subject to damage during original engagement of stub  26 . The sealing action is maintained against both the stub  26  and the housing inside surface  72  by the movement inhibiting action of the body lock ring  40  against threads  38  in the housing  12 . In this condition, the seal is maintained indefinitely and the patch is secured. 
         [0023]    In one embodiment the seal is a metal seal, which then forms a metal-to-metal seal between the patch and stub when actuated. In such embodiment, high pressure differentials are easily supported. It is to be understood however that if desired, an elastomeric material or other seal material could be substituted in the patch disclosed. In one metal seal embodiment, three sections  76 ,  78 ,  80  (as shown) are utilized and are disposed in angular position relating to one another. This configuration facilitates deformation of the seal into an actuated position when subjected to compressive load. Alternatively, the seal may have a more cylindrical configuration and include lines of weakness in the material of the seal. Effective lines of weakness are positioned at an inside apex of a deformation site (a place where the metal is angularly configured as shown) such that if the line of weakness is a groove, the groove would close upon actuation of the seal; or if the line of weakness is material weakness based, the material would flow to allow the same movement direction to be achieved. Embodiments of metal-to-metal seals that may be utilized in the casing patch described herein include those disclosed in U.S. Pat. No. 6,896,049 to Moyes, which is incorporated herein in its entirety by reference. 
         [0024]    Alluded to above is the ability the system has to be removed from the well. This is possible in one embodiment by the provision of slip teeth that are left hand threads. If such has been manufactured into the patch, then neutral weight and right hand torque, will effectively unscrew the patch from the stub  26  thereby allowing retrieval of the patch to surface or to another location. 
         [0025]    In another embodiment, referring to  FIGS. 3 and 4 , stub  26  will be recognized from  FIGS. 1 and 2  but the balance of that illustrated in  FIGS. 3 and 4  is different. The casing patch  110  embodiment of  FIGS. 3 and 4  includes a body  112 , attached to which is a bottom sub  114  and a top sub  116 . Adjacent bottom sub  114  is a seal structure  118 , which may as in previously discussed embodiment be a metal-to-metal seal and may in some embodiments be as disclosed in the &#39;049 patent previously incorporated herein by reference. Seal structure  118  includes end housings  120  and  122 , the latter of which is inclusive of a body lock ring groove  124  that is receptive to a body lock ring  126 . The body lock ring  126  is interactive with a ratchet thread  128  located appropriately (as shown) on an inside dimension of the body  112 . Ring  126  is configured to ratchet along ratchet thread  128  in a direction causing seal  118  to be energized and then held in that position. Seal  118  further includes a stop ring  129  to physically prevent over compression of the seal  118 . 
         [0026]    Adjacent end housing  122  is positioned a slip sleeve  130  which is movably disposed at the inside dimension of the body  112 . Sleeve  130  is positioned between ratchet thread  128  and a stop shoulder  132  provided at the inside dimension of body  112 . The shoulder  132  may be integrally formed as shown or may be created with a device such as a snap ring, etc. 
         [0027]    Slip sleeve  130  further includes an angled face  134  that is configured to “slip” in one direction and “stick” in the opposite direction. In the event a thread is used as the surface feature that causes the slip and stick, then the sleeve  130  may be backed off and the casing patch retrieved by “unscrewing” the same using right or left hand rotation of a string (not shown) as appropriate. The top sub  116  is attached to body  112  at an uphole end thereof by suitable connection such as a thread  138 . 
         [0028]    Finally, the casing patch  110  includes a slip  140  and friction pad  142 . The pad  142  is configured to tightly grip against the target stub  26  while the slip interacts with angled face  134  through its own angular surface  144 . Slip  140  is further possessed of a ratcheting arrangement  146  at the interface of surface  144  and face  134  such that movement occurs relative to sleeve  130  in one direction but is inhibited in the opposite direction. 
         [0029]    In operation, this embodiment of a casing patch  110  is run on a string (not shown) to depth to interact with stub  26 . It is to be appreciated that stub  26  may be previously dressed conventionally or may be dressed at the same time as the casing patch  110  is being run if the casing patch is configured with an alternate bottom sub  114   a  (shown in  FIG. 5 ). Sub  114   a  includes as illustrated carbide or other similar hard material abrasive elements  150  that are capable of machining the stub  26 , during run-in rotation, to a precise outside diameter to ensure appropriate sealing thereto. 
         [0030]    Whether dressed in a separate run or dressed simultaneously, the casing patch  110  is run over the stub  26  until top sub  116  comes into contact with stub  26  at edge  60  thereof. This is the position illustrated in  FIG. 3  prior to actuating the patch. Once casing patch  110  is fully seated (as illustrated in  FIG. 3 ) and the slip  140  is urged into engagement with the stub and the slip sleeve  130  by stop shoulder  132  (and the resilient nature of the slip in the radial direction due to longitudinal cuts alternating from the top and bottom of the slip, not specifically shown), the patch is pulled uphole. The uphole pull causes the slip sleeve  130  to leave contact with stop shoulder  132  as it moves toward bottom sub  14  due to the slip  140  being “stuck” to the stub  26 . The movement of slip sleeve  130  toward bottom sub  114  causes a shortening of the dimension between sleeve  130  and sub  114  thereby impacting the available axial space for seal  118 . Seal  118  is thus compressively axially loaded between sub  114  and sleeve  130  thereby deforming the same into contact with stub  26 . The deformation is intended to and is capable of creating a high-pressure seal with stub  26 . In the event seal  118  is metal it is as described hereinbefore, the resulting seal is a metal-to-metal seal. Axial loading on the seal  118  is ensured by the body lock ring  126  acting upon thread  128  due to being forced therealong by sleeve  130 . Comparison of  FIGS. 3 and 4  side-by-side will complement the immediately foregoing discussion of the operation of the device.