Abstract:
A wellbore packer and slip combination for production tubing and the like comprises a plurality of slip elements that are caged together around the periphery of a cylindrical mandrel. An axially displaced actuator simultaneously engages all of the elements to ramp one end of all elements against a casing wall. After the one end of the slip and packer unit is set, further displacement of the actuator expands the other end of the elements against the casing wall. The packer and slip assembly may be retracted and recovered by a simultaneous lift and rotation of the tool string.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a Continuation of U.S. patent application Ser. No. 09/598,830 entitled “Combined Sealing and Gripping Unit for Retrievable Packers” and filed on Jun. 21, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to the art of well drilling and earth boring. More particularly, the invention relates to packer devices for closing annular space between well tubing and well casing or the borehole wall.  
           [0004]    2. Description of Related Art  
           [0005]    Well production tubing, for example, is surrounded by an annular space between the exterior wall of the tubing and the interior wall of the well casing or borehole wall. Frequently, it is necessary to seal this annular space between upper and lower portions of the well depth. Appliances for accomplishing the sealing function are known in the well drilling arts as “packers”. Traditionally, the sealing element of a packer is a ring of rubber or other elastomer that is in some manner secured and sealed to the interior well surface which may be the interior casing wall or the raw borehole wall. By compression or inflation, for example, the ring of rubber is expanded radially against the casing or borehole wall.  
           [0006]    As an incident to the sealing function of a packer, the annular space sealing apparatus must be secured at the required position along the well length. The position securing operation is characterized in the art as “setting”. Packers are usually set by a mechanism known to the art as a “slip”. Slips are wedging devices in which a pair of ramped or tapered surfaces are mutually engaged to increase the combined dimension of radial thickness. Resultantly, a hardened surface penetration element such as serrated edges, teeth or diamond points are, by an axially directed force such as by hydraulic pressure or screw threads, pressed radially into a surrounding casing wall or borehole wall.  
           [0007]    With but few exceptions, packer and slip devices are separately placed and engaged. Consequently, the physical size and length of a prior art tool string is long and expensive. Since each device is engaged separately, the complete engagement procedure is protracted. It is, therefore, an object of the present invention to combine the gripping and sealing elements of a downhole tool into one unit that is deployed in one procedural operation.  
           [0008]    Another object of the present invention is a well packer unit that is shorter and requires less total movement or stroke for actuation. Shorter tool length also facilitates downhole placement and borehole navigation through tight borehole positions.  
           [0009]    Also an object of the invention is a gripping/sealing tool having relatively few component parts that are less expensive to manufacture, require less interaction between the cooperative elements and allows an inventory reduction.  
           [0010]    A further object of the invention is a symmetrical gripping/sealing system that may be set from either direction thereby making it possible to use many of the same components for a wireline set device (set from above) and a hydraulically set device (set from below).  
           [0011]    Other advantages of the invention include a substantial elimination of body movement during actuation thereby permitting hydraulically set tools to be set more closely to one another without affecting the tubing or the other tools. Moreover, the invention gripping features extend substantially around the entire circumference of the tool thereby spreading the gripping forces more evenly across the casing ID and directly into the casing wall.  
         SUMMARY OF THE INVENTION  
         [0012]    These and other objects of the invention are accomplished by a plurality of wicker faced slip elements that are loosely aligned around the perimeter of a cylindrical mandrel as sectors of a cylinder. Each slip element is saddle-shaped with the wicker faces on both ends and a saddle seat in between. A full-circle caging ring has an inside diameter sufficient to slide over the O.D. of a cylindrical tool mandrel. A plurality of axially oriented slots cut radially into the caging ring from the I.D. span the slip element saddle seats to loosely confine the respective slip elements. A peripheral slot from the I.D. around the middle of the caging ring accommodates a belt spring that biases the slip elements collectively against a cylindrical body surface. Full circle packer seals fitted around deformable metal base rings fit, collectively, over both ends of the slip elements. The slip element assembly is confined between two, oppositely facing ramps. One ramp is integral with to the tool body. The other ramp is advanced axially toward the fixed first ramp by a sliding push ring. The push ring is driven by an axially directed force such as hydraulic pressure or a threaded lead advance. The push ring directly engages a plurality of keys that are confined in slots to axial movement. Each key is secured to the caging ring by a threaded, set-screw type of shear fastener. The caging ring bears directly upon the saddle seat wall of each slip element. Consequently, upon initial advancement of the push ring, the entire assembly slides axially as a unit against the fixed ramp. Further advancement of the push ring slides the slip element end that is contiguous with the fixed ramp along and radially out from the fixed ramp to engage inside surface of a well casing.  
           [0013]    Continued closure of the sliding ramp toward the fixed ramp shears the fasteners between the slip elements and the caging ring. Thereby released, the sliding ramp may advance under the other end of the slip element and wedge it radially against the casing I.D.  
           [0014]    The slip and packer seal assembly may be retracted and recovered by a simultaneous lifting and rotation of the tool string. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    Preferred embodiments of the invention are described by reference to the drawings wherein like reference characters are used to describe like or similar elements throughout the several figures of the drawings and:  
         [0016]    FIG. 1  is an orthographic elevation of the invention in assembly with downhole tubing;  
         [0017]    [0017]FIG. 2 is an isometric view of the slip and packer section of the invention.  
         [0018]    [0018]FIG. 3 is an exploded assembly section of the invention;  
         [0019]    [0019]FIG. 4 is a half cylinder section of the invention at an initial setting for running into a well;  
         [0020]    [0020]FIG. 5 is a half cylinder section of the invention at a partially deployed setting;  
         [0021]    [0021]FIG. 6 is a half cylinder section of the invention at a fully deployed setting in a maximum casing bore;  
         [0022]    [0022]FIG. 7 is a half cylinder section of the invention at a fully deployed setting in a minimum casing bore; and,  
         [0023]    [0023]FIG. 8 is a half cylinder section of the invention at a fully retracted setting. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    The elevation view of FIG. 1 illustrates the invention in a downhole environment as a intermediate tool sub  10  near the bottom end of a tubing string  16  and above a downhole operational tool  18 . The central core of the invention  10  is a mandrel  20  having an integral joint box  12  at the upper end and a pin  14  at the lower end. Traditional with industry convention, the box  12  carries an internal tapered thread and the pin  14  carries an external tapered thread.  
         [0025]    Between the box  12  and pin  14 , the mandrel is turned to provide a stepped abutment face  23  and a closely proximate  0 -ring seal channel  66 . Further down the mandrel length are one or more fluid flow ports  21  that traverse the mandrel wall. Below the fluid flow ports  21  is an inner pickup ring  52  that preferably circumscribes the mandrel. Below the pickup ring  52  is an assembly thread  44 .  
         [0026]    Concentrically overlying the substantially cylindrical mandrel  20  and in juxtaposition with the abutment face  23  is a tool body  22  having a conical ramp  34  at the upper end and longitudinal splines  49  around the lower end. Adjacently above the splines  49  is an outer pickup ring  50  that circumscribes the tool body  22 . Above the pickup ring  50  are one or more fluid flow ports  27  that penetrate the tool body wall. The outer turned surface of the body below the conical ramp  34  is cut by a plurality of shallow, longitudinal key slots  72  that are spaced substantially equally around the tool body circumference.  
         [0027]    Also concentrically overlying the mandrel  20  below the tool body  22  is an annular piston  24  having mating end splines  49  for an axial slip fit with the splines  49  of the tool body  22 . Below the end splines  49  is a circumferential rib  29  that carries an O-ring seal  58 . The lower end of the piston  24  carries an internal O-ring  64  that seals with the outer surface of the mandrel  20 . Approximately midway between the ends of the piston  24  are internal assembly threads  44  that mate with corresponding threads on the mandrel  20 . The outer surface of the piston  24  carries external ratchet threads  62  to receive a body lock ring  28  having internal ratchet threads to match threads  62  on the piston surface.  
         [0028]    Concentrically overlying the piston  24  is a cylinder  26  having the lower end thereof secured by assembly threads  60  to the body lock ring  28 . The upper end of the cylinder  26  is attached by assembly threads  47  to a push ring  30 . The internal volume of a fluid pressure chamber  46  is sealed by O-rings  54 ,  56 ,  58 ,  64  and  66 .  
         [0029]    Oppositely, below the ramp face of the upper cone  34  is a sliding conical sleeve  32 . A pressure face of the sleeve  32  is separated from the pressure face of the push ring  30  by a plurality of ring springs  31 . Between the opposing ramp faces is the packer seal  42  and slip  35  assembly.  
         [0030]    With respect to FIGS. 2 and 3, in particular, the internal geometry of a circumferential cage ring  38  includes a circumferential belt slot  74 . At uniform angular stations around the internal circumference of the cage ring  38  are a plurality of longitudinal saddle slots  76 . Each of the saddle slots  76  receives the bridging bar  78  of a slip set  35 . Each slip set includes a pair of wickers (teeth)  36 ; a wicker set at each end of the bridging bar  78 . The opposite distal ends of the slip sets mesh with full circle packer seals  42  and  43  comprising elastomer or rubber rings molded to deformable metal rings  40 . A circular belt spring  39  traverses the belt slot  74  and overlies the slip set bridging bars  78  to bias the slip sets  35  against the outer surface of the tool body  22 . Keys  70 , respective to each of the slots  72  and the number of slip sets  35 , are attached directly to the cage ring by shear screws  37 .  
         [0031]    Relative to FIG. 4, the invention is prepared for downhole deployment with the cylinder  26  and push ring  30  retracted from the slip sets  35 . The body lock ring  28 , in fixed assembly with the lower end of the cylinder  26 , is turned along the ratchet threads  62  to the desired position that places the cooperative train of components in loosely assembled contact.  
         [0032]    When located at the desired downhole position, the internal bore of the upper tubing string  16  is pressurized to transmit fluid pressure to the internal bore  17  of the mandrel  20 . Fluid pressure within the mandrel bore  17  is further transmitted through the fluid flow ports  21  and  27  into the pressure chamber  46 . Pressure forces within the chamber  46  are exerted upon the internal edge of the push ring  30  thereby advancing the push ring against the prestress of ring springs  31 . Collapse of the ring spring prestress drives the component train against the lower cone  32  and the cone  32  into the lower edge of the keys  70 . The keys  70  are structurally linked to the cage  38  by the shear screws  37 . Consequently, displacement of the keys  70  along the key slots  72  in the tool body  22  drives the cage  38  against the upper wicker set  36  and upper packer seal  42  along the ramp of upper cone  34  as shown by FIG. 5. Simultaneously, the body lock ring  28  is forcibly advanced over the rachet threads  62  which are ratchet biased to allow overhaul slippage of the body locking ring  28  in the up-hole direction but to oppose overhauling in the down-hole direction.  
         [0033]    As the upper wicker set  36  and upper packer seal  42  advances along the ramp of upper cone  34 , the wicker  36  and seal  42  are also advanced radially against the internal casing wall  11  or borehole wall whichever may be the case. When the structural limit of radial displacement is reached, continued pressure increase within the chamber  46  imposes sufficient force on the screws  37  to shear the screw diameter. Shear failure of the screws  37  decouples the keys  70  from the cage  38  and permits the lower cone  32  to advance under the lower wicker set  35  as shown by FIGS. 6 and 7. Displacement of the lower cone  32  ramp under the lower wicker set  35  expands the lower wicker set and lower packer seal  43  against the casing wall  11  without releasing the seal or grip secured by the upper seal  42  or wicker set  36 .  
         [0034]    Release of the packer seal and slip structure from the associated casing or borehole wall is illustrated by FIG. 8. The upper tubing string  16  is simultaneously lifted and rotated. This surface controlled manipulation of the tubing string rotates the mandrel assembly threads  44  over those of the piston  24 . Note that the keys  70  and slots  72  transmit rotational counter torque between the casing wall anchored slip wickers  35  and  36  to the tool body  22 . The end spline joint  49  transmits torque countering force onto the piston  24 . Hence, as the mandrel assembly threads are rotated against the piston  24  threads, the piston is displaced axially in the downhole direction. Continued rotation of the tubing string  16  advances the circumferential rib  29  of the piston  24  against the bottom end of the cylinder bore  26 .  
         [0035]    As the mandrel  20  is lifted against the wicker grip on the casing wall and the assembly thread  44  is rotated beyond relative engagement, the tool body  22  is released to slip axially along the mandrel  20  until the mandrel counterbore base  68  engages the inner pickup ring  52 . Simultaneously, the inner edge of the push ring  30  engages the outer pickup ring  50 . These pickup ring abutments prevent the assembly from being drawn axially further along the mandrel  20  and release the radial loads on the slip wickers  35  and  36 . Due to the standing bias of the belt spring  39 , the slips are extracted from the casing wall and returned to the retracted position.  
         [0036]    In a non-illustrated, purely mechanical embodiment of the invention, the push ring  30  is advanced axially along a thread lead against the ring springs cone  32  by rotation of the tubing string  16 . Distinctively, however, the vertical orientation of the invention is preferably reversed to dispose the rotational drive elements of the invention more proximate of the surface.  
         [0037]    Although the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the scope and spirit of the present invention. For example, those of ordinary skill in the art will recognize that a threaded screw mechanism may be substituted for the hydraulic fluid and piston mechanism described herein for forcibly displacing the sliding sleeve member  32 .