Patent Publication Number: US-7210533-B2

Title: Disposable downhole tool with segmented compression element and method

Description:
BACKGROUND 
   Methods and apparatus for preparing and treating a well, and more particularly to a disposable downhole tool with a segmented compression element and method are disclosed. 
   In treating and preparing a subterranean well for production, a packer or plug is often used to isolate zones of the wellbore. Packers and plugs are selectively expandable downhole devices that prevent or control the flow of fluids from one zone of the wellbore to another. For example, during production enhancement operations a packer or plug may be used to isolate a treatment zone from the remaining zones of the wellbore. 
   Packers and plugs are run into a wellbore on a work string. Seal elements are expanded radially to seal the packer or plug against the wellbore. The seal elements may be hydraulically or mechanically expanded. After a packer has been set, it seals the annulus of the wellbore to block movement of fluids through the annulus past the packer location. After a plug has been set, it seals the entirety of the wellbore to block the movement of fluids past the plug location. A plug may include a check value to permit flow in one direction while preventing flow in the other direction. Once set, packers and plugs typically maintain the sealing engagement against the wellbore until released. 
   Packers and plugs may be retrievable or drillable (millable). A retrievable tool is typically released from the wellbore by manipulation of the connected work string and then retrieved to the surface. A drillable tool may be composition cast-iron disposed of by inserting a drill bit or other drilling tool into the wellbore and mechanically breaking up the tool by drilling. 
   SUMMARY 
   A disposable downhole tool with a segmented compression element is provided for use in oil, gas, and other wells. The segmented compression element may in one embodiment be segmented prior to deployment of the disposable downhole tool. In another embodiment, the segmented compression element may be segmented downhole in response to setting or release of the disposable downhole tool or other downhole event. For example, the segmented compression element may be cut during or after setting. 
   In accordance with a particular embodiment, a disposable downhole tool includes a body and a compression element situated about the body. The compression element includes at least one preconfigured division at disposal of the disposable downhole tool, which may aid the disposal process. 
   More specifically, the compression element may in some embodiments include a plurality of preconfigured divisions segmenting the compression element into a plurality of segments. The segments may be substantially uniform in size and shape or may be differently configured. In specific embodiments, the preconfigured divisions may be at least partially preformed prior to deployment of the disposable downhole tool in the wellbore. In some of these and other embodiments, the preconfigured divisions may be at least partially formed downhole in a wellbore in response to a segmenting event. The segmenting event may be the setting of the disposable downhole tool, release of the disposable downhole tool, or other suitable event. 
   Technical advantages of one or more embodiments of the disposable downhole tool and method include providing a disposable downhole tool that can be readily disposed of in a wellbore without drilling. In a particular embodiment, one or more compression elements of the disposable downhole tool are segmented into a plurality of segments to aid the disposal process by, for example, preventing or reducing the likelihood of the compression element becoming lodged in the wellbore. The segments may be configured to sink to the bottom of the wellbore with a remainder or other part of the disposable downhole tool or may be removed by circulation of fluid in the wellbore. As a result, a packer, plug, or other suitable downhole tool may be disposed of in the wellbore without costly and time consuming retrieval or drilling operations. 
   Another technical advantage of one or more embodiments of the disposable downhole tool and method include providing a packer, plug, or other sealing tool with a segmented sealing element. The segmented sealing element may include a plurality of segmented compression elements. Divisions in the segmented compression elements may be offset from each other to prevent or reduce fluid flow through the sealing element. 
   Various embodiments of the disposable downhole tool and method may include all, some, or none of the above or elsewhere described advantages. Moreover, other technical advantages may be readily apparent from the following figures, descriptions, and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates one embodiment of a disposable downhole tool; 
       FIG. 2  illustrates one embodiment of a center compression element of the disposable downhole tool of  FIG. 1 ; 
       FIG. 3  illustrates one embodiment of an end compression element of the downhole disposable tool of  FIG. 1 ; 
       FIG. 4  illustrates one embodiment of segmentation of the compression elements of the disposable downhole tool of  FIG. 1 ; 
       FIG. 5  illustrates one embodiment of deployment of a disposable downhole tool in a wellbore; 
       FIG. 6  illustrates one embodiment of disposal of the disposable downhole tool of  FIG. 5 ; and 
       FIG. 7  illustrates one embodiment of a method for deploying and disposing of a disposable downhole tool. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates one embodiment of a disposable downhole tool  10 . In this embodiment, the disposable downhole tool  10  is a disposable well plug  12 . The disposable well plug  12  may be, for example, a free plug. In other embodiments, the disposable downhole tool  10  may be a disposable well packer or other disposable downhole device with an annularly expandable seal or other assembly with one or more compression elements. 
   Referring to  FIG. 1 , the disposable well plug  12  includes an elongated body  20 , a cage  22  at the upper end of the elongated body  20 , a spacer ring  24 , slips  26 , wedges  28 , extrusion limiters  30 , a sealing element  32 , and a mule shoe  34 . The slips  26 , wedges  28 , extrusion limiters  30 , and sealing element  32  as well as other components of the disposable well plug  12  may each be an annular element situated about the elongated body  20 . 
   A main longitudinal passageway  36  extends through elongated body  20  along the longitudinal axis and forms the interior of the elongated body  20 . The elongated body  20  is substantially longer than it is wide and may have a cross-section that is circular or otherwise suitably shaped. In the circular cross-section embodiment, the elongated body  20  is cylindrical. The elongated body  20  forms a frame for the disposable well plug  12  and may be formed of one or more pieces. The elongated body  20  may comprise a composite, magnesium, ceramic, or other suitable material for the disposable downhole tool  10 . The elongated body  20  and other elements of the disposable well plug  12  may be structural elements in that they provide strength, rigidity, or other characteristics for the disposable downhole tool  10 . 
   The cage  22  receives a ball  40 . The ball  40  seals in a ball seat  42  to prevent downward fluid flow and lifts from the ball seat  42  to allow upward fluid flow. Thus, the ball  40  prevents fluid flow downwardly through the main longitudinal passageway  36  of the elongated body  20 , but permits fluid flow upwardly through the main longitudinal passageway  36 . 
   The slips  26  may include an upper slip  26   a  and a lower slip  26   b.  The slips  26  may each be formed of a number of segments held in place by slip retaining rings  44 . The slips  26  may each comprise cast iron, composite, or other suitable rigid material. A rigid material is any material that is at least substantially rigid, substantially non-flexible, and/or essentially non-compressible. 
   The wedges  28  may include an upper wedge  28   a  and a lower wedge  28   b.  The wedges  28  each include a ramp for setting the corresponding adjacent slip  26  and are held in place by a pin  46 . The wedges  28  may be comprised of phenolic or other suitable rigid materials. 
   The extrusion limiters  30  may include an upper extrusion limiter  30   a  and a lower extrusion limiter  30   b.  The extrusion limiters  30  each include an anti-extrusion lip that engages the corresponding edge of the sealing element  32 . The extrusion limiters  30  may each be formed of a number of segments held in place by retaining rings  48 . The segments may comprise complex overlapping shapes and be formed of Phenolic or other rigid materials. 
   The sealing element  32  comprises a radially expandable seal assembly situated about the elongated body  20 . The sealing element  32  has an outer axial surface  49   a  and an inner axial surface  49   b . When the disposable well plug  12  is in a relaxed position, for example during positioning the disposable well plug  12  in a wellbore, a gap exists between the outer axial surface  49   a  of the sealing element  32  and the wall or casing of the wellbore. As described in more detail below, when the disposable well plug  12  is set in a wellbore, the sealing element  32  is compressed along the longitudinal axis of the disposable well plug  12  and expanded to form a seal between the elongated body  20  of the disposable well plug  12  and the casing  130  ( FIG. 5 ) of the wellbore. 
   In one embodiment, the sealing element  32  comprises one or more compression elements  50 . The compression elements  50  are each an elastic, compressive, and deformable element. The compression elements  50  may comprise any suitable material that deforms substantially or otherwise suitably under pressure or other application of force, that provides an annular or other suitable seal, and/or that stores energy when set. The compression elements  50  may be rubber or other suitable elastomer having a shore durometer A scale hardness above about thirty. For example, the compression elements  50  may be formed of nitrile rubber, AFLAS fluororubber, VITON rubber, and the like. Other suitable materials may be used depending on the temperatures and pressures to be experienced by the disposable well plug  12 . 
   In the illustrated embodiment, the sealing element  32  comprises a center compression element  52  bounded on each side by an end compression element  54 . In this and other embodiments, the compression elements  50  are each a pre-segmented annular sealing ring disposed about the elongated body  20  and held in place by one or more retaining rings  56 . The retaining rings  56  may be a flexible, rubber or other suitable o- ring, a flexible metal or other band, a garder or other suitable spring. The retaining rings  56  may also comprise any fracturable constraint, such as composite bands. The retaining rings  56  may extend completely, substantially, or partially around the end compression elements  54  and may be formed from one or more parts. Further details of the center compression element  52  and the end compression elements  54  are described in connection with  FIGS. 2–3 . 
   The compression elements  50  may in one embodiment vary in hardness in the longitudinal direction of the sealing element  32 . In this embodiment, the outermost or end compression elements  54  may be the hardest and the innermost or center compression element  52  the softer. In a particular embodiment, the end compression elements  54  may have a shore durometer A scale hardness of between about forty and about ninety-five. In this embodiment, the center compression element  52  may have a shore durometer A scale hardness of between about fifty and about seventy-five. 
     FIG. 2  illustrates details of the center compression element  52  in accordance with one embodiment. In this embodiment, the center compression element  52  is situated and configured to fit between the set of end compression elements  54 . It will be understood that the center compression element  52  may be otherwise suitably situated and/or shaped without departing from the scope of the present invention. 
   Referring to  FIG. 2 , the center compression element  52  may have a trapezoidal cross-sectional shape. In this embodiment, the major base of the trapezoid may be at an inside axial surface  80  of the center compression element  52 . As a result, the center compression element  52  is thicker, in the axial direction of the disposable well plug  12 , at the inside axial surface  80  than at an outside axial surface  82 . The axial direction of the disposable well plug  12  is the direction parallel to the longitudinal axis of the elongated body  20 . 
   The seams  84  of the center compression element  52  are substantially straight, and, as viewed in cross-section, diverge toward the inside axial surface  80  of the center compression element  52 . In one embodiment, the seams  84  may diverge on an acute, or shallow, angle. The center compression element  52  may be otherwise suitably shaped. 
     FIG. 3  illustrates details of the end compression elements  54  in accordance with one embodiment. In this embodiment, the end compression elements  54  bound the center compression element  52  and form the outermost layers of the sealing element  32 . 
   Referring to  FIG. 3 , the end compression element  54  has an inner axial surface  100  and an outer axial surface  102 . An inner seam  104  may be configured to abut and/or mate with the adjacent seam  84  of the center compression element  52 . An outer seam  106  of the end compression element  54  may be angled or otherwise configured to abut and/or mate with the corresponding edge of the extrusion limiter  30 . In a particular embodiment, the inner seam  104  may have an acute angle less than about ninety degrees and the outer seam  106  about a thirty-six degree angle. The end compression elements  54  may be otherwise suitably shaped. 
     FIG. 4  illustrates one embodiment of segmentation of the compression elements  50 . In this embodiment, the sealing element  32  comprises the center compression element  52  and the end compression elements  54 . Each of the center compression element  52  and end compression elements  54  are segmented into a plurality of segments  120  by preconfigured divisions  122 . 
   The one or more preconfigured divisions  122  are fully formed in the compression elements  50  at least at disposal of the disposable well plug  12 . Thus, the preconfigured divisions  122  may be partially or fully formed prior to deployment of the disposable well plug  12  or partially or fully formed during deployment of the disposable well plug  12 . In the latter embodiment, the preconfigured divisions  122  may be partially or fully formed in response to at least a segmenting event, which may be a disposal event such as destruction of a substantial part of the disposable well plug  12  or an operational event such as upon the setting and/or release of the disposable well plug  12 . 
   In a specific embodiment, the preconfigured divisions  122  may be fully formed prior to deployment of the disposable well plug  12  with the compression elements  50  held together by the retaining rings  56 , glue or other adhesive, interlocking geometry, or otherwise. Where an adhesive is used, the compression elements  50  may fracture downhole. Where an interlocking geometry is used, the compression elements  50  may release upon, for example, release of the disposable well plug  12 . 
   In another embodiment, for example, the preconfigured divisions  122  may be substantially formed prior to deployment and may be completed upon release of the disposable well plug  12  from a set position at disposal of the disposable well plug  12 . The preconfigured divisions  122  may be otherwise suitably formed in the compression elements  50  without departing from the scope of the present invention. 
   The preconfigured divisions  122  are preconfigured in that they are fully, substantially, or otherwise partly formed prior to deployment of the disposable well plug  12  or fully, substantially, or otherwise partially formed during deployment of the disposable well plug  12  in response to at least one predefined event designed to form or initiate formation or completion of the preconfigured divisions  122  at a point, area, or section of the compression element  50 . 
   The preconfigured divisions  122  may be a cut or other separation of part of a compression element  50  from another part of the compression element  50 . The preconfigured divisions  122  may be axial, lateral, longitudinal, straight, angled, curved, simple, complex, interlocking, wrapping, or otherwise. In one embodiment, the preconfigured divisions  122  are configured to allow segmentation of the compression elements  50  while preventing fluid from flowing through the sealing element  32  when the disposable well plug  12  is in the set position. 
   The segments  120  formed by preconfigured divisions  122  may be substantially uniform in shape or size or disparate from one another. The segments  120  may be directly or indirectly bound or otherwise held together or held in place relative to each other during deployment of the disposable well plug  12 . The segments  120  may have a specific gravity or be otherwise suitably configured to sink or rise in a wellbore. 
   Referring to  FIG. 4 , in the illustrated embodiment, the preconfigured divisions  122  are preformed in the center compression element  52  and the end compression elements  54  prior to deployment of the disposable well plug  12 . Also in this embodiment, the preconfigured divisions  122  are each a straight longitudinal cut, or divide, through a compression element  50 . As previously described, in other embodiments, the preconfigured divisions  122  may be substantially but not entirely preformed or otherwise partially preformed prior to deployment of the disposable well plug  12 . In this embodiment, the preconfigured divisions  122  in the compression elements  50  may be completed during deployment of the disposable well plug  12 , release of the disposable well plug  12  in a wellbore, or otherwise. 
   The preconfigured divisions  122  in the end compression elements  54  may be offset from the preconfigured divisions  122  in the center compression element  52  such that no set of preconfigured divisions  122  extend longitudinally through the entirety of the sealing element  32 . Offset of the preconfigured divisions  122  may prevent, reduce, or minimize any leakage longitudinally of fluids across the sealing element  32  along the axis of elongated body  20  when the disposable well plug  12  is in the set position. The preconfigured divisions  122  may be otherwise suitably offset or partially or otherwise aligned without departing from the scope of the present invention. 
   As illustrated, the segments  120  may each be substantially uniform in size and shape and comprise substantially one third of the associated compression element  50 . Each of the compression elements  50  may include one or more recessed channels configured to receive the retaining rings  56  to hold the segments  120  together during deployment of the disposable well plug  12 . The retaining rings  56  may be otherwise suitably positioned on or about the compression elements  50 . In addition, when the preconfigured divisions  122  are not substantially preformed prior to deployment, the retaining rings  56  may be omitted. The retaining rings  56  may have characteristics or be made of a material that is the same as or comparable with the corresponding compression element  50  or may be suitably varied. 
     FIGS. 5–6  illustrate use of the disposable well plug  12  in a wellbore in connection with a downhole process. The process may be a well completion process, a production enhancement process, or other suitable process for treating a wellbore. In the illustrated embodiment, the disposable well plug  12  is used in connection with a fracture process. 
   Referring to  FIGS. 5–6 , a wellbore  125  includes a first, or lower, production zone (Zone  1 )  123  and a second, or upper, production zone (Zone  2 )  124 . The wellbore  125  is cased with casing  130  and cemented with cement  132 . 
   Initially, a plurality of perforations  140  are formed in the casing  130  and cement  132  at the first production zone  123 . The perforations  140  may be formed by lowering a perforating tool (not shown) into the wellbore  125 , performing the perforation operation, and thereafter removing the perforating tool from the wellbore  125 . 
   After formation of the perforations  140 , the first production zone  123  may be stimulated by pumping a fracture, or frac, fluid into the wellbore  125 . The fracture fluid passes from the wellbore  125  through the perforations  140  into the first production zone  123 . The fracture fluid may be introduced into wellbore  125  by, in one embodiment, lowering a fracture tool containing discharge nozzles or jets for discharging the fracture fluid at a high pressure or, in another embodiment, by pumping the fracture fluid directly from a rig or pump truck directly into the wellbore  125 . After completion of the fracing operation, production fluids may pass from the first production zone  123 , through perforations  140 , and into the wellbore  125  for production to the surface. 
   The disposable well plug  12  may be deployed in the wellbore  125  between the second production zone  124  and the first production zone  123  upon completion of the fracture operation for the first production zone  123 . The disposable well plug  12  may be conventionally deployed by lowering the disposable well plug  12  on a work string (not shown) and setting for the disposable well plug  12  mechanically by twisting the work string or otherwise. The disposable well plug  12  may also be set by other suitable means such as electrical setting. During the setting operation, the sealing element  32  of the disposable well plug  12  is radially expanded to create a seal between the disposable well plug  12  and the casing  130  of the wellbore  125 . The disposable well plug  12  seals the wellbore  125  between the second production zone  124  and the first production zone  123  to prevent fracture fluids used in connection with the second production zone  124  from entering into the first production zone  123 . 
   After the disposable well plug  12  is set in the wellbore  125 , a plurality of perforations  150  may be conventionally formed in the casing  130  and cement  132  at the second production zone  124 . The second production zone  124  may then be stimulated by pumping a fracture fluid into the wellbore  125  as previously described. The fracture fluid flows through the wellbore  125  through the perforations  150  and into the second production zone  124 . The disposable well plug  12  prevents fracture fluid from passing down to the first production zone  123 . 
   After the completion of the fracing operation for the second production zone  124 , the disposable well plug  12  may be disposed of in the wellbore  125 . In one embodiment, the disposable well plug  12  may include a small quantity of explosives (not shown) to break up and/or loosen the slips  26 , wedges  28 , extrusion limiters  30 , and/or sealing element  32 . In this and other embodiments, the compression elements  50  are segmented either prior to deployment, during deployment, and/or during detonation of the explosives or other disposal event. Segmentation of the compression elements  50  may prevent the compression elements  50  from wedging in the wellbore  125  and/or prevent the compression elements  50  from wedging the elongated body  20  or other part of the disposable well plug  12  in the wellbore  125 . 
   Upon disposal, the elongated body  20 , pieces of the slips  26 , wedges  28 , and extrusion limiters  30 , as well as segments  120  of the compression elements  50  may sink to a bottom of the wellbore  125 , which may be a rat hole, a lateral, or other horizontal bore. In this embodiment, disposal of the disposable well plug  12  at the bottom of the wellbore  125  may prevent any part of the disposable well plug  12  from interfering with production operations of the wellbore  125 . In another embodiment, the segments  120  of the compression elements  50  may be weighted or otherwise configured to rise in the wellbore  125 . In this embodiment, the segments  120  may be removed from the wellbore  125  by circulation or other suitable operation. After disposal of the disposable well plug  12 , the first and second production zones  123  and  124  may be produced, completed, or other operations may be performed. This operation may be repeated along the wellbore  125  in the upward direction. For example, a plurality of disposable well plugs  12  may be disposed of sequentially or in groups. 
     FIG. 7  illustrates a method for deploying and using the disposable downhole tool  10 . The method will be described in connection with the disposable well plug  12 . The method may be used in connection with any other suitable disposable downhole tool  10 . 
   Referring to  FIG. 7 , the method begins at step  200  in which the disposable well plug  12  is deployed in the wellbore  125 . As previously described, the disposable well plug  12  may be deployed on a work string. The work string may comprise segmented or coiled tubing. At step  202 , the disposable well plug  12  is set in the wellbore  125 . The disposable well plug  12  may be set by mechanical, fluid, or other suitable mechanism. 
   Proceeding to step  204 , a downhole operation is performed in the wellbore  125  with the disposable well plug  12  isolating a lower portion of the wellbore  125  from the portion in which the operation is being performed. The downhole operation may be a stimulation or other production enhancement operation such as fracing, acidizing, or the like or any other suitable completion, production, workover, or other operation. At step  206 , the disposable well plug  12  is disposed of in the wellbore  125 . The disposable well plug  12  may be disposed of during and/or as part of release, which may be performed by twisting of the work string or other suitable process such as electrical or wire line. In another embodiment, the disposable well plug  12  may be released by detonation of explosives within the disposable well plug  12 . 
   Prior to and/or during disposal, the compression elements  50  of the disposable well plug  12  are segmented. As previously described, the compression elements  50  may be presegmented prior to deployment of the disposable well plug  12 , partially segmented prior to deployment of the disposable well plug  12 , and/or entirely segmented during deployment and/or disposal of the disposable well plug  12 . Thus segmentation may occur at any suitable point or points of the method. 
   At step  208 , the segments  120  and remainder of the disposable well plug  12  are disposed of in the wellbore  125 . In one embodiment, the segments  120  of the compression elements  50  and the remainder of the disposable well plug  12  may be weighted or otherwise configured to sink in the wellbore  125 . Thus, the disposable well plug  12  will not interfere with further production or other operations in the wellbore  125 . 
   Although the present invention has been described in several embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims.