Patent Publication Number: US-6702031-B2

Title: Anchoring device removal method and apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/266,086, filed Feb. 2, 2001, for “Anchoring Device Removal Method and Apparatus”. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is in the field of apparatus used to remove an anchoring device, such as a packer, from a well, when the anchoring device has been anchored in place between the production tubing and the casing. 
     2. Background Art 
     When an oil or gas well is drilled, it is common to insert a casing into the well bore to maintain the well bore and to provide numerous options for modifying the well bore and producing oil or gas from downhole formations. A production tube, usually composed of threaded steel tubular members, is then typically lowered into the casing to deliver fluids from the well. At various depths, one or more packer assemblies are often installed between the production tubing and the casing, to seal off the annular space between the production tubing and the casing. This allows production of oil or gas fluids from different formations at various depths, which are separated by these packer assemblies. 
     Packer assemblies usually have one or more elastomeric elements which are expanded radially outwardly, to forcefully contact the casing, to create a liquid tight seal between the production tubing and the casing. Further, packer assemblies usually have one or more slip assemblies which expand radially outwardly, to forcefully contact the casing, to mechanically hold the packer assembly in place relative to the casing. The slip assemblies are usually segmented metallic members with multiple teeth on their outwardly facing surfaces. The expansion mechanisms, including the elastomeric elements and the slip assemblies, are often expanded radially by the longitudinal movement of a setting mechanism, which often includes a hydraulically driven piston. The piston can act against a ramp contour, for example, to convert the longitudinal motion of the piston to the outward radial motion required to expand the expansion mechanisms. 
     Anchoring devices other than packer assemblies may have only slip assemblies and no sealing elements. Where the terms packer or packer assembly are used in this application, it should be understood that reference is also made to nonsealing types of anchoring devices, where the language permits. 
     Since the packer assembly is usually mechanically attached to the production tubing, such as by threaded connections, anchoring the packer in the casing also fixes the production tubing in place in the casing. Therefore, if it becomes necessary to remove the production tubing, it is necessary to remove the packer assemblies, either separately or along with the production tubing. It can also sometimes be desirable to release a packer assembly and leave it in place. It is common to provide a means of releasing a packer assembly, by adapting the setting mechanism to be released in some way, such as by relieving the hydraulic pressure on a piston to allow the piston to retract, or by forcefully retracting the piston. Others are designed to enable the releasing of the packer by rotation of an operating element, or by other means. A packer assembly which has been designed to release is often referred to as a “retrievable” packer, since it can be easily released and retrieved. 
     Other packer assemblies are not designed to be easily released, either for economic or operational reasons. That is, when the setting mechanism has been set, the packer will remain set, with no built-in provision for releasing the setting mechanism. This is sometimes accomplished by using detent mechanisms or other locking mechanisms to lock the setting mechanism in place. It would be desirable to have a method and apparatus for releasing and retrieving an anchoring device that may not have been designed as a retrievable device. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention includes a method and apparatus for releasing and retrieving from a well bore a packer assembly, or other anchoring device, which may otherwise be designed and implemented as a non-retrievable assembly. More specifically, the packer assembly is designed to expand and set its expansion mechanism by generating a longitudinal force which is converted into an outward radial force on the expansion mechanism. Once set, the setting mechanism is locked into place by a snap ring, detent mechanism, or some other locking mechanism. 
     A locator profile is included in the design and installation of the packer assembly, with the locator profile being utilized to precisely longitudinally locate a cutting tool which can later be lowered into the well, if it becomes necessary to release and retrieve the packer. A locator element is included in the design of the cutting tool, with the locator element being designed to land in, and in some cases latch into, the locator profile on the packer assembly. The cutting tool has either a cutting blade or another type of cutting element, such as a chemical cutter, laser, or torch. The distance between the locator element and the cutting element, on the cutting tool, is selected to precisely place the cutting element at a position where the body mandrel can be safely cut, once the cutter locator element has landed in the cutter locator profile. 
     Where the term body mandrel is used in this application, it should be understood that it is not intended to be limited to a specific type of member, except as the function of the body mandrel is described herein, relative to the operation of the packer assembly or other anchoring device. 
     The cutting element cuts through the body mandrel at the selected location. The depth of the cut is also precisely controlled to allow the cutting element to penetrate the body mandrel without penetrating the remainder of the packer assembly. This allows the ends of the packer assembly to move apart, to retract the setting mechanism, assisted if necessary by subsequent lifting on the packer assembly; it also allows the entire packer assembly and its tailpipe to be pulled from the well. A stop member is provided on the body mandrel for limiting the extent to which the anchor device can be pulled apart, to provide support for pulling the device out of the hole. 
     In one embodiment, the locator profile can include either an internal shoulder, or some other internal restriction, in a landing sub mounted to the production tubing. This shoulder can be located either above or below the packer. The cutting tool can include an external collar as a locator element, with the collar being designed to land on the shoulder for precise longitudinal positioning of the cutting element. In this embodiment, the upper end of the anchoring device or packer assembly is left attached to the production tubing. The cutting tool can be lowered through the production tubing, on either wireline or coil tubing, to cut through the body mandrel and release the packer. The packer can then be pulled out of the well, along with its tailpipe, by pulling the production tubing. In this embodiment, a chemical cutting element, torch, or laser can be lowered on either a wireline or coil tubing. A cutting tool having a blade can be lowered on coil tubing, with the blade being rotated by a downhole motor. 
     In another embodiment, the locator profile can be in a connector on the top of the packer assembly or anchoring device. This can be a removable seal bore, a threaded connector, or any other type of connector that may be present on the top of the anchoring device. The cutting tool can include a connector on its lower end, such as a latching mechanism, with the connector on the lower end of the cutting tool being designed to land on, and latch to, the connector on the upper end of the packer assembly, for precise longitudinal positioning of the cutting element. In this embodiment, the upper end of the packer assembly is first disconnected from the production tubing, and the production tubing above the packer is removed from the hole. The upper end of the packer assembly can then be prepared for connection to the cutting tool, if necessary, such as by removal of a seal bore. The cutting tool can be lowered through the casing, on a threaded tubular workstring, to land the connector on the lower end of the cutting tool in the connector on the upper end of the packer assembly. Once the cutting tool has been attached to the upper end of the packer assembly, the workstring can be rotated, if required to rotate the cutting element, to cut through the body mandrel and release the packer. The packer can then be pulled out of the well, along with its tailpipe, by pulling the workstring. In this embodiment, the cutting element can be either a blade, a chemical cutter, a torch, a laser, or some other type of cutting element. Similarly, as an alternative to rotating the workstring, a downhole motor can be used to rotate the blade or other cutting element. 
     The novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters refer to similar parts, and in which: 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a longitudinal section view of a portion of a packer assembly according to the present invention, configured to be run into a casing on production tubing; 
     FIG. 2 is a longitudinal section view of the device shown in FIG. 1, configured to set within the casing; 
     FIG. 3 is a longitudinal section view of the device shown in FIG. 1, showing the cutting blade cutting the body mandrel to release the expansion mechanism; 
     FIG. 4 is a longitudinal section view of a cutter locator profile in a landing sub on the production tubing, and a cutter locator element on a wireline-conveyed or coil-tubing-conveyed cutting tool, according to the present invention; 
     FIG. 5 is a longitudinal section view of a cutter locator profile in the upper end of the packer, and a cutter locator element on a workstring-conveyed cutting tool, according to the present invention; and 
     FIG. 6 is a longitudinal partial section view of a workstring-conveyed cutting tool according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIGS. 1 through 3, a packer assembly  10  according to the present invention can include a hollow cylindrical body mandrel  12 , one or more expansion elements  13 ,  14  on an upper portion of the body mandrel  12 , and a longitudinally movable annular piston  16  on a lower portion of the body mandrel  12 . The packer assembly  10  is threaded, or otherwise attached, to production tubing PT at its lower end. The expansion mechanism can include one or more sets of segmented metallic slips  13 , and their associated upper and lower ramps. The metallic slips  13  can have teeth or other gripping features on their outer surfaces. The expansion mechanism may or may not also include one or more sets of elastomeric annular sealing elements  14 , and their associated upper and lower ramps. The upper end of the expansion mechanism is fastened to the body mandrel  12 , by a stationary collar threaded to the body mandrel  12 , or by some other fixed attachment means. One or more ramps can be associated with the stationary collar to interface with the upper ramps on the expansion mechanism. 
     The setting mechanism includes the annular piston  16 , an annular piston cover  17 , an annular piston sleeve  15 , and one or more associated ramps. A snap ring  21  can also be provided between the annular piston  16  and the annular piston cover  17 . Alternatively, a snap ring or other type of capture mechanism may be provided between the body mandrel  12  and the annular piston  16  or some other element of the setting mechanism. The lower end of the annular piston  16  is positioned in an annular cylinder  19  formed between the annular piston cover  17  and the lower portion of the body mandrel  12 . The upper end of the annular piston  16  is attached to the lower end of the annular piston sleeve  15 , and ultimately to its associated ramps next to the lower ramps of the expansion mechanism. An actuation port  18  is provided through the lower portion of the body mandrel  12 , from the bore  11  of the body mandrel  12  to the annular cylinder  19 . 
     FIG. 1 shows the packer assembly  10  in the configuration in which it is run into a casing in a well bore. The annular piston  16  is shown at the lower end of its travel, and the lower end of the annular piston sleeve  15  is shown latched to the upper end of the annular piston cover  17 . Because of the lower position of the annular piston sleeve  15 , its associated ramps are withdrawn from the lower ramps associated with the expansion elements  13 ,  14 , and the expansion elements  13 ,  14  are therefore retracted or radially relaxed onto the body mandrel  12 . In this condition, the body mandrel  12  supports the weight of the expansion mechanism, the setting mechanism, and the production tube PT, or tailpipe, attached to the lower end of the body mandrel  12 . 
     FIG. 2 shows the packer assembly  10  in the configuration it assumes when it has been set against the casing C. Hydraulic pressure from a source at the well head (not shown) has been applied via the bore  11  of the body mandrel  12 , and through the actuation port  18  to the annular cylinder  19 . This hydraulic pressure has driven the annular piston  16  longitudinally upwardly, unlatching the annular piston sleeve  15  from the annular piston cover  17 , and forcing the annular piston sleeve  15  upwardly. The annular piston sleeve  15  forces its associated ramps to interact with the lower ramps in the expansion mechanism, and forcing the expansion elements  13 ,  14  against the stationary collar above the expansion elements  13 ,  14 . It can be seen that the reactive force from the expansion elements  13 ,  14  places the annular piston  16  and the annular piston sleeve  15  in compression, and the body mandrel  12  in tension. The interactions between the various sets of ramps convert the upward force of the annular piston sleeve  15  into an outward radial force causing the expansion elements  13 ,  14  to expand radially outwardly. This forces the slips  13  into forceful contact with the casing C to hold the packer assembly  10  in place. This also forces the elastomeric sealing elements  14  into forceful contact with the casing C to create a fluid tight seal. The expansion mechanism and setting mechanism can be locked in place by a releasable capture mechanism, such as the snap ring  21  between the annular piston  16  and the annular piston cover  17 . It can be seen that this leaves the annular piston sleeve  15 , the annular piston  16 , and the annular piston cover  17  in compression, and the body mandrel  12  in tension. Conversely, the releasable capture mechanism could lock the setting mechanism in place relative to the body mandrel  12 . 
     FIG. 3 shows the cutting tool  20  after it has been lowered into place within the packer assembly  10 , precisely positioning the cutting blade  22  at a selected longitudinal point on the lower portion of the body mandrel  12  below the expansion mechanism, preferably below the annular piston  16 . The selected or target cut location is chosen to insure that the body mandrel  12  can be severed at a location which will allow the expansion mechanism to be released, without damaging other elements of the packer assembly  10 . The cutter body  24  has been rotated to rotate the cutting blade  22  and sever the body mandrel  12  at the selected point. Other types of cutting tools and cutting elements, such as a chemical cutter, torch, or laser, could also be used in place of the cutting blade  22 . The cutting element is designed to precisely penetrate only the body mandrel  12 , without further penetrating other elements of the packer assembly  10 , such as the annular piston cover  17 . 
     Once the body mandrel  12  is severed, the lower production tube PT and the annular piston cover  17  are free to fall, if not supported from below, until a shoulder on the setting mechanism abuts a stop member, such as a lock ring  23 , on the body mandrel  12 . Where the releasable capture mechanism, such as the snap ring  21 , locks the annular piston  16  to the annular piston cover  17 , this falling of the annular piston cover  17  will normally be forceful enough to pull the annular piston  16  and the remainder of the setting mechanism downwardly, by abutment of the shoulders shown on the annular piston  16  and the annular piston cover  17 , to retract the expansion elements  13 ,  14 . This frees the packer assembly  10  to be pulled out of the well, along with the production tube PT, by means of the abutment of shoulders on the annular piston  16  and the annular piston sleeve  15  with a shoulder on the annular piston cover  17  and a lock ring  23  on the body mandrel  12 , respectively. Where the releasable capture mechanism locks the annular piston  16  to the body mandrel  12 , rather than to the annular piston cover  17  as with the snap ring  21 , this falling of the annular piston cover  17  may not be forceful enough to pull the annular piston  16  and the remainder of the setting mechanism free from the releasable capture mechanism, or to retract the expansion elements  13 ,  14 . In this situation, the anchoring device or packer assembly  10  can be pulled upwardly to release the capture mechanism. Similarly, if the lower production tube PT is supported below, the packer assembly  10  can be pulled upwardly, thereby releasing the expansion elements. 
     FIG. 4 shows the upper portion of a first embodiment of the present invention, where the upper end of the packer assembly  10  is left attached to the upper production tubing PT. An extension tube  32  can be attached to the upper end of the packer assembly  10 , such as by threaded connectors (not shown). A landing sub  34  can be attached to the upper end of the extension tube  32 . A cutter locator profile such as an internal shoulder  35  can be provided on the internal surface of the landing sub  34 , protruding into the bore of the upper production tubing PT. A nipple  36  or other connector can be attached above the landing sub  34  to connect the landing sub  34  and the remainder of the packer assembly  10  to the production tube PT thereabove. 
     The upper end of the cutting tool body  24  is attached to a cutter locator element, such as a collar  28  on an externally threaded sub  26 . The collar  28  can be attached to the outer surface of the sub  26  by being threaded thereon and held in place by a set screw. The upper end of the sub  26  can have a suitable connector  29  for a wireline or for coil tubing, as desired. 
     The cutter locator shoulder  35  is located a first distance from the desired cut point on the body mandrel  12 , with this first distance being largely dependent upon the length of the extension tube  32 . The cutter locator collar  28  is located a second distance from the cutting element  22  on the cutting tool  20 , with this second distance being largely dependent upon the length of the cutting tool  20 . The lengths of these tubular elements are selected to insure that the second distance is substantially the same as the first distance, thereby insuring that the cutting element severs the body mandrel  12  essentially at the desired cut point. Precise adjustment of the second distance can be achieved by threading the collar  28  either up or down on the sub  26 . 
     The particular anchoring device being retrieved may have either an appreciable length, or a very limited length, over which the desired cut point may be located, while still achieving the release of the expansion mechanism. The important thing is for the selected cut point to sever the body mandrel, or other structural member, at a location which then permits the other members of the anchoring device to separate longitudinally, to an extent which releases the expansion mechanism. 
     FIG. 5 shows the upper portion of a second embodiment of the present invention, where the upper end of the packer assembly  10  is disconnected from the upper production tubing PT, and the upper production tubing PT is removed from the well. A suitable connector  40  is provided on the upper end of the packer body mandrel  12 . This connector can be threaded. The upper end of the cutter tool body  24  has attached thereto a latch body  42 , a latch  44 , and a suitable workstring connector  46 . The latch  44  can be a segmented slip assembly designed to latch into a thread on the upper end of the connector  40 . 
     Where rotation of the cutting tool  20  is required, the cutter body  24  can be rotatable in the latch body  42 , and a bearing assembly  48  can also be provided, allowing the workstring connector  46  and the cutter tool body  24  to rotate relative to the packer body mandrel  12  and the connector  40 . Here again, other suitable connectors can also be used on the upper end of the cutting tool  20 , without departing from the spirit of the invention. 
     Important features are that the connectors used in this embodiment accurately locate the cutting element  22  longitudinally, to cut the body mandrel  12  in the target longitudinal location, and that the connectors latch together. Further, where a rotating cutting element is used, the connectors must allow rotation of the cutting tool  20  relative to the body mandrel  12 . After this workstring conveyed tool is used to sever the body mandrel  12 , the latch  44  remains engaged in the upper packer connector  40 , to allow the workstring to pull upwardly on the packer body  12  and release the expansion mechanism. Further, the latch  44  remains engaged to pull the packer assembly  10  out of the hole. 
     FIG. 6 shows a more complete example of one type of workstring-conveyed cutting tool that can be used in the second embodiment of the invention where the production tubing above the packer assembly  10  is removed, and where the workstring is used to both release and retrieve the packer assembly  10 . The cutter blade  22  is selectively extendable to protrude through a window in the cutter tool body  24 . The latch body  42  can include two engageable clutch elements slidably mounted on the cutter body  24 , thereby allowing unthreading of the latch  44  from the threads in the upper packer assembly connector  40 , if necessary. Rotatable cutters similar to the lower portion of this cutting tool can also be lowered on coil tubing, and driven by a downhole motor, to sever the body mandrel  12 , in the first embodiment of the invention where the packer assembly  10  is left attached to the production tubing. 
     While the particular invention as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages hereinbefore stated, it is to be understood that this disclosure is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended other than as described in the appended claims.