Abstract:
A downhole affixation and release assembly including a first component; a second component, and an interconnection device for at least temporarily securing the first component to the second component. The interconnection device operatively arranged to at least partially degrade upon exposure to a fluid. Also included is a method of affixing and releasing two components.

Description:
BACKGROUND 
       [0001]    In the drilling and completions industry it is common to run a whipstock and a mill in the same run by hanging the whipstock from the end of the mill string. Once the whipstock has landed at a selected position and orientation within the borehole, the whipstock is anchored in place and will bear weight. Because the whipstock is necessarily thinner at the uphole end thereof, it has commonly been a practice in the industry to use a relatively large lug at the uphole end of the whipstock to support a set down weight from the mill string that is used to separate the mill from the whipstock, such as by shearing a screw. This arrangement presents a heavy piece of material that must be removed from the path of the mill. Milling the lug often damages the mill due to interrupted cuts, but is nevertheless often performed because of a lack of alternatives. Accordingly, improvements in affixation and release arrangements, particularly for mills, are well received by the industry. 
       BRIEF DESCRIPTION 
       [0002]    A downhole affixation and release assembly includes a first component; a second component, and an interconnection device for at least temporarily securing the first component to the second component, the interconnection device operatively arranged to at least partially degrade upon exposure to a fluid. 
         [0003]    A cutting assembly includes a mill operatively arranged to cut through a wall; a whipstock for directing the mill into the wall, the whipstock including an interconnection device for securing the mill to the whipstock during run-in, the interconnection device operatively arranged to at least partially degrade upon exposure to a downhole fluid. 
         [0004]    A method of affixing and releasing two components includes, affixing a first component to a second component with an interconnection device; running the first and second components downhole; and degrading the interconnection device by exposing the interconnection device to a fluid. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0006]      FIG. 1  is a schematic view of an affixation and release assembly for a mill; 
           [0007]      FIG. 2  is a schematic view of the assembly of  FIG. 1  illustrating the mill separated from a whipstock; 
           [0008]      FIG. 3  is a schematic view of the assembly of  FIGS. 1 and 2  illustrating removal of a lug via a flow of fluid; and 
           [0009]      FIG. 4  is a schematic view of the assembly of  FIG. 1  illustrating both a lug and a release member being degraded by a flow of fluid. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0011]    Referring now to  FIG. 1 , an affixation and release assembly  10  is shown, with a mill  12  secured to a whipstock  14  via an interconnection device  15 . Throughout the Figures, the mill  12  is shown resembling a tapered starting mill, although it is to be appreciated that other mill types, such as a window mill, could be similarly used. As the end of the whipstock  14  to which the mill  12  is secured is relatively thin, the interconnection device  15  includes a lug  16  affixed to the whipstock  14 . The interconnection device  15  also includes a release member  18  extending through the lug  16  in order to secure the whipstock  14  to the mill  12 . The releasable member  18  takes the form, for example, of a shear screw, hydraulically actuatable piston or other slidable component, degradable member, etc. The lug  16  is substantially larger than the end of the whipstock  14  and supports the whipstock  14  in order to prevent undue distortion of, or damage to, the whipstock  14  when releasing the mill  12  from the whipstock  14 , due to forces exerted on the whipstock  14  while positioning the whipstock  14 , etc. However, the lug  16  creates an obstacle to the mill  12  that results in an interrupted cutting operation of the mill  12 , as the lug  16  is formed essentially on only one side of the mill  12 . The lug  16  can be welded to the whipstock  14 , secured to the whipstock  14  via the release member  18 , etc. The mill  12  and the whipstock  14  are installed in an annulus  20  formed by a wall  22 , which wall could be formed for or by a casing, a borehole, a tubular, cement, a combination of the foregoing, etc. 
         [0012]      FIGS. 1-3  show one example of how the assembly  10  can be utilized to release the mill  12 . The assembly  10  is shown run in the annulus  20  in  FIG. 1 , with the mill  12  secured to the whipstock  14  via the release member  18  and the lug  16 , as described above. The whipstock  14  is set in position and properly oriented, for example, by use of an anchor assembly or the like (not shown) further downhole in the annulus  20 . The whipstock  14  can have a known form, e.g., being a tapered for directing the mill  12  into the wall  22  in order to cut a window or opening in the wall  22 . The whipstock  14  could take any other form for, e.g., directing or guiding the mill  12 . The mill  12  could similarly take any known form corresponding to the whipstock  14  in order to achieve a window or opening in the wall  22 . 
         [0013]    After the whipstock  14  and the mill  12  are in place, e.g., by use of an anchor assembly for the whipstock  14 , an event is triggered to release the release member  18 . For example, if the release member  18  takes the form of a shear screw, applying a set down weight to the mill  12  will shear the release member  18 , thereby freeing the mill  12  from the whipstock  14 , as shown in  FIG. 2 . After release of the member  18 , the lug  16  presents a significant obstacle to operation of the mill  12 . The lug  16  is made from a degradable material in order to remove the lug  16  from the path of the mill  12  without having to mill the lug  16 . “Degradable” is intended to mean that the lug is disintegratable, dissolvable, weakenable, corrodible, or otherwise removable. It is to be understood that any use herein of the term “degrade”, or any of its forms, incorporates the stated meaning. In one embodiment, for example, the lug  16  is degraded by exposure to a downhole fluid, such as water, oil, acid, etc. For example, after release of the member  18 , as shown in  FIG. 3 , a flow of fluid  24 , is pumped through the annulus  20  or otherwise delivered to the lug  16  in order to degrade the lug. In another embodiment, the mill is hollow or includes a passage therethrough and the flow of fluid is pumped down the mill string to the release member  18  or out an opening proximate to the interconnection device  15 . Advantageously, degrading the lug prevents the need for the mill  12  to remove the lug  16  (or the lug is weakened or reduced in size, resulting in easier removal), thereby avoiding potentially significant wear on the mill  12  and extending the life of the mill. Additionally, since removal of the lug does not have to be accounted for, the mill  12  can be more specifically designed to enhance the speed and efficiency with which the mill  12  cuts through the wall  22 . 
         [0014]    Alternatively, as shown in  FIG. 4 , the release member  18  could also be made from a degradable material, such that the release member  18  is also degradable, thereby removing another obstacle, although a relatively minor one, from the path of the mill  12 . In some embodiments including a degradable release member, the release member  18  is not sheared, but instead, the mill  12  is released from the whipstock  14  by degrading the release member  18  due to exposure to the flow of fluid  24 . In other embodiments, the degrading process may weaken the release member before it is sheared or broken by a set down weight. It is to be understood that the same fluid or different fluids could be used to degrade the various components. Thus, the release member  18  could be formed by a rivet, a bolt, a pin, a rod, a plate, or any other element extending between the whipstock  14  and the mill  12 , and could either be either integrally formed with the lug  16  (e.g., an extruded rivet) or formed as a separate component. It is to be appreciated that the lug  16  and the release member  18  could be utilized to temporarily connect together other components in a similar way, with the interconnection device  15  (i.e., the lug  16  and/or the release member  18 ) degrading for enabling relative movement between the components that was previously prevented by the presence of the interconnection device or a portion thereof. 
         [0015]    The interconnection device  15  can be formed from materials that are degradable by exposure to a variety of fluids capable of being pumped, present, or delivered downhole such as water, acid, oil, etc. The degradable material could be a metal, a composite, a polymer, etc., or any other material that is suitably degradable and that can withstand the loads necessary to initially hang the whipstock  14  from the mill  12  during run-in, prevent distortion of the whipstock  14  during loading, etc. However, as described above, it may be possible to avoid very high set down loading by simply degrading the release member  18  after the whipstock is locked by the downhole anchor assembly, and thus, the interconnection device  15  may comprise just a release member in some embodiments. In one embodiment, the interconnection device  15 , (i.e., the lug  16  and/or the release member  18 ) is manufactured from a high strength controlled electrolytic metallic material and is degradable by brine, acid, or aqueous fluid. 
         [0016]    That is, materials appropriate for the purpose of degradable interconnection devices as described herein are lightweight, high-strength metallic materials. Examples of suitable materials, e.g., high strength controlled electrolytic metallic materials, and their methods of manufacture are given in United States Patent Publication No. 2011/0135953 (Xu, et al.), which Patent Publication is hereby incorporated by reference in its entirety. These lightweight, high-strength and selectably and controllably degradable materials include fully-dense, sintered powder compacts formed from coated powder materials that include various lightweight particle cores and core materials having various single layer and multilayer nanoscale coatings. These powder compacts are made from coated metallic powders that include various electrochemically-active (e.g., having relatively higher standard oxidation potentials) lightweight, high-strength particle cores and core materials, such as electrochemically active metals, that are dispersed within a cellular nanomatrix formed from the various nanoscale metallic coating layers of metallic coating materials, and are particularly useful in borehole applications. Suitable core materials include electrochemically active metals having a standard oxidation potential greater than or equal to that of Zn, including as Mg, Al, Mn or Zn or alloys or combinations thereof For example, tertiary Mg—Al—X alloys may include, by weight, up to about 85% Mg, up to about 15% Al and up to about 5% X, where X is another material. The core material may also include a rare earth element such as Sc, Y, La, Ce, Pr, Nd or Er, or a combination of rare earth elements. In other embodiments, the materials could include other metals having a standard oxidation potential less than that of Zn. Also, suitable non-metallic materials include ceramics, glasses (e.g., hollow glass microspheres), carbon, or a combination thereof In one embodiment, the material has a substantially uniform average thickness between dispersed particles of about 50 nm to about 5000 nm. In one embodiment, the coating layers are formed from Al, Ni, W or Al 2 O 3 , or combinations thereof In one embodiment, the coating is a multi-layer coating, for example, comprising a first Al layer, a Al 2 O 3  layer, and a second Al layer. In some embodiments, the coating may have a thickness of about 25 nm to about 2500 nm. 
         [0017]    These powder compacts provide a unique and advantageous combination of mechanical strength properties, such as compression and shear strength, low density and selectable and controllable corrosion properties, particularly rapid and controlled dissolution in various borehole fluids. The fluids may include any number of ionic fluids or highly polar fluids, such as those that contain various chlorides. Examples include fluids comprising potassium chloride (KCl), hydrochloric acid (HCl), calcium chloride (CaCl 2 ), calcium bromide (CaBr 2 ) or zinc bromide (ZnBr 2 ). For example, the particle core and coating layers of these powders may be selected to provide sintered powder compacts suitable for use as high strength engineered materials having a compressive strength and shear strength comparable to various other engineered materials, including carbon, stainless and alloy steels, but which also have a low density comparable to various polymers, elastomers, low-density porous ceramics and composite materials. 
         [0018]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.