Patent Publication Number: US-8973651-B2

Title: Modular anchoring sub for use with a cutting tool

Description:
BACKGROUND 
     1. Field of Invention 
     The invention relates generally to operations in a wellbore. More specifically, the present invention relates to an apparatus and method for maintaining stability while severing a tubular. 
     2. Description of Prior Art 
     Tubular members, such as those disposed within a hydrocarbon producing wellbore, can be severed from the inside by inserting a cutting device within the hollow space. From time to time, portions of tubulars may become unusable and require replacement; while some tubulars or their segments have a pre-determined lifetime and are scheduled for replacement. Moreover, some wellbore tubulars have sections that are removed during completion of the wellbore. When a tubular is to be severed, either for repair, replacement, demolishment, or some other reason, a cutting tool is typically inserted within the tubular, positioned for cutting at the desired location, and activated to cut the tubular. The cutting tools are generally outfitted with a blade or other cutting member for severing the tubular. 
     SUMMARY OF THE INVENTION 
     The present disclosure provides a method and apparatus for severing a tubular. An example embodiment of a cutting tool for severing a tubular includes a motor section with an enclosed motor and a cutting head driven by the motor. An anchor section is between the motor section and cutting head, where anchoring members in the anchor section selectively engage an inner surface of the tubular to anchor the cutting tool. Also included is a modular anchoring sub mounted on an end of the motor section distal from the anchor section. Elements on the modular anchoring sub engage the tubular. Ends of the modular anchoring sub having modular connectors. This allows selective placement of the modular anchoring sub to be between the motor section and an additional section or on an end of the additional section opposite from the motor section. Optionally, the additional section is a controller sub. The modular connectors, in one example, provide connectivity to a control line used for controlling the cutting tool. A spacer sub can be disposed between the motor section and the modular anchoring sub. Elements of the modular anchoring sub can be axially spaced apart and independently moveable. An umbilical may be disposed axially through the modular anchoring sub and having opposing ends that connect to modular connectors on opposing ends of the modular anchoring sub. The modular anchoring sub can optionally be on the end of the additional section distal from the motor section, and the modular connector on the end of the modular anchoring sub distal from the additional section can couple to a control line for controlling the cutting tool. 
     Also disclosed herein is an example embodiment of a method of severing a tubular that involves providing a cutting tool that includes a motor section having a motor, and a cutting blade. An anchor section is included that is between the motor section and cutting head and has anchoring members. The cutting tool also has a controller section and a modular anchoring sub with anchoring elements. The method further includes coupling the modular anchoring sub and the controller section on an end of the motor section distal from the anchor section in a sequence or order based on an expected use of the cutting tool. The cutting tool is inserted into the tubular and the cutting blade is rotated by the motor to sever the tubular. Optionally, the cutting tool can be anchored by extending the anchoring members and the anchoring elements. The order of how the modular anchoring sub and the controller section are coupled positions the modular anchoring sub such that an anchoring force is exerted on the cutting tool by the anchoring members and anchoring elements that is greater than an anchoring force exerted on the cutting tool by the anchoring members and anchoring elements in any other possible sequence. In an example, the modular anchoring sub has opposing ends each fitted with a modular coupling and an umbilical connected between the modular couplings. Thus when the modular anchoring sub couples on one end to the controller section, and on an opposite end to the motor section, the modular couplings on the modular anchoring sub engage modular couplings on the controller section and the motor section to provide communication between the controller section and motor section through the umbilical. In an example, the expected use of the cutting tool is within a non-linear portion of the tubular. Alternatively, the cutting tool is disposed in a horizontal wellbore and wherein the anchoring members and the anchoring elements support and centralize the cutting tool within the tubular. The modular anchoring sub can include a first modular anchoring sub between the motor section and the controller section, where the method further includes coupling a second modular anchoring on an end of the controller section distal from the first modular anchoring sub. 
     Also included is an alternate method of wellbore operations at a wellbore site that in one example includes providing a cutting tool to the site. In this example the cutting tool is made up of a motor section having a motor, a cutting blade, and an anchor section with anchoring members. The anchor section is between the motor section and cutting head. Also included with the cutting tool is a modular anchoring sub with anchoring elements and a controller section coupled to an end of the motor section distal from the anchor section. An anchoring force exerted onto the cutting tool by the modular anchoring sub is estimated for the modular anchoring sub being positioned between the motor section and controller section and positioned on an end of the controller section distal from the motor section. While at the site the modular anchoring sub is coupled with the controller section and in the position where the modular anchoring sub provides maximum anchoring force. The tubular is severed by inserting the cutting tool into the tubular and rotatingly engaging the tubular with the cutting blade. Alternatively, communication is provided through the modular anchoring sub between the motor section and a conveyance means for deploying and controlling the cutting tool. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a side partial sectional view of an example embodiment of a cutting tool in accordance with the present invention. 
         FIG. 2  is a side partial sectional view of the cutting tool of  FIG. 1  in a deviated portion of a wellbore. 
         FIG. 3  is a side partial sectional view of an alternate embodiment of a cutting tool in a deviated portion of a wellbore in accordance with the present invention. 
         FIG. 4  is a side partial sectional view of the cutting tool of  FIG. 1  in a horizontal portion of a wellbore. 
         FIG. 5  is a side partial sectional view of the cutting tool of  FIG. 3  in a portion of a wellbore having a bend. 
         FIG. 6  is a side partial sectional view of an alternate embodiment of a cutting tool in a portion of a wellbore having a bend in accordance with the present invention. 
         FIG. 7  is a side partial sectional view of an alternate embodiment of a cutting tool in accordance with the present invention. 
         FIG. 8  is a side sectional view of a portion of the cutting tool of  FIG. 1 . 
     
    
    
     While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention. 
     DETAILED DESCRIPTION OF INVENTION 
     The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. 
     It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the improvements herein described are therefore to be limited only by the scope of the appended claims. 
     Cutting tools for severing tubulars typically include an anchor or other stabilizing device for bracing against the tubular to counter the reactive forces generated by cutting. Often, cutting tools for wellbore tubulars are relatively elongated so the components making up the cutting tool can be packaged in a single unit for insertion into the usually narrow wellbore tubular. The elongate configuration can be difficult to stabilize when subjected to the reactive forces of cutting. 
     Referring now to  FIG. 1 , one example of a cutting assembly  10  is shown inserted within a tubular  12  and deployed on a conveyance means  14 . Examples of the conveyance means  14  include wireline, slick line, coil tubing, and the like. The conveyance means  14  depends within the tubular  12  from a wellhead assembly  16  on surface  18 . The tubular  12  is shown inserted within a wellbore  19 ; examples of a tubular  12  include production tubing, casing, a downhole tool, and any annular member in a wellbore. In the example embodiment of  FIG. 1 , the cutting assembly  10  is an elongate member having a cutting head  20  disposed on a lower end. The cutting head  20  which is rotatable, includes a selectively extendable and retractable cutting blade  22  that projects radially outward from a lateral side of the cutting head  20 . The cutting assembly  10  further includes an anchoring section  24  shown coupled on an upper end of the cutting head  20  and including anchoring legs  26  shown extending radially from the anchoring section  24  and into engagement with an inner surface of the tubular  12 . An example of a device for anchoring a cutting tool in a tubular is found in U.S. Pat. No. 7,575,056, which is owned by the assignee of the present application and incorporated by reference herein in its entirety. Motor section  28  is also included with the cutting assembly  10  and has a motor (not shown) for driving the cutting head  20  and cutting blade  22 . A shaft (not shown) extends from the motor and downward to the cutting head  20  for rotating the cutting head  20 . 
     A modular anchoring sub  30  is shown releaseably coupled on an upper end of the motor section  28 . The anchoring sub  30  includes anchoring elements  32  that, similar to the anchoring legs  26 , selectively project radially outward and into anchoring engagement with an inner surface of the tubular  12 . On an upper end of the modular anchoring sub  30  is a controller section  34 . The upper end of the controller section  34  is shown connecting to the conveyance means  14 . As will be discussed in further detail below, signaling and control means are provided within the conveyance means  14  that are directed to other devices within the cutting assembly  10 . The signaling and control means includes hardware, such as controllers, processors, and other information handling systems for monitoring and controlling operation of the cutting assembly  10  Providing the modular anchoring sub  30  within the cutting assembly  10  and at a position distal from the permanently included anchoring section  24  enhances the stability of the cutting assembly  10  when set within the tubular  12 . This is especially so when the reactive cutting forces generated by cutting the tubular  12  with the cutting blade  22  are exerted onto the cutting assembly  10 . 
       FIG. 2  depicts the cutting assembly  10  set within a deviated tubular  12 A and at an angle θ with respect to an axis Y vertical to gravity; thereby also angling an axis A x  of the cutting assembly  10  with respect to axis Y. Distally placing the modular anchoring sub  30  stabilizes the cutting assembly  10  within the tubular  12 A so that as the cutting head  20  rotates thereby cutting along the circumference of the tubular  12 A, a substantially constant anchoring force may be obtained tor preventing vibration and other movement of the cutting assembly  10 . 
     An optional embodiment of the cutting assembly  10 A is shown in a side view in  FIG. 3 . In this example embodiment, the cutting assembly  10 A is set within a deviated tubular  12 A and at an angle with vertical. In this example, the modular anchoring sub  30  is shown set on an end of the controller section  34  distal from the motor section  28 . As such, the distance from the permanent anchoring section  24  to the anchoring elements  32  of the modular anchoring sub is increased over the embodiment of  FIGS. 1 and 2 , thereby further enhancing the stabilizing effect realized by use of the modular anchoring sub  30 . Couplings on the opposing ends of the modular anchoring sub  30  provide for quick and releasable engagement with couplings on the ends of the controller section  34  and on the end of the motor section  28 . The modular couplings allow for selective repositioning of the modular anchoring sub  30  along the cutting assembly  10 . 
     As a further illustration of the stability of use of the modular anchoring sub  30  with the cutting assembly  10 , the cutting assembly  10  is shown in a horizontal tubular  12 B. In this example, the respective anchoring legs  26  and anchoring elements  32  of the anchoring section  24  and modular anchoring sub  30  may be coordinated to centralize the cutting assembly  10  within the tubular  12 B, while at the same time of stabilizing the cutting assembly  10 . The effect of centralizing and stabilizing the cutting assembly  10  provides an even cut as the cutting blade  22  is used to sever a section of the tubular  12 B. 
     A further advantage of the modular anchoring sub  30  is shown in a side view in  FIG. 5 . In this example, the cutting assembly  10 A is set within a substantially vertically disposed tubular  12 C having a bend  36  coinciding along the length of the cutting assembly  10 A. In this example, the anchoring elements  32  on one side of the modular anchoring sub  30  are substantially retracted. While on an opposing side of the bend  36  the anchoring elements  32  are substantially extended so that the portion of the cutting assembly  10  extending past the bend  36  may be substantially centered within the tubular  12 C. Centering the blade portion of the cutting assembly  10  allows for a more stable and generally cleaner cutting action than if the cutting head  20  were asymmetrically disposed within the tubular  12 C. 
     Another alternate embodiment of the cutting assembly  10 B is shown in the tubular  12 C wherein separate and distinct anchoring elements  32 B are disposed on the modular anchoring sub  30 B and that are axially spaced apart. As such, the radial distance each individual anchoring element  32 B projects from the modular anchoring sub  30 B may vary depending on its respective axial and/or angular location on the modular anchoring sub  30 B. This provides yet additional flexibility of accurately and concisely disposing the cutting assembly  10  for concentrically placing the cutting head  20  within the portion of the tubular  12 C to be severed. 
     In yet another optional embodiment, a spacer sub  38  is provided with an embodiment of the cutting assembly  10 C. In the example of  FIG. 7 , the spacer sub  38  is disposed between the motor sub  28  and modular anchoring sub  30 . This provides more flexibility for setting the axial distance between the permanent anchoring section  24  and modular anchoring sub  30 . 
     Referring now to  FIG. 8 , shown in a side sectional view is a portion of the cutting assembly  10  of  FIG. 1 . In the example of  FIG. 8 , umbilicals  40 ,  42 ,  44  extend vertically through each of the controller section  34  modular anchoring sub  30  and motor section  28 . The upper end of the uppermost umbilical  40  couples with the conveyance means  14 . The umbilicals  40 ,  42 ,  44  include control lines for sending control signals to components within the cutting assembly  10  as well as power such as electrical or hydraulic for powering actuatable devices within the cutting assembly  10 . Modular connectors  46  are shown on the upper and lower ends of both the controller section  34  and modular anchoring sub  30 . The connectors  46  enable selectively positioning the controller section  34  and modular anchoring sub  30  in the various sequences as illustrated in  FIGS. 1 and 3 . As far as the mechanical couplings between these sections, they may be threaded or bolt on type flanges. In one example embodiment, the mechanical connectors are configured so that connections between these sections may be performed on the site where the tubular is located. 
     One example of a component controlled and powered by lines through the umbilicals  40 ,  42 ,  44  is an actuator  48  schematically illustrated within the modular anchoring sub  30 . More specifically, a power line  50  is shown connecting the actuator  48  with the umbilical  42  and a control line  52  extends between the actuator  48  and umbilical  42 . In the example embodiment of  FIG. 8 , the actuator  48  is used for selectively extending and retracting the anchoring elements  32  provided with the modular anchoring sub. Similarly, a motor  54  set within the motor section  28  receives power through a power line  56  connecting the motor  54  with umbilical  44  and may receive control signals via a control line  58  extending from the umbilical  44  to the motor  54 . 
     The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.