Patent Publication Number: US-11041353-B2

Title: Tubular cutting tool

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure generally relates to a tool for cutting a tubular in a wellbore. 
     Description of the Related Art 
     A wellbore is formed to access hydrocarbon bearing formations, e.g. crude oil and/or natural gas, by the use of drilling. Drilling is accomplished by utilizing a drill bit that is mounted on the end of a tubular string, such as a drill string. To drill within the wellbore to a predetermined depth, the drill string is often rotated by a top drive or rotary table on a surface platform or rig, and/or by a downhole motor mounted towards the lower end of the drill string. After drilling to a predetermined depth, the drill string and drill bit are removed, and a section of casing is lowered into the wellbore. An annulus is thus formed between the string of casing and the formation. The casing string is temporarily hung from the surface of the well. The casing string is cemented into the wellbore by circulating cement into the annulus defined between the outer wall of the casing and the borehole. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas of the formation behind the casing for the production of hydrocarbons. 
     It is common to employ more than one string of casing in a wellbore. In this respect, the well is drilled to a first designated depth with the drill string. The drill string is removed. A first string of casing is then run into the wellbore and set in the drilled-out portion of the wellbore, and cement is circulated into the annulus behind the casing string. Next, the well is drilled to a second designated depth, and a second string of casing or liner, is run into the drilled-out portion of the wellbore. If the second string is a liner string, the liner is set at a depth such that the upper portion of the second string of casing overlaps the lower portion of the first string of casing. The liner string may then be fixed, or “hung” off of the existing casing by the use of slips which utilize slip members and cones to frictionally affix the new string of liner in the wellbore. If the second string is a casing string, the casing string may be hung off of a wellhead. This process is typically repeated with additional casing/liner strings until the well has been drilled to total depth. In this manner, wells are typically formed with two or more strings of casing/liner of an ever-decreasing diameter. 
     In certain operations, it is desirable to remove the innermost string of casing/liner from the wellbore by cutting the innermost casing/liner. Conventional approaches to cutting the innermost casing/liner may cause damage to the next-largest casing/liner. Therefore, there is a need for an apparatus and method of cutting the innermost liner without damaging the next-largest casing/liner. 
     SUMMARY OF THE INVENTION 
     A method of cutting a tubular includes providing a rotatable cutting tool in the tubular, the cutting tool having a blade with a cutting structure thereon; extending the blade relative to the cutting tool; rotating the cutting tool relative to the tubular; guiding the cutting structure into contact with the tubular; cutting the tubular using the blade; and limiting extension of the blade. 
     A rotatable blade for cutting a tubular includes a blade body extendable from a retracted position; a cutting structure disposed on a leading edge of the blade body, the cutting structure configured to cut the tubular; a stop on a first surface of the blade body; and an initial engagement point on a second surface of the blade body, the initial engagement point configured to guide the cutting structure into contact with the tubular. 
     A method of cutting a tubular includes positioning a rotatable cutting tool in the tubular, the cutting tool having a blade and a cutting structure; extending the blade relative to the cutting tool; rotating the cutting tool relative to the tubular; guiding the cutting structure into contact with the tubular; cutting the tubular using the cutting structure; and limiting a sweep of the cutting structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1A  illustrates a cross sectional view of an embodiment of a tool for selectively cutting an inner tubular, the tool being in a first position. 
         FIG. 1B  is a cross sectional view of the tool of  FIG. 1A  in a second position. 
         FIG. 1C  is a cross sectional view of the tool of  FIG. 1A  in a third position. 
         FIG. 2A  illustrates an exemplary embodiment of a blade on the tool of  FIG. 1A . 
         FIG. 2B  is a side view of the blade of  FIG. 2A . 
         FIG. 3  is a top cross sectional view of the tool of  FIG. 1A , wherein the blade is in contact with the inner tubular. 
         FIG. 4  is an enlarged, side view of the blade of  FIG. 3 . 
         FIG. 5  is an enlarged, side view of the blade of  FIG. 1C . 
     
    
    
     DETAILED DESCRIPTION 
     In the description of the representative embodiments of the invention, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. In general, “above”, “upper”, “upward” and similar terms refer to a direction toward the earth&#39;s surface along a longitudinal axis of a wellbore, and “below”, “lower”, “downward” and similar terms refer to a direction away from the earth&#39;s surface along the longitudinal axis of the wellbore. 
       FIG. 1A  illustrates a rotatable cutting tool  10  for cutting a tubular in a wellbore  20 . The tubular may be an inner tubular  50  at least partially disposed in an outer tubular  60 , as shown in  FIG. 1A . However tool  10  may be equally well used in tubulars that are not surrounded by any other tubulars. Exemplary tubulars include casing, liner, drill pipe, drill collars, coiled tubing, production tubing, pipeline, riser, and other suitable wellbore tubulars. The tool  10  includes an actuation assembly  30  and a blade assembly  40  both shown in  FIG. 1A  positioned in a housing  15 . The tool  10  is configured to be disposed within a tubular such that the longitudinal axis of the tool  10  is essentially parallel (within +/−10°) with the longitudinal axis of the tubular. The tool  10  is configured to rotate around its longitudinal axis. 
     The actuation assembly  30  acts to extend blades  116  of the blade assembly  40 . In one embodiment, actuation assembly  30  includes a retaining member  102  having at least one aperture  106  and a bore therethrough. The bore of the retaining member  102  is configured to receive a movable member  104 . The movable member  104  includes a bore therethrough. In one embodiment, the movable member  104  is biased upward, for example by a spring  108 . The movable member  104  includes a thick bottom portion that prevents disengagement from the retaining member  102 . In one embodiment, a bottom surface of the movable member  104  is initially sealingly engaged with a bushing  31  which is threadedly engaged with a piston  112 , each having a bore therethrough. The bore of the bushing  31  and the piston  112  have a larger diameter than the bore of the movable member  104 . The piston  112  includes a packing seal  114  for preventing fluid flow around the piston  112 . In one embodiment, the piston  112  is biased upward against the bottom surface of the movable member  104 , for example by a spring  115 , as shown in  FIG. 1A . 
     The blade assembly  40  includes at least one blade  116  in a respective recess  118  of the housing  15 , as shown in  FIG. 1A . Any appropriate number of blades  116  may be used in the blade assembly  40 . In some embodiments, the number of blades  116  ranges from 2 to 10. In other embodiments, the number of blades  116  ranges from 3 to 6. In yet other embodiments, the number of blades  116  ranges from 2 to 4. Each blade  116  is rotatable with respect to the tool  10 , for example about a pivot point  120 , between a retracted position ( FIG. 1A ) and a series of extended positions ( FIGS. 1B, 1C, and 3 ). In the retracted position, the blade  116  is disposed in the recess  118 . In an extended position, the blade  116  is at least partially extended outward from the recess  118 . In some embodiments, the blade  116  extends radially outward from the longitudinal axis of cutting tool  10 . In one embodiment, the blades  116  are biased towards the retracted position, for example by a spring  122 , which urges a bushing  124  against an inner surface of the blades  116 . For example, the spring  122  urges the bushing  124  against an end of each blade  116  such that the blades  116  rotate about the pivot point  120  into the retracted position. In some embodiments, the blade assembly  40  includes a bumper, ratchet, catch plate, group thereof, or other component(s) configured to limit the extension of blade  116 . A person of ordinary skill in the art with the benefit of this disclosure would appreciate that other configurations of blade assemblies  40  and actuator assemblies  30  could serve to provide one or more blades that move from a retracted position to an extended position within the spirit of this disclosure. 
     An exemplary embodiment of the blade  116  is shown in  FIGS. 2A and 2B . The blade  116  includes a blade body  200  with an aperture  201  for receiving a pivot pin at pivot point  120 . The blade  116  also includes an attachment  202 . In one embodiment the blade body  200  and the attachment  202  are integrally formed. In another embodiment, the attachment  202  is operably coupled to the blade body  200 . For example, the blade body  200  includes a slot for receiving the attachment  202 . The attachment  202  may be fastened in the slot of the blade body  200  using any appropriate fastener, such as a pin and/or a screw. In one embodiment, the blade body  200  includes holes  212  for receiving the fasteners, as shown in  FIGS. 2A and 2B . In one embodiment, the attachment  202  is replaceable. For example, the attachment  202  may have a useful life defined by the ability of the attachment  202  to cut through an entire wall thickness of the inner tubular  50  as described herein. After exhausting the useful life of the attachment  202 , the attachment  202  may be unfastened and removed from the blade body  200 . Thereafter, a new attachment  202  may be fastened to the blade body  200 . When blade body  200  and the attachment  202  are integrally formed, after exhausting the useful life of the attachment  202 , the attachment  202  may be reconditioned, for example by welding, coating, milling, sharpening, etc. In one embodiment, the attachment  202  is adjustable in the slot of the blade body  200 . For example, the attachment  202  may be unfastened and moved to a new position relative to the blade body  200  to change or improve how the blade  116  engages the inner tubular  50  as described herein. After the adjustment, the attachment  202  may again be fastened to the blade body  200 . 
     The attachment  202  includes a cutting structure  204  configured to cut a tubular, such as the inner tubular  50 . In some embodiments, cutting structure  204  is configured to cut through a tubular, thereby making a full-thickness cut. In some embodiments, cutting structure  204  is configured to make a partial-thickness cut, thereby reducing the thickness of the tubular at the proximity of the cut. Cutting structure  204  may be configured to cut the tubular with a desired shape or geometry, such as a groove, dovetail, or other desired cut shape or profile. In some embodiments, cutting structure  204  cuts a profile into the tubular that prepares the tubular for subsequent device latching. In some embodiments, cutting structure  204  cuts a notch into the tubular, thereby scoring the tubular for later axial separation at the proximity of the cut. In some embodiments, the profile may be a substantially uniform (within +/−10%) feature machined into the inner wall of the tubular. Cutting structure  204  may cut the tubular in any fashion that removes material, including milling, grinding, machining, chipping, boring, plaining, shaving, etc. In one embodiment, the attachment  202  includes a protrusion  203 . The cutting structure  204  may be disposed on the protrusion  203  of the attachment  202 . The protrusion  203  extends outward, as shown in  FIGS. 2A and 2B . In some embodiments, rotational axis A serves as pivot point  120 . In some embodiments, the blade  116  includes a pivot pin in aperture  201  along axis A. In some embodiments, as the blade  116  extends radially outward from the longitudinal axis of cutting tool  10 , the cutting structure  204  moves upward within the tubular. Consequently, the amount of extension of the blade  116  from the cutting tool  10  may be expressed as a measurement of rotation angle about axis A. The cutting structure  204  is disposed on a leading edge of the protrusion  203  of the blade body  200  such that the cutting structure  204  cuts the inner tubular  50  when the tool  10  rotates 300 about its longitudinal axis and the blade  116  is in an extended position, as shown in  FIG. 3 . The sweep of the tool  10  is the diameter of the circle formed by the outermost extension of the cutting structure  204  as the tool  10  rotates 300 about its longitudinal axis. The cutting structure  204  may be disposed in a groove formed at the leading edge of the protrusion  203  of the blade body  200 . In one embodiment, a top surface  205  of the cutting structure  204  is flush with a top surface  209  of the protrusion  203 . The cutting structure  204  includes any suitable material suitable for cutting the inner tubular  50 . In one embodiment, the cutting structure  204  includes at least one carbide insert, as shown in  FIGS. 2A and 2B . In another embodiment, the cutting structure  204  includes crushed carbide in a braze matrix. In yet another embodiment, the cutting structure  204  includes at least one polycrystalline diamond compact insert. The cutting structure  204  may be brazed onto the attachment  202  using any suitable material, such as a copper nickel alloy. For any given tubular, a suitable cutting structure  204  may include any material that is at least as hard as the material of the inner surface of that tubular. 
     In some embodiments, attachment  202 ′ may include a non-cutting structure  204 ′ in place of cutting structure  204 . Non-cutting structure  204 ′ may be dimensionally similar to cutting structure  204 , however non-cutting structure  204 ′ may be configured to deform the tubular, displacing rather than removing material therefrom. Non-cutting structure  204 ′ may be configured to deform the tubular with a desired shape or geometry, such as a groove, dovetail, or other desired deformation shape or profile. In some embodiments, non-cutting structure  204 ′ deforms a profile into the tubular that prepares the tubular for subsequent device latching. In some embodiments, the profile may be a substantially uniform (within +/−10%) feature pressed into the inner wall of the tubular. 
     The attachment  202  may be modified to accommodate for the anticipated wear of the cutting structure  204 . The attachment  202  may also be modified to accommodate for cutting through tubulars of various thicknesses. For example, a plurality of carbide inserts may be combined to form a cutting structure  204  having a length L at least as long as the thickness of the inner tubular  50  at the proximity of the cut. The length L of the cutting structure  204  may also be selected such that the cutting structure  204  does not substantially contact or cut outer tubular  60 , thereby avoiding damaging the outer tubular  60 , when the blade  116  has cut through the inner tubular  50 , as shown in  FIGS. 1C and 5 . For example, substantial contact includes cutting through more than 25% of the thickness of the outer tubular  60  at the proximity of the cut. In another example, substantial contact includes cutting through more than 15% of the thickness of the outer tubular  60  at the proximity of the cut. In yet another example, substantial contact includes cutting through more than 10% of the thickness of the outer tubular  60  at the proximity of the cut. In some embodiments, the length L of the cutting structure  204  ranges from 1/32 inches to ½ inches greater than the thickness of the inner tubular  50  at the proximity of the cut. In other embodiments, the length L of the cutting structure  204  ranges from 1/16 inches to ⅛ inches greater than the thickness of the inner tubular  50  at the proximity of the cut. 
     The attachment  202  may include a stop  208  configured to limit the extension of the blade  116 , and thereby limit the sweep of the tool  10 . The stop  208  may be positioned on an outward-facing surface of the attachment  202 , as shown in  FIGS. 2A and 2B . The stop  208  may be positioned adjacent the cutting structure  204 . In one example, the stop  208  is positioned above the cutting structure  204 . In another example, the stop  208  is positioned below the cutting structure  204 . At least a portion of the stop may be made of a low-friction material. In one embodiment, the stop  208  is configured to limit a depth of cut of the cutting structure  204 . The depth of cut is defined by a radial (with respect to the longitudinal axis of the tubular) cutting distance extending from the stop  208  to the edge of cutting structure  204 . The stop  208  may be formed at an angle relative to the top surface  205  of the cutting structure  204 . In some embodiments, the angle between the stop  208  and the top surface  205  of the cutting structure  204  ranges from 60 degrees to 90 degrees, from 90 degrees to 120 degrees, and/or from 60 degrees to 120 degrees. In other embodiments, the angle ranges from 80 degrees to 90 degrees, from 90 degrees to 110 degrees, and/or from 80 degrees to 110 degrees. In yet other embodiments, the angle ranges from 85 degrees to 90 degrees, from 90 degrees to 95 degrees, and/or from 85 degrees to 95 degrees. In some embodiments, the stop  208  may be configured to limit the extension of the blade  116 , and thereby limit the sweep of the tool  10 , to produce a partial thickness cut in the inner tubular  50 . In some embodiments, the stop  208  may be configured to limit the extension of the blade  116 , and thereby limit the sweep of the tool  10 , to make a full-thickness cut (cut through) inner tubular  50 , while preventing a substantial cut in the outer tubular  60 . In one embodiment, a carbide rod is brazed onto the stop  208  and provides a low-friction surface against the inner tubular  50  when the blade  116  has cut through the inner tubular  50 . For example, a longitudinal axis of the carbide rod is parallel or substantially parallel with a longitudinal axis of the inner tubular  50  when the blade  116  has cut through the inner tubular  50 . In another embodiment, the stop  208  includes a low-friction surface, such as a layer of smooth hard metal. For example, the stop  208  includes a hardfacing alloy  210  that is bonded to the attachment  202  using a laser and/or plasma arc process as is known in the art. The hardfacing alloy  210  may provide a low-friction surface against the inner tubular  50  when the blade  116  has cut through the inner tubular  50 . The hardfacing alloy  210  may be configured to not cut the inner tubular  50 . The hardfacing alloy  210  may have a non-uniform thickness. For example, the hardfacing alloy  210  may include a contoured profile corresponding to the inner tubular  50 . Alternatively, the hardfacing alloy  210  may have a uniform thickness, as shown in  FIG. 2B . In some embodiments, a thickness of the hardfacing alloy  210  ranges from 0.005 inches to 0.02 inches. In other embodiments, the thickness of the hardfacing alloy  210  ranges from 0.008 inches to 0.012 inches. 
     The attachment  202  of blade  116  also may include an initial engagement point, for example a wearable member  206 , configured to contact the tubular prior to other portions or components of blade  116 . The initial engagement point thereby may prevent the deformation and/or chipping of the cutting structure  204 . As such, the initial engagement by wearable member  206  guides the cutting structure into contact with the tubular. For example, the wearable member  206  may act to cushion the impact between the blade  116  and the inner tubular  50 . In one embodiment, the wearable member  206  is disposed on a outward-facing surface of the cutting structure  204 . In another embodiment, the wearable member  206  is disposed on a outward-facing surface, such as outer surface  207  of the protrusion  203 , as shown in  FIG. 2A . The outer surface  207  may be parallel or, alternatively, angled relative to the stop  208  as shown in  FIG. 3 . In one embodiment, the wearable member  206  is centered on the outer surface  207 . In another embodiment, the wearable member  206  is positioned on the outer surface  207  towards the leading edge of the blade body  200 . The wearable member  206  includes any appropriate material, such as metal alloy. Exemplary materials in the wearable member  206  include nickel, silver solder, rubber, elastomer, and/or epoxy. The wearable member  206  may have any appropriately shaped outer surface, such as a rounded outer surface as shown in  FIGS. 2A and 2B . In one embodiment, the wearable member  206  is spherically shaped. For example, the outer surface  207  of the protrusion  203  includes a groove therein for receiving the spherically shaped wearable member  206 . The spherically shaped wearable member  206  is bonded to the attachment  202  in the groove. In another embodiment, the wearable member  206  is hemispherically shaped. For example, a flat side of the hemispherically shaped wearable member  206  may be bonded to the outer surface  207  of the protrusion  203 . The wearable member  206  may have a thickness  214  measured from the outer surface  207  of the protrusion  203  to an apex of the wearable member  206 , as shown in  FIG. 2B . The thickness  214  of the wearable member  206  is selected in order to provide a gradual engagement between the cutting structure  204  and the tubular inner  50 , or to guide cutting structure  204  into contact with inner tubular  50  as described herein. In some embodiments, the thickness  214  of the wearable member  206  ranges from 0.05 inches to 0.3 inches. In other embodiments, the thickness  214  of the wearable member  206  ranges from 0.10 inches to 0.15 inches. 
     During operation, the tool  10  may be lowered into the inner tubular  50  with the blades  116  in the retracted position. In one embodiment, the tubular  50  is tubing disposed in casing. In another embodiment, the inner tubular  50  is casing/liner disposed in the wellbore  20 . In yet another embodiment, the inner tubular  50  is an inner casing/liner disposed in an outer casing/liner, such as outer tubular  60 , as shown in  FIG. 1A . Cement may or may not be disposed on an outer surface of any one or more of the nested tubulars. In one embodiment, the inner tubular  50  and the outer tubular  60  are concentrically aligned in the wellbore  20 . In another embodiment, the inner tubular  50  and the outer tubular  60  are not concentrically aligned, as shown in  FIG. 3 . The tool  10  may be positioned at a desired depth. As shown in  FIG. 1A , the inner and outer tubulars  50 ,  60  may overlap at the desired depth. Thereafter, the blades  116  may be extended outwardly, as shown in  FIG. 1B . The blades  116  may thereby extend radially outwardly relative to the longitudinal axis of cutting tool  10 , and the cutting structure  204  may move upwardly within the tubulars  50 ,  60 . 
     Actuation assembly  30  may act to extend blades  116  of the blade assembly  40 . In some embodiments, actuation assembly  30  is hydraulic. To actuate the blades  116  into an extended position, fluid is injected through the tool  10 . A first portion of the injected fluid enters the bore of the movable member  104  before entering the larger bore of the piston  112 . Thereafter, the first portion of fluid passes through a bottom of the housing  15 . A second portion of the injected fluid passes through the apertures  106  of the retaining member  102  and may act on the packing seal  114  of the piston  112 . Fluid pressure in the housing  15  is increased, thereby moving the movable member  104  downward and compressing the spring  108  against the retaining member  102 . In turn, the movable member  104  urges the piston  112  downward, thereby compressing the spring  115 . The piston  112  acts on the blades  116 , thereby actuating the blades  116  into an extended position.  FIG. 1B  shows the blades  116  extending toward the inner tubular  50 . In this example, a bottom of the piston  112  acts on a shoulder of each blade  116 , thereby causing each blade  116  to rotate about its respective pivot point  120 . As would be apparent to one of ordinary skill in the art with the benefit of this disclosure, actuation assembly  30  can be other than hydraulic while still being capable of selectively extend blades  116  of the blade assembly  40 . For example, actuation assembly  30  could be an electromagnetic device. 
     In one embodiment, the tool  10  provides an indication at the surface of the wellbore  20  that the blades  116  have cut through the inner tubular  50 . For example, the actuation assembly  30  is configured such that the movable member  104  and the piston  112  disengage when the blades  116  cut through the wall of the inner tubular  50 . Upon cutting through the inner tubular  50 , the movable member  104  reaches a stop and the fluid acting on the piston surface of the piston  112  causes the piston  112  to move downward relative to the movable member  104 . As a result, the piston  112  disengages from the bottom surface of the movable member  104 , as shown in  FIG. 1C . In turn, the second portion of the injected fluid enters the bore of the piston  112  and causes the fluid pressure in the housing  15  to decrease. In one embodiment, the pressure drop corresponds to the blades  116  being perpendicularly positioned relative to the inner tubular  50 , thereby indicating that the blades  116  have cut through the inner tubular  50 . In another embodiment, the pressure drop corresponds to the blades  116  having cut through the inner tubular  50 . As would be apparent to one of ordinary skill in the art with the benefit of this disclosure, actuation assembly  30  can be other than hydraulic while still being capable of providing an indication at the surface of the wellbore  20  that the blades  116  have cut through the inner tubular  50  and responding appropriately. 
     Upon indication that the blades  116  have cut through the inner tubular  50 , the blades  116  are returned to the retracted position. In some embodiments, to return the blades  116  to the retracted position, fluid pressure in the housing  15  may be decreased. As a result, the spring  115  may overcome the fluid force acting on the packing seal  114 . The piston  112  is urged upwards into engagement with the bottom surface of the movable member  104 . By moving upwards, the piston  112  disengages from the blades  116  and the spring  122  urges the blades  116  into the retracted position. 
     In one embodiment, the wearable member  206  is positioned between the cutting structure  204  and the inner tubular  50  when the blade  116  engages the inner tubular  50 , as shown in  FIG. 4 . As such, when the blade  116  initially engages the inner tubular  50 , the wearable member  206  protects the cutting structure  204  from impact against the inner tubular  50 . For example, upon actuation by the actuation assembly  30 , the blade  116  may engage the inner tubular  50  with such intensity that, in the absence of wearable member  206 , the cutting structure  204  may deform and/or chip. Due to the position of the wearable member  206  relative to the cutting structure  204 , the wearable member  206  may absorb all or substantially all of the impact between the blade  116  and the inner tubular  50 , thereby preventing deformation and/or chipping of the cutting structure  204 . In one example, the cutting structure  204  does not contact the inner tubular  50  when the blade  116  initially engages the inner tubular  50 . As a result, the wearable member  206  absorbs all of the impact between the blade  116  and the inner tubular  50 . In another example, the wearable member  206  and the cutting structure  204  both contact the inner tubular  50  when the blade  116  initially engages the inner tubular  50 . As a result, the wearable member  206  may absorb substantially all of the impact between the blade  116  and the inner tubular  50 . 
     In one embodiment, the tool  10  is rotated relative to the inner tubular  50  while the blades  116  are extending toward the inner tubular  50 . In one embodiment, a mud motor rotates the tool  10 . 
     As the tool  10  rotates, the wearable member  206  may protect the cutting structure  204  by deforming temporarily or permanently. For example, the thickness of the wearable member  206  may gradually decrease during the rotation of the tool  10 . In one embodiment, the thickness of the wearable member  206  may decrease by 5% to 25% per revolution. In another embodiment, the thickness of the wearable member  206  may decrease by 10% to 20% per revolution. In one embodiment, the wearable member  206  may flatten during the rotation of the tool  10 . In another embodiment, the wearable member  206  may wear away. As a result, the wearable member  206  may guide the cutting structure  204  into contact with the inner tubular  50  by allowing the blade  116  to extend to and into the inner tubular  50 . By guiding the cutting structure  204  into contact with the inner tubular  50 , the wearable member  206  prevents interrupted cutting. In one embodiment, interrupted cutting happens when the tool  10  skips, jumps, and/or bumps against a surface. For example, abrupt contact between the cutting structure  204  and the inner tubular  50  may cause at least one of the blades  116  to temporarily disengage from the inner tubular  50 . This is referred to as a jump. After the jump, the tool  10  may experience a bump. For example, the tool  10  bumps the inner tubular  50  when the blade  116  reengages the inner tubular  50  with such intensity that the cutting structure  204  on the blade  116  is subject to deforming and/or chipping. In one embodiment, the tool  10  may bump the inner tubular  50  without deforming and/or chipping the cutting structure  204  on the blade  116 . Due to the composition and dimensions of the wearable member  206 , the cutting structure  204  may avoid abrupt contact with the inner tubular  50 . As a result, the wearable member  206  may prevent the deformation and/or chipping of the cutting structure  204 . In one embodiment, the entire thickness of the wearable member  206  may wear away or flatten before the cutting structure  204  engages the inner tubular  50 . In another embodiment, only a portion of the thickness of the wearable member  206  wears away or flattens before the cutting structure  204  engages the inner tubular  50 . 
     As the cutting structure  204  cuts the inner tubular  50 , the blade  116  may further extend, for example by rotating about the pivot point  120 , thereby increasing the sweep of the tool  10 . For example, the actuation assembly  30  may act to provide a constant downward force on the shoulders of the blade  116  during cutting, which urges the blade  116  into further extension. As a result, the cutting structure  204  cuts through the inner tubular  50 , as shown in  FIG. 5 . In one embodiment, the top surface  205  of the cutting structure  204  is perpendicular or substantially perpendicular to the longitudinal axis of the inner tubular  50  when the cutting structure  204  cuts through the inner tubular  50 . In some embodiments, the blade  116  may rotate 90° about axis A from the retracted position to the extended position wherein cutting structure  204  is perpendicular or substantially perpendicular to the longitudinal axis of the inner tubular  50 . 
     After the cutting structure  204  has made the desired cut to inner tubular  50 , for example making a full-thickness cut through the inner tubular  50 , extension of the blade  116 , and consequently sweep of the tool  10 , is limited regardless of the fluid pressure in the housing  15 . For example, the stop  208  may engage the inner tubular  50  when the cutting structure  204  cuts through the inner tubular  50 , thereby preventing the blade  116  from substantially damaging the structural integrity of the outer tubular  60 . Thereafter, the stop  208  may remain engaged with the inner tubular  50 . As a result, the stop  208  stabilizes the tool  10  in the inner tubular  50 . For example, the stop  208  prevents interrupted cutting by providing continuous engagement between the tool  10  and the inner tubular  50 . In one embodiment, the stop  208  prevents any engagement between the blade  116  and the outer tubular  60  when the blade  116  has cut through the inner tubular  50 , as shown in  FIG. 5 . In another embodiment, the stop  208  prevents significant engagement between the blade  116  and the outer tubular  60 . In one example, significant engagement includes cutting through more than 25% of the thickness of the outer tubular  60  at the proximity of the cut. In another example, significant engagement includes cutting through more than 15% of the thickness of the outer tubular  60  at the proximity of the cut. In yet another example, significant engagement includes cutting through more than 10% of the thickness of the outer tubular  60  at the proximity of the cut. In some embodiments, after the stop  208  engages inner tubular  50 , the rotation of blade  116  about axis A does not increase. For example, the action of actuation assembly  30  may not further extend blade  116  after the stop  208  engages inner tubular  50 . In some embodiments, after the stop  208  engages inner tubular  50 , the sweep of tool  10  is limited and does not increase when actuation assembly  30  actuates piston  112 , for example, when fluid pressure in the housing  15  changes. In some embodiments, after the cutting structure  204  has cut through the inner tubular  50 , increase in either the rotation of the blade  116  about axis A or the sweep of the tool  10  is limited and prevented from increasing when actuation assembly  30  actuates piston  112 , for example, when the fluid pressure in the housing  15  changes. The stop  208  may stabilize the Engagement of the stop  208  with the inner tubular  50  may provide a more uniform cut. For example, by preventing interrupted cutting, engagement of the stop  208  with the inner tubular  50  may result in less damage around the cut, such as pitting, chipping, or splintering. Likewise, the engagement of stop  208  may prevent torque spikes while rotating the tool  10 . 
     In one embodiment, when the tool  10  is positioned at the proper depth in the inner tubular  50 , the tool  10  is not centralized in the inner tubular  50 . This may result in an unevenly distributed cut wherein the rotating blades  116  contact only a portion of the inner tubular  50 . For example, a mule shoe cut may result. As a result, the blades  116  may create a cut that spans only a portion of the circumference of the inner tubular  50 . 
     In one embodiment, the actuation assembly  30  provides an evenly distributed cut by actuating the blades  116  into an extended position, as shown in  FIG. 3 . For example, the piston  112  of the actuation assembly  30  may provide a substantially equal (within +/−10%) force on the shoulder of each blade  116  such that each blade  116  engages the inner tubular  50  with a substantially equal radial force. The radial forces from the blades  116  may cause the tool  10  to move laterally, thereby causing each blade  116  to engage the inner tubular  50 . For example, in the event that tool  10  is not centralized in inner tubular  50 , the radial forces from the blades  116  engaging with inner tubular  50  may cause the tool  10  to move laterally, thereby repositioning tool  10  to be more centralized in inner tubular  50 . In another embodiment, the stop  208  is configured to limit the extension of the blade  116 , thereby providing an evenly distributed cut. For example, the stop  208  may provide a radial force against the inner tubular  50  causing the tool  10  to move laterally in response. In one embodiment, the stop  208  centralizes the tool  10  in the inner tubular  50  by moving the tool  10  laterally. In turn, the tool  10  engages each blade  116  with the inner tubular  50 . As a result, the cut created by the tool  10  spans the entire circumference of the inner tubular  50 . 
     In one embodiment, after the tool  10  cuts through the inner tubular  50  and along the entire circumference of the inner tubular  50 , a portion of the inner tubular  50  below the cut formed by the tool  10  is allowed to fall downward in the wellbore  20 . For example, the portion of the inner tubular  50  below the cut falls into a cavern at a lower end of the wellbore  20 . 
     Thereafter, the blades  116  may be retracted and the cutting operation described herein may be repeated any number of times. For example, the tool  10  may be moved axially upward in the wellbore  20  the inner tubular  50  may be cut into shorter portions. 
     As will be understood by those skilled in the art, a number of variations and combinations may be made in relation to the disclosed embodiments all without departing from the scope of the invention. 
     In one embodiment, a method of cutting a tubular includes providing a rotatable cutting tool in the tubular, the cutting tool having a blade with a cutting structure thereon; extending the blade relative to the cutting tool; rotating the cutting tool relative to the tubular; guiding the cutting structure into contact with the tubular; cutting the tubular using the blade; and limiting extension of the blade. 
     In one or more of the embodiments described herein, an actuation assembly acts to extend the blade relative to the cutting tool. 
     In one or more of the embodiments described herein, the actuation assembly is hydraulic, the method further comprising limiting extension of the blade regardless of a fluid pressure in the housing of the cutting tool. 
     In one or more of the embodiments described herein, limiting extension of the blade comprises engaging a stop with the tubular. 
     In one or more of the embodiments described herein, a method of cutting a tubular includes at least one of: stabilizing the cutting tool by engaging the stop with the tubular, laterally moving the cutting tool by engaging the stop with the tubular, and centralizing the cutting tool by engaging the stop with the tubular. 
     In one or more of the embodiments described herein, the extending the blade relative to the cutting tool happens while at least one of: the rotating the cutting tool relative to the tubular, the guiding the cutting structure into contact with the tubular, a moving the cutting structure upward within the tubular, and a pivoting the blade about a pivot point. 
     In one or more of the embodiments described herein, guiding the cutting structure into contact with the tubular includes making initial contact with the tubular with a wearable member on the blade. 
     In one or more of the embodiments described herein, rotating the cutting tool includes deforming the wearable member. 
     In one or more of the embodiments described herein, guiding the cutting structure into contact with the tubular includes decreasing a thickness of the wearable member. 
     In one or more of the embodiments described herein, the cutting the tubular using the blade comprises a full-thickness cut, and the limiting extension of the blade follows the full-thickness cut. 
     In one or more of the embodiments described herein, a method of cutting a tubular includes providing a second tubular surrounding the tubular; and after cutting through the tubular using the blade, avoiding damaging the second tubular with the cutting tool. 
     In one embodiment, a rotatable blade for cutting a tubular includes a blade body extendable from a retracted position; a cutting structure disposed on a leading edge of the blade body, the cutting structure configured to cut the tubular; a stop on a first surface of the blade body; and an initial engagement point on a second surface of the blade body, the initial engagement point configured to guide the cutting structure into contact with the tubular. 
     In one or more of the embodiments described herein, the first surface of the blade body is the same as the second surface of the blade body. 
     In one or more of the embodiments described herein, at least one of the first surface and the second surface is an outward-facing surface. 
     In one or more of the embodiments described herein, the stop comprises a low-friction material. 
     In one or more of the embodiments described herein, the initial engagement point comprises wearable member. 
     In one or more of the embodiments described herein, the stop is configured to limit at least one of: an extension of the blade body, and a depth of cut of the cutting structure. 
     In one or more of the embodiments described herein, the blade is rotatable about a pivot point. 
     In one or more of the embodiments described herein, a rotatable blade for cutting a tubular includes a pivot pin, wherein the blade is rotatable about the pivot pin. 
     In one or more of the embodiments described herein, the stop is disposed at an angle relative to a top surface of the cutting structure. 
     In one or more of the embodiments described herein, the cutting structure includes at least one of: a carbide insert, a polycrystalline diamond compact insert, and crushed carbide in a braze matrix. 
     In one or more of the embodiments described herein, a length of the cutting structure at least as long as a thickness of the tubular. 
     In one or more of the embodiments described herein, the cutting structure, the stop, and the initial engagement point are disposed on an attachment. 
     In one or more of the embodiments described herein, the attachment is at least one of: integrally formed with the blade body, operably coupled to the blade body, and replaceable. 
     In one embodiment, a method of cutting a tubular includes positioning a rotatable cutting tool in the tubular, the cutting tool having a blade and a cutting structure; extending the blade relative to the cutting tool; rotating the cutting tool relative to the tubular; guiding the cutting structure into contact with the tubular; cutting the tubular using the cutting structure; and limiting a sweep of the cutting structure. 
     In one or more of the embodiments described herein, the cutting tool further has a plurality of blades extendable relative to the cutting tool. 
     In one or more of the embodiments described herein, a length of the cutting structure is at least as long as a thickness of the tubular at a proximity of the cutting. 
     In one or more of the embodiments described herein, limiting the sweep includes selecting an angle between the cutting structure and a stop of the blade. 
     In one or more of the embodiments described herein, a method of cutting a tubular includes avoiding damaging a second tubular surrounding the tubular after cutting through the tubular using the cutting structure. 
     In one or more of the embodiments described herein, the cutting the tubular comprises: making a partial-thickness cut; and cutting a profile into the tubular.