Abstract:
The tubular cutter disclosed herein is useful for severing downhole tubulars and comprises a drive system, a pivoting system, a cutting head, and a cutting member. Cutting is accomplished by rotatingly actuating the cutting head with an associated motor, and then radially extending the cutting blade away from the cutting head. In one embodiment, the cutting head includes a cutting member that pivotally extends from the cutting head upon rotation of the cutting head.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The disclosure herein relates generally to the field of severing a tubular member. More specifically, the present disclosure relates to an apparatus for cutting downhole tubulars. Yet more specifically, described herein is a method and apparatus for optimizing cutting tubulars wherein lubrication is maintained between the cutting member and the tubular. 
   2. Description of Related Art 
   Tubular members, such as production tubing, coiled tubing, drill pipe, casing for wellbores, pipelines, structural supports, fluids handling apparatus, and other items having a hollow space can be severed from the inside by inserting a cutting device within the hollow space. As is well known, hydrocarbon producing wellbores are lined with tubular members, such as casing, that are cemented into place within the wellbore. Additional members such as packers and other similarly shaped well completion devices are also used in a wellbore environment and thus secured within a wellbore. From time to time, portions of such tubular devices may become unusable and require replacement. On the other hand, some tubular segments have a pre-determined lifetime and their removal may be anticipated during completion of the wellbore. Thus when it is determined that a tubular needs to be severed, either for repair, replacement, demolishment, or some other reason, a cutting tool can be inserted within the tubular, positioned for cutting at the desired location, and activated to make the cut. These cutters are typically outfitted with a blade or other cutting member for severing the tubular. In the case of a wellbore, where at least a portion of the casing is in a vertical orientation, the cutting tool is lowered (such as by wireline, tubing, or slickline) into the casing to accomplish the cutting procedure. 
   BRIEF SUMMARY OF THE INVENTION 
   Disclosed herein is a tubular cutting system and method wherein lubrication is delivered during cutting. The system employs a rotating blade and a lubrication system for dispensing lubrication between the blade&#39;s cutting surface and the tubular to be cut. Optionally an isolation material may be included for retaining the lubrication in the cutting region. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1 . is a side view of an embodiment of a cutting tool in a tubular. 
       FIG. 2  is a side view of an alternative embodiment of a cutting tool in a tubular. 
       FIG. 3  is a side view of an alternative embodiment of a cutting tool in a tubular. 
       FIG. 4   a  is a side view of a cutting tool having a lubrication system. 
       FIG. 4   b  is a magnified side view of a cutting tool with a lubrication system. 
       FIG. 5  is an overhead view of a cutting blade having lubrication delivery ducts. 
       FIG. 6  is a partial cut away view of a cutting tool disposed in a cased wellbore. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Described herein is a method and apparatus for cutting and severing a tubular. While the apparatus and method described herein may be used to cut any type and length of tubular, one example of use involves severing tubing disposed within a wellbore, drill pipe, wellbore tubular devices, as well as wellbore casing. One embodiment of a cutting tool  10  as described herein is shown in side partial cut away view in  FIG. 1 . In this embodiment, the cutting tool  10  comprises a body  11  disposed within a tubular  5 . As noted, the tubular  5  may be disposed within a hydrocarbon producing wellbore, thus in the cutting tool  10  may be vertically disposed within the wellbore tubular. Means for conveying the cutting tool  10  in and out of the wellbore include wireline, coiled tubing, slick line, among others. Other means may be used for disposing the cutting tool  10  within a particular tubular. Examples of these include drill pipe, line pigs, and tractor devices for locating the cutting tool  10  within the tubular  5 . 
   Included within the body  11  of the cutting tool  10  is a cutting member  12  shown pivotingly extending out from within the body  11 . A lubricant  18  is shown (in cross hatch symbology) disposed in the cutting zone  22  formed between the outer surface of the tool  10  and the inner circumference  6  of the tubular  5 . For the purposes of discussion herein, the cutting zone  22  is designed as the region on the inner circumference of the tubular, as well as the annular space between the tool and the tubular proximate to the portion of the tubular that is being cut by the cutting tool. Examples of lubricants include hydrogenated polyolefins, esters, silicone, fluorocarbons, grease, graphite, molybdenum disulfide, molybdenum sulfide, polyolefins,ethylene, animal oils, vegetable oils, mineral oils, and petroleum based oils. 
   Lubricant  18  inserted between the cutting member and the inner circumference  6  enhances tubular machining and cutting. The lubricant  18  may be injected through ports or nozzles  20  into the annular space between the tool  10  and the tubular  5 . These ports  20  are shown circumferentially arranged on the outer surface of the tool housing  11 . The size and spacing of these nozzles  20  need not be arranged as shown, but instead can be fashioned into other designs depending upon the conditions within the tubular as well as the type of lubricant used. As discussed in more detail below, a lubricant delivery system may be included with this device for storing and delivering the lubricant into the area between the cutting member and the inner circumference of the tubular  6 . In many situations when disposing a cutting tool within a tubular, especially a vertically oriented tubular, lubricants may be quickly drawn away from where they are deposited by gravitational forces. Accordingly, proper lubrication during a cutting sequence is optimized when lubrication is maintained within the confines of the cutting zone  22 . 
   Additional ports  16  are shown disposed on the outer surface of the housing  11  for dispensing an isolation material  14  into the space between the tubular  5  and the tool  10 . The lubricant port  20  location with respect to the isolation port  16  location enables isolation material  14  to be injected on opposing sides of the lubricant  18 . Isolation material being proximate to the lubricant can retain a lubricant within or proximate to the cutting zone  22 . Referring again to  FIG. 1 , an isolation material  14  is disposed in the annular space between the tool  10  and the tubular  5  and on opposing ends of the lubricant  18 . Thus the isolation material should possess sufficient shear strength and viscosity to retain its shape between the tool  10  and the tubular and provide a retention support for the lubricant  18 . 
   Examples of isolation materials include a gel, a colloidal suspension, a polysaccharide gum, xanthan gum, and guar gum. One characteristic of suitable isolation material may include materials that are thixotropic, i.e. they may change their properties when external stresses are supplied to them. As such, the isolation material should have a certain amount of inherent shear strength, high viscosity, and surface tension in order retain its form within the annular space and provide a retaining force to maintain the lubricant in a selected area. Thus, as shown in  FIG. 1 , the presence of the isolating material on opposite sides of the lubricant helps retain the lubricant within the cutting zone. 
   An alternative embodiment of a cutting tool  10   a  is provided in side partial cross sectional area in  FIG. 2 . In this embodiment, a single set of nozzles  16  is provided on the body  11   a . Optionally, in this situation, the isolation material nozzles  16  could be disposed lower than the lubrication nozzles  20 . 
   Yet another embodiment of a cutting tool  10   b  for use in cutting tubulars with added lubrication is provided in side view in  FIG. 3 . In this embodiment the cutting member  12   a  is a straight blade affixed to a portion of the body  11   b . Although in this embodiment a single set of nozzles  16  is shown for disposing isolation material  14  into the annular space between the cutting tool  10   b  and the inner surface  6  of the tubular  5 , multiple sets of nozzles can be included with this embodiment along the length of the cutting tool l 0   b . As shown, the lubricant  18  has been injected into the tubular  5  between the tool  10   b  and the tubular inner circumference  6 . Thus, the cutting zone  22  includes lubrication for enhancing any machining or cutting by the tool  10   b . Isolation material  14  is also injected into the annular space between the tool  10   b  and the tubular thereby providing a retaining support for the lubricant  18 . 
   Another embodiment for delivering lubrication to a cutting surface is provided in  FIGS. 4   a  and  4   b . Here an example is provided of delivering a lubricant  18  to the cutting surface of a cutting blade by installing conduits within the blade itself. More specifically a cutting tool  10   c  is shown in side view in  FIG. 4   a . In this embodiment the cutting member  12   b  is a blade attached to a portion of the body  11   c . The cutting tool  10   c  is rotated thereby urging the single blade into rotational cutting contact with the inner surface  6  of a tubular  5 . A reservoir (not shown) is disposed within the body  11   c  for delivering lubricant  18  in this space between the cutting surface and the tubular inner surface  6 . A series of passages or conduits attached to the reservoir for the lubricant to flow to the tip of the cutting member  12   b . As shown in partial cut away side view in  FIG. 4   b , is a supply line  24  formed co-planerly along the length of the blade and terminating in a nozzle exit  26  at the tip of the blade  12   b  on its cutting surface  27 . As such, lubricant  18  may be constantly supplied out into the nozzle exit  26  during a tubular cutting procedure. Thus lubricant is provided between the cutting surface  27  and the inner surface  6  for enhancing machining of the tubular by the cutting tool  10   c . 
     FIG. 5  provides an overhead view of one example of a cutting member  12   c . In this view the cutting member comprises a blade  15  having conduits formed within its surface for delivering lubricant to a cutting surface. In this embodiment, the cutting member  12   c  includes an inlay  28  on its cutting surfaces. The blade  15  can be rotationally attached and rotated during cutting so that the opposing cutting surfaces  26   a  may be used for severing a tubular. As with the cutting member of  FIG. 4   b , a supply line  24   a  is shown traveling along the side length of the cutting surface and terminating at an exit nozzle  26   a  proximate to the cutting surface. Therefore during cutting operations delivering a lubricant through a nozzle exit  26   a  will deliver lubricant on the cutting surface during a cutting sequence for optimizing machining of the tubular. By injecting lubricant on the cutting surface just prior to cutting that surface ensures lubricant will be in place during cutting. Optionally a nozzle could be formed on the blade  15  cutting edge so that lubricant is added during the entire cutting sequence and is present between the cutting blade  15  and the cutting surface. 
     FIG. 6  provides a partial side cut away view of an embodiment of a cutting system used in cutting a tubular  7 . In this embodiment a cutting tool  10   d  is shown disposed in a cased wellbore  4  by a conveyance means  8 . The tubular  7  is coaxially disposed within the wellbore casing. Optionally, the cutting tool  10   d  may be employed for cutting the wellbore casing and used in the same fashion it is used for cutting the tubular  7 . Examples of means used in deploying the tool in and out of a wellbore by the conveyance means include wireline, slick line, coil tubing, and any other known manner for disposing a tool within a wellbore. This embodiment of the cutting tool  10   d  includes a controller  38 , a lubricant delivery system  40 , an isolation material delivery system  46 , and a cutting member  12 . The controller  38 , which may include an information handling system, is shown integral with the cutting tool  10   d  and used for controlling the operation of the cutting tool  10   d  when disposed within the tubular. The controller may be configured to have preset commands stored therein, or can receive commands offsite or from another location via the conveyance means  8 . 
   As its name suggests, the lubricant delivery system  40  comprises a system for delivering lubricant within the space between the cutting member and the tubular. In this embodiment the system comprises a lubricant pressure system  42  in communication with a lubricant reservoir  44 . Here the pressure system  42  (which may be spring loaded, a motor driven pump, or have pressurized gas) is used for propelling lubricant within the reservoir  44  through the tool  10   d  and adjacent the cutting member  12  as described above. 
   Similar to the lubricant delivery system, the isolation material delivery system  46  also comprises a pressure supply  48  and a reservoir  50 . The pressure supply  48  (may also be a pump, spring loaded device, or have compressed gas) is used in propelling the isolation material from the reservoir  50  and out into the annular space surrounding the tool  10   d  and inside the tubular. It should be pointed out that the sequence of introducing the isolation material and the lubricant into the tubular can be simultaneous. Optionally either the isolation material or the lubricant may be delivered into the annular space before the other in sequential or time step fashion. As far as the amount of lubricant or isolation material delivered, it depends on the particular dimensions of the tool as well as the tubular being severed, it is believed it is well within the capabilities of those skilled in the art to design a system for delivering a proper amount of lubricant as well as isolation material. 
   As shown with the embodiment of  FIG. 6 , the cutting member is in a cutting sequence for cutting the tubular  7  and isolation material  14  is shown retaining a quantity of lubricant adjacent the cutting member  12  thereby maintaining the lubricant in the space between the cutting member and the tubular  7 . A controller  34  disposed at surface may be employed to control the tool  10   d . The controller may be a surface truck disposed at the surface as well as any other currently known or later developed manner of controlling a wellbore tool from the surface. Included optionally is an information handling system  36  that may be coupled with the controller  34  either in the same location or via some communication either wireless or hardwire. 
   It should be pointed out that the exit nozzles can have the same cross sectional area as the supply lines leading up to these nozzles, similarly other types of nozzles can be employed, such as a spray nozzle having multiple orifices, as well as an orifice type arrangement where the cross sectional area at the exit is substantially reduced to either create a high velocity stream or to atomize the lubricant for more dispersed application of a lubricant. 
   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.