Abstract:
A method for cleaning and/or altering an inside surface and shape of a tubular in a wellbore. The method includes placing a surface finishing tool in the tubular, energizing the surface finishing tool, and causing extendable assemblies therein to extend radially to contact an inside diameter of the tubular. Moving the surface finishing tool axially and/or rotationally while the extended members are in contact with the inside diameter of the tubular cleans debris from the inside surface of the tubular. In another aspect of the invention, the tool burnishes the inside diameter of the tubular, thereby altering the surface characteristics and rounding the tubular.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to methods of cleaning scale and deposits and altering the surface and shape of the inside diameter of tubulars within an oil and gas wellbore. 
     2. Description of the Related Art 
     Hydrocarbon wells typically, begin by drilling a borehole from the earth&#39;s surface to a selected depth in order to intersect a formation. Steel casing lines the borehole formed in the earth during the drilling process. This creates an annular area between the casing and the borehole that is filled with cement to further support and form the wellbore. Thereafter, the borehole is drilled to a greater depth using a smaller diameter drill than the diameter of the surface casing. A liner may be suspended adjacent the lower end of the previously suspended and cemented casing. Production operations often require lining the borehole with a filtration medium. Examples of common filtration media include slotted pipe or tube, slotted screens or membranes, and sand-filled screens. In general, the diameter, location, and function of the tubular that is placed in the well bore determines whether it is known as casing, liner, or tubing. However, the general term tubular or tubing encompasses all of the applications. 
     After completing various operations during the completion of the wellbore, ledges and debris are often left on the inside diameter of the tubular. Excess cement sometimes hardens on the inside of the tubulars after cementing of the liner or casing in the wellbore. Certain downhole milling operations leave metal pieces on the inside of tubulars from either equipment remnants or burrs on the tubular itself. For example, drilling out a packer in order to remove it from the tubular may not fully eliminate all of the metal that comprised the packer. Also, milling a window in the casing to run a horizontal bore causes metal burrs on the inside of the casing around the window. 
     Well tubulars often become plugged or coated during production from corrosion products, sediments, and hydrocarbon deposits such as paraffin. At elevated temperatures underground paraffin is a liquid and flows easily; however, the petroleum and paraffin cools off as the petroleum travels up the well bore toward the surface. At some point the temperature drops low enough to allow the paraffin to solidify on the tubulars in the well bore. Paraffin deposits primarily present a problem for sub-sea tubulars. Other scum and deposits on the inside of tubulars consist of silicates, sulphates, sulphides, carbonates, calcium, and organic growth. Soft deposits such as clay and sand from the formations can enter the bore at locations where the casing or liner has been perforated for production. Highly deviated and horizontal bores are particularly susceptible to collecting debris. 
     Debris that collects on the inside surface of the tubular that defines the bore can obstruct passage through the bore of tubing, equipment, and tools used in various exploration and production operations. Even if the tool can pass through the bore, debris often causes wear and damage to the tubing, equipment, and tools that pass through it. Sustaining production rates requires periodic cleaning since deposits and solidified paraffin on the inside of production tubulars slows down production of oil from the well. 
     Pressure changes in the wellbore, swelling of surrounding formations, earth movements, and formation changes deform downhole tubulars. Therefore, a cross section of downhole tubulars becomes more irregular and non-round over time. Exposure to erosion and corrosion add to the roughness and inconsistent roundness of the inside surface of the tubulars. Even initially, the inside surface of a tubular is typically rough and inconsistently round. Many tools used in downhole operations require a smooth round surface in order to properly operate or make a sealing engagement with the tubular. In addition, a polished bore receptacle that allows for a non-leaking engagement between two tubulars requires a smooth, clean, and substantially round surface. Placing a seal within a polished bore receptacle insures a fluid tight seal between the tool or tubular seated within the polished bore receptacle. 
     In order to create a polished bore receptacle, the roughness of the tubular&#39;s inside diameter must be smoothed, and the inside diameter of the tubular must be reformed into a more uniformly round surface. Since burnishing alters a tubular&#39;s surface characteristics, burnishing the inside diameter of the tubular can establish a polished bore receptacle. Therefore, the burnished inside diameter creates a smooth and substantially round surface. 
     Current operations to clean the inside of tubulars include circulating treating and cleanout fluids such as water, oil, acid, corrosion inhibitors, hot oil, nitrogen, and foam in the tubular. However, physical dislodging of the debris on the tubular walls is sometimes required. Fixed diameter reaming members, scrappers, shoes on the end of tubulars, and circulating cleanout fluids do not allow the ability to clean, alter the surface finish, and/or round various sizes of tubulars during one downhole operation. 
     Therefore, there exists a need for an improved method of physically removing debris from the inside diameter of a wellbore tubular. There exists a further need for an improved method of burnishing the inside diameter of a wellbore tubular, thereby altering and rounding its surface characteristics. 
     SUMMARY OF THE INVENTION 
     The present invention generally relates to a method for cleaning and/or altering an inside surface finish and shape of a tubular in a wellbore. The method includes placing a surface finishing tool in the tubular, energizing the tool, and causing extendable assemblies therein to extend radially into contact with an inside diameter of the tubular. Moving the tool axially and/or rotationally while a portion of the extendable assembly is in contact with the inside diameter of the tubular cleans out debris that has collected in the tubular. In another aspect of the invention, the tool burnishes the inside diameter of the tubular, thereby altering the surface characteristics and rounding the tubular. 
    
    
     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. 1 is an exploded view of an embodiment of the surface finishing tool used for cleaning, resurfacing, and/or rounding wellbore tubulars. 
     FIG. 1A is a section view across line  1 A— 1 A of FIG.  1 . 
     FIG. 2 is an exploded view of an alternative embodiment of the surface finishing tool. 
     FIG. 3 is a longitudinal section view of an embodiment of the surface finishing tool as it would appear in a well bore prior to actuating the extendable assemblies. 
     FIG. 4 is a view of the embodiment in FIG. 3 after actuating the extendable assemblies inside the tubular and moving the tool within the tubular. 
     FIG. 5 is a longitudinal section view of an embodiment of the surface finishing tool as it would appear within casing having a window formed in a wall thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows an exploded view of the surface finishing tool  100  with a body  102  that is hollow and generally tubular. FIG. 1A presents the same surface finishing tool  100  in cross-section, with the view taken across line  1 A— 1 A of FIG.  1 . The central body  102  has a plurality of recesses  114  to hold a respective extendable assembly  110 . Each of the recesses  114  has substantially parallel sides and holds a respective piston  120 . The pistons  120  are radially slidable, one piston  120  being slidably sealed within each recess  114 . The backside of each piston  120  is exposed to the pressure of fluid within a hollow bore  115  of the surface finishing tool  100 . In this manner, pressurized fluid provided from the surface of the well can actuate the pistons  120  and cause them to extend outwardly. 
     Disposed above each piston  120  is a roller  116 . In one embodiment of the surface finishing tool  100 , the rollers  116  are near cylindrical and slightly barreled. Each of the rollers  116  is supported by a shaft  118  at each end of the respective roller  116  for rotation about a respective axis. The rollers  116  are generally parallel to the longitudinal axis of the tool  100 . In the arrangement of FIG. 1, the plurality of rollers  116  is radially offset at mutual 120-degree circumferential separations around the central body  102 . In the arrangement shown in FIG. 1, two offset rows of rollers  116  are shown. However, only one row, or more than two rows of roller  116 , may be incorporated into the body  102 . An abrasive surface may be added to the outer circumference of the rollers  116 . 
     FIG. 2 illustrates an alternative embodiment of the extendable assembly  110  of the surface finishing tool  100 . Solid independent non-rolling members  200  disposed above each piston  120  replaced the rollers  116  from FIG. 1. A portion of the non-rolling member  200  opposite the piston  120  possesses a plurality of edges that form teeth. Similarly, the ends of the non-rolling members  200  that extend from the tool  100  may be hard bristles that form a brush, sharpened edges, or blades. The non-rolling member  200  can replace one or more of the rollers  116  from the embodiment shown in FIG.  1 . For example, a leading offset row of extendable assemblies  110  may comprise non-rolling members  200  with brush ends while a tailing offset row of extendable assemblies  110  includes the rollers  116  shown in FIG.  1 . 
     FIG. 3 illustrates an embodiment of the present invention as it would appear positioned inside a casing  300  within a wellbore  302 . In this embodiment, a plurality of non-compliant rollers  312  positioned parallel to the longitudinal axis of the tool  100  and on a portion of the tool with a gradually increasing outer diameter prevent the tool from jamming in areas of the tubulars that have a constricted inside diameter. Common known methods of lowering the surface finishing tool  100  into the wellbore include attaching the tool to a tubing string  304  or coiled tubing (not shown). If coiled tubing is utilized, a mud motor (not shown) disposed on the coiled tubing provides rotational force to the surface finishing tool  100 . Both a mud motor&#39;s structure and its function are well known in the industry. In FIG. 3, the surface finishing tool  100  is illustrated in a section of casing  300  adjacent to debris  308  that is to be cleaned from the casing&#39;s inside surface and the deformation  310  that is to be rounded. While FIG. 3 illustrates the surface finishing tool positioned in casing  300 , the surface finishing tool can be utilized in any downhole tubular such as liners or production tubulars. 
     FIG. 4 shows the device in FIG. 3 after the surface finishing tool  100  has been actuated and moved relative to the tubular  300 . After the surface finishing tool is in place and at a predetermined time, fluid pressure applied through the tubing string  304  and into the surface finishing tool  100  extends the extendable assembly  110  radially outward into contact with the inside diameter of the tubular  300 . At least one aperture  400  at the lower end of the tool  100  permits fluid to pass through the tool and circulate back to the surface. Rotating the surface finishing tool  100  in the tubular and/or moving the surface finishing tool  100  axially in the tubular while a portion of the extendable assemblies  110  contact the inside diameter of the tubular  300  physically dislodges debris  308  from the inside surface of the tubular  300 . While FIG. 4 shows extendable assemblies  110  with rollers  116  contacting the inside diameter of the tubular, extendable assemblies  110  with the solid independent non-rolling members described herein can be utilized to clean debris  308  from the tubular  300 . The type of debris  308  to be cleaned from the inside surface determines whether the roller  116  or one of the non-rolling members that utilize brushes, teeth, or edges will provide the most efficient cleaning. Outward radial force applied by the surface finishing tool  100  reshapes the inside circumference of the tubular  300  into a more uniformly round shape as the tool rotates inside the irregular section  310  (shown in FIG.  3 ). Axial and rotational movement of the tubing string  304  from the surface moves the surface finishing tool  100  respectively within the tubular. 
     A surface finishing tool with the same features as described in FIG. 1 or FIG. 2 can be used to burnish the inside diameter of a tubular in order to prepare a polished bore receptacle. The term burnish refers broadly to any changes in the surface characteristics of the tubular&#39;s inside diameter. Continued rotation of the tool  100  while the rollers  116  contact the inside diameter of the tubular  300  burnishes a section of the inside diameter of the tubular. Prior to burnishing, the surface finishing tool  100  has cleaned the inside surface of the tubular and reformed the inside surface into a more rounded shape. Burnishing and rounding the inside surface of the tubular  300  with the finishing tool  100  after removing debris  308  with other known apparatuses utilizes the finishing tool in conjunction with other known cleaning devices. The smoothed, cleaned, polished, and substantially rounded inside surface of the tubular as shown in FIG.  4 . provides the required surface and finish needed for a polished bore receptacle. Therefore, a second tubular or tool can be seated within the polished bore receptacle to provide a fluid tight seal. 
     FIG. 5 illustrates the surface finishing tool  100  inside a casing  300  that a window  500  has been milled through a wall thereof. The milling process left metal burrs  502  circumscribing the window  500 . Fluid pressure applied to the surface finishing tool  100  extends the extendable assembly  110  until the rollers  116  contact the inside diameter of the casing  300 . Therefore, moving the actuated surface finishing tool  100  across the window  500  removes the metal burrs  502 . As the surface finishing tool moves axially through the casing  300  the irregularity  310  is formed into a more rounded inside surface and debris  308  is removed. Therefore, the altered inside surface of the casing  300  permits substantially unobstructed fluid flow through the casing and allows passage of subsequent downhole tools without the risk of damage or becoming stuck since the burr  502 , the irregular shape  310 , and the debris  308  have all been removed or reformed. During one downhole operation with the finishing tool  100 , tubulars with multiple sizes of inside diameters can be refinished since the tool&#39;s diameter varies with the extension of the extendable assemblies  110 . 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.