Abstract:
A well bore tool with a torsional resistant slip mechanism for resisting axial and torsional forces comprising a mandrel, a plurality of slips disposed about the circumference of the mandrel. The slips include a plurality of inserts oriented to resist axial forces and torsional forces. The tool also comprises a setting means adjacent each to slip for radially expanding and setting said slips.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to Provisional Application Ser. No. 60/322,617 filed on Sep. 17, 2001 in the name of William Roberts as inventor. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a slip mechanism in anchors or packers used in the oil and gas industry, and more particularly to a mechanically set retrievable packer with a torsional resistant slip mechanism. The disclosure of U.S. patent application Ser. Nos. 09/302,738, now U.S. Pat. No. 6,164,377 issued Dec. 26, 2000, and 09/302,982, now U.S. Pat. No. 6,305,474, are incorporated herein by reference. 
   2. Background of the Invention 
   It is often desirable to sidetrack or deviate from an existing well borehole for various reasons. For instance, when a well bore becomes unusable, a new bore hole may be drilled in the vicinity of the existing cased bore hole or alternatively, a new bore hole may be sidetracked from the serviceable portion of the cased well bore. Such sidetracking from a cased borehole may also be useful for developing multiple production zones. This drilling procedure can be accomplished by milling through the side of the casing with a mill that is guided by a wedge or whipstock component. It is well known in the industry that whipstocks are used to sidetrack drill bits or mills at an angle from a borehole. The borehole may be lined with pipe casing or uncased. More often than not, the previous borehole is cased. 
   To complete a sidetracking operation, a typical down hole assembly consists of a whipstock attached to some form of packer or anchor mechanism that holds the whipstock in place once the whipstock has been set at the desired location and angle orientation. The upper end of a whipstock comprises an inclined face. Once the whipstock is properly set and aligned, as a mill is lowered, the inclined face guides the mill laterally with respect to the casing axis. The mill travels along the face of the whipstock to mill a window and/or to create the deviated borehole. 
   Mechanically set anchors typically utilized to support whipstocks have one or more slips which engage the casing or borehole. Often, the holding capabilities of these conventional devices are not enough to prevent slippage or movement during sidetracking operations. It has been found that conventional whipstock supports may be susceptible to small, but not insignificant amounts of rotational movement. If a misalignment were to occur during a window milling operation, the mill could become stuck in the hole resulting in a difficult and expensive fishing operation. Another unintended result could be that a lateral well bore is drilled in the wrong direction. 
   Typical slip mechanisms provide minimal upward loading capability and very little torque resistant capacity. These traditional slip mechanisms use wickers or grooves machined into the outer surface of the slip to grip the well bore and resist torsional and longitudinal (axial) forces. These gripping mechanisms allowed for very limited penetration into the casing or borehole, and therefor were prone to unwanted movement. These known problems with tools in the prior art demand that drillers limit the amounts of force applied during such milling and drilling operations. This results in lower rates of penetration, and ultimately, a more costly well. 
   Hence, it is desired to provide an anchor and whipstock setting apparatus that effectively resists torsional forces and prevents a whipstock from rotating. It is a further desire to provide an effective whipstock support that can be run into a borehole and set using conventional wireline methods. 
   Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention provides a wellbore anchoring tool with a torsional resistant slip mechanism that effectively resists both axial and rotational forces. According to the preferred embodiment, the present tool includes a mandrel, a plurality of slips disposed about the circumference of the mandrel. The slips include a first set of inserts oriented to resist axial forces and a second set of inserts oriented to resist rotational forces. The present invention further provides a setting means adjacent each slip for radially expanding and setting said slips, so as to resist rotation about the tool axis when the slips engage the casing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which: The present invention will be more fully understood by reference to the following figures illustrating the preferred embodiment of the present invention: 
       FIG. 1  is a quarter section view of the preferred embodiment of a packer with the torsional resistant slip mechanism of the present invention. 
       FIG. 2  is a circumferential plane view of the torsional resistant slip mechanisms of the present invention. 
       FIG. 3  is a top cross section view of the tool wherein one slip is shown in an engaged position. 
       FIG. 4  is a top cross section view of an embodiment of the invention comprising eight slips. 
   

   NOTATION AND NOMENCLATURE 
   Certain terms are used throughout the following description and claims to refer to particular system components. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . .”. 
   The present invention is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the present invention with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. 
   In particular, various embodiments of the present invention provide a number of different constructions and methods of operation. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. Reference to up or down will be made for purposes of description with “up” or “upper” meaning toward the surface of the well and “down” or “lower” meaning toward the bottom of the primary wellbore or lateral borehole. 
   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1   a – 1   g  there is shown a side view of a wireline set retrievable whipstock seal bore packer with the torsional resistant slips mechanism of the present invention. Tool  100  has an upper cone  101  and a lower cone  102 . Each slip  10  includes an upper and lower slip camming surface  11 ,  12 . A packer assembly  40  is disposed above the slip and cone mechanisms. 
   The upper cone  101  preferably includes an upper camming surface  111  to engage lower slip camming surface  11 . The lower cone  102  is disposed below the slip  10  and has a camming surface  112  to engage lower slip camming surface  12 . In the preferred embodiment, the camming surfaces of the cones and slips are flat surfaces, resulting in uniform forces applied between these members. Slips known in the prior art had conical shaped back surfaces; thus, contact between those cones and slips resulted in an undesirable bending moment. No bending moments result from the contact between the flat camming surfaces of the cones and slips of the present invention. The above description of setting the slips is the preferred method of this invention; however, other methods of radially extending and setting the slips are well known by those skilled in the arts. Any such method may be practiced without departing from the spirit and scope of this invention. 
   Referring to  FIG. 2 , the slips  10  in the preferred embodiment of the wellbore tool comprise a first and second set of carbide inserts  20 ,  21  on the outer surface  18  of the slips. A first set of inserts  20  is oriented so that they most effectively resist axial forces. Inserts  20  preferably comprise generally cylindrical disks that are mounted with their axes inclined with respect to the tool axis and their faces oriented upward or downward and radially outward to resist axial forces. 
   As best shown in  FIGS. 1   d  and  2 , the inserts are inclined with respect to the tool axis and their faces oriented upward or downward and radially outward. The smaller surface area of the insert when so oriented allows for greater penetration into the casing inner wall and thereby improves the resistance to any movement once the slips  10  are set. Wickers milled on slips, as is common in the prior art, are known to penetrate the casing by approximately 0.030″. In contrast, inserts configured as in the present invention can penetrate the casing by more that 0.096″. Increased penetration allows the inserts to better resist axial and torsional loads. 
   A second set of inserts  21  is also likewise oriented and then rotated 90 degrees in a transverse plane. Thus, the second set of inserts  21  is configured to most effectively resist torsional forces. As will be readily recognized by one skilled in the art, degrees of rotation between the first set of inserts  20  and the second set of inserts  21  need not be 90 degrees and may vary without departing from the spirit of the inventions. However, in the preferred embodiment of this invention, the first and second set of inserts  20 ,  21  are rotated by at least 45 degrees in a transverse plane. In the most preferred embodiment, the inserts are rotated about 90 degrees in a transverse plane. 
   In the embodiment illustrated in  FIG. 2 , the first set of inserts  20  are configured to resist both upward and downward axial forces. Inserts  20   a  are inclined with respect to the tool axis and their faces oriented upward and radially outward such that they are most resistant to upward axial forces. The faces of inserts  20   b  are oriented downward such that they are most resistant to downward axial forces. 
   Similarly, the second set of inserts  21  is configured to resist both clockwise and counterclockwise torsional forces. Inserts  21   a  are oriented such that they best resist clockwise rotational forces. Inserts  21   b  are oriented such that they best resist counterclockwise torsional forces. 
   In the preferred embodiment, the inserts are carbide discs; however, one skilled in the art will recognize that the inserts may be constructed from a variety of materials, including tungsten carbide, diamond, or carbonized steel. In the preferred embodiment, the inserts may be constructed of any material that is harder than the material used in common casing so that the inserts can easily bite into the casing wall. 
   As is also shown in  FIG. 2 , the inserts  20  are inserts that are generally cylindrical in shape. While a preferred configuration for the inserts is shown, it will be understood that any insert shape can be used. One skilled in the art will recognize that inserts of other geometric shapes, such are cubes, triangular or rectangular shapes may also be used as the insert of the rotational resistant slip mechanism. 
   As shown in  FIG. 3 , one preferred embodiment of a tool utilizing the rotational resistant slip mechanism comprises six slip mechanisms arranged at 60 degree intervals on the tool so as to create a “full circle” of slip members  10 . The under faces of the slips are keyed to the remaining parts of the tool. Alternative embodiments may include various numbers of slips. For example,  FIG. 4   a  shows an embodiment of the present invention where eight slips are utilized. However, it is preferred that regardless the number of slips, the slips are configured or otherwise sized to create a “full circle” around the tool mandrel. 
   The foregoing detailed description has been given for understanding only and no unnecessary limitations should be understood there from as some modifications will be obvious to those skilled in the art without departing from the scope and spirit of the apparatus.