Abstract:
Extrusion resistant inflatable tool having a biaxially oriented woven material disposed about at least one elastomeric element of the inflatable tool and radially inwardly of a rib structure of the inflatable tool. The woven material prevents extrusion of the elastomeric element between individual ribs of the ribs structure during the inflation of the tool.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of an earlier filing date from U.S. Provisional Application Ser. No. 60/144,508 filing date Jul. 19, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to downhole oil field tools. More particularly, the invention relates to performance enhancing devices for inflatable elements. 
     2. Prior Art 
     Inflatable elements such as packers have been known and used in the hydrocarbon production industry for a substantial period of time. During this time they have been reliable and favored by oil well operators in many sealing operations. Prior art inflatable elements have however had difficulty with setting in noncylindrical boreholes. Noncylindrical boreholes include oval boreholes, unconsolidated boreholes, windows, etc. The problems of the prior art inflatable elements in noncylindrical boreholes has been that the rubber of the inflatable boot is extruded through the ribs of the element. This can cause severe damage to the rubber of the boot and to the ribs of the element and may result in failure of the device. Thus, the art is in need of a means to avoid extrusion of the rubber boot of the inflatable element through the rib portion of the inflatable element during inflation of a tool in a noncylindrical environment. 
     SUMMARY OF THE INVENTION 
     The above-identified drawbacks of the prior art are overcome or alleviated by the extrusion resistant inflatable tool of the invention. 
     In the invention, a biaxially woven sleeve is interposed between the boot/inner-tube and the ribs of a tool having otherwise conventional components. The sleeve is preferably constructed of carbon fiber, aramid fiber, fiber glass or suitable alternative fiber which provides a bridge between the ribs of the inflatable tool as the element expands into the noncylindrical environment. The existence of the biaxially woven sleeve in an annular area outside the boot and inside the ribs of the element prevents the boot from being extruded through the ribs when they open excessively during expansion into a noncylindrical borehole environment. The sleeve further prevents excessive bending of the ribs which would otherwise create difficulties in removing the tool from the downhole environment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: 
     FIG. 1 is a schematic cross section of the device of the invention illustrating the position of the extrusion resistant biaxially woven sleeve; 
     FIG. 2 is a view of the sleeve itself illustrating the pattern thereof; 
     FIG. 3 is an illustration of the sleeve disposed around the rubber boot; and 
     FIG. 4 is an illustration of a sleeve around the rubber boot after inflation and deflation. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, one of ordinary skill in the art will recognize the typical cross section of an end assembly of an external casing packer (ECP)  10 . Within the ECP  10 , a mandrel  12  is disposed at the inside diameter of the tool. Radially outwardly of mandrel  12  is an inflatable element such as an expandable boot or inner-tube  14 , which most commonly is constructed of rubber, although other expandable materials may be employed as desired. 
     Located radially outwardly of boot  14  is an extrusion resistant mechanism which preferably is biaxially woven sleeve  16 , which is critical to the functionality of the invention. The sleeve  16  is interposed between the boot  14  and ribs  18  which are mounted within the outer cover  20  and end sleeve  22  of the tool of the invention. Ribs  18  are constructed and overlapped according to industry standards, known to one of ordinary skill in the art. Upon expansion of boot  14 , in a noncylindrical shaped borehole environment, ribs  18  expand beyond the intended amount and subject the tool to damage. The distorted ribs  18 , even after deflation of the inflatable tool may hinder removal of the tool from the borehole costing both time and money. The interposition of sleeve  16 , between boot  14  and ribs  18  provides an effective bridge between the ribs when they open upon inflation, which is sufficient to retain boot  14  and prevent extrusion thereof through ribs  18 . Sleeve  16  is about 18″ long and is located substantially over the intersection between end sleeve  22  and rubber outer cover  20  to prevent the deformation of ribs  18  as well as the extrusion of boot  14 . 
     Sleeve  16  may preferably be constructed of carbon fiber or aramid fiber (or kevlar), fiberglass or other similiar fiber material having comparable properties. It is noted that the stronger fibers, i.e. carbon, kevlar are preferred. The fibers are at an acuate angle relative to one another. The acuate angle illustrated in FIG. 2 is about 45 degrees. 
     In construction of the device of the invention referring to FIG. 3, the uphole end  24  of sleeve  16  is tightly wrapped about boot  14  and generally does not move from its original location. In order to allow the sleeve  16  to expand however, it is preferable to provide a friction lowering material  26 . Such material may be applied to the inflatable element or to the sleeve or both. Additionally the friction lowering material  26  could simply be dispersed between the two. Wrap boot  14  with Teflon tape or other similar friction reducing material under all but the uphole end  24  of sleeve  16 . The sleeve  16  is commercially available from A&amp;P Technology, Covington, Ky. 
     FIG. 4 illustrates the condition of the sleeve after inflation of boot  14  and deflation thereof. Although damage is notable on the sleeve, it is also apparent that the boot  14  did not extrude through the ribs of the inflatable device. Thus, the construction of the device of the invention overcomes the prior art difficulty of a rubber boot being extruded through the ribs of the inflatable device during inflation in a noncylindrical borehole environment. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.