Drillable Oilfield Tubular Plug

Abstract

A drillable oilfield tubular plug that employs clutch faces, drilling features, anti-rotation features, and composite materials to facilitate quicker drill-out operations after the plugs have been utilized.

1 . A drillable plug assembly, which is settable using a tool, for isolating differential pressures in a tubular, comprising:
 a mandrel, formed of composite material, having a cylindrical body with a first clutch face formed on a proximate end thereof, and having a tool thread formed within a central bore thereof that shears at a first predetermined axial force, and having a setting thread disposed about the exterior thereof, and having an anvil connector disposed at a distal end thereof;   a setting sleeve disposed about said cylindrical body, and threadably engaged with said setting thread to shear at a second predetermined axial force applied thereagainst;   an anvil, formed of composite material, connected to said anvil connector, having a second clutch face formed on a distal end thereof;   a seal assembly, including an elastomeric seal and a slip for sealably and fixedly engaging the tubular upon setting by the tool, disposed about said cylindrical body between said setting sleeve and said anvil, and wherein   said first ratchet clutch face and said second ratchet clutch face are configured to cooperatively engage one another and prevent rotation therebetween, to thereby enable plural drillable plug assemblies in the tubular to resist rotation therebetween as they are drilled out of the tubular.   
     
     
         2 . The assembly of  claim 1 , and wherein:
 said composite material is fiber reinforced plastic.   
     
     
         3 . The assembly of  claim 1 , and wherein:
 said composite material comprises epoxy resin reinforced with filament wound fiber selected from glass, aromatic polyamide, and carbon.   
     
     
         4 . The assembly of  claim 1 , and wherein:
 said first clutch face and said second clutch face are configured as interlocking crown gears.   
     
     
         5 . The assembly of  claim 1 , and wherein:
 said first clutch face and said second clutch face are configured as mating Hirth coupling faces.   
     
     
         6 . The assembly of  claim 1 , and wherein:
 said first clutch face and said second clutch face are configured as ratchet clutches.   
     
     
         7 . The assembly of  claim 6 , and wherein:
 said ratchet clutches comprise a series of asymmetrical teeth, each having an inclined surface meeting a drive face at an acute angle.   
     
     
         8 . The assembly of  claim 1 , and wherein:
 said second predetermined axial force is greater than said first predetermined axial force, to thereby cause said setting sleeve to shear from said mandrel prior to the tool shearing from said tool thread.   
     
     
         9 . The assembly of  claim 1 , and wherein:
 said setting sleeve includes a sleeve thread the that shears at said second predetermined axial force.   
     
     
         10 . The assembly of  claim 1 , and wherein:
 said anvil connector is an anvil thread disposed adjacent to said distal end on said cylindrical body, and wherein said anvil threadably engages said anvil thread.   
     
     
         11 . The assembly of  claim 1 , and wherein said seal assembly slidably engages said tubular body between said setting sleeve and said anvil, and further comprising:
 a first setting cone and a second setting cone disposed on either side of said elastomeric seal, each having a conical portion extending away from said elastomeric seal, and wherein   said slip comprises a pair of iron slips having conical interior surfaces that cooperatively engage said pair of setting cones such that they are driven radially into the tubular in response to axial force that exceeds said first predetermined axial force, to thereby compress said elastomeric seal, and locate and set the drillable plug assembly in the tubular.   
     
     
         12 . The assembly of  claim 11 , and wherein:
 said setting sleeve and said first and second cone are formed of composite material, and wherein   said pair of iron slips are fabricated from ductile iron.   
     
     
         13 . The assembly of  claim 1 , and wherein:
 said anvil is configured with a frustoconical surface extending from said second clutch face, and wherein   plural helical flutes are formed upon said frustoconical surface, to thereby facilitate removable of material within the tubular as the drillable plug assembly is drilled.   
     
     
         14 . The assembly of  claim 13 , and wherein:
 said second clutch face on said distal end of said anvil comprises and plural inclined surfaces and plural drive surfaces that meet and at plural acute angle vertexes, and wherein   said plural helical flutes each intersect one of said plural acute angle vertexes.   
     
     
         15 . The assembly of  claim 1 , and wherein
 said slip includes a proximate planar surface that is engaged by a distal planar surface of said setting sleeve, to thereby transmit axial force from said setting sleeve to said slip as the drillable plug assembly is set by the setting tool.   
     
     
         16 . The assembly of  claim 15 , and wherein:
 said slip includes plural sections that fracture into slip section pieces as the drillable plug assembly is set by the setting tool, and wherein   said distal planar surface of said setting sleeve includes plural recesses formed therein, which are configured to engage said slip section pieces to thereby prevent rotation therebetween as the drillable plug assembly is drilled out of the tubular.   
     
     
         17 . The assembly of  claim 16 , and wherein:
 said plural recesses are formed as radial grooves in said distal planar surface of said setting sleeve.   
     
     
         18 . The assembly of  claim 16 , and wherein:
 said plural recesses have a width selected to correspond to the size of said slip section pieces to thereby facilitate engagement therebetween.   
     
     
         19 . The assembly of claim, and wherein:
 said second clutch face of said anvil is configured to retain a ball forced against it by a pressure differential, but without sealing thereagainst, to thereby relieve said pressure differential by flow of fluids between said ball and said second clutch face.   
     
     
         20 . The assembly of  claim 1 , and wherein:
 said central bore of said anvil extents continuous from said proximate end to said distal end, and comprises a ball seat disposed there along for retaining a ball, to thereby provide a passage through which fluids may pass and a means for sealing said central bore using a ball placed against said ball seat.   
     
     
         21 . The assembly of  claim 1 , and wherein:
 said slip is fabricated from iron which has been surface hardened by ferritic nitrocarburization.   
     
     
         22 . The assembly of  claim 1 , and wherein:
 said slip is fabricated as a ring that has plural holes formed therethrough to facilitate fracturing of said slip when set by the tool, and wherein   said slip has been surface hardened by ferritic nitrocarburization.   
     
     
         23 . The assembly of  claim 11 , and wherein:
 said pair of iron slips have been surface hardened by ferritic nitrocarburization.   
     
     
         24 . The assembly of  claim 11 , and wherein:
 said pair of slip are fabricated as rings that have plural holes formed therethrough to facilitate fracturing of said slips when set by the tool, and wherein   said slips have been surface hardened by ferritic nitrocarburization.