Elastomeric ball seat for a frac plug

Abstract

A composite frac plug ( 12 ) is provided which is formed of composite polymer materials, except for shear pins ( 52 ) and anchor cleats ( 96, 112 ) which are formed of metal. The composite materials provide for easy drilling of the frac plug ( 12 ) at the end of fracturing operations. The frac plug ( 12 ) has an elastomeric ball seat ( 44 ) which sealing engages with a frac ball ( 18 ). A ratchet lock assembly ( 26 ) has a split ratchet ring ( 82 ) which moves over the mandrel ( 22 ) in a downward direction only, and prevents movement of the mandrel ( 22 ) downward within the ratchet ring ( 92 ). An anchor assembly ( 28 ) has slip bodies ( 92, 108 ) which are segmented and separately urge anchor cleats ( 96, 112 ) into the interior surface of a well casing ( 136 ).

What is claimed is: 
     
         1 . A downhole tool for sealing a well casing comprising:
 a mandrel defining a longitudinal axis for said downhole tool, said mandrel having an upper portion, an intermediate portion and a lower end, said lower end of said mandrel having a larger diameter than said upper portion and said intermediate portion, and said mandrel having a mandrel bore;   a seal assembly having elastomeric packer elements which are squeezed when the plug is set to sealingly engage between said mandrel and casing within a well;   at least one slip body disposed on at least one side of said seal assembly;   said at least one slip body having anchor cleats which are disposed in spaced apart relation, extending about a longitudinal axis of said;   wherein said downhole tool is moved to a set position by moving said slip body to move outward and upon a conically shaped surface of said downhole tool;   a ball seat disposed in an upper end of said mandrel, said ball seat having a central bore and an upwardly facing surface defined adjacent to said central bore for receiving a ball and sealingly engaged against said ball; and   wherein said ball seat is formed of elastomeric materials.   
     
     
         2 . The downhole tool according to  claim 1 , further comprising a ball seat pocket formed into an uppermost end of said mandrel, adjacent said mandrel bore, wherein said ball seat is disposed in said ball seat pocket. 
     
     
         3 . The downhole tool according to  claim 1 , wherein said at least one upper slip body has a smooth interior bore, a conically-shaped interior recess in one end, and a plurality of slots extending longitudinally into said slip body, said slots being spaced apart in angular alignments about said longitudinal axis to define shear portions disposed adjacent opposite ends to the elongate slots and to define slip segments disposed between said shear portions. 
     
     
         4 . The downhole according to  claim 3 , wherein said slip body has at least one circumferentially extending groove extending into exterior surfaces thereof for receiving an elastomeric band for retaining slip segments against said mandrel during run-in. 
     
     
         5 . The downhole according to  claim 1 , further comprising:
 a lock ring which is threadingly secured to said mandrel, said lock ring having an annular-shaped body which extends circumferentially about said mandrel; and   a lock ring sleeve disposed circumferentially around and projecting beneath said lock ring.   
     
     
         6 . A downhole tool for sealing a well casing comprising:
 a mandrel defining a longitudinal axis for said downhole tool and having an upper portion, an intermediate portion and a lower end, said lower end of said mandrel having a larger diameter than said upper portion and said intermediate portion, and said mandrel having a mandrel bore which extending interiorly within said mandrel;   a seal assembly having elastomeric packer elements which are squeezed when the plug is set to sealingly engage between said mandrel and casing within a well;   an upper slip body and a lower slip body disposed around said mandrel, spaced apart along said longitudinal axis on opposite sides said seal assembly;   said upper slip body and said lower slip body each having an annular shaped groove formed into an exterior surface thereof for receiving anchor cleats which are secured by fasteners within respective one of said grooves and disposed in spaced apart relation, extending about said longitudinal axis of said mandrel, and fasteners securing said anchor cleats within respective ones of said grooves in said upper slip body and said lower body;   wherein said downhole tool is moved to a set position by moving said sleeve and said ratchet sleeve downward to urge upper slip body to move outward and upon a conically shaped surface of said downhole tool; and   a ball seat disposed in an upper end of said mandrel, said ball seat having a central bore and an upwardly facing surface defined adjacent to said central bore for receiving a ball and sealingly engaged against said ball; and   wherein said ball seat is formed of elastomeric materials.   
     
     
         7 . The downhole tool according to  claim 6 , further comprising a ball seat pocket formed into an uppermost end of said mandrel, adjacent said mandrel bore, wherein said ball seat is disposed in said ball seat pocket. 
     
     
         8 . The downhole tool according to  claim 7 , wherein said upper slip body and said lower slip body have a smooth interior bore, a conically-shaped interior recess in one end, and a plurality of slots extending longitudinally into respective bodies of said slip bodies, said slots being spaced apart in angular alignments about said longitudinal axis to define shear portions disposed adjacent opposite ends to the elongate slots and to define slip segments disposed between said shear portions. 
     
     
         9 . The downhole according to  claim 8 , wherein said upper slip body and said lower slip body each have at least one circumferentially extending groove extending into exterior surfaces thereof for receiving an elastomeric band for retaining slip segments against said mandrel during run-in. 
     
     
         10 . The downhole according to  claim 6 , further comprising:
 a lock ring which is threadingly secured to said mandrel, said lock ring having an annular-shaped body which extends circumferentially about said mandrel; and   a lock ring disposed circumferentially around and projecting beneath said lock ring.   
     
     
         11 . A downhole tool for sealing a well casing comprising:
 a mandrel formed of composite material defining a longitudinal axis for said downhole tool, said mandrel extending longitudinally about said longitudinal axis, having an upper portion, an intermediate portion and a lower end, said lower end of said mandrel having a larger diameter than said upper portion and said intermediate portion, and said mandrel having a mandrel bore extending interiorly within and continuously through said mandrel for passing fluids through said mandrel bore;   a seal assembly having elastomeric packer elements which are squeezed when the plug is set to sealingly engage between said mandrel and casing within a well;   an upper slip body and a lower slip body, each formed of composite materials and disposed around said mandrel, spaced apart along said longitudinal axis on opposite sides said seal assembly;   said upper slip body and said lower slip body each having an annular shaped groove formed into an exterior surface thereof for receiving anchor cleats which are secured by fasteners within respective one of said grooves and disposed in spaced apart relation, extending about said longitudinal axis of said mandrel, and fasteners securing said anchor cleats within respective ones of said grooves in said upper slip body and said lower body;   said upper slip body and said lower slip body each having a smooth interior bore, a conically-shaped interior recess in one end, and a plurality of slots extending longitudinally into respective bodies of said slip bodies, said slots being spaced apart in angular alignments about said longitudinal axis to define shear portions disposed adjacent opposite ends to the elongate slots and to define slip segments disposed between said shear portions;   wherein said downhole tool is moved to a set position by moving said sleeve and said ratchet sleeve downward to urge upper slip body to move outward and upon a conically shaped surface of said downhole tool;   a ball seat disposed in an upper end of said mandrel, said ball seat having a central bore and an upwardly facing surface defined adjacent to said central bore for receiving a ball and sealingly engaged against said ball; and   wherein said ball seat is formed of elastomeric materials.   
     
     
         12 . The downhole tool according to  claim 11 , further comprising a ball seat pocket formed into an uppermost end of said mandrel, adjacent said mandrel bore, wherein said ball seat is disposed in said ball seat pocket. 
     
     
         13 . The downhole according to  claim 12 , wherein said upper slip body and said lower slip body each have at least one circumferentially extending groove extending into exterior surfaces thereof for receiving an elastomeric band for retaining slip segments against said mandrel during run-in. 
     
     
         14 . The downhole according to  claim 11 , further comprising:
 a lock ring formed of composite materials which is threadingly secured to said mandrel, said lock ring having an annular-shaped body which extends circumferentially about said mandrel; and   a lock ring sleeve formed of composite materials, said lock ring sleeve disposed circumferentially around and projecting beneath said lock ring.