Disintegrating ball for sealing frac plug seat

Abstract

A composition for a ball that disintegrates, dissolves, delaminates or otherwise experiences a significant degradation of its physical properties over time in the presence of hydrocarbons and formation heat. The ball may be used in methods and apparatus for hydraulically fracturing a subterranean zone in a wellbore.

1 . A fracturing system for a wellbore, said system comprising:
 a tube having a wall comprising an interior surface and an exterior surface;   a ball seat carried by the tube, the ball seat comprising an opening of a first diameter; and   a ball having a second diameter larger than the first diameter, the ball comprising a first material, wherein the first material is disintegrated by hydrocarbons.   
     
     
         2 . The system of  claim 1 , wherein the first material comprises polystyrene. 
     
     
         3 . The system of  claim 2 , wherein the first material comprises general purpose polystyrene. 
     
     
         4 . The system of  claim 2 , wherein the ball further comprises a second material, wherein the second material comprises fibers or particles of at least one member selected from the group consisting of aramid, glass, carbon, boron, polyester, cotton and ceramics. 
     
     
         5 . The system of  claim 2 , wherein the ball further comprises a second material, wherein the second material comprises one or more layers of a composite fabric material, said composite fabric material comprising at least one member selected from the group consisting of aramid, glass, carbon, boron, polyester, cotton and ceramic fibers. 
     
     
         6 . The system of  claim 2 , wherein the ball comprises from about 30 percent to about 90 percent by weight of the first material. 
     
     
         7 . The system of  claim 2 , wherein the ball comprises from about 50 percent to about 70 percent by weight of the first material. 
     
     
         8 . The system of  claim 2 , wherein the ball comprises about 60 percent by weight of the first material. 
     
     
         9 . The system of  claim 4 , wherein the ball comprises about 60 percent by weight of the first material and about 40 percent by weight of the second material. 
     
     
         10 . The system of  claim 1 , wherein the ball is seated in the opening of the ball seat so that a first portion of the ball is exposed above the opening and a second portion of the ball is exposed below the opening, the system further comprising a volume of hydrocarbon disposed in the tube and in contact with the first portion of the ball. 
     
     
         11 . The system of  claim 1 , wherein the ball is seated in the opening of the ball seat and prevents fluid communication between a first portion of the tube above the ball and a second portion of the tube below the ball. 
     
     
         12 . The system of  claim 11 , wherein the ball prevents fluid communication between the first and second portions of the tube at a pressure of up to about 10,000 psi. 
     
     
         13 . The system of  claim 1 , wherein the ball seat comprises a flange disposed around the interior surface of the tube wall. 
     
     
         14 . The system of  claim 1 , wherein the ball seat comprises a sleeve slidingly mounted within the tube between a first position and a second position. 
     
     
         15 . The system of  claim 14 , wherein the sleeve has an interior surface and an exterior surface, and further comprises a shoulder defined adjacent the interior surface. 
     
     
         16 . The system of  claim 15 , wherein the ball seat further comprises a collar abutting the shoulder and in which the opening is defined. 
     
     
         17 . The system of  claim 14 , wherein the tube further comprises a plurality of apertures disposed in the tube wall, wherein the sleeve in the first position is adjacent the apertures so as to impede fluid flow therethrough. 
     
     
         18 . The system of  claim 14 , further comprising a plurality of ball seats, wherein each of the plurality of ball seats has an opening of a diameter different from those of the other ball seats; and
 a plurality of balls, each disposed to seat within one of the openings of the ball seats, wherein each of the plurality of balls has a diameter different from those of the other balls.   
     
     
         19 . The system of  claim 18 , further comprising a pipe string in which the seats are disposed, wherein the plurality of seats are arranged consecutively along the pipe string from the seat with the largest diameter opening to the seat with the smallest diameter opening. 
     
     
         20 . A fracturing system for a wellbore, said system comprising:
 a tube having a wall comprising an interior surface and an exterior surface;   a ball seat carried by the tube, the ball seat comprising an opening of a first diameter; and   a ball having a second diameter larger than the first diameter, the ball comprising a first material, wherein the first material degrades at a temperature greater than 150° F.   
     
     
         21 . The system of  claim 20 , wherein the first material degrades at a temperature range of from about 150° F. to about 350° F. 
     
     
         22 . The system of  claim 20 , wherein the first material degrades at a temperature range of from about 150° F. to about 220° F. 
     
     
         23 . The system of  claim 20 , wherein the first material degrades at a temperature range from about 150° F. to about 200° F. 
     
     
         24 . The system of  claim 20 , wherein the ball does not deform at a pressure of up to about 10,000 psi. 
     
     
         25 . The system of  claim 20 , wherein the first material is selected from the group consisting of thermosetting polymers, thermoplastic polymers, elastomers and adhesives. 
     
     
         26 . The system of  claim 20 , wherein the first material comprises a thermosetting polymer selected from the group consisting of phenolic resins, urea-formaldehyde resins, epoxy resins, melamine resins, crosslinked polyesters, polyimides, polyurethanes, cyanate esters, polycyanurates and melamine formaldehyde. 
     
     
         27 . The system of  claim 20 , wherein the first material comprises a thermoplastic polymer selected from the group consisting of acrylonitrile butadiene styrene, acrylates such as poly methyl methacrylate, polyoxymethylene, polyamides, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polyester, polyethylene, polyetheretherketone, polypropylene, polystyrene, polyvinylidene chloride and styrene-acrylonitrile. 
     
     
         28 . The system of  claim 20 , wherein the first material comprises an elastomer selected from the group consisting of ethylene propylene, polyisoprene, polybutadiene, chloroprene rubber, butyl rubber, styrene-butadiene rubber and nitrile rubber. 
     
     
         29 . The system of  claim 20 , wherein the first material comprises an adhesive selected from the group consisting of acrylates, methacrylates, and cyanoacrylate. 
     
     
         30 . The system of  claim 20 , wherein the first material is selected from the group consisting of polystyrene, tert-butyl vinyl ether, 3-chlorostyrene, cyclohexyl methacrylate, cyclohexyl vinyl ether, N,N-dimethylacrylamide, 4-ethoxystyrene, ethylene terephthalate, ethyl methacrylate, 4-fluorostyrene, 2-hydropropyl methacrylate, indene, isobornyl acrylate, N-isopropylacrylamide, isopropyl methacrylate, phenylene vinylene, phenyl vinyl ketone, atactic styrene, isotactic styrene, trimethylsilyl methacrylate, vinyl alcohol, vinyl benzoate, vinyl chloride, vinylcyclohexanoate and vinyl pivalate. 
     
     
         31 . The system of  claim 20 , wherein the ball further comprises a second material, wherein the second material comprises fibers or particles of at least one member selected from the group consisting of aramid, glass, carbon, boron, polyester, cotton and ceramics. 
     
     
         32 . The system of  claim 20 , wherein the ball further comprises a second material, wherein the second material comprises one or more layers of a composite fabric material, said composite fabric material comprising at least one member selected from the group consisting of aramid, glass, carbon, boron, polyester, cotton and ceramic fibers. 
     
     
         33 . A method for fracturing the formation around a wellbore, the method comprising:
 deploying a pipe string into a wellbore, the pipe string having perforations disposed in a wall of the pipe string and a ball seat positioned in the interior of the pipe string;   setting packers above and below the perforations to seal the annulus formed between the pipe string and the formation;   introducing a disintegratable ball comprised of a first material into the pipe string;   seating the ball on the ball seat by applying a fluid pressure to the ball, which fluid pressure is greater than the pressure of the wellbore, wherein the ball when seated, has an upstream portion and a downstream portion;   introducing fracturing fluids into the wellbore to initiate fracturing of the formation adjacent the perforations;   cooling the upstream portion of the disintegratable ball during fracturing of the formation to inhibit disintegration of the ball;   upon completion of the fracturing, introducing a hydrocarbon pad into the pipe string;   contacting the upstream portion of the ball with the hydrocarbon pad to promote disintegration of the ball by the hydrocarbon pad; and   allowing disintegration of the ball to continue until the ball unseats from the ball seat.   
     
     
         34 . The method of  claim 33 , wherein a pressure differential across the ball is maintained during fracturing. 
     
     
         35 . The method of  claim 34 , wherein the upstream pressure applied to the ball is greater than the downstream pressure applied to the ball. 
     
     
         36 . The method of  claim 35 , wherein the upstream pressure is up to 10,000 psi. 
     
     
         37 . The method of  claim 33 , wherein a temperature differential across the ball is maintained during fracturing. 
     
     
         38 . The method of  claim 37 , wherein the upstream temperature applied to the ball is less than the downstream temperature applied to the ball. 
     
     
         39 . The method of  claim 33 , wherein the fracturing fluid has a fluid temperature less than the temperature of the wellbore fluid; 
     
     
         40 . The method of  claim 39 , wherein the fracturing fluid is used to cool the ball during fracturing. 
     
     
         41 . The method of  claim 33 , wherein the hydrocarbon pad is diesel. 
     
     
         42 . The method of  claim 33 , wherein the heat of the formation is used to accelerate degradation. 
     
     
         43 . The method of  claim 33 , wherein the first material comprises a thermosetting polymer selected from the group consisting of phenolic resins, urea-formaldehyde resins, epoxy resins, melamine resins, crosslinked polyesters, polyimides, polyurethanes, cyanate esters, polycyanurates and melamine formaldehyde. 
     
     
         44 . The method of  claim 33 , wherein the first material comprises a thermoplastic polymer selected from the group consisting of acrylonitrile butadiene styrene, acrylates such as poly methyl methacrylate, polyoxymethylene, polyamides, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polyester, polyethylene, polyetheretherketone, polypropylene, polystyrene, polyvinylidene chloride and styrene-acrylonitrile. 
     
     
         45 . The method of  claim 33 , wherein the first material comprises an elastomer selected from the group consisting of ethylene propylene, polyisoprene, polybutadiene, chloroprene rubber, butyl rubber, styrene-butadiene rubber and nitrile rubber. 
     
     
         46 . The method of  claim 33 , wherein the first material comprises an adhesive selected from the group consisting of acrylates, methacrylates, and cyanoacrylate. 
     
     
         47 . The method of  claim 33 , wherein the first material is selected from the group consisting of polystyrene, tent-butyl vinyl ether, 3-chlorostyrene, cyclohexyl methacrylate, cyclohexyl vinyl ether, N,N-dimethylacrylamide, 4-ethoxystyrene, ethylene terephthalate, ethyl methacrylate, 4-fluorostyrene, 2-hydropropyl methacrylate, indene, isobornyl acrylate, N-isopropylacrylamide, isopropyl methacrylate, phenylene vinylene, phenyl vinyl ketone, atactic styrene, isotactic styrene, trimethylsilyl methacrylate, vinyl alcohol, vinyl benzoate, vinyl chloride, vinylcyclohexanoate and vinyl pivalate. 
     
     
         48 . The method of  claim 33 , wherein the ball further comprises a second material, wherein the second material comprises fibers or particles of at least one member selected from the group consisting of aramid, glass, carbon, boron, polyester, cotton and ceramics. 
     
     
         49 . The method of  claim 33 , wherein the ball further comprises a second material, wherein the second material comprises one or more layers of a composite fabric material, said composite fabric material comprising at least one member selected from the group consisting of aramid, glass, carbon, boron, polyester, cotton and ceramic fibers.