Tool and method for fracturing a wellbore

Abstract

A fracturing tool is used for hydraulically fracturing multiple stages of a well bore with treatment fluid. The tool includes a tubular housing retaining a longitudinally sliding sleeve which moves between a first position concealing fluid ports in the tubular housing and a second position in which the ports are uncovered. A deformable seat disposed in the sliding sleeve cooperates with an actuating member which is directed downwardly through a fracturing string locating a plurality of tools therein associated with respective stages of an isolated zone to sequentially uncover the fluid ports. Disposed in the fluid ports are burst plugs arranged to open when exposed to a threshold pressure. All uncovered burst plugs of the tools within the isolated zone can thus be sequentially uncovered and then opened when exposed to the threshold pressure to permit the treatment fluid to exit from the housing into the surrounding well bore.

1 . A fracturing tool for use with an actuating member in a fracturing string for hydraulically fracturing a wellbore with treatment fluid, the fracturing tool comprising:
 a tubular housing extending longitudinally between opposing first and second ends arranged for connection in series with the fracturing string, the tubular housing having:
 an inner surface defining a central bore extending through the tubular housing from the first end to the second end, and 
 at least one fluid port extending from the inner surface to an outer surface of the tubular housing for fluid communication between the central bore and the wellbore; 
   a burst plug disposed in said at least one fluid port, the burst plug being operable from a closed condition in which the burst plug prevents the treatment fluid flowing through the fluid port to an open condition in which the burst plug is arranged to allow treatment fluid flowing through the fluid port in response to a prescribed threshold hydraulic pressure level of the treatment fluid; and   a sleeve member supported within the central bore of the tubular housing so as to be longitudinally slidable relative to the tubular housing between a first position in which said at least one fluid port is covered by the sleeve member and a second position in which said at least one fluid port is substantially unobstructed by the sleeve member, the sleeve member comprising:
 a central passageway extending longitudinally therethrough; and 
 a deformable seat disposed in the central passageway so as to be operable between a first condition in which the deformable seat is adapted to receive the actuating member seated thereon and a second condition in which the deformable seat is adapted to allow the actuating member to pass through the central passageway; 
 the deformable seat being operable from the first condition to the second condition only upon displacement of the sleeve member into the second position. 
   
     
     
         2 . The fracturing tool according to  claim 1  in combination with the actuating member, wherein the deformable seat and the actuating member seated thereon are arranged to substantially form a seal against the flow of treatment fluid whereby the sleeve member is movable from the first position to the second position when the deformable seat and actuating member seated thereon are exposed to an actuation hydraulic pressure level of treatment fluid which is less than the threshold hydraulic pressure level of the treatment fluid. 
     
     
         3 . The fracturing tool according to  claim 2  wherein the central passageway of the sleeve member has a prescribed inner diameter which is substantially equal to an inner diameter of at least a portion of the central bore of the tubular housing and wherein the actuating member has an outer diameter which is substantially equal to said prescribed inner diameter. 
     
     
         4 . The fracturing tool according to  claim 2  wherein the actuating member comprises a generally cylindrical shuttle member having a central passage extending longitudinally therethrough and a ball seat disposed in the central passage of the actuating member so as to be arranged to form a seal against flow of treatment fluid when a ball is seated on the ball seat, wherein the shuttle member is arranged to pass through the central passageway of the tubular housing when the sleeve member is displaced to the second position and the deformable seat of the sleeve member is displaced to the second condition. 
     
     
         5 . The fracturing tool according to  claim 2  wherein the actuating member comprises a ball arranged to be seated on the deformable seat so as to form the seal against the flow of treatment fluid. 
     
     
         6 . The fracturing tool according to  claim 5  wherein the central passageway includes a constriction having a prescribed inner diameter which is less than an inner diameter of the inner surface of at least a portion of the central bore of the tubular housing, the deformable seat being disposed within the constriction. 
     
     
         7 . The fracturing tool according to  claim 1  in combination with an actuating member wherein at least a portion of the actuating member is arranged to be supported on a tubing string and has an outer diameter which is arranged to be greater than an outer diameter of the tubing string. 
     
     
         8 . The fracturing tool according to  claim 1  in combination with a plurality of other fracturing tools of like configuration connected in series with one another in a fracturing string spanning a plurality of isolated zones having multiple stages associated with each zone such that each fracturing tool is associated with a respective stage of a respective isolated zone, wherein there is provided an actuating member associated with each isolated zone, each actuating member being arranged to sequentially actuate all of the fracturing tools within the respective isolated zone. 
     
     
         9 . The fracturing tool according to  claim 8  wherein a lowermost one of the fracturing tools within each isolated zone is arranged to prevent displacement of the actuating member through the fracturing string beyond a bottom end of the respective isolated zone. 
     
     
         10 . The fracturing tool according to  claim 8  wherein the actuating member of each isolated zone comprises a ball having a prescribed diameter which is different than the other actuating members, each actuating member being arranged to pass through each fracturing tool associated with one of the isolated zones above the respective isolated zone without displacing the sleeve member into the second position of any fracturing tool above the respective isolated zone. 
     
     
         11 . The fracturing tool according to  claim 8  wherein the actuating member of each isolated zone comprises a generally cylindrical shuttle member and a respective ball associated therewith, the shuttle member having a central passage extending longitudinally therethrough and a ball seat disposed in the central passage of the actuating member so as to be arranged to form a seal against the flow of treatment fluid when the respective ball is seated on the ball seat, wherein the ball of each isolated zone is arranged to pass through the shuttle member of each fracturing tool associated with one of the isolated zones above the respective isolated zone without actuating the shuttle member to displace the sleeve members of the respective fracturing tools into the second position. 
     
     
         12 . A method of hydraulically fracturing multiple stages within a lower isolated zone in a wellbore with a treatment fluid, the method comprising the steps of:
 i) providing an actuating member associated with the lower isolated zone;   ii) providing a plurality of fracturing tools connected in series with one another in a fracturing string spanning the lower isolated zone such that each fracturing tool is associated with a respective stage of the lower isolated zone, each fracturing tool comprising:
 a tubular housing extending longitudinally between opposing first and second ends and having an inner surface defining a central bore extending through the tubular housing and at least one fluid port extending from the inner surface to an outer surface of the tubular housing for fluid communication between the central bore and the wellbore; 
 a burst plug disposed in said at least one fluid port, the burst plug being operable from a closed condition in which the burst plug prevents the treatment fluid flowing through the fluid port to an open condition in which the burst plug is arranged to allow treatment fluid flowing through the fluid port in response to a prescribed threshold hydraulic pressure level of the treatment fluid; and 
 a sleeve member supported within the central bore of the tubular housing so as to be longitudinally slidable relative to the tubular housing between a first position in which said at least one fluid port is covered by the sleeve member and a second position in which said at least one fluid port is substantially unobstructed by the sleeve member, the sleeve member comprising a central passageway extending longitudinally therethrough and a deformable seat disposed in the central passageway so as to be operable between a first condition in which the deformable seat is adapted to receive the actuating member seated thereon and a second condition in which the deformable seat is adapted to allow the actuating member to pass through the central passageway, wherein the deformable seat is operable from the first condition to the second condition only upon displacement of the sleeve member into the second position; 
   iii) directing the actuating member downwardly through the fracturing string to sequentially displace the sleeve member of each fracturing tool associated with the lower isolated zone into the second position;   iv) locating the actuating member within a lowermost one of the fracturing tools associated with the lower isolated zone so as to form a seal against a flow of the treatment fluid; and   v) pumping the treatment fluid to achieve the threshold hydraulic pressure level to open the burst plugs in the fluid ports and hydraulically fracture the well bore within the lower isolated zone.   
     
     
         13 . The method according to  claim 12  wherein the actuating member comprises a ball and a generally cylindrical shuttle member arranged to be seated on the deformable seat of each fracturing tool of the lower isolated zone, the shuttle member having a central passage extending longitudinally therethrough and a ball seat disposed in the central passage of the actuating member so as to be arranged to form a seal against flow of treatment fluid when the ball is seated on the ball seat, and wherein the method further comprises directing the ball of the actuating member downwardly through the fracturing string such that the shuttle member sequentially passes through the tubular housings of the fracturing tools of the lower isolated zone. 
     
     
         14 . The method according to  claim 12  wherein the actuating member comprises a ball arranged to be seated on the deformable seat of each fracturing tool of the lower isolated zone, and wherein the method includes directing the ball downwardly through the fracturing string such that the ball sequentially passes through the tubular housings of the fracturing tools of the lower isolated zone. 
     
     
         15 . The method according to  claim 12  further comprising sequentially seating the actuating member on the deformable seat of each fracturing tool of the lower isolated zone so as to substantially form a seal against the flow of treatment fluid; and driving the sleeve member of each fracturing tool from the first position to the second position by pumping the treatment fluid to expose the respective deformable seat and the actuating member seated thereon to an actuation hydraulic pressure level of treatment fluid which is less than the threshold hydraulic pressure level of the treatment fluid. 
     
     
         16 . The method according to  claim 12  further comprising sequentially seating the actuating member on the deformable seat of each fracturing tool of the lower isolated zone by supporting at least a portion of the actuating member on a tubing string and lowering the tubing string within the fracturing string. 
     
     
         17 . The method according to  claim 12  further comprising hydraulically fracturing multiple stages within an upper isolated zone above the lower isolated zone by the steps of:
 associating one of the plurality of fracturing tools with each of the stages of the upper isolated zone; 
 providing an actuating member associated with the upper isolated zone in addition to the actuating member associated with the lower isolated zone; 
 each actuating member being arranged to sequentially actuate only the fracturing tools within the respective isolated zone. 
 
     
     
         18 . The method according to  claim 17  further comprising preventing the actuating member from being displaced downwardly through the fracturing string beyond a bottom end of the respective isolated zone. 
     
     
         19 . The method according to  claim 17  wherein the actuating member of the lower isolated zone comprises a ball having a prescribed diameter which is arranged to be seated on the deformable seat of each fracturing tool of the lower isolated zone and which is arranged to pass through the deformable seat of each fracturing tool of the upper isolated zone without being seated thereon, wherein the actuating member of the upper isolated zone comprises a ball having a prescribed diameter which is arranged to be seated on the deformable seat of each fracturing tool of the upper isolated zone, and wherein the method further comprises:
 i) directing the ball of the lower isolated zone downwardly through the fracturing string such that the sleeve members in the upper isolated zone remain in the first position and the sleeve members in the lower isolated zone are sequentially displaced into the second position; 
 ii) pumping the treatment fluid to achieve the threshold hydraulic pressure level to open the burst plugs in the fluid ports and hydraulically fracture the well bore within the lower isolated zone; 
 iii) directing the ball of the upper isolated zone downwardly through the fracturing string such that the sleeve members in the upper isolated zone are sequentially displaced into the second position; 
 iv) locating the ball of the upper isolated zone within a lowermost one of the fracturing tools associated with the upper isolated zone so as to form a seal against a flow of the treatment fluid; and 
 v) pumping the treatment fluid to achieve the threshold hydraulic pressure level to open the burst plugs in the fluid ports and hydraulically fracture the well bore within the upper isolated zone. 
 
     
     
         20 . The method according to  claim 17  wherein the actuating member of each isolated zone comprises a generally cylindrical shuttle member and a respective ball associated therewith, the shuttle member of each isolated zone being arranged to be seated on the deformable seat of each fracturing tool of the respective isolated zone and having a central passage extending longitudinally therethrough within which is disposed a ball seat, the ball of the lower isolated zone having a prescribed diameter which is arranged to be seated on the ball seat of the shuttle member of the lower isolated zone and which is arranged to pass through the ball seat of the shuttle member of the upper isolated zone without being seated thereon, and the ball of the upper isolated zone having a prescribed diameter which is arranged to be seated on the ball seat of the shuttle member of the upper isolated zone, and wherein the method further comprises:
 i) directing the ball of the lower isolated zone downwardly through the fracturing string such that the ball passes unseated through the shuttle member of the upper isolated zone and the sleeve members in the upper isolated zone remain in the first position and such that the ball is seated on the shuttle member of the lower isolated zone and the sleeve members in the lower isolated zone are sequentially displaced into the second position; 
 ii) pumping the treatment fluid to achieve the threshold hydraulic pressure level to open the burst plugs in the fluid ports and hydraulically fracture the well bore within the lower isolated zone; 
 iii) directing the ball of the upper isolated zone downwardly through the fracturing string such that the ball is seated on the shuttle member of the upper isolated zone and the sleeve members in the upper isolated zone are sequentially displaced into the second position; 
 iv) locating the ball and shuttle member of the upper isolated zone within a lowermost one of the fracturing tools associated with the upper isolated zone so as to form a seal against a flow of the treatment fluid; and 
 v) pumping the treatment fluid to achieve the threshold hydraulic pressure level to open the burst plugs in the fluid ports and hydraulically fracture the well bore within the upper isolated zone.