Methods for Refracturing a Subterranean Formation

Abstract

Methods for refracturing a subterranean formation via a hydrocarbon well that includes a downhole tubular extending within a wellbore formed within the subterranean formation. The methods include positioning a plurality of isolation structures within a tubular conduit defined by the downhole tubular to define a plurality of spaced-apart stimulation zones. The downhole tubular includes a plurality of spaced-apart existing perforations. The methods also include stimulating an initial region of the subterranean formation, which is associated with an initial stimulation zone of the plurality of spaced-apart stimulation zones, via an initial subset of the plurality of spaced-apart existing perforations and subsequently sealing the initial subset of the plurality of spaced-apart existing perforations. The methods further include establishing fluid communication between the initial stimulation zone and an adjacent stimulation zone and stimulating an adjacent region of the subterranean formation that is associated with the adjacent stimulation zone.

What we claim: 
     
         1 . A method for refracturing a subterranean formation via a hydrocarbon well including a downhole tubular extending within a wellbore formed within the subterranean formation, the method comprising:
 positioning a plurality of isolation structures within a tubular conduit defined by the downhole tubular to define a plurality of spaced-apart stimulation zones within the tubular conduit, wherein the downhole tubular includes a plurality of spaced-apart existing perforations that provides fluid communication between the tubular conduit and the subterranean formation, and further wherein each stimulation zone of the plurality of spaced-apart stimulation zones includes a corresponding subset of the plurality of spaced-apart existing perforations;   subsequent to the positioning, stimulating an initial region of the subterranean formation associated with an initial stimulation zone of the plurality of spaced-apart stimulation zones, wherein the initial stimulation zone includes an initial subset of the plurality of spaced-apart existing perforations, wherein the stimulating the initial region includes injecting a stimulant fluid from a surface region, via the tubular conduit, through the initial subset of the plurality of spaced-apart existing perforations, and into the subterranean formation while resisting flow of the stimulant fluid through stimulation zones of the plurality of spaced-apart stimulation zones that are downhole from the initial stimulation zone;   sealing the initial subset of the plurality of spaced-apart existing perforations;   establishing fluid communication between the initial stimulation zone and an adjacent stimulation zone of the plurality of spaced-apart stimulation zones within the tubular conduit while maintaining the sealing the initial subset of the plurality of spaced-apart existing perforations, wherein the adjacent stimulation zone is downhole from the initial stimulation zone; and   stimulating an adjacent region of the subterranean formation associated with the adjacent stimulation zone, wherein the adjacent stimulation zone includes an adjacent subset of the plurality of spaced-apart existing perforations, wherein the stimulating the adjacent region includes injecting the stimulant fluid from the surface region, via the tubular conduit, through the initial stimulation zone, through the adjacent subset of the plurality of spaced-apart existing perforations, and into the subterranean formation while resisting flow of the stimulant fluid through stimulation zones of the plurality of spaced-apart stimulation zones that are downhole from the adjacent stimulation zone.   
     
     
         2 . The method of  claim 1 , wherein the positioning includes sequentially positioning the plurality of isolation structures within the tubular conduit to define the plurality of spaced-apart stimulation zones, wherein the sequentially positioning includes positioning such that each isolation structure of the plurality of isolation structures is uphole from previously positioned isolation structures of the plurality of isolation structures. 
     
     
         3 . The method of  claim 1 , wherein the positioning includes positioning a plurality of frangible isolation structures, wherein each frangible isolation structure of the plurality of frangible isolation structures resists fluid flow from an uphole region of the tubular conduit, which is uphole therefrom, to a downhole region of the tubular conduit, which is downhole therefrom. 
     
     
         4 . The method of  claim 3 , wherein the positioning includes positioning an initial frangible isolation structure of the plurality of frangible isolation structures, which hydraulically isolates the initial stimulation zone from the adjacent stimulation zone, and further wherein the establishing includes shattering the initial frangible isolation structure. 
     
     
         5 . The method of  claim 4 , wherein the shattering includes at least one of:
 (i) generating a shockwave within a wellbore fluid, which extends within the tubular conduit, to provide a motive force for the shattering;   (ii) providing a transition signal to the initial frangible isolation structure, wherein the initial frangible isolation structure is configured to shatter responsive to receipt of the transition signal; and   (iii) pressurizing the wellbore fluid to greater than a threshold shattering pressure.   
     
     
         6 . The method of  claim 5 , wherein the transition signal includes at least one of:
 (i) a pressure pulse of a predetermined magnitude;   (ii) a predetermined pressure pulse sequence;   (iii) a predetermined acoustic signal; and   (iv) a predetermined wireless signal.   
     
     
         7 . The method of  claim 1 , wherein the positioning includes positioning a plurality of isolation device seats within the tubular conduit, wherein each isolation device seat, when combined with a corresponding isolation device, resists fluid flow from an uphole region of the tubular conduit, which is uphole therefrom, to a downhole region of the tubular conduit, which is downhole therefrom. 
     
     
         8 . The method of  claim 7 , wherein, subsequent to the positioning and prior to the stimulating the initial region, the method further includes positioning an initial isolation device on an initial isolation device seat to hydraulically isolate the initial stimulation zone from the stimulation zones of the plurality of spaced-apart stimulation zones that are downhole from the initial stimulation zone. 
     
     
         9 . The method of  claim 8 , wherein the positioning includes flowing the initial isolation device into contact with the initial isolation device seat. 
     
     
         10 . The method of  claim 8 , wherein the tubular conduit provides fluid communication among the stimulation zones of the plurality of spaced-apart stimulation zones that are downhole from the initial stimulation zone. 
     
     
         11 . The method of  claim 8 , wherein the establishing includes at least one of:
 (i) shearing the initial isolation device seat; and   (ii) forcing the initial isolation device through the initial isolation device seat.   
     
     
         12 . The method of  claim 8 , wherein, subsequent to the establishing and prior to the stimulating the adjacent region of the subterranean formation, the method further includes positioning an adjacent isolation device on an adjacent isolation device seat to hydraulically isolate the adjacent stimulation zone from stimulation zones of the plurality of spaced-apart stimulation zones that are downhole from the adjacent stimulation zone. 
     
     
         13 . The method of  claim 1 , wherein the stimulating the initial region of the subterranean formation includes at least one of:
 (i) injecting a fracturing fluid into the initial region of the subterranean formation to fracture the initial region of the subterranean formation;   (ii) injecting a proppant into the initial region of the subterranean formation to prop one or more fractures that extend within the initial region of the subterranean formation;   (iii) injecting an acid into the initial region of the subterranean formation to dissolve at least a portion of the initial region of the subterranean formation; and   (iv) bullheading the stimulant fluid into the tubular conduit from the surface region.   
     
     
         14 . The method of  claim 1 , wherein the stimulating the adjacent region of the subterranean formation includes at least one of:
 (i) injecting a fracturing fluid into the adjacent region of the subterranean formation to fracture the adjacent region of the subterranean formation;   (ii) injecting a proppant into the adjacent region of the subterranean formation to prop one or more fractures that extend within the adjacent region of the subterranean formation;   (iii) injecting an acid into the adjacent region of the subterranean formation to dissolve at least a portion of the adjacent region of the subterranean formation; and   (iv) bullheading the stimulant fluid into the tubular conduit from the surface region.   
     
     
         15 . The method of  claim 1 , wherein the sealing the initial subset of the plurality of spaced-apart existing perforations includes sealing with a plurality of initial sealing devices. 
     
     
         16 . The method of  claim 1 , wherein, subsequent to the stimulating the adjacent region of the subterranean formation, the method further includes:
 sealing the adjacent subset of the plurality of spaced-apart existing perforations;   establishing fluid communication between the adjacent stimulation zone and a subsequent stimulation zone of the plurality of spaced-apart stimulation zones, which is downhole from the adjacent stimulation zone, while maintaining the sealing the initial subset of the plurality of spaced-apart existing perforations and also maintaining the sealing the adjacent subset of the plurality of spaced-apart existing perforations; and   stimulating a subsequent region of the subterranean formation associated with the subsequent stimulation zone, wherein the stimulating the subsequent region includes flowing the stimulant fluid from the surface region, via the tubular conduit, through the initial stimulation zone, through the adjacent stimulation zone, through a subsequent subset of the plurality of spaced-apart existing perforations, which is associated with the subsequent stimulation zone, and into the subterranean formation while resisting flow of the stimulant fluid through stimulation zones of the plurality of spaced-apart stimulation zones that are downhole from the subsequent stimulation zone.   
     
     
         17 . The method of  claim 1 , wherein the method includes sequentially stimulating a region of the subterranean formation associated with each stimulation zone of the plurality of spaced-apart stimulation zones, wherein each subsequently stimulated region of the subterranean formation is downhole from a previously stimulated stimulation zone. 
     
     
         18 . The method of  claim 1 , wherein, prior to the stimulating the initial region of the subterranean formation, the method further includes adding new perforations to the downhole tubular, wherein the adding new perforations to the downhole tubular includes generating a plurality of spaced-apart new perforations within the downhole tubular. 
     
     
         19 . The method of  claim 17 , wherein the initial stimulation zone includes a plurality of initial perforations, which includes both the initial subset of the plurality of spaced-apart existing perforations and an initial subset of the plurality of spaced-apart new perforations, and further wherein the stimulating the initial region of the subterranean formation further includes:
 (i) injecting the stimulant fluid into the subterranean formation via both the initial subset of the plurality of spaced-apart existing perforations and the initial subset of the plurality of spaced-apart new perforations for a first stimulation time period;   (ii) sealing a most fluid-receptive fraction of the plurality of initial perforations; and   (iii) injecting the stimulant fluid into the subterranean formation via a remainder of the plurality of initial perforations for a second stimulation time period.   
     
     
         20 . The method of  claim 1 , wherein the stimulating the initial region of the subterranean formation includes:
 (i) injecting the stimulant fluid into the subterranean formation via the initial subset of the plurality of spaced-apart existing perforations for a first stimulation time period;   (ii) sealing a most fluid-receptive fraction of the initial subset of the plurality of spaced-apart existing perforations; and   (iii) injecting the stimulant fluid into the subterranean formation via a remainder of the initial subset of the plurality of spaced-apart existing perforations for a second stimulation time period.   
     
     
         21 . The method of  claim 1 , wherein the sealing comprises using at least one of:
 (i) a plurality of ball sealers;   (ii) a plurality of conformable sealers;   (iii) a plurality of beads;   (iv) a plurality of poly lactic acid beads;   (v) a plurality of fibers;   (vi) a plurality of poly lactic acid fibers;   (vii) a plurality of rods;   (viii) a plurality of poly lactic acid rods; and   (ix) combinations thereof.   
     
     
         22 . The method of  claim 1 , wherein, prior to the positioning the initial stimulation device, the method further includes cleanout of the tubular conduit. 
     
     
         23 . The method of  claim 22 , wherein the cleanout includes flushing solids from the tubular conduit. 
     
     
         24 . The method of  claim 22 , wherein the cleanout includes utilizing coiled tubing. 
     
     
         25 . The method of  claim 1 , wherein, subsequent to stimulation of a desired number of regions of the subterranean formation via corresponding stimulation zones of the plurality of spaced-apart stimulation zones, the method further includes cleanout the tubular conduit. 
     
     
         26 . The method of  claim 25 , wherein the cleanout includes at least one of:
 (i) removing the plurality of isolation structures from the tubular conduit;   (ii) removing a plurality of isolation devices from the tubular conduit; and   (iii) removing a plurality of sealing devices from the tubular conduit.   
     
     
         27 . The method of  claim 25 , wherein the cleanout includes at least one of:
 (i) running a mill through the tubular conduit; and   (ii) providing an acid to the tubular conduit.