Method and System for Fracture Stimulation by Cyclic Formation Settling and Displacement

Abstract

The present techniques provide methods and systems for fracturing reservoirs without directly treating them. For example, an embodiment provides a method for fracturing a subterranean formation. The method includes causing a volumetric decrease in a zone proximate to the subterranean formation so as to apply a mechanical stress to the subterranean formation.

What is claimed is: 
     
         1 . A method for fracturing a subterranean formation, comprising:
 using a wellbore to perform one of the steps of;   (a) reducing the geomechanical stress in a zone proximate to the subterranean formation to translate a geomechanical stress change to the subterranean formation to cause a mechanical dislocation of at least a portion of the subterranean formation and create fractures within at least a portion of the subterranean formation; and   (b) applying stress in the zone proximate to the subterranean formation to translate a geomechanical stress change to the subterranean formation to cause a mechanical dislocation of at least a portion of the subterranean formation and create fractures within at least a portion of the subterranean formation; and   thereafter, performing the other of step (a) and step (b).   
     
     
         2 . The method of  claim 1 , wherein step (a) is performed prior to step (b). 
     
     
         3 . The method of  claim 1 , wherein step (b) is performed prior to step (a). 
     
     
         4 . The method of  claim 1 , wherein the geomechanical stress of the zone proximate in step (a) is reduced from an initial in-situ geomechanical stress state in the zone proximate to a geomechanical stress state in the zone proximate that is less than the original in-situ geomechanical stress of the zone proximate, prior to performing step (b). 
     
     
         5 . The method of  claim 1 , wherein the geomechanical stress of the zone proximate in step (a) is reduced from the applied geomechanical stress in the zone proximate after first performing step (b). 
     
     
         6 . The method of  claim 5 , wherein the geomechanical stress of the zone proximate in step (a) is reduced to a geomechanical stress state that is less than the in-situ geomechanical stress of the zone proximate prior to performing step (a). 
     
     
         7 . The method of  claim 1 , wherein the geomechanical stress of the zone proximate in step (b) is increased from an initial in-situ geomechanical stress state in the zone proximate to a geomechanical stress state in the zone proximate that is greater than the original in-situ geomechanical stress of the zone proximate prior to performing step (a). 
     
     
         8 . The method of  claim 1 , wherein the geomechanical stress of the zone proximate in step (b) is increased from the reduced geomechanical stress in the zone proximate after first performing step (a). 
     
     
         9 . The method of  claim 8 , wherein the geomechanical stress of the zone proximate in step (b) is increased to a geomechanical stress state that is greater than the in-situ geomechanical stress of the zone proximate prior to performing step (a). 
     
     
         10 . The method of  claim 1 , wherein the geomechanical stress of the zone proximate in step (b) is increased from the reduced geomechanical stress in the zone proximate after first performing step (a), to a geomechanical stress level in the zone proximate that is greater than the geomechanical stress level in the zone proximate prior to previously performing step (a) in the zone proximate. 
     
     
         11 . The method of  claim 1 , wherein the geomechanical stress of the zone proximate in step (a) is decreased from the increased geomechanical stress in the zone proximate after first performing step (b), to a geomechanical stress level in the zone proximate that is less than the geomechanical stress level in the zone proximate prior to previously performing step (a) in the zone proximate. 
     
     
         12 . A method for fracturing a subterranean formation, comprising:
 using a wellbore to perform one of the steps of;   (a) reducing the geomechanical stress in a zone proximate to the subterranean formation to translate a geomechanical stress change to the subterranean formation to cause a mechanical dislocation of at least a portion of the subterranean formation and create fractures within at least a portion of the subterranean formation; and   (b) applying stress in the zone proximate to the subterranean formation to translate a geomechanical stress change to the subterranean formation to cause a mechanical dislocation of at least a portion of the subterranean formation and create fractures within at least a portion of the subterranean formation; and   thereafter, using the wellbore to perform the other of step (a) and step (b).   
     
     
         13 . The method of  claim 12 , wherein the subterranean formation comprises a hydrocarbon formation. 
     
     
         14 . The method of  claim 12 , wherein the zone proximate comprises a formation layer in an underburden. 
     
     
         15 . The method of  claim 12 , wherein step (a) creates a volumetric decrease in bulk volume of the zone proximate and the volumetric decrease is caused by a decrease in pore pressure within the zone proximate. 
     
     
         16 . The method of  claim 12 , wherein step (b) creates a volumetric increase in bulk volume of the zone proximate and the volumetric increase is caused by an increase in pore pressure within the zone proximate. 
     
     
         17 . The method of  claim 15 , wherein the decrease in pore pressure results in subsidence of the subterranean formation. 
     
     
         18 . The method of  claim 12 , wherein step (a) creates a volumetric decrease in the zone proximate and the volumetric decrease is effected by a method that comprises pumping a fluid into the zone proximate to create a chemical reaction that reduces bulk volume of the zone proximate. 
     
     
         19 . The method of  claim 18 , wherein the chemical reaction comprises chemicals which dissolve regions of the zone. 
     
     
         20 . The method of  claim 18 , wherein the chemical reaction comprises and endothermic reaction that contracts the zone. 
     
     
         21 . The method of  claim 12 , wherein step (a) creates a volumetric decrease in the zone proximate and the volumetric decrease is effected producing fluid from the zone proximate. 
     
     
         22 . The method of  claim 12 , wherein creating the volumetric decrease comprises material excavation from the zone proximate. 
     
     
         23 . The method of  claim 22 , wherein the excavation within the zone proximate comprises at least one of introduction of abrasive fluids into the zone proximate, creating a wellbore tunnel within the zone proximate, collapsing a wellbore within the zone proximate, creating perforation tunnels within the zone proximate, leaching a soluble material from the zone proximate, dissolving soluble material from the zone proximate, gasification of material from the zone proximate, and eroding formation material from the zone proximate. 
     
     
         24 . The method of  claim 12 , further comprising producing a hydrocarbon from the subterranean formation. 
     
     
         25 . The method of  claim 12 , further comprising producing a geothermally heated fluid from the subterranean formation. 
     
     
         26 . A method for production of a hydrocarbon from a hydrocarbon bearing formation, comprising: 
       cycling a contraction and expansion of a zone proximate to a hydrocarbon bearing subterranean formation to mechanically stress the hydrocarbon bearing subterranean formation and create an arch in the hydrocarbon bearing subterranean formation; and
 creating a relative movement across a fracture surface to enhance conductivity; 
 
     
     
         27 . The method of  claim 26 , wherein the hydrocarbon bearing subterranean formation comprises a tight gas reservoir. 
     
     
         28 . The method of  claim 26 , wherein the hydrocarbon bearing subterranean formation comprises a shale gas reservoir. 
     
     
         29 . The method of  claim 26 , wherein the hydrocarbon bearing subterranean formation comprises a coal bed methane reservoir. 
     
     
         30 . The method of  claim 26 , wherein the hydrocarbon bearing subterranean formation comprises a tight oil reservoir. 
     
     
         31 . The method of  claim 26 , further comprising cycling the contraction of the zone proximate by reducing the in-situ stress in the zone proximate so as to cause at least a portion of the subterranean formation to arch in a direction toward the zone proximate. 
     
     
         32 . The method of  claim 26 , further comprising cycling the expansion of the zone proximate by applying stress to the zone proximate so as to cause at least a portion of the subterranean formation to arch in a direction away from the zone proximate. 
     
     
         33 . The method of  claim 26 , wherein the relative movement across a fracture surface creates a stimulated formation volume 
     
     
         34 . The method of  claim 32 , further comprising producing a hydrocarbon from the hydrocarbon bearing subterranean formation. 
     
     
         35 . The method of  claim 32 , comprising drilling a production well from the stimulation well into the hydrocarbon bearing subterranean formation. 
     
     
         36 . The method of  claim 26 , further comprising drilling a production well into the hydrocarbon bearing subterranean formation after the treatment is completed. 
     
     
         37 . The method of  claim 26 , further comprising drilling a production well into the hydrocarbon bearing subterranean formation before the treatment is completed. 
     
     
         38 . The method of  claim 26 , further comprising where the cycling cause the zone to rubblize a layer of material along a delamination joint with the hydrocarbon bearing subterranean formation. 
     
     
         39 . A hydrocarbon production system, comprising:
 a hydrocarbon bearing subterranean formation;   a zone proximate to the hydrocarbon bearing subterranean formation;   a stimulation well drilled to the zone; and   a stimulation system configured to comprise:
 creating a volumetric decrease; and 
 reversing the volumetric decrease; and 
 repeating the volumetric decrease for one or more cycles. 
   
     
     
         40 . The hydrocarbon production system of  claim 39 , wherein the hydrocarbon bearing subterranean formation comprises a tight gas layer. 
     
     
         41 . The hydrocarbon production system of  claim 39 , wherein the hydrocarbon bearing subterranean formation comprises a shale gas layer. 
     
     
         42 . The hydrocarbon production system of  claim 39 , wherein the hydrocarbon bearing subterranean formation comprises a coal bed methane layer. 
     
     
         43 . The hydrocarbon production system of  claim 39 , wherein the hydrocarbon bearing subterranean formation comprises a tight oil layer. 
     
     
         44 . The hydrocarbon production system of  claim 39 , wherein the zone comprises a formation layer in an underburden. 
     
     
         45 . The hydrocarbon production system of  claim 39 , comprising a production well drilled into the hydrocarbon bearing subterranean formation. 
     
     
         46 . The hydrocarbon production system of  claim 39 , comprising a production well drilled into the hydrocarbon bearing subterranean formation from the stimulation well. 
     
     
         47 . A method for fracturing a subterranean formation, comprising:
 causing a volumetric decrease in a zone proximate the subterranean formation so as to apply a geomechanical stress change to the subterranean formation, wherein the geomechanical stress change creates an arch-like bending movement in at least a portion of the subterranean formation and causes fractures to form in the subterranean formation;   reversing the volumetric decrease in the zone proximate to cause a volumetric increase in the zone proximate so as to at least partially reverse the geomechanical stress change in the subterranean formation; and   thereafter repeating the volumetric decrease in the zone proximate to cause further fracturing in the subterranean formation.   
     
     
         48 . The method of  claim 47 , wherein the caused fractures within the subterranean formation are caused through delamination of rock layers within the subterranean formation during arching of the subterranean formation. 
     
     
         49 . The method of  claim 47 , further comprising changing stress in the zone proximate to cause at least a portion of the subterranean formation to arch in a direction away from the zone proximate. 
     
     
         50 . The method of  claim 47 , further comprising changing stress in the zone proximate to cause at least a portion of the subterranean formation to arch in a direction toward the zone proximate.