Method to optimize perforations for hydraulic fracturing in anisotropic earth formations

Abstract

The subject disclosure relates to determining an optimum orientation for perforations around the circumference of a subsurface borehole and optimum wellbore fluid initiation pressure for hydraulic fracturing in anisotropic formations.

What is claimed is: 
     
         1 . A method for determining a perforation orientation for hydraulic fracturing in an anisotropic earth formation comprising:
 determining anisotropic rock properties;   determining far-field stresses in the anisotropic earth formation;   determining borehole stresses in the anisotropic earth formation; and   determining an optimum perforation orientation and optimum wellbore fluid initiation pressure.   
     
     
         2 . The method according to  claim 1  further comprising perforating a well in the determined optimum perforation orientation. 
     
     
         3 . The method according to  claim 1  wherein the determining anisotropic rock properties further comprises:
 acquisition of a sonic log with a 3D deviation survey; 
 data processing to characterize borehole sonic anisotropy. 
 
     
     
         4 . The method according to  claim 3  wherein the acquisition of the sonic log uses a monopole mode. 
     
     
         5 . The method according to  claim 3  wherein the acquisition of the sonic log uses a dipole mode. 
     
     
         6 . The method according to  claim 3  wherein the acquisition of the sonic log uses a monopole mode, a dipole mode or a Stoneley mode, or any combination of 
     
     
         7 . The method according to  claim 2  wherein the well is a deviated well. 
     
     
         8 . The method according to  claim 2  wherein the well is a horizontal well. 
     
     
         9 . The method according to  claim 2  wherein the well is a vertical well. 
     
     
         10 . The method according to  claim 2  wherein the perforating the well in the optimum perforation orientation is performed with at a shaped charge. 
     
     
         11 . A method for perforating a well traversing a subterranean area including one or more transversely isotropic formations with a tilted axis of symmetry comprising:
 determining formation properties;   determining far-field stresses in the formation;   determining borehole stresses in the formation;   determining an optimum perforation orientation and optimum wellbore fluid initiation pressure; and   perforating the well in the determined optimum perforation orientation.   
     
     
         12 . The method according to  claim 11  wherein the well comprises one or more portions of a group consisting of a deviated portion, a horizontal portion, or a vertical portion. 
     
     
         13 . The method according to  claim 11  wherein the perforating of the well is done with one or more shaped charges. 
     
     
         14 . The method according to  claim 11  further comprising:
 determination of borehole stresses in the well at different depths; 
 positioning perforation clusters at one or more depth points with borehole stresses similar to a previous perforation depth; and 
 perforating the well at the one or more depth points for placement of hydraulic fracturing stages along the well. 
 
     
     
         15 . A method for hydraulic fracturing in an anisotropic earth formation comprising:
 determining anisotropic rock properties;   determining far-field stresses in the anisotropic earth formation;   determining borehole stresses in the anisotropic earth formation;   determining an optimum perforation orientation and optimum wellbore fluid initiation pressure;   perforating a well in the determined optimum perforation orientation; and   hydraulic fracturing the well at a pressure at least at the optimum wellbore fluid initiation pressure.   
     
     
         16 . The method according to  claim 15  wherein the well comprises one or more portions of a group consisting of a deviated portion, a horizontal portion, or a vertical portion. 
     
     
         17 . The method of  claim 15  in which the determining anisotropic rock properties comprises acquisition of wireline sonic logs with all modes with a 3D deviation survey. 
     
     
         18 . The method of  claim 15  in which the determining anisotropic rock properties comprises acquisition of logging while drilling sonic logs with all modes with a 3D deviation survey. 
     
     
         19 . The method of  claim 15  in which the perforating of the well comprises one or more shape charges. 
     
     
         20 . The method according to  claim 17  wherein the acquisition of the sonic log uses a monopole mode, a dipole mode or a Stoneley mode, or any combination of