Perforation strategy

Abstract

A method includes determining a stress variation of a geological formation disposed on a wellbore; determining a breakdown pressure of each perforation of a plurality of perforations along a length of the wellbore based on the stress variation; calculating a flow rate of a pumping operation of a hydraulic fracturing process based on the breakdown pressure of each perforation of the plurality of perforations; and hydraulically fracturing a geological formation disposed on the wellbore based on the flow rate.

What is claimed is: 
     
         1 . A method, comprising:
 determining a stress variation of a geological formation disposed on a wellbore;   determining a breakdown pressure of each perforation of a plurality of perforations along a length of the wellbore based on the stress variation;   calculating a flow rate of a pumping operation of a hydraulic fracturing process based on the breakdown pressure of each perforation of the plurality of perforations;   hydraulically fracturing a geological formation disposed on the wellbore based on the flow rate.   
     
     
         2 . The method according to  claim 1 , wherein the stress variation is along a length of the wellbore. 
     
     
         3 . The method according to  claim 1 , wherein the stress variation is about a cross section of the wellbore. 
     
     
         4 . The method according to  claim 1 , wherein calculating the flow rate comprises:
 ordering each perforation of the plurality of perforations based on the breakdown pressure of each perforation;   determining the flow rate through the perforation having a lowest breakdown pressure for a test flow rate into the wellbore;   determining a breakdown state of a perforation of the plurality of perforations having a breakdown pressure greater than the lowest breakdown pressure based on the test flow rate.   
     
     
         5 . A method, comprising:
 determining a stress variation of a geological formation disposed on a wellbore;   generating a first plurality of perforations having a having a first breakdown pressure and a second plurality of perforations having a second breakdown pressure greater than the first breakdown pressure based on the stress variation;   hydraulically fracturing a first portion of the geological formation corresponding to the first plurality of perforations;   isolating the first plurality of perforations;   hydraulically fracturing a second portion of the geological formation corresponding to the second plurality of perforations.   
     
     
         6 . The method according to  claim 5 , wherein each perforation of the first plurality of perforations has a location along the wellbore corresponding to a low stress location of the stress variation. 
     
     
         7 . The method according to  claim 5 , wherein each perforation of the second plurality of perforations has a location along the wellbore corresponding to a high stress location of the stress variation. 
     
     
         8 . The method according to  claim 5 , wherein each perforation of the first plurality of perforations has a perforation direction corresponding to a low stress perforation direction of the stress variation. 
     
     
         9 . The method according to  claim 5 , wherein each perforation of the second plurality of perforations has a perforation direction corresponding to a high stress perforation direction of the stress variation. 
     
     
         10 . The method according to  claim 5 , further comprising:
 overflushing the wellbore while the first plurality of perforations is isolated;   removing the isolation of the first plurality of perforations.   
     
     
         11 . A method, comprising:
 determining a stress variation of a geological formation disposed on a wellbore;   generating a first plurality of perforation groups having a first breakdown pressure based on the stress variation;   generating a second plurality of perforation groups having a second breakdown pressure based on the stress variation;   hydraulically fracturing a first portion of the geological formation corresponding to the first plurality of perforation groups;   isolating the first plurality of perforation groups;   hydraulically fracturing a second portion of the geological formation corresponding to the second plurality of perforation groups.   
     
     
         12 . The method according to  claim 11 , wherein the majority of each perforation group of the first plurality of perforation groups is disposed along the wellbore at a location where a nearest neighboring perforation group is a perforation group of the second plurality of perforation groups. 
     
     
         13 . The method according to  claim 11 , wherein each perforation group of the first plurality of perforation groups is disposed along a first length of the wellbore and each perforation group of the second plurality of perforation groups is located along a second length of the wellbore. 
     
     
         14 . The method according to  claim 11 , wherein each perforation group of the first plurality of the first plurality of perforation groups has a perforation depth based on the first breakdown pressure. 
     
     
         15 . The method according to  claim 11 , wherein each perforation group of the first plurality of the first plurality of perforation groups has a perforation direction based on the first breakdown pressure. 
     
     
         16 . A method, comprising:
 pumping a fluid into a wellbore at a first rate for a first period of time and determining a first bottom hole pressure;   determining a rate of change of the first bottom hole pressure during the first time period;   normalizing the determined rate of change of the bottom hole pressure to a volume of the fluid pumped during the first time period.   
     
     
         17 . The method according to  claim 16 , further comprising:
 pumping the fluid into the wellbore at a second rate for a second period of time and determining a second bottom hole pressure;   determining a second rate of change of the second bottom hole pressure during the second time period;   normalizing the determined second rate of change of the second bottom hole pressure to a second volume of the fluid pumped during the second time period,   wherein the second rate is less than the first rate.   
     
     
         18 . The method according to  claim 17 , further comprising:
 determining a state of the wellbore based on the normalized first rate of change of the first bottom hole pressure and the normalized second rate of change of the second bottom hole pressure.   
     
     
         19 . The method according to  claim 18 , wherein the state of the wellbore is determined as highly tortuous if the magnitude of the normalized first rate of change of the first bottom hole pressure is less than magnitude of the normalized second rate of change of the second bottom hole pressure. 
     
     
         20 . The method according to  claim 18 , further comprising:
 determining a leakoff rate by interpolating a rate at which a normalized rate of pressure change is reduced to zero based on the normalized first rate of change of the first bottom hole pressure and normalized second rate of change of the second bottom hole pressure.