Phased stimulation methods

Abstract

A method of stimulating a subterranean formation is provided. The method includes determining a final fracture spacing. The method includes creating a first set of fractures at a first fracture spacing, the first fracture spacing being larger than the final fracture spacing. The method includes allowing production of fluids from the formation through the well bore via the first set of fractures for a period of time. The method includes, after the period of time, creating a second set of fractures. The final fracture spacing is less than or equal to an average fracture spacing between the first set of fractures and the second set of fractures.

What is claimed is: 
     
         1 . A method of stimulating a subterranean formation having a well bore therein, the method comprising:
 determining a final fracture spacing;   creating a first set of fractures at a first fracture spacing, the first fracture spacing being larger than the final fracture spacing;   allowing production of fluids from the formation through the well bore via the first set of fractures for a period of time;   after the period of time, creating a second set of fractures;   wherein the final fracture spacing is less than or equal to an average fracture spacing between the first set of fractures and the second set of fractures.   
     
     
         2 . The method of  claim 1 , wherein the first fracture spacing is at least double the final fracture spacing. 
     
     
         3 . The method of  claim 1 , wherein the final fracture spacing comprises an economically optimized fracture spacing, and wherein the step of determining the final fracture spacing comprises determining the economically optimized fracture spacing. 
     
     
         4 . The method of  claim 1 , wherein the period of time comprises sufficient time to permit the relief of stress created by the first set of fractures. 
     
     
         5 . The method of  claim 1 , wherein the period of time comprises less than one year. 
     
     
         6 . The method of  claim 5 , wherein the period of time comprises from 1 month to 6 months. 
     
     
         7 . The method of  claim 5 , wherein the period of time comprises from 1 week to 1 month. 
     
     
         8 . The method of  claim 5 , wherein the period of time comprises from 1 hour to 1 week. 
     
     
         9 . The method of  claim 1 , further comprising stopping production of fluids from the first set of fractures prior to creating the second set of fractures. 
     
     
         10 . The method of  claim 1 , further comprising:
 allowing production of fluids from the formation through the well bore via the second set of fractures for a second period of time;   after the second period of time, creating a third set of fractures;   wherein the final fracture spacing is less than or equal to an average fracture spacing between the first set of fractures, the second set of fractures, and the third set of fractures.   
     
     
         11 . A method of phased stimulation of a zone in a subterranean formation, the method comprising:
 stimulating the zone via a first set of fractures originating at a well bore and having a first fracture spacing;   allowing primary production from the zone via the first set of fractures;   providing isolation between the first set of fractures and the well bore before the primary production reaches a predetermined threshold;   further stimulating the zone via a second set of fractures originating at the wellbore, wherein at least one of the fractures of the second set of fractures lies between adjacent fractures in the first set of fractures;   allowing production from the zone via the second set of fractures; and   removing the isolation between the first set of fractures and the well bore thereby allowing secondary production from the zone via the first set of fractures.   
     
     
         12 . The method of  claim 11 , wherein the predetermined threshold comprises a percentage of a maximum projected production from the zone. 
     
     
         13 . The method of  claim 12 , wherein the percentage is no more than 50%. 
     
     
         14 . The method of  claim 13 , wherein the percentage is no more than 25%. 
     
     
         15 . The method of  claim 14 , wherein the percentage is no more than 5%. 
     
     
         16 . The method of  claim 11 , wherein the predetermined threshold comprises a time of production from the zone. 
     
     
         17 . The method of  claim 16 , wherein the time of production is no more than 1 year. 
     
     
         18 . The method of  claim 11 , wherein the first set of fractures and the second set of fractures have an average fracture spacing and wherein the first fracture spacing is at least twice the average fracture spacing. 
     
     
         19 . The method of  claim 11 , wherein the first fracture spacing is at least four times a final fracture spacing. 
     
     
         20 . The method of  claim 11 , wherein the step of providing isolation comprises running tubing with external packers into the well bore. 
     
     
         21 . The method of  claim 11 , further comprising re-stimulating the first set of fractures. 
     
     
         22 . A method comprising:
 (a) determining a threshold stress value indicative of presence of a stress shadow;   (b) obtaining a formation stress value;   (c) allowing production when the formation stress value exceeds the threshold stress value; and   (d) ceasing production when the formation stress value drops below the threshold stress value.   
     
     
         23 . The method of  claim 22  further comprising:
 before step (c), stimulating a zone in a subterranean formation via a first set of fractures originating at a well bore; 
 providing isolation between the first set of fractures and the well bore before the production reaches the threshold stress value; 
 further stimulating the zone via a second set of fractures originating at the wellbore, wherein at least one of the fractures of the second set of fractures lies between adjacent fractures in the first set of fractures; 
 allowing production from the zone via the second set of fractures; and 
 removing the isolation between the first set of fractures and the well bore thereby allowing secondary production from the zone via the first set of fractures.