Fracture initiation with auxiliary notches

Abstract

Improved notching techniques are described for transverse fracture initiation from the wellbore (cased or open). One or more auxiliary notches are formed that are sealed from borehole pressure increase, yet still deformable under the fracturing pressure in the wellbore. Through the use of the auxiliary notches, lower fracturing pressure and/or shallower notches can be used when compared to known notching techniques without auxiliary notching. The described approaches can also provide greater control over the initial direction of the fracture.

1 . A method of fracturing a subterranean formation from a borehole penetrating the formation, the method comprising:
 creating a fracture initiation notch extending from a wall of the borehole into the formation;   creating at least one auxiliary notch extending from the borehole wall into the formation positioned and configured to facilitate fracture initiation from said fracture initiation notch;   protecting said at least one auxiliary notch from direct fluid communication with said borehole; and   increasing fluid pressure within the borehole and said fracture initiation notch thereby initiating a fracture from said fracture initiation notch, wherein said at least one auxiliary notch being protected from said fluid pressure increase and being deformable such that said fracture initiation occurs at a lower pressure than if the auxiliary notch did not exist.   
     
     
         2 . The method according to  claim 1  wherein said borehole is an open-hole or cased borehole in the location of the fracture initiation notch and the at least one auxiliary notch. 
     
     
         3 . (canceled) 
     
     
         4 . The method according to  claim 1  wherein said fracture initiation notch and said at least one auxiliary notch are shaped. 
     
     
         5 . The method according to  claim 4  wherein said fracture initiation notch and said at least one auxiliary notch have a shape selected from a group consisting of a U-shape and a V-shape. 
     
     
         6 . The method according to  claim 1  wherein protecting said at least one auxiliary notch from direct fluid communication with said borehole includes sealing an opening to said at least one auxiliary notch. 
     
     
         7 . The method according to  claim 6  wherein protecting said at least one auxiliary notch from direct fluid communication with said borehole includes sealing an opening to said at least one auxiliary notch with a polymer resin material. 
     
     
         8 . The method according to  claim 1  wherein said at least one auxiliary notch is spaced from said fracture initiation notch by less than six times a radius of the borehole. 
     
     
         9 . The method according to  claim 1  wherein said fracture initiation notch is created having a depth that is less than would have been needed for fracture initiation at an equivalent pressure if said auxiliary notch did not exist. 
     
     
         10 . The method according to  claim 1  wherein said fracture initiation notch is planar and approximately perpendicular to a central borehole axis. 
     
     
         11 . The method according to  claim 1  wherein said fracture initiation notch is planar and non-perpendicular to a central borehole axis. 
     
     
         12 . The method according to  claim 1  where said at least one auxiliary notch includes two auxiliary notches positioned with the fracture initiation notch between the two auxiliary notches. 
     
     
         13 . The method according to  claim 12  wherein each of the two auxiliary notches is spaced away from the fracture initiation notch by less than about 3 times a radius of the borehole. 
     
     
         14 . The method according to  claim 12  wherein the two auxiliary notches are spaced away from the fracture initiation notch by non-equal distances. 
     
     
         15 . The method according to  claim 1  where said at least one auxiliary notch includes at least three auxiliary notches. 
     
     
         16 . The method according to  claim 1  wherein said fracture initiation notch and said at least one auxiliary notch are created using a jet cutting tool deployed via coiled tubing. 
     
     
         17 . The method according to  claim 1  wherein protecting said at least one auxiliary notch from direct fluid communication with said borehole includes at least partially filling said at least one auxiliary notch with a degradable plugging material. 
     
     
         18 . The method according to  claim 1  wherein the subterranean formation is a hydrocarbon-bearing formation. 
     
     
         19 . The method according to  claim 1  further comprising repeating said creating a fracture initiation notch, creating at least one auxiliary notch, and protecting, such that said increasing fluid pressure initiates a plurality of fractures from a plurality of fracturing initiation notches. 
     
     
         20 . The method according to  claim 1  further comprising repeating said creating a fracture initiation notch, creating at least one auxiliary notch, protecting, and increasing fluid pressure, thereby sequentially fracturing the formation from each of several fracturing initiating notches. 
     
     
         21 . The method according to  claim 1  wherein fractures are not initiated from said at least one auxiliary notch. 
     
     
         22 . A system for fracturing a subterranean formation from a borehole penetrating the formation, the system comprising:
 a notch forming tool configured to form a fracture initiation notch extending from a wall of the borehole into the formation, and at least one auxiliary notch extending from the borehole wall into the formation, the at least one auxiliary notch being positioned and configured to facilitate fracture initiation from said fracture initiation notch;   a notch sealing system configured to sealingly protect said at least one auxiliary notch from direct fluid communication with said borehole;   a fluid pressurizing system configured to increase pressure in the borehole; and   a control system programmed and configured to cause the pressurizing system to increase the pressure in the borehole to a fracture initiation pressure which is calculated to initiate a fracture from said fracture initiation notch and wherein said fracture initiation pressure is lower than a pressure that would be needed to initiate fracturing if the at least one auxiliary notch did not exist.   
     
     
         23 . The system according to  claim 22  wherein said control system and said notch forming tool are configured to form the at least one auxiliary notch and the fracture initiation notch such they are spaced apart by no more than six times a radius of the borehole. 
     
     
         24 . The system according to  claim 22  wherein said control system and said notch forming tool are configured to form the at least one auxiliary notch and the fracture initiation notch such they are spaced apart by no more than three times a radius of the borehole. 
     
     
         25 . The system according to  claim 22  wherein said control system and said notch forming tool are configured to form the fracture initiation notch having a depth that is less than would have been needed for fracture initiation at an equivalent pressure if said at least one auxiliary notch did not exist. 
     
     
         26 . The system according to  claim 22  where said at least one auxiliary notch includes two auxiliary notches positioned with the fracture initiation notch between the two auxiliary notches. 
     
     
         27 . The system according to  claim 22  wherein said notch forming tool is a jet cutting tool deployable via coiled tubing.