Method of over-pressured well fracturing with periodic shock waves

Abstract

Fractures are initiated or extended into earth formations from a well by providing pressured fluid in said wellbore at pressures exceeding the fracture gradient pressure of said formation and by generating a cyclic shock waves. Periodic shock waves applied simultaneously with a high pressured fluid on a formation increases the length of fractures/cracks in the formation.

1 . A method for forming at least one fracture in a formation having a wellbore penetrating said formation and communicating therewith through a multiplicity of perforations comprising the steps of:
 a) arranging a shock wave generating tool in the vicinity of the said perforations inside the wellbore;   b) providing a pressured fluid in said wellbore at pressures exceeding the fracture gradient pressure of said formation;   c) generating a periodic shock waves from said shock wave generating tool with the amplitude P a  of shock waves determined by following expression:
   4 P   p −0.8ρg H≦P   a   ≦P   c ,
 
   
       where P p  is the formation pore pressure, ρ is the formation density, g is a gravity acceleration, H is the depth of said perforations, P a  is amplitude of shock wave and P c  is a collapse resistance stress of the shock wave generating tool; 
     
     
         2 . A method as defined in  claim 1 , wherein the amplitude of generated shock waves is at least not less than fracture gradient pressure of productive formation. 
     
     
         3 . A method as defined in  claim 1 , wherein said shock wave generating tool is sealed from perforations by means of packer; 
     
     
         4 . A method as defined in  claim 1 , wherein the tool generating the shock waves is installed opposite a non-perforated formation.