Method for Increasing Productivity of Wells

Abstract

A method for increasing productivity of oil and gas wells includes carrying out a secondary opening in formations which were opened before, by first using a hydro-sandblasting operation and thereafter using a hydro-fracturing operation.

What is desired to be protected by Letters Patent is set forth in particular in the appended claims: 
     
         1 . A method for increasing productivity of oil and gas wells, comprising the steps of:
 carrying out a secondary opening in formations which were opened before; and   performing the secondary opening first by a hydro-slotting process, and thereafter by a hydro-fracturing process.   
     
     
         2 . The method according to  claim 1 , wherein the hydro-slotting process includes forming slots around an axis of a well and along it over a whole thickness of a formation with retention of partitions in the formation, which are self-destructing partitions. 
     
     
         3 . The method according to  claim 1 , wherein the hydro-slotting process includes forming of slots providing at least four slot cavities in one plane along a well shaft with the use of at least four nozzles of a perforator. 
     
     
         4 . The method according to  claim 1 , wherein the hydro-slotting process includes forming of slots and orienting the slots in a direction extending substantially perpendicular to maximum horizontal stresses. 
     
     
         5 . The method according to  claim 1 , wherein the hydro-slotting process includes forming of slots and orienting the slots with consideration of location and orientation of cracks in an area which surrounds the well. 
     
     
         6 . The method according to  claim 1 , further comprising using ecologically acceptable powders for dissolving cement in the well. 
     
     
         7 . The method according to  claim 2 , wherein the distance between the partitions is as follows:
     h> 0.5· d·σ/σ   cube ·{1+[1+4·σ cube /σ]½}  (1)
   
       wherein d is a diameter, m,
 σ is horizontal stress at a depth of formation, Mpa, 
 σ cube  is a cube strength of rock of formation, Mpa. 
 
     
     
         8 . The method according to  claim 2 , wherein values of sizes of the partitions and distances between them to be self-destructive are as follows:
     h= 0.5· d·σ/σ   cube ·{1+[1+4·σ cube /σ]½}  (2)
   
       wherein h and d are in mm.