Method for cutting slot-like key seats in producing formation of producing or pumping wells

Abstract

This method relates to the fields of mining, specifically oil, gas and hydro-geological industries and is intended for relief of tangential stress which originates in well side areas of producing formation from underground pressure by means of cutting vertical slot-shaped seats in well side zones of producing formation. The determined task is solved by introducing essential changes into the known method of constructing slot-like key seats from the well wall inside the rock consisting of generation of hydro-abrasive jet, its transportation to the perforator's nozzle, which is lowered into the well inside the casing pipe and directed towards the rock, and the nozzle's travel along the surface of the forming seat. The changes are as follows:—The slot-like seat is automatically formed out of the series of drainage canals on the seat surface which are performed one after another;—The perforator is moved from the place of the previous drainage canal to the place of forming the next one by step when it is switched off; Each drainage canal is formed when the perforator is in immovable position with regard to the casing pipe walls;—The moment of casing pipe cutting is fixed by spasmodic drop of hydro-abrasive jet pressure in pressure line which is not less than 10%;—Time T of forming each drainage canal after cutting the casing pipe is calculated according to the following formula (1): T = σ   mr Mabr   V   min ( 1 ) where: σ—breaking point of rock, in which the drainage canal is formed; mr—body of rock which carried out the drainage canal; mabr—mass of operating fluid with abrasive, pumped in time T; Vmin—minimal speed of abrasive particle in working jet that ruins the rock, in which the drainage canal is formed. It s calculated by the following formula: Vmin=σ/mabr; The process of drainage canal formation is stopped T min after the casing pipe cutting; Then the perforator is switched off and moved to the place of cutting the next opening in the casing pipe in order to form the next drainage canal;—The process of forming the next and subsequent canals is stopped T min after not less than 10% uneven reduction of the abrasive jet pressure. To optimize the construction of slot-like key seat, centers of the adjacent drainage canals are placed at a distance of the drainage port diameter ±5%. The moment of destruction the crosspiece between the previous and the drained canals can be determined by the second jumping reduction of the abrasive jet pressure which took place in the process of the next canal drainage. The number of drainage canals is determined by means of dividing the producing formation thickness by the drain port diameter. In order to construct vertically oriented seat the drainage canals are placed vertically one under another by means of lowering the perforator nozzle. In order to construct horizontal seat the drainage canals are placed horizontally by means of turning the perforator nozzle. In order to construct sloping seat the drainage canals are placed slanted by means of vertical movement of the perforator nozzle with its simultaneous turn.

1 . A method for construction of a slot-like key seat from the well wall inside the rock consisting of the generation of hydro-abrasive jet, its transportation to the perforator's nozzle, which is lowered into the well inside the casing pipe and directed towards the rock and the nozzle's travel along the surface of the forming seat. The method includes the exposure of producing formation, defining of its thickness, calculation of the slot-like seat depth and height;
 the distinction of the method lies in the fact that   
     the slot-like seat is formed out of series of subsequently performed drainage canals which are situated along the seat surface. The canals automatically unite into the slot-like key seat of necessary parameters. The perforator slowly moves from canal to canal, and each drainage canal is formed when the perforator is in a stationary position with regard to the casing pipe walls. The process of drainage canal formation lasts not less than T minutes after the moment of cutting the casing pipe by abrasive jet; time T is calculated by the following formula (1) 
     
       
         
           
             T 
             = 
             
               
                 σ 
                  
                 
                     
                 
                  
                 
                   m 
                   r 
                 
               
               
                 
                   M 
                   abr 
                 
                  
                 
                     
                 
                  
                 
                   V 
                   min 
                 
               
             
           
         
       
     
     where 
     σ—breaking point of rock, in which the drainage canal is formed; 
     m r —body of rock which carried out the drainage canal 
     m abr —mass of operating fluid with abrasive, pumped in time T; 
     V min —minimal speed of an abrasive particle in working jet that ruins the rock, in which the drainage canal is formed. It s calculated by the following formula:
     V   min   =σ/m   abr ; 
 
     Then the perforator is switched off and moved to the place of cutting the next opening in the casing pipe to form the next drainage canal. It is then switched on, the casing pipe is cut and the drainage process of the next canal lasts not less than T min after the cutting of the casing pipe. The perforator is switched off again. These operations of switching off, moving to the place of next opening cutting and the next canal drainage are repeated until all drainage canals along the whole thickness of the producing formation are constructed. 
   
   
       2 . Method as in  claim 1 , the distinction lies in the fact that the moment of cutting the pipe with abrasive jet is defined by not less than 10% uneven pressure drop of the abrasive jet in pressure line. 
   
   
       3 . Method as in  claim 1 , the distinction lies in the fact that the drainage of the second and following canals goes on until the crosspiece between the previous and the drained canals is destroyed. 
   
   
       4 . Method as in  claim 1 , the distinction lies in the fact that the moment of the crosspiece destruction is determined by not less than 10% uneven reduction of the abrasive jet pressure in the drainage process. 
   
   
       5 . Method as in  claim 1 , the distinction lies in the fact that the drainage canals are placed at a distance of the drainage canal diameter ±5% from each other. 
   
   
       6 . Method as in  claim 1 , the distinction lies in the fact that the number of drainage canals is determined by means of dividing the producing formation thickness by the drain port diameter. 
   
   
       7 . Method as in  claim 1 , the distinction lies in the fact that in order to construct vertically oriented seats the drainage canals are placed vertically one under another by means of lowering the perforator's nozzle. 
   
   
       8 . Method as in  claim 1 , the distinction lies in the fact that in order to construct horizontal seats the drainage canals are placed horizontally by means of turning the perforator's nozzle. 
   
   
       9 . Method as in  claim 1 , the distinction lies in the fact that in order to construct sloping seats the drainage canals are placed slanted by means of vertical movement of the perforator nozzle with its simultaneous turn.