A method for energy efficient and fast rotary drilling in inhomogeneous and/or hard rock formations

Abstract

It is described a rotary drilling system ( 10 ) for drilling a borehole ( 12 ) in inhomogeneous and/or hard rock formations. The system ( 10 ) comprising: a rotary drill bit ( 20; 50 ), and at least two electrodes ( 21, 22, 23, 51, 52, 53 ) arranged for pulsing between said electrodes of at least one high voltage electro pulse ( 41 ), wherein said at least one high voltage electro pulse ( 41 ) is generated in response to a detected resistance on the drill bit ( 20 ) from a rock formation ( 40 ) in front of the drill bit ( 20 ) while rotating, in order to create small/micro-cracks ( 45 ) in the rock formation ( 40 ).

1 - 25 . (canceled) 
     
     
         26 . A rotary mechanical drilling system for mechanical drilling of a borehole in inhomogeneous and/or hard rock formations, the system comprising:
 a rotary drill bit, and   at least two electrodes arranged for pulsing between said electrodes of at least one high voltage electro pulse,   wherein said at least one high voltage electro pulse is generated in response to a detected resistance on the drill bit from a rock formation in front of the drill bit while drilling, in order to create small-cracks/micro-cracks in the rock formation, wherein said at least one high voltage electro pulse is generated only when the detected resistance on the drill bit exceeds a predetermined limit under drilling.   
     
     
         27 . The rotary drilling system according to  claim 26 , further comprising at least one sensor arranged in the drill bit for detecting the resistance on the drill bit from the rock formation. 
     
     
         28 . The rotary drilling system according to  claim 26 , further comprising at least one sensor arranged in the drilling system for detecting the resistance on the drill bit from the rock formation. 
     
     
         29 . The rotary drilling system according to  claim 26 , further comprising a radar or sonar for pre-detecting the resistance on the drill bit from the rock formation. 
     
     
         30 . The rotary drilling system according to  claim 26 , wherein the detected resistance is in the form of a detected torque on the drill bit from the rock formation. 
     
     
         31 . The rotary drilling system according to  claim 30 , wherein said at least one high voltage electro pulse is generated when the detected torque on the drill bit exceeds a predetermined torque limit under rotary drilling. 
     
     
         32 . The rotary drilling system according to  claim 26 , wherein at least two electrodes are incorporated in the drill bit. 
     
     
         33 . The rotary drilling system according to  claim 26 , further comprising an electro pulse device connected to said electrodes and adapted for generating said at least one high voltage electro pulse. 
     
     
         34 . The rotary drilling system according to  claim 26 , further comprising a torque sensing device arranged for detecting the drill bit torque from the rock formation in front of the drill bit under drilling. 
     
     
         35 . The rotary drilling system according to  claim 26 , further comprising an electronic switch for electro pulsing. 
     
     
         36 . The rotary drilling system according to  claim 26 , wherein the electro pulse device comprises at least one of: a capacitor, a rectifier and a transformer of low to high voltage and/or current. 
     
     
         37 . The rotary drilling system according to  claim 26 , wherein the system further comprises an electrical source comprising at least one of: a battery pack or batteries, a mud driven generator, a water driven generator, a compressed air driven generator, a rotary drill string driven generator, and cables to surface. 
     
     
         38 . The rotary drilling system according to  claim 26 , further comprising a drilling assembly. 
     
     
         39 . The rotary drilling system according to  claim 38 , wherein the rotary drill bit is arranged in the drilling assembly. 
     
     
         40 . The rotary drilling system according to  claim 38 , wherein the electro pulse device is arranged in the drilling assembly. 
     
     
         41 . The rotary drilling system according to  claim 26 , wherein the drill bit comprises at least one of: teeth, scrapers and cutter disks, and wherein said at least two electrodes are incorporated in at least one of: the drill bit itself, the teeth, the scrapers and the cutter disks. 
     
     
         42 . The rotary drilling system according to  claim 26 , wherein the system is adapted for tunneling, and the drill bit is a rotary tunnel excavator. 
     
     
         43 . A method for rotary mechanical drilling of a borehole in inhomogeneous and/or hard rock formations, comprising:
 rotary mechanical drilling a borehole using a rotary drill bit,   pulsing between at least two electrodes of at least one high voltage electro pulse, wherein said at least one high voltage electro pulse is generated in response to a detected resistance on the drill bit from a rock formation in front of the drill bit while rotating, creating small cracks/micro-cracks in the rock formation, wherein said at least one high voltage electro pulse is generated only when the detected resistance on the drill bit exceeds a predetermined limit under rotary drilling.   
     
     
         44 . Method according to  claim 43 , further comprising detecting the resistance by detecting a torque on the drill bit from the rock formation. 
     
     
         45 . Method according to  claim 43 , further comprising detecting by using a radar or sonar for pre-detecting the resistance on the drill bit from the rock formation. 
     
     
         46 . The rotary drilling method according to  claim 43 , wherein at least two electrodes are incorporated in the drill bit. 
     
     
         47 . The rotary drilling method according to  claim 43 , further comprising excavating the micro-cracked rock lattice or matrix. 
     
     
         48 . The rotary drilling method according to  claim 43 , wherein the method is adapted for tunneling, and the drill bit is a rotary tunnel excavator.