Horizontal directional drilling system

Abstract

The invention relates to a horizontal directional drilling system, comprising a dual string ( 1 ), said dual string ( 1 ) comprising an inner string ( 2 ), and an outer string ( 3 ), said inner string ( 2 ) is rotatable independently of said outer string ( 3 ), a first rotary drive system ( 4 ) to drive said inner string ( 2 ), a second rotary drive system ( 5 ) to drive said outer string ( 3 ), a frame ( 11 ) to movably support said rotary drive systems ( 4, 5 ), a front casing ( 7 ) fitted to a distal end of said outer string ( 3 ), a drive shaft ( 8 ) coaxially positioned into said front casing ( 7 ) and connected with said inner string ( 2 ) and a hammer ( 9 ) connected to said front casing ( 7 ) and operable in response to rotation of said drive shaft ( 8 ), said hammer ( 9 ) comprising a drill head ( 90 ) and a drill bit ( 91 ) wherein said drill head ( 90 ) generating percussive energy using pressurized fluid, e.g. pressurized air, supplied through an annular passage between said outer string ( 3 ) and said inner string ( 2 ).

1 - 11 . (canceled) 
     
     
         12 . A directional drilling system comprising
 a dual string, said dual string comprising:
 an inner string; 
 an outer string, wherein said inner string is rotatable independently of said outer string; 
 a first rotary drive system to drive said inner string; 
 a second rotary drive system to drive said outer string; 
 a frame to movably support said rotary drive systems; 
 a front casing comprising a bend fitted to a distal end of said outer string; 
 a drive shaft coaxially positioned into said front casing and connected with said inner string; and 
 a drilling tool connected to said front casing and operable in response to rotation of said drive shaft, and 
   said drilling tool comprising a drill head with drilling teeth, wherein said drill head is arranged to generate percussive energy by means of supplying pressurized fluid via said dual string characterized by supplying said pressurized fluid to the spacing between the drive shaft and the front casing via at least one inlet passage and further to the drilling tool via at least one outlet passage in said drive shaft, said drive shaft extending in one integral part between said connections.   
     
     
         13 . A directional drilling system according to  claim 12 , wherein said fluid is pressurized air. 
     
     
         14 . A directional drilling system according to  claim 12 , wherein said system includes a positioning sensor fixed on an opening on said front casing through a sealed lid. 
     
     
         15 . A directional drilling system according to  claim 12 , wherein said drive shaft comprises a plurality radially extending transfer passages positioned such that a break line is not created. 
     
     
         16 . A directional drilling system according to  claim 15 , wherein at least some of said radially extending transfer passages are inclined to eliminate disturbing turbulent flow within said outlet. 
     
     
         17 . A directional drilling system according to  claim 12 , wherein said bend is arranged at about half of its length of the front casing to arrange for an angle of an end part of said front casing. 
     
     
         18 . A directional drilling system according to  claim 12 , wherein said dual string comprises sections of said inner string and said outer string. 
     
     
         19 . A directional drilling system according to  claim 18 , wherein said inner string is a tube or a pipe comprising a central bore to enable transportation of a working fluid to said hammer. 
     
     
         20 . A directional drilling system according to  claim 12 , wherein said drive shaft is coaxially positioned into said front casing by means of a plurality of bearings. 
     
     
         21 . A directional drilling system according to  claim 20 , wherein said plurality of bearings are sealed from an influence of a working medium using a seal. 
     
     
         22 . A directional drilling system according to  claim 12 , wherein said drive shaft comprises a group of at least two transfer passages positioned axially offset in relation to each other. 
     
     
         23 . A directional drilling system according to  claim 15 , wherein all of said radially extending transfer passages are inclined to about 45° to eliminate disturbing turbulent flow within said outlet. 
     
     
         24 . A directional drilling system according to  claim 12 , wherein said bend is arranged at about half of its length of the front casing to arrange for an angle between 1-3° of an end part of said front casing. 
     
     
         25 . A directional drilling system according to  claim 12 , wherein said dual string comprises sections of said inner string and said outer string in the range of 3-6 m. 
     
     
         26 . A method for horizontal directional drilling under the ground, the method comprising:
 rotating a drill head of a drilling tool by rotating an inner string of a dual string; and   generating percussive energy using pressurized fluid, supplied via a channel in said inner string and via a front casing with a drive shaft, said casing, to said drill head, supplying said pressurized fluid through at least one passage in said drive shaft, and through an annular passage between said shaft and said casing, and wherein said drive shaft extends as one integral part.   
     
     
         27 . A method according to  claim 22 , wherein said fluid is pressurized air.