Air Percussion Drilling In Horizontal Wells

Abstract

A method of drilling a subterranean formation includes positioning a drill string in a well bore in the subterranean formation. The drill string includes a hammer bit, a bend in a housing of the drill string, and a guidance system that determines inclination and azimuth of at least a portion of the drill string in the well bore. Once positioned in the well bore, the hammer bit is caused to repeatedly strike the end of the well bore while rotating about an axis of the hammer bit thereby drilling the subterranean formation and forming a new length of the well bore in the subterranean formation. The orientation of the bend of the drill string in the well bore is controlled based on the determined inclination and azimuth such that the hammer bit drills the new length of the well bore substantially horizontally in the subterranean formation.

1 . A method of drilling a subterranean formation comprising:
 (a) forming a well bore from a surface into the subterranean formation;   (b) positioning a bottom hole assembly at an end of the well bore in the subterranean formation, the bottom hole assembly including in order between the end of the well bore and the surface:
 a hammer bit; 
 a percussion hammer operative for causing the hammer bit to move alternately into and out of contact with the end of the well bore; 
 a motor assembly having a first end coupled to the percussion hammer, the motor assembly including a motor operative for rotating the percussion hammer and the hammer bit about central axes of the percussion hammer and the hammer bit, the motor assembly including a motor housing having a bend therein that defines an angle between the first end of the motor assembly and a second end of the motor assembly; and 
 a guidance system operative for determining inclination and azimuth of at least a portion of the bottom hole assembly in the well bore and for generating one or more signals regarding the inclination and azimuth; 
   (c) following step (b), causing the percussion hammer to move the hammer bit alternately into and out of contact with the end of the well bore while simultaneously causing the motor to rotate the percussion hammer and the hammer bit about the central axes of the percussion hammer and the hammer bit thereby forming a new length of the well bore in the subterranean formation; and   (d) concurrent with step (c), controlling the orientation of the bend in the motor housing in the well bore based on the one or more signals regarding the inclination and azimuth generated by the guidance system such that the new length of the well bore is within ±5°, inclusive, of horizontal in the subterranean formation.   
     
     
         2 . The method of  claim 1 , wherein a direction of movement of the hammer bit into and out of contact with the end of the well bore is substantially parallel with the central axes of the percussion hammer and the hammer bit. 
     
     
         3 . The method of  claim 1 , wherein the new length of the well bore that is within ±5°, inclusive, of horizontal in the subterranean formation is desirably longer than 500 feet, more desirably longer than 1,000 feet, and most desirably longer than 2,000 feet. 
     
     
         4 . The method of  claim 1 , wherein:
 step (a) includes drilling the well bore utilizing a first drill bit; and   the method further includes, prior to step (b), removing the first drill bit from the well bore.   
     
     
         5 . The method of  claim 1 , wherein:
 the bottom hole assembly further includes a drill pipe coupled between the guidance system and the surface; and   the weight of the drill pipe and the bottom hole assembly urge the hammer bit toward the end of the well bore.   
     
     
         6 . The method of  claim 1 , wherein a rate of penetration of the hammer bit in the subterranean formation to form the new length of the well bore is desirably greater than 40 feet per hour, more desirably greater that than 60 feet per hour, and most desirably greater than 80 feet per hour. 
     
     
         7 . The method of  claim 1 , wherein the bottom hole assembly further includes a shock assembly coupled between the guidance system and the motor assembly, the shock assembly operative for mitigating vibration received by the guidance system caused by the operation of the hammer bit, the percussion hammer, and the motor. 
     
     
         8 . The method of  claim 1 , wherein step (c) includes providing compressed fluid to the percussion hammer to cause the percussion hammer to move the one end of the hammer bit alternately into and out of contact with the end of the well bore. 
     
     
         9 . The method of  claim 1 , wherein step (c) includes providing compressed fluid to the motor to cause the motor to rotate the percussion hammer and the hammer bit about the central axes of the percussion hammer and the hammer bit. 
     
     
         10 . The method of  claim 1 , wherein the angle is between 0.2° and 1.5°. 
     
     
         11 . A method of drilling a subterranean formation comprising:
 (a) positioning a drill string in a well bore in a subterranean formation, the drill string including: a hammer bit positioned at an end of the well bore, a bend in a housing of the drill string, and a guidance system operative for determining inclination and azimuth of at least a portion of the drill string in the well bore and for generating one or more signals regarding the inclination and azimuth;   (b) following step (a), causing the hammer bit to repeatedly strike the end of the well bore while rotating the hammer bit about an axis of the hammer bit thereby drilling the subterranean formation and forming a new length of the well bore in the subterranean formation; and   (c) controlling the orientation of the bend of the drill string in the well bore based on the one or more signals regarding the inclination and azimuth generated by the guidance system such that the hammer bit drills the new length of the well bore substantially horizontally in the subterranean formation.   
     
     
         12 . The method of  claim 11 , wherein the hammer bit moves in a direction along its axis when the hammer bit repeatedly strikes the end of the well bore. 
     
     
         13 . The method of  claim 11 , wherein the new length of the well bore that is substantially horizontal in the subterranean formation is between ±5°, inclusive, of horizontal in the subterranean formation. 
     
     
         14 . The method of  claim 13 , wherein the new length of the well bore that is within ±5°, inclusive, of horizontal in the subterranean formation is desirably longer than 500 feet, more desirably longer than 1,000 feet, and most desirably longer than 2,000 feet. 
     
     
         15 . The method of  claim 11 , wherein a rate of penetration of the hammer bit in the subterranean formation to form the new length of the well bore is desirably greater than 40 feet per hour, more desirably greater than 60 feet per hour, and most desirably greater than 80 feet per hour.