Apparatus for drilling underground arcuate paths and installing production casings, conduits, or flow pipes therein

Claim 1

Apparatus for drilling along an underground inverted path comprising: a directional drill including an in-hole motor; a trailing drill string of non-uniform external diameter attached to said directional drill, the largest external diameter of said drill string being less than the diameter of the hole produced by said directional drill, said in-hole motor including a rotor and a stator, said drill including a bit connected to said rotor, one end of said drill string being connected to said stator, said drill string including a plurality of integral external concentric collars disposed at intervals along said drill string, the diameter of each of said collars being less than the diameter of the hole produced by said directional drill, said collars comprising external upsets at the ends of the joints making up said trailing drill string, a drill rig providing means at the other end of said drill string for crowding said drill string into said hole and for azimuthally positioning said drill string in the hole, washover pipe connected at one end to said drill rig and disposed about said drill string and extending from said one end of the drill string toward but separated from said one end of the drill string, leaving an exposed portion of the drill string without said washover pipe, and forming with the covered portion of the drill string therewithin an inner annulus, cutting means connected to the other end of said washover pipe, said drill rig providing means to rotate said washover pipe around said drill string and advance the washover pipe along said path, said washover pipe having an outer diameter larger than said drill bit but smaller than said cutting means whereby to form an outer annulus for drilling mud returns around the washover pipe as it is advanced along said path, said drill rig providing means to deliver drilling mud to said drill string and said inner annulus, fresh drilling mud from the drill rig flowing in said inner annulus forwardly past said collars toward said cutting means providing lubricant between said collars of said covered portion of the drill string and said washover pipe spindled on the drill string and rotating about said collars, detritus laden drilling mud flowing backwards along the path back from the drill bit along the exterior of the exposed portion of the drill string past said collars which help size the hole drilled by said bit along said path by directing the detritus outwardly from the drill string, said collars tending to prevent the exposed portion of said drill string from sticking when it is moved axially along said path without continuous rotation in the hole.