Patent ID: 7896108

Claim:
A dual string drilling system connected to a drilling rig for drilling a well bore in an earth formation comprising: a rotatable, tubular outer drill string having a longitudinal axis; an upper rotatable tubular inner drill string having a longitudinal axis and an interior passageway with the upper inner drill string concentrically disposed in spaced apart relation within the outer drill string; an upper end of the outer drill string and an upper end of the upper inner drill string connected to the drilling rig for rotating the drill strings independently of one another; an elongate tubular driver shoe mounted to a distal end of the outer drill string; the tubular driver shoe provided with an interior passageway having a longitudinal axis which is inclined with respect to the longitudinal axis of the outer drill string; the interior passageway of the driver shoe positioned for fluid communication with the interior passageway of the tubular outer drill string; the tubular driver shoe further provided with a cutaway portion extending through a wall of the tubular outer drill string; a tubular sleeve bearing disposed within the interior passageway of the tubular driver shoe and extending outwardly through the cutaway portion; a lower rotatable tubular inner drill string having a longitudinal axis and concentrically disposed within the tubular sleeve bearing; the lower tubular inner drill string having an interior passageway in fluid communication with an interior passageway of the upper tubular inner drill string; a drill bit mounted to a distal end of the lower inner drill string and is sized to extend beyond the driver shoe mounted to the outer drill string; and means for coupling the lower inner drill string to the upper inner drill string for causing the lower inner drill string to rotate with the upper inner drill string.