Patent ID: 7753141
Filing Date: 2010-07-13
Classification: E21B

Abstract:
1. A drilling rig for drilling underground boreholes, the rig including a length of semi-rigid tubing wound onto a drum rotatably mounted in a drum frame and arranged such that the semi-rigid tubing can be unwound from the drum and deployed through an injector unit into a borehole, the drum frame being rotatably mounted in turn in a support cradle such that the frame is controllably rotatable about an axis perpendicular to the axis of rotation of the drum and parallel to the axis of the semi-rigid tubing deployed through the injector unit; the semi-rigid tubing being deployed into the borehole through a peripheral seal, allowing borehole fluid to be constantly pressurized during drilling operations; the rig further including a drilling assembly mounted on the end of the semi-rigid tubing and incorporating an offset feature causing the drilling assembly to deviate from a straight path as the semi-rigid tubing is advanced by the injector unit during drilling operations, whereby the direction of deviation is controlled by rotating the semi-rigid tubing about its longitudinal axis effected by rotating the drum frame relative to the support cradle.