Abstract: A method and apparatus for drilling straight bores into the earth is made up of a series of articulated joints which are interpositioned between a drill string and drill bit with an enlarged stabilizer member positioned between each pair of joints and the initial or lowermost section between the drill bit and first joint cooperating with the stabilizer members in such a way as to cause the entire assembly to drill on a straight line or course. In one modified form of invention, a stabilizer member is fixed for rotation behind the drill bit to straighten the drilling course, and may be employed alone or in combination with additional stabilizers and joints in the drill string.

Abstract: A reamer apparatus is adapted for use in combination with a radial whipstock assembly in drilling a curved bore in a subsurface formation at a predetermined angle of build. The reamer apparatus is comprised of a drill bit, at least one articulated joint or drill collar connected to the lower end of the drill string, and a stabilized reamer interconnected for rotation behind the drill bit which includes cutter blades overgauged in relation to the drill bit and projecting substantially in outward radial directions from the reamer body, each blade having an elongated cutting edge which extends substantially parallel to the direction of drilling and a stabilized leading end so as to stabilize the reamer and avoid preferential cutting as the drill bit proceeds along the desired course.

Abstract: Directional drilling is carried out by orienting and positioning a whipstock having a curved guide surface at a predetermined rotational angle with respect to the desired azimuth so as to compensate for lateral deviation of the original bore or rathole. The curved guide surface of the whipstock is given a radius of curvature in a longitudinal direction corresponding to that of the drainhole section radius and is provided with a concave face in a transverse direction which defines lateral wings along the guide surface to control the advancement of the drilling tool along the desired course and avoid objectionable helixing. Proper orientation and guidance of the drill tool by means of the radius whipstock as described permits accurate determination of the drainhole orientation vertical drill distance between the zenith and nadir of the drainhole as well as the actual drilled depth between those points.