Abstract: An articulated directional drilling tool assembly for use in drilling a borehole having a short radius of curvature includes a mud motor having an upper housing that is pivotally connected to a lower housing having upper and lower sections. Such sections are joined together in a manner to define a bend angle. The drill bit box carries a stabilizer that centers it in the borehole. The upper housing section carries an eccentric stabilizer assembly which tilts it toward the low side of the borehole to increase the effectiveness of the bend angle. A hydraulic piston also can be used to increase the side loading on the bit and cause it to drill a sharply curving borehole. The upper housing of the motor is connected to the lower housing by an articulative, torque transmitting coupling, and the upper motor housing is connected to an orientation measuring sub thereabove in the same manner.

Abstract: In accordance with illustrative embodiments of this invention, a downhole adjustable stabilizer includes a sleeve having outwardly extending blades and mounted for limited rotation on a mandrel, vertically aligned sets of radially movable buttons mounted in bores in the blades, and longitudinal flats on the outer periphery of the mandrel that when radially aligned with the respective sets of buttons allows them to shift inward to positions where the stabilizer becomes undergage and can be tilted in the borehole. Some spring loaded buttons drag against the borehole wall to provide frictional restraint against rotation of the housing. The blades can each have an inclined side surface that causes the sleeve to be rotated to its position relative to the mandrel where the sets of buttons are retracted as the stabilizer slides downward in the borehole.

Abstract: Methods are provided for controlling the direction of a borehole drilled by a downhole motor, including the steps of positioning downhole adjustable bent housing and near-bit stabilizer in the drill string, adjusting the bent housing from its normally straight condition to its bent condition to effect borehole curvature, and using the stabilizer in its undergage condition to enhance the inclination. The Measurements are made from which the inclination with respect to the vertical and the azimuth can be determined and telemetered uphole for processing, display, and recording. Preferably the directional measurements are made at two locations, one below the bent point and one above it. These two sets of measurements can be compared to confirm the bend angle and to obtain a definition of the orientation of the plane of the bend angle so that the drilling path can be accurately controlled.

Abstract: In accordance with an illustrative embodiment of the present invention, a downhole adjustable apparatus for creating a bend angle in a drill string includes a mandrel mounted for rotation between first and second angular positions within a housing, the mandrel being telescoped into the housing on an axis that is inclined with respect to the principle axial centerline of the housing, so that in one rotational position of the mandrel the housing is axially aligned with the centerline of a drilling motor and in another rotational position that is 180.degree. from the initial position the housing is slightly inclined with respect to the centerline of such drilling motor to establish a bend angle. Further manipulation of the mandrel is used to return the members to their original positions for straight-ahead drilling.

Abstract: In accordance with an illustrative embodiment of the present invention, a hydraulic drilling jar includes a mandrel and a housing movable between extended and retracted relative positions to deliver jarring blows to a struck object, a piston on the mandrel that slides in a cylinder in the housing, and a restriction assembly on the housing having an internal seal that engages an enlarged section of the mandrel to enclose a high pressure, oil-filled chamber between the piston and the restriction assembly, the restriction assembly including a pin check valve that provides a very slow leakage of oil from the high pressure chamber while the enlarged section of the mandrel is engaged with the seal. An oil-filled compensating chamber on the opposite side of the restriction means from the high pressure chamber has its pressure equalized with the pressure inside the mandrel by ports through the wall of the mandrel.