Abstract: According to the invention, a downhole anchor assembly is employed for absorbing reaction torque from a downhole mud motor in a directional drill string so as to minimize azimuthal deviation from such reaction torque. The anchor assembly has as its main structural basis an elongated, generally cylindrical housing with upper and lower ends formed as tool joints for coupling the body into a directional drill string. Three elongated chain support bodies are longitudinally mounted in the housing, evenly circumferentially spaced about the periphery, and each support body supports an endless anchor block chain so that elongated portions of the chains are longitudinally arranged and generally radially exposed externally of the bodies. The chain support bodies are radially shiftable under the influence of hydraulic drilling fluid pressure from retracted positions in the body to extended positions in which the exposed chain portions grip the well casing against twisting of the drill string.

Abstract: An overshot for the handling and retrieval of "drop" type well survey instruments that are employed in directional drilling. The overshot has an elongated, generally cylindrical body with a pair of elongated, generally longitudinally arranged, diametrically opposed locking arms mounted therein for both longitudinal sliding and radial tilting movement. The locking arms are longitudinally biased by means of a spring-loaded plunger axially centered in the body, such biasing causing the arms to be cammed radially inwardly toward their locking positions.

Abstract: A system for minimizing frictional stress and wear between elements of a well string and a surrounding casing or other conduit containing the string. According to the invention, a generally longitudinally arranged, linear array of recirculating rollable bearing elements, preferably ball bearings, projects radially outwardly from a well string member so as to reduce primarily lineal friction. A plurality of such linear arrays of recirculating rollable bearing elements are regularly spaced about the periphery of the string at each of a series of locations along the string, and at each such location the arrays are provided in a bearing cage which may be connected to the string through annular rollable bearing means for reducing rotational friction. The bearing cages containing the linear arrays of recirculating rollable bearing elements may be mounted on separate subs or attached over the string.

Abstract: An axially extensible telescoping joint is employed in a directional drilling string to reduce the number of times for a given footage of well drilled that the wireline from the downhole survey or steering tool to the surface readout must be tripped through the string for adding more drill pipe. By drilling the first half of a drilling sequence with the telescoping joint collapsed, and then the second half of the sequence with the telescoping joint extended, twice the conventional footage can be drilled between wireline trips, and two stands of drill pipe can be added rather than the conventional single stand each time the wireline is tripped.

Abstract: A jarring tool for use in a drill string to prevent sticking of the drill string during drilling operations. The jarring tool has a torque assembly for continually torquing the jar and thus the drilling operation need not be discontinued upon encountering an interfering object. The jarring tool is particularly suited for high viscosity drilling operations and eliminates hydrostatic sticking of the drill string by providing an immediate jarring action utilizing a simple hammer and anvil construction. The jarring tool is also suitable for use in a "fishing" string.