Abstract: An apparatus for assisting the advancement of a work string. In the preferred embodiment, the work string is concentrically disposed within a highly deviated tubular member. The apparatus comprises a cylindrical member having a first half clamp and a second half clamp having an arcuate inner portion, with the first half clamp and second half clamp being connected with a hinge. The apparatus further includes a first housing attached to the first half clamp and a second housing attached to the second half clamp. The apparatus further comprises a first roller inserted into the first housing and a second roller inserted into the second housing. In the preferred embodiment, the first and second rollers are spherical. The apparatus may further comprise a first deflector plate operatively associated with a first side of the first housing and the second housing. The first deflector plate has a first end adjacent the cap member and a second end adjacent the first half body so that an angled end is formed.

Abstract: A downhole tool for engaging a borehole wall of a well, with outwardly displacing gripping elements to engage the borehole wall in such a way as to prevent rotation of the tool relative to the borehole wall, thereby preventing a downhole motor from imposing a reactive torque on the workstring uphole from the tool. The gripping elements can have one or more rolling elements, such as wheels, to roll longitudinally along the borehole wall in either the uphole or downhole direction, or both, while preventing transmission of reactive torque to the workstring. The gripping elements can also be configured to prevent longitudinal motion of the tool, such as blades. Displacement of the gripping elements can be hydraulically actuated.

Abstract: A fitting for reducing friction between a drilling string and the wall of a well. In a first aspect the fitting has recesses (6) provided along the bore of the fitting to lubricate the interface between the fitting and the drill string to minimise friction. In a second aspect a fitting is provided on a drill string having rotatable roller means (21) which can rotate about a point of rotation (23) so as to minimise both axial and rotational friction. According to a third aspect the fitting comprises an inner section (30) secured to a drill pipe (35) or other fitting and an outer section (31) rotatable about the inner section (30). Preferably a sealed bearing (36, 42-47, 37, 38) is provided between the inner section (30) and outer section (31).