A clamp assembly, for mounting around a tool joint coaxially joining cylindrical upper and lower workpieces, comprises an upper collar assembly and a lower collar assembly, each having semi-cylindrical left and right collar segments. The left and right collar segments of each collar assembly are removably connectable to each other by threaded fasteners to form the collar assembly. The upper and lower collar assemblies are coaxially mountable around the upper and lower workpieces, respectively, such that tightening the fasteners will urge the upper and lower collar assemblies to grip the upper and lower workpieces, respectively, and thus to provide increased resistance to relative rotation between the two workpieces about the tool joint axis. The upper and lower left collar segments, and/or the upper and lower right collar segments, may be interlockingly and radially slidable relative to each other to accommodate differences between the outside diameters of the two workpieces.

A clamp assembly, for mounting around a tool joint coaxially joining cylindrical upper and lower workpieces, comprises an upper collar assembly and a lower collar assembly, each having semi-cylindrical left and right collar segments. The left and right collar segments of each collar assembly are removably connectable to each other by threaded fasteners to form the collar assembly. The upper and lower collar assemblies are coaxially mountable around the upper and lower workpieces, respectively, such that tightening the fasteners will urge the upper and lower collar assemblies to grip the upper and lower workpieces, respectively, and thus to provide increased resistance to relative rotation between the two workpieces about the tool joint axis. The upper and lower left collar segments, and/or the upper and lower right collar segments, may be interlockingly and radially slidable relative to each other to accommodate differences between the outside diameters of the two workpieces.

Drill collars may be constructed using solid-state welding processes. Solid-state welding produces robust drill collars with high fatigue lifespans and permits individual segments of the drill collar to be optimized based on their intended use. A drill collar may be formed of a first segment with a different material, density, modulus of elasticity and/or geometry than an adjacent second segment fused thereto. If a segment of a drill collar is damaged in use, the damaged segment may be removed and replaced, possibly without de-rating the drill collar. Methods of forming the solid-state welds may include friction welding adjacent segments to one another such that features in each segment are circumferentially aligned when the weld is formed. Supplemental energy sources may provide additional heat at the welded surfaces to ensure the segments are effectively fused.

Drill collars may be constructed using solid-state welding processes. Solid-state welding produces robust drill collars with high fatigue lifespans and permits individual segments of the drill collar to be optimized based on their intended use. A drill collar may be formed of a first segment with a different material, density, modulus of elasticity and/or geometry than an adjacent second segment fused thereto. If a segment of a drill collar is damaged in use, the damaged segment may be removed and replaced, possibly without de-rating the drill collar. Methods of forming the solid-state welds may include friction welding adjacent segments to one another such that features in each segment are circumferentially aligned when the weld is formed. Supplemental energy sources may provide additional heat at the welded surfaces to ensure the segments are effectively fused.

A tubing string, such as a coiled tubing or jointed tubing string, has an agitator mounted within an interior of the tubing string at an intermediate position between an uphole end and a downhole end of the tubing string. A tubing agitator is structured to be installed within a tubing string. A method includes: forming or installing a seat within an interior of a tubing string at an intermediate position between an uphole end and a downhole end of the tubing string; and conveying an agitator through the interior of the tubing string until the agitator contacts the seat. A hammer drift tool is also described.

A retention system for attaching a collar to a pipe. The collar has an internally-disposed groove configured for placement of a ring. The ring is sized such that in one orientation, it can enter the collar between torque-transmitting features into the internally-disposed groove. Once in the groove, the ring may be adjusted such that its aperture is generally aligned with the axis of the collar. In this orientation, the features retain the ring within the groove. A bolt and a pipe may then be placed within the collar from opposite sides. The bolt is attached to the pipe through the ring. Once joined, the collar is joined to the pipe, forming its box end. Such a retention system may be used to join a series of inner pipe members of a dual-member pipe assembly, as in horizontal directional drilling.

A drive shaft assembly for a downhole drilling motor includes a drive shaft having a first end portion engaging a first housing and a second end portion engaging a second housing. The first end portion and the first housing form the first constant velocity joint and the second end portion and the second housing form the second constant velocity joint of the drive shaft assembly. Each end portion including a base surface having a pair of prongs extending away from the base surface and a cylindrical side wall having a plurality of ball bearings held in a plurality of circumferentially spaced pockets. Each housing includes a cavity to retain respective end portions of the drive shaft. An inner side wall of each housing includes a plurality of cylindrical grooves to receive the plurality of ball bearings to transfer torque. An internal wall of the housing includes a first chamber and a second chamber to receive and retain the first prong and the second prong to transfer torque and thrust loads between the shaft and the housings.

A drive shaft assembly for a downhole drilling motor includes a drive shaft having a first end portion engaging a first housing and a second end portion engaging a second housing. The first end portion and the first housing form the first constant velocity joint and the second end portion and the second housing form the second constant velocity joint of the drive shaft assembly. Each end portion including a base surface having a pair of prongs extending away from the base surface and a cylindrical side wall having a plurality of ball bearings held in a plurality of circumferentially spaced pockets. Each housing includes a cavity to retain respective end portions of the drive shaft. An inner side wall of each housing includes a plurality of cylindrical grooves to receive the plurality of ball bearings to transfer torque. An internal wall of the housing includes a first chamber and a second chamber to receive and retain the first prong and the second prong to transfer torque and thrust loads between the shaft and the housings.

A downhole apparatus includes a casing string with a fluid barrier connected therein defining a lower end of a buoyancy chamber. A rupture disk is spaced from the fluid barrier and defines an upper end of the buoyancy chamber. A degradable plug is connected in the casing string above the rupture disk. The degradable plug defines a flow path to permit flow therethrough to the rupture disk, and is movable from a first to a second position in the casing string.

A downhole apparatus includes a casing string with a fluid barrier connected therein defining a lower end of a buoyancy chamber. A rupture disk is spaced from the fluid barrier and defines an upper end of the buoyancy chamber. A degradable plug is connected in the casing string above the rupture disk. The degradable plug defines a flow path to permit flow therethrough to the rupture disk, and is movable from a first to a second position in the casing string.