The present invention relates to a drill bit assembly for fluid-operated percussion drill tools. The drill bit assembly comprises a percussion bit having a head portion formed with an axially extending shank, a first plurality of axially extending splines on the shank slideably engageable with a first plurality of complementary splines formed internally of a drive chuck whereby rotational drive from the chuck may be transmitted to the shank. The assembly also comprises engagement means on the chuck adapted for connecting the chuck to a drive means of the fluid-operated percussion drill tool. During drilling, the bit and the chuck are held in a first relative orientation in which the bit is retained in the chuck, and the bit is moveable axially relative to the chuck to a bit removal position, in which the bit is rotatable relative to the chuck to a second relative orientation in which the bit is removable from the chuck. The bit is moveable to the bit removal position while the chuck is fully engaged with the drive means.

Systems and methods for damping torsional oscillations of downhole systems are described. The systems include a downhole drilling system disposed at an end of the downhole system in operative connection with a drill bit. A damping system is installed on the downhole drilling system, the damping system having at least one damper element configured to dampen at least one HFTO mode. At least one mode-shape tuning element is arranged on the drilling system. The at least one mode-shape tuning element is configured and positioned on the drilling system to modify at least one of a shape of the HFTO mode, a frequency of the HFTO mode, an excitability of the HFTO mode, and a damping efficiency of the at least one damper element.

An apparatus for damping vibrations includes an inertial mass disposed in a cavity in a rotatable downhole component, the rotatable component configured to be disposed in a borehole in a subsurface formation, such as a resource bearing formation, the inertial mass coupled to a surface of the cavity by a damping fluid and configured to move within the cavity relative to the downhole component. The apparatus also includes a damping fluid disposed in the cavity between the inertial mass and an inner surface of the cavity, where rotational acceleration of the rotatable downhole component causes shear in the damping fluid to dissipate energy from rotational acceleration of the rotatable downhole component and causing the rotational acceleration to be reduced.

A vibration isolating coupler for isolating torsional vibration in a drill string includes a first coupler portion including a first annular wall having an external surface and an internal surface defining a first central bore portion and a second coupler portion disposed within the first central bore portion. The second coupler portion includes a second annular wall having an external surface section and an internal surface section defining a second central bore portion, and a plurality of connecting elements extending from the internal surface of the first annular wall through the second annular wall across the second central bore portion and connecting with the internal surface of the second annular wall.

An oscillation reduction tool configured to prevent or reduce high frequency torsional oscillation by torsionally decoupling a rotary steerable system from a bottom hole assembly, which includes a drilling motor. The tool may convert high frequency torsional oscillation into an internal axial movement without axial displacement of the tool's outer housing. The oscillation reduction tool may flatten an amplitude of high frequency torsional oscillation spikes throughout a spring arrangement. The mechanical energy associated with the internal axial movement is reduced through an internal shock absorbing mechanism, such as fluid movement through a nozzle or annular space. The oscillation reduction tool functions to reduce high frequency torsional oscillation independent of the weight on the bit of the drill string.

A vibration isolating coupler including a first coupler portion, a second coupler portion including an external surface and an internal surface portion, and a vibration isolating portion extending between the first coupler portion and the second coupler portion. The vibration isolating portion including a first solid annular portion and a second solid annular portion. The vibration isolating portion including a plurality of slots extending from the first solid annular portion toward the second solid annular portion forming a plurality of vibration isolating elements. Each of the plurality of vibration isolating elements is disconnected from adjacent ones of the plurality of vibration isolating elements by a corresponding one of the plurality of slots. The plurality of vibration isolating elements enabling torsional rotation of the first coupler portion relative to the second coupler portion.

The invention relates to a composite shock absorber for a polycrystalline diamond compact bit, comprising a drilling tool body having a water inlet, an impact body having a water outlet and forming a shock absorption cavity, a disc spring group having an annular pressing sleeve, a cylindrical torsion bar spring which has an external thread and a spline, is connected to the drilling tool body through threads and extended into an impactor and connected thereto through the spline, and the annular pressing sleeve, wherein bit vibration impact force is transmitted therebetween through a torsion transmission joint, and a bearing group is arranged between the lower end surface of the annular pressing sleeve and an annular step of the impact body. The composite shock absorber can weaken damage of the slippage effect to polycrystalline diamond compact cutting teeth, absorb axial vibration from a drill stem and prolong the service life of the bit.

An interference apparatus is provided for a motor shaft transmission assembly. The interference apparatus may include split-ring shells and a retaining device. The interference apparatus may be mounted to an intermediate sleeve of the motor shaft transmission assembly. The interference apparatus is configured to prevent the loss of certain motor shaft transmission assembly components downhole in the event of a failure of the motor transmission due to dynamic loads.

A retaining system (100) for a DTH hammer drill bit (25) having an outer surface with a plurality of stops (31) at an up-hole end (29) of the drill bit (25) the stops projecting radially outward from the outer surface and spaced by respective gaps (35). The retaining system has a ring (102) which is configured to pass over the stops (31) when in a first rotational position relative to the drill bit (25). However when the ring (102) is in a second rotational position relative to the drill bit (25) it prohibits passage of the stops (31) through the ring (102).

A bit for a percussive hammer includes an elongated shank, a head at a first end of the shank, and an array of lengthwise extending spline portions defining outwardly extending retention lugs at or toward a further end of the shank. At least a side face of at least one lug is blended into the shank of the bit.