Various drill bits, drilling systems and related methods are provided. In one embodiment, a drill bit comprises a bit body having a face and a shank, at least one insert having a convex engagement surface coupled with the face and at least one wear insert coupled with the shank. In one particular embodiment, the at least one wear insert may be positioned immediately adjacent a coupling end of the shank. The at least one wear insert may include a superabrasive table which may be bonded with a substrate. The at least one wear insert includes a wear surface defined in the superabrasive table. In one embodiment, the superabrasive table may comprise polycrystalline diamond. Similarly, the inset having a convex engagement surface may include a superabrasive material, such as polycrystalline diamond, bonded with a substrate. Such a drill bit may be used, for example, in a top hammer percussion drilling operation.

Various drill bits, drilling systems and related methods are provided. In one embodiment, a drill bit comprises a bit body having a face and a shank, at least one insert having a convex engagement surface coupled with the face and at least one wear insert coupled with the shank. In one particular embodiment, the at least one wear insert may be positioned immediately adjacent a coupling end of the shank. The at least one wear insert may include a superabrasive table which may be bonded with a substrate. The at least one wear insert includes a wear surface defined in the superabrasive table. In one embodiment, the superabrasive table may comprise polycrystalline diamond. Similarly, the inset having a convex engagement surface may include a superabrasive material, such as polycrystalline diamond, bonded with a substrate. Such a drill bit may be used, for example, in a top hammer percussion drilling operation.

The rotary-percussive hydraulic perforator includes a body; a shank; a striking piston configured to strike the shank and provided with a braking surface; a braking chamber configured to hydraulically brake the striking piston; a stop piston configured to apply a pushing force on the shank and provided with a bearing surface configured to abut against a stop surface provided on the body, so as to limit the stroke of displacement of the stop piston towards the shank. The rotary-percussive hydraulic perforator is configured such that the bearing surface and the stop surface are axially spaced apart by a predetermined spacing distance simultaneously when (i) the shank bears on the stop piston and is in contact with the striking piston, and (ii) the braking surface is located at an inlet edge of the braking chamber.

The rotary-percussive hydraulic perforator includes a body; a shank; a striking piston configured to strike the shank and provided with a braking surface; a braking chamber configured to hydraulically brake the striking piston; a stop piston configured to apply a pushing force on the shank and provided with a bearing surface configured to abut against a stop surface provided on the body, so as to limit the stroke of displacement of the stop piston towards the shank. The rotary-percussive hydraulic perforator is configured such that the bearing surface and the stop surface are axially spaced apart by a predetermined spacing distance simultaneously when (i) the shank bears on the stop piston and is in contact with the striking piston, and (ii) the braking surface is located at an inlet edge of the braking chamber.

A downhole oscillation tool and method for axially vibrating a drill bit. In some embodiments, modular actuation assemblies may be provided, which may be readily interchanged between a housing and a shaft to axially vibrate the shaft with respect to the housing. Modular actuation assemblies may be mechanical, hydraulic, electric, or piezoelectric, for example, and may be characterized by differing oscillation frequencies. In some embodiments, a piezo element may be provided between the housing and the shaft.

A downhole oscillation tool and method for axially vibrating a drill bit. In some embodiments, modular actuation assemblies may be provided, which may be readily interchanged between a housing and a shaft to axially vibrate the shaft with respect to the housing. Modular actuation assemblies may be mechanical, hydraulic, electric, or piezoelectric, for example, and may be characterized by differing oscillation frequencies. In some embodiments, a piezo element may be provided between the housing and the shaft.

A weight-on-bit self-adjusting drill bit includes a reaming bit, a WOB adjusting element, a transmission mechanism and a pilot bit and a pulsating impact generating mechanism; the pulsating impact generating mechanism includes a centralizing element, a driving element, a rotating element and a throttling element which are placed and connected successively, the centralizing element, the driving element and the rotating element are connected successively, the throttling element is in clearance fit with the rotating element, both of the centralizing element and the throttling element are respectively provided with a flow-through passage for the drilling fluid to flow through, the driving element drives the rotating element to rotate, the rotating element rotates relative to the flow-through passage on the throttling element.

A system for harvesting energy from the operation of a downhole jar is disclosed. The system converts the kinetic energy associated with the operation of the jar to electrical energy by associating the relative movement between a magnet and a coil to the relative movement between a movable member and a stationary member in the jar. Electrical energy is generated in the coil as a result of the relative motion between the magnets and the coil. This electrical energy may be stored in an electrical energy storage subsystem and provided to a downhole tool for use in the wellbore. The downhole tool may be used to power other tools, to take measurements, to communicate with other devices, to actuate other devices, and to otherwise control such other devices.

The present application relates to a weight-on-bit self-adjusting drill bit, namely a pulsed jet type weight-on-bit self-adjusting drill bit, comprising a reaming bit, a WOB adjusting element, a transmission mechanism and a pilot bit and a pulsating impact generating mechanism; the pulsating impact generating mechanism comprises a centralizing element, a driving element, a rotating element and a throttling element which are placed and connected successively, the centralizing element, the driving element and the rotating element are connected successively, the throttling element is in clearance fit with the rotating element, both of the centralizing element and the throttling element are respectively provided with a flow-through passage for the drilling fluid to flow through, the driving element drives the rotating element to rotate, the rotating element rotates relative to the flow-through passage on the throttling element. Compared with the prior art, the present application can realize the rotary percussion drilling of the pilot bit, reduce the chip hold down effect of the pilot bit and the reaming bit, and realize the automatic and reasonable distribution of the weight on bit, thus to protect the bit, improve the bit service life and rate of penetration, and improve the drilling effect.

A drill assembly for percussive drilling, comprising a drill bit and a percussion device. The drill assembly further includes a hollow cylindrical foot valve partially received within a first central flushing channel thereof and extending therefrom in the uphole direction, such that the foot valve is also partially received within a central recess of an impact piston of the percussion device, at least when the impact piston is in a lowermost position of its reciprocation cycle, and such that the foot valve is no longer received within the central recess, at least when the impact piston is in an uppermost position of its reciprocation cycle. The foot valve includes an internal stiffener extending radially inwardly from at least two circumferential positions of an inner surface of the foot valve.