Dynamic damper for use in a drill string

Abstract

A dynamic damper for installation in a drill string (1), the purpose of which damper is to reduce the risk of jamming the drill bit (5), thereby avoiding damages in the event of unwanted extreme oscillations and rotational speed of the drill string caused by uncontrolled release of torsional energy in the drill string when the drill string suddenly breaks free of the jam. For this purpose, the damper is constructed from an outer and an inner string section (11) and (12), supported concentrically and interconnected through a helical threaded connection (10), so that relative rotation between the sections caused by torque (8) will give an axial movement that lifts and loosens the drill bit from the bottom of the hole in critical jamming situations. The spring (9) maintains the outer string section in an axial position against the shoulder (22). A hydraulic damping effect on the axial movements is achieved by oil volumes (16) and (17) being interconnected through narrow bores (18). Logging of the damping function is carried out by sensor (20), which registers and stores data to be read when the damper is retrieved to the surface.

Dependencies are inferred from the claim text.