CORE MARKER Russian patent published in 1994 - IPC

FIELD: well drilling. SUBSTANCE: core marker is made in form of cylinder 1 with recesses 2 on outer surface 3. Changeable plates 4 are arranged between recesses 2 on outer surface. Changeable plates have S-shaped cutters 5. Center of gravity 6 of core marker is displaced relative to its central axis. This is ensured by the fact that recesses 2 or core marker holes 7 are disposed irregular along circumference of core marker cylinder 1. Tool break-off, its lifting and lowering onto bottom are carried out during rotation of tool to increase core recovery due to improved cleaning of walls of core receiver by increased force of pressing cutters to core marker plane. EFFECT: higher efficiency. 4 cl, 1 dwg