CASING STRING BIT AND SPUDDING BIT Russian patent published in 2015 - IPC E21B10/64 E21B10/26 E21B17/14 

FIELD: oil and gas industry.

SUBSTANCE: end tool of the casing string comprises dish-shaped body with the central axis formed by outer convex surface and inner concave surface placed opposite the convex one. The inner concave surface is non-axisymmetric to the central axis while the outer convex surface is axisymmetric to the central axis. According to one embodiment of end tool the inner concave surface comprises plurality of non-axisymmetric areas formed by thicker parts of the wall. According to the other embodiment of end tool the inner concave surface comprises at least one channel zone in the wall where the above channel zone is made as non-continuous cut or dead-end hole for improved fragmentation of the casing string end tool at its drilling.

EFFECT: group of inventions is related to embodiments of the casing string end tool; it ensures effective and even drilling of the end tool, improved fragmentation of the casing string end tool at its drilling, improved operational efficiency of the tool at drilling and drilling out, improved resistivity to destruction, abrasing effect, impact loading.

49 cl, 11 dwg