WHIPSTOCK CASING MILLING SYSTEM

摘要

This invention relates to a whipstock casing milling system and, more particularly, to such a system in which a window mill is secured to a whipstock so that the system may be run into a well, set and operated to ope n a window in a casing during a single trip. The milling system of the present invention comprises a protrusion (B) provided on the whipface of the whipsto ck wherein the protrusion (B) forms an extension of a relatively steep ramp surface (45) of the whipface so as to reduce damage to said surface (45) at a juncture (A) of said surface (45) with a relatively shallow ramp surface or parallel surface (46) during use of the system. The protrusion (B) thereby avoids an undercutting of a casing and a thinning of the whipstock.