US 7,571,769 B2
Casing window milling assembly
Mohan L. Soni, Katy, Tex. (US); and Calvin J. Stowe, II, Bellaire, Tex. (US)
Assigned to Baker Hughes Incorporated, Houston, Tex. (US)
Filed on Feb. 23, 2007, as Appl. No. 11/710,161.
Prior Publication US 2008/0202754 A1, Aug. 28, 2008
Int. Cl. E21B 29/06 (2006.01)
U.S. Cl. 166—298  [166/55] 26 Claims
OG exemplary drawing
 
1. An improved casing window milling assembly having a tubular and a mill head disposed at a lower end of the tubular, the improvement comprising:
a conically shaped section of the tubular that is tapered toward the mill head, the conically shaped section comprising an upper portion and a lower portion, the upper portion having an outer diameter greater than an outer diameter of the lower portion, and an outer layer disposed along an outer surface of the conically shaped section, the outer layer comprising a wear resistant, nonabrasive, material,
wherein the outer diameter of the upper portion is sized to cause engagement of the upper portion with a whipstock surface of a whipstock disposed in a wellbore at a non-parallel angle relative to a longitudinal axis of the whipstock.