Abstract: A guide lug for a starting or window mill is provided at the upper end of the whipstock. A back-up shoulder is provided to act against any tendencies of the mill to whirl. A taper is provided for use in guiding the mill toward the casing for the cutting of the window. The lug is configured to be worn by a guide for the window mill or starter mill rather than being milled away. As a result of the use of the lug, the upper sections of the whipstock are protected from the mill. In turn, any holes or other projections provided for subsequent retrieval of the whipstock are functional for such a retrieval at the conclusion of the milling process for the window.

Abstract: A support mechanism for a mill, particularly usable with a whipstock and driven by a downhole motor supported by coiled tubing is disclosed. The support mechanism comprises a wearable ring adjacent the cutting structure which, when assembled into the downhole assembly, keeps the rotating blades away from the whipstock face and oriented toward the casing to be cut. As the milling progresses, the support mechanism wears away to allow advancement of the mill into the casing to complete the formation of the window or opening.

Abstract: A retrieval tool for whipstocks is disclosed. A latch is retractable into the tool upon application of hydraulic pressure. A locking pin securely fastens the whipstock and retrieving tool together. The hydraulic pressure acts a cleaning force on the top of the whipstock and the retrieving slot to facilitate engagement. The offset stabilizer, when oriented opposite the lug on the retrieving tool, creates a force in the direction of the lug, whereby latching the retrieving tool will start. A joint of drillpipe or heavyweight drillpipe is run above the eccentric stabilizer. An offset stabilizer is provided to ensure proper initial orientation and avoid sticking the tool. The latch can firmly grip lugs within a slot in the whipstock. A overshot design is also disclosed using a similar hydraulically actuated latch assembly where the latch grabs the whipstock without having to use an opening therein, if for any reason the opening has been fouled with debris or damaged due to milling.

Abstract: A guide lug for a starting or window mill is provided at the upper end of the whipstock. A back-up shoulder is provided to act against any tendencies of the mill to whirl. A taper is provided for use in guiding the mill toward the casing for the cutting of the window. The lug is configured to be worn by a guide for the window mill or starter mill rather than being milled away. As a result of the use of the lug, the upper sections of the whipstock are protected from the mill. In turn, any holes or other projections provided for subsequent retrieval of the whipstock are functional for such a retrieval at the conclusion of the milling process for the window.