WHIPSTOCK

摘要

A whipstock (10) has a flowchannel (41) therethrough to facilitate the rapid lowering of the whipstock through liquid in an oil well. A whipstock (10) has a guide surface and a sacrificial element (20) spaced from the guide surface. In use, the sacrificial surface prevents the starting mill damaging the guide surface during the formation of the initial opening in a casing. The undamaged guide surface can later be used for accurately guiding tubulars and tools to help ensure that lateral bores are correctly positioned.