DIRECTIONAL DRILLING APPARATUS

摘要

Directional drilling apparatus having a non-rotating mass rotatably mounted on a mandrel and with a centre-of-gravity spaced form the mandrel axis. An offsetting arrangement is coupled to the mass, and has an outer profile defining an offset relative to the mandrel axis, and a bearing portion rotatably mounted on the offsetting portion. The apparatus is run on a string, and the offsetting portion is oriented relative to the mass. When the string is rotated the mass tends towards an orientation with its centre-of-gravity positioned towards the low side of the bore and tends to maintain the offsetting portion in a desired relative orientation.