Rat hole pipe is used for drill site preparation. The pipe is used to create a hole in the rig floor that is typically used for storage of different drill tools for the upcoming job site. The rat hole is typically 20-35 ft deep, and it is lined with this rat hole pipe that sticks out of the ground.
1. A slanting hole about 25 feet deep into which the grief stem is lowered to lubricate or adjust the swivel or to add a joint of drill pipe to the drilling string.
2. A borehole reduced in size by coring. Synonym = Kelly hole.
3. To prepare for rotary drilling by drilling with a small bit and leaving a seat for the casing.
4. To reduce the size of the borehole and feel ahead.