Pivotal and releasable rat hole assembly

摘要

The rat hole assembly includes a rat hole comprised of a casing large enough to receive a kelly used in drilling of a well. The casing is perforated to permit passage of fluid when inserting or withdrawing the kelly, thus avoiding a piston effect. The rat hole is free at its upper end and includes a releasable pivot connection and support or anchor assembly at its lower end so that the upper portion of the rat hole can be swung adjacent to the rotary table used for drilling for insertion of the kelly into the rat hole and withdrawal of the kelly from the rat hole in normal drilling operations, and the rat hole, either with or without the kelly in it, can be swung over to an out of the way position when not in use.