Valve apparatus for deep drilling

摘要

A valve apparatus adapted for connection in a drill stem comprises a sleeve member slidably guided in a body having a longitudinal fluid passage and lateral openings that communicate with an annular space surrounding the sleeve member. The sleeve member also comprises lateral holes of small diameter and bottom orifices or channels of large diameter. In a first position of the sleeve member, the fluid flows from the drill stem towards the annular space through the holes of small diameter. When the rate of flow reaches a sufficient value, the sleeve member is moved against a biasing spring to a second position, where the small holes are closed and the large channels permit the passage of the fluid through the valve, towards the lower part of the drill stem, without any noticeable pressure drop. The sleeve member is retained in the said second position through the pressures in the drill stem and in the annular space acting on different areas of the sleeve member. When the pressure in the annular space suddenly increases, the sleeve member is moved to a third position wherein any communication between the drill stem and the annular space is avoided.