Patent ID: 8567507

Claim:
A marine oil and gas well drilling apparatus comprising: (a) a marine drilling platform; (b) a drill string that extends between the marine drilling platform and a formation to be drilled, the drill string having a flow bore; (c) a mandrel having upper and lower end sections and connected to and rotatable with upper and lower sections of the drill string, the mandrel having an external diameter and including a longitudinal passage forming a continuation of a flow bore of the drill string sections, the mandrel having an area of reduced external diameter; (d) a sleeve having a longitudinal sleeve passage and an internal diameter, the sleeve being rotatably and reciprocably connected to the mandrel; (e) an interstitial space between the internal diameter of the sleeve and the external diameter of the mandrel which interstitial spaced is sealed by a pair of spaced apart first and second packing units, and wherein the interstitial space overlapping the mandrel's area of reduced external diameter; (f) a pressure relief mechanism that gradually relieves pressure in the interstitial space when the mandrel and sleeve are elevated in a well bore, the pressure relief mechanism including the second packing unit, and the pressure relief mechanism being in an activated state when the second packing unit at least partially extends over the mandrel's area of reduced external diameter, and the pressure relieve mechanism being in a deactivated state when the second packing unit does not extend at least partially over the area of reduced external diameter of the mandrel.