Disconnectable riser for deep water operation

Claim 1

In an offshore system for drilling well bores through a well head in the ocean floor, and which includes; a drilling vessel floatably positioned at the water's surface, an elongated riser extending between, and connected at its opposed ends to the vessel and to the said well head whereby to define an elongated continuous passage therethrough, pumping means on said vessel communicated with said riser for circulating a flow of drilling fluid therethrough during a well drilling operation, and opening means in said riser upper end for passing a rotating drill string through said riser to form said well bore in the ocean floor, the improvement therein of; said riser including separable upper and lower segments, remotely actuated coupling means being operable to removably engage said upper and lower segments to form said continuous passage, and buoyancy means positioned on said riser lower segment to externally support said lower segment whereby to maintain the latter in a substantially upright position when said lower segment has disengaged from the riser upper segment and regulating means for controlling the amount of drilling fluid which is retained in said riser upper and lower segments respectively during a disconnect of said segments.