Rotating blowout preventer and method

The present invention relates to blowout preventers and, more particularly, relates to a rotating blowout preventer with spherical packing elements for use in hydrocarbon recovery operation. The blowout preventer of this invention is able to reliably withstand high pressure while maintaining sealed engagement with a tubular rotating at relatively high speeds, and also may be used to seal with a non-rotating tubular. The rotatable blowout preventer comprises a stationary outer housing and a rotatable inner housing having a curved surface thereon defining a portion of a sphere. An annular packer assembly includes spherical packer elements for sliding engagement with the curved surface of the inner housing such that a packer assembly may seal against various sized tubulars. A lower rotary seal between a piston and the outer housing is exposed to the differential between pressurized hydraulic fluid and the well pressure within a lower end of the bore within the outer housing. A flow restriction member between the rotatable inner housing and the outer housing reduces fluid pressure downstream from the flow restriction to less than 40% of the upstream pressure. The upper rotary seal is open to atmospheric pressure and is subjected to this reduced pressure. Improved techniques are provided for passing hydraulic fluid through the blowout preventer for both closing and opening the sealing assembly