Abstract: A guidance apparatus for re-entering a sub-sea wellhead or christmas tree after the guidelines extending to the water surface have been removed. The apparatus includes a remotely actuated marker buoy secured by a reeled line to an upwardly projecting keyed buoy post at the wellhead and a second upwardly projecting keyed post is positioned near the well centerline adjacent to the buoy post and the wellhead. The apparatus also includes a re-entry funnel adapted to be run from the surface on a cable attached to either post and having an internal cam engageable by the key on the post to orient the re-entry funnel and align any tools carried thereby with respect to the wellhead, tree or other parts of the sub-sea wellhead structure.

Abstract: A control valve providing various predesignated output signals in response to changes in the pressure of a fluid input signal including a position responsive member mounted for operative connection with such fluid input signal for movement to various positions to direct the fluid input signal outwardly as a selective output signal.

Abstract: A buoyant marine riser system adapted to extend from a floating platform to a subsea wellhead wherein one or more riser sections include a series of circumferentially spaced, elongated, hollow, closed buoyant tanks containing a gaseous medium to make such riser sections substantially buoyant.