Marine production riser system and method of installing same

Abstract

A free-standing, marine production riser and a method of installing same for use in deep-water areas to conduct fluids between the marine bottom and the surface. The riser system is comprised of a lower rigid section and an upper flexible section. The lower rigid section has a casing extending from a preset base on the marine bottom to a point just below the zone of turbulence which exists near the surface of the water. A variable-buoyant buoy having a curved upper surface and a central passage therethrough is mounted on the upper end of the casing to support the casing in a substantially vertical position when the casing is in position on the preset base. A remotely actuated connector assembly is provided on the lower end of the casing for connecting the casing to the preset base. A plurality of conduits are run through the passage in the buoy and through guide means in the casing and are remotely connected to mating conduits on the base. Each of a plurality of flexible flowlines is connected to a respective conduit at a point within the passage in the buoy. Each of the flexible flowlines is of sufficient length to extend over the upper curved surface of the buoy which provides a natural bending radius for the flexible flowlines and then downward through a catenary loop before extending upward to the surface. The flowline length also will be sufficient to maintain a catenary loop in the flowline at all times during normal operating conditions. All of the upper ends of the flexible flowlines are connected to a single flange which, in turn, is adapted to be quickly connected to and disconnected from a floating facility at the surface. In turn, each flexible flowline can be individually installed and/or removed.