초록 ▼

An offshore system is provided of the type that includes riser pipes (30) extending up from the seafloor (44) to a tall and narrow caisson (12) at the sea surface, with the caisson moored by mooring lines (34) extending to the seafloor and anchored thereat, which minimizes bending of the upper porti

An offshore system is provided of the type that includes riser pipes (30) extending up from the seafloor (44) to a tall and narrow caisson (12) at the sea surface, with the caisson moored by mooring lines (34) extending to the seafloor and anchored thereat, which minimizes bending of the upper portion of the riser pipes when the caisson drifts in severe weather. Although the caisson has a Ballasted lower end and buoyant upper end to keep its axis (20) vertical, a device is provided for applying a horizontal force (54) to a location along the caisson that is vertically spaced from the upper ends of the mooring lines, to tilt the caisson so the axis of the caisson is parallel to portions (82) of the riser pipes lying immediately below the caisson. In one arrangement, a second set of mooring lines (60) is provided, that have upper ends coupled to second locations (64) along the caisson that are vertically spaced from the upper ends of the first mooring lines. Also, a motor driven device (70) is provided for pulling on selected ones of the lines to tilt the caisson. In another arrangement, largely horizontal force transmitting members (132) extend from a lower portion of the caisson to a location (136) along a single set of mooring lines (126). In still another system, thrusters (152, 154) are used to push at locations along the caisson to tilt it.

대표청구항 ▼

[ What is claimed is:] [1.] In a spar system that includes a tall narrow caisson that is buoyant and that floats at the sea surface and that has upper and lower portions and a primarily vertical caisson axis, and at least one riser pipe that extends up from the sea floor and that has a riser guided

[ What is claimed is:] [1.] In a spar system that includes a tall narrow caisson that is buoyant and that floats at the sea surface and that has upper and lower portions and a primarily vertical caisson axis, and at least one riser pipe that extends up from the sea floor and that has a riser guided portion that is coupled to said caisson lower portion, with said riser pipe having an upper end connected to said caisson upper end portion, where said spar system includes a first set of mooring lines that have upper ends that are coupled to said caisson at first caisson locations with said mooring lines extending in different headings and at downward inclines to the sea floor and having lower ends anchored to the sea floor, and where said riser pipe extends substantially vertically from the sea floor to said caisson in a quiescent position of said caisson, the improvement of apparatus for minimizing bending of said riser pipes when said caisson drifts away from said quiescent position, comprising:means for creating a controlled tilt from the vertical, of said caisson axis to reduce any angle between said caisson axis and a longitudinal axis of said riser pipe at a location immediately below said caisson.