Riser moving and guiding using shuttle plates

Abstract

A riser tube tower for stabilizing riser tubes extending from respective wellheads associated with a seabed frame on the seabed to a platform, preferably a tension leg platform, at the sea surface. The riser tube tower includes vertical wires connecting the platform with the seabed frame. Horizontally disposed guide plates are fixed in position at one or more levels of the tower. Vertically movable shuttle plates are located in the vertical spaces over, between, and under the guide plates. The vertical wires and riser tubes pass through spaced apertures in the guide plates and the shuttle plates. The apertures in the shuttle plates are aligned with respective apertures in the guide plates. Bushings are disposed in the apertures of the guide plates and the shuttle plates for protecting the guide plates and shuttle plates from the riser tubes and wires, and for reducing friction therebetween. Elevator devices move the shuttle plates vertically above, below, or between the guide plates. The shuttle plates move between the platform and the seabed frame together with the riser tubes and guide the riser tubes to respective apertures in the guide plates, and to respective wellheads in the seabed frame.