Hybrid riser tower and methods of installing same

A riser system comprising a plurality of conduits extending in use from a seabed toward a sea surface and having an upper end supported at a depth below the sea surface, the plurality of conduits forming a riser bundle and the riser system further comprising a central structural core, wherein said riser system further comprises a plurality of guide frames adapted to guide the plurality of conduits and spaced at intervals around at least a part of a length of the central structural core, wherein each guide frame of the plurality of guide frames has two or more buoyant blocks mounted thereto, and wherein for each guide frame, said two or more buoyant blocks attached thereto are arranged symmetrically around said central structural core to form a substantially circular cross-section but are retained by said guide frame so that each buoyant block of the two or more buoyant blocks is separated from each other buoyant block of the two or more buoyant blocks by a fluid permeable gap, wherein a width of the gap is greater than a radius of each conduit of the plurality of conduits guided by a respective guide frame to allow access to the plurality of conduits without removing any of the buoyant blocks.