Twin-hull offshore structure comprising an interconnecting central deck

Floating hydrocarbon processing and storage structure (1) with a first and a second assembly (2,2′) each comprising a hull (3,3′) having spaced-apart side walls (5,6;5′,6′), one or more storage tanks (7,7′) and a deck structure (4,4′), a connection structure interconnecting the first and second hulls (3,3′), processing equipment (10,10′) being situated on the hull deck structures (4,4′), at least one hydrocarbon riser (15) connected to a subsea hydrocarbon well and to the processing equipment (10,10′) and/or to the storage tanks (7,7′), and with a mooring system (8,13, 35,35′) connecting the hydrocarbon processing and storage (1) structure to the sea bed (12), wherein

• each hull (3,3′) comprises a respective hull deck structure (4,4′) bridging the side walls (5,6;5′,6′),
• the interconnection structure comprises a central deck (20) extending at or near the height of the hull deck structures (4,4′) along at least along 70% of the length of the hulls (3,3′), the central deck (20) supporting one of the following features or a combination thereof:
• a number of risers (54,54′) vertically extending from the central deck (20) between the hulls (3,3′) to the sea bed, along a length of at least one third of the length of the central deck, preferably along half of its length,
• a number of fluid ducts (31) horizontally supported on the central deck along at least one third of the length of the central deck, preferably along half of its length, and
• at least one drilling or work-over rig or crane (51,52).