Patent ID: 8522880

Claim:
A floating offshore structure for offshore hydrocarbon production, the offshore structure comprising: a moonpool for receiving multiple production risers having a lower end connected to a hydrocarbon well on a sea floor and an upper end located in the moonpool; a drilling station located at the moonpool, the drilling station comprising drilling equipment defining a firing line; a production riser support system for supporting the multiple risers at their upper ends while lower ends are connected to the hydrocarbon well, the production riser support system comprising: a plurality of carts, each cart comprising: a support frame; and one or more riser tensioners for connecting the support frame to the upper end of one of the multiple risers while the lower ends are connected to the hydrocarbon well, such that each cart is suitable for in a production dock supporting one of the multiple risers in a production position, and in a drilling dock supporting one of the multiple risers in a drilling position under the drilling station and in line with the firing line; a cart support structure, the cart support structure defining multiple production docks and at least one drilling dock, each dock suitable for supporting one of said carts; and a crane which is movable supported by a crane guide for movement along a transport track, the crane guide extends within a substantial horizontal plane and bridges at least part of the moonpool, for transferring one of the multiple carts between one of the multiple production docks and the at least one drilling dock, wherein each cart is suitable for being transferred by the crane between a production dock and the drilling dock.