Heat-preserving and buoyancy-supplying dual-purpose device for deep water top tensioning marine riser

The invention discloses a heat-preserving and buoyancy-supplying dual-purpose device for a deep water top tensioning marine riser. The device comprises the top tensioning marine riser, an anticorrosive layer, a polyurethane composite material insulating layer and a buoyancy tank which are arranged in turn from inside to outside, wherein the annuluses of the buoyancy tank and the insulating layer are filled with air, so that waterproof protection can be provided for the insulating layer and sufficient buoyancy can be provided for the marine riser. In the device, an outer protection steel pipe of the insulating layer is replaced by the buoyancy tank, so that material cost is saved, the long-term stable heat-insulating property of the insulating layer is ensured, the total weight of a marine riser system and the requirement on top tension provided by a production device are lowered and two purposes, namely, heat preservation and buoyancy supply can be realized simultaneously by the device.