Abstract
Anti-typhoon drilling riser, a solution to overcome high time cost of offshore drilling riser emergency retrieval under the situation of imminent arrival of a typhoon, is to modify the existing drilling riser to make it disconnectable closer to the surface and leave the long riser string below (and subsea blowout preventer (BOP)) in a safe and freestanding mode to survive the typhoon. The freestanding riser is held up by a buoyancy can system. And during the normal drilling operation, the buoyancy can maintain neutral thus it has limited effect on the riser overall global performance. However, locally the buoyancy can system will have some effect on the riser system nearby. To study these effects, numerical analytical methodology and results of anti-typhoon drilling rise under connected mode and freestanding mode are proposed, and a model test of 1:21 scale factor is designed. Three configuration modes: freestanding mode, connected mode and disconnecting mode are simulated in the tank test. A series of load cases under various current and wave, buoyancy upthrust are conducted in the experimental test to evaluate the hydrodynamic and strength performance of the riser near buoyancy can. The numerical solution and model test design can be a significant basis of water tank test for anti-typhoon drilling riser and a valuable reference for deepwater drilling engineering.
