Internal waves near the ocean surface have been observed in many parts of the world including the Andaman Sea, Sulu Sea and South China Sea. The factors that cause and propagate these large-amplitude waves include bathymetry, density stratification and ocean currents. Although their effects on floating drilling platforms and their riser systems have not been extensively studied, in the past these waves have seriously disrupted offshore exploration and drilling operations. In particular, a drill pipe was ripped from the Blow-Out Preventer (BOP) and lost during drilling operations in the Andaman Sea. Drilling riser damages were also reported from the South China Sea and other places. The motivations of this study were to find a valid numerical model conforming to the physics of internal waves and to study the effects on offshore drilling semisubmersibles, different types of offshore hull forms and riser systems, including the large diameter cold water pipe of floating Ocean Thermal Energy Conversion (OTEC) systems. The influence of internal waves on offshore systems was studied through nonlinear fully coupled time-domain analysis. The numerical model was implemented in a coupled analysis program where the hull, moorings and riser were considered an integrated system. The program HARP was modified and then utilized to study the effects of the internal wave on the platform global motions and riser system integrity. The study could be useful as future guidance for offshore exploration and operations in areas where the internal wave phenomenon is prominent.
Internal waves near the ocean surface have been observed in many parts of the world including the Andaman Sea, Sulu Sea and South China Sea. The factors that cause and propagate these large-amplitude waves include bathymetry, density stratification and ocean currents. Although their effects on floating drilling platforms and their riser systems have not been extensively studied, in the past these waves have seriously disrupted offshore exploration and drilling operations. In particular, a drill pipe was ripped from the Blow-Out Preventer (BOP) and lost during drilling operations in the Andaman Sea. Drilling riser damages were also reported from the South China Sea and other places.
The motivations of this study were to find a valid numerical model conforming to the physics of internal waves and to study the effects on offshore drilling semisubmersibles, different types of offshore hull forms and riser systems, including the large diameter cold water pipe of floating Ocean Thermal Energy Conversion (OTEC) systems.
The influence of internal waves on offshore systems was studied through nonlinear fully coupled time-domain analysis. The numerical model was implemented in a coupled analysis program where the hull, moorings and riser were considered an integrated system. The program HARP was modified and then utilized to study the effects of the internal wave on the platform global motions and riser system integrity. The study could be useful as future guidance for offshore exploration and operations in areas where the internal wave phenomenon is prominent.
