Design and simulation research of riser flexible hang-off system based on variable damping for drilling platform to avoid typhoon

Abstract Inspired by the technical characteristics of the two modes of hard hang-off and soft hang-off commonly used when hanging risers on drilling platforms to avoid typhoons, a new riser flexible hang-off scheme is proposed to compensate the riser heave dynamic load. The mechanical mechanism of riser flexible hang-off is designed. Two compensation strategies are proposed, including the proportional compensation strategy and the back-pressure variable damping compensation strategy. Aiming at the control method of the compensation strategy of back-pressure variable damping with better compensation effect, the hydraulic system scheme of riser flexible hang-off is designed. In order to verify the feasibility of the hydraulic system, the compensation performance of the riser flexible hang-off scheme subjected to the designed hydraulic system is investigated using Simulink software. The results show that the riser flexible hang-off compensates riser heave dynamic load by 30% under the once-in-a-decade sea conditions in the Western Pacific Ocean. The filling pressure of the gas cylinder and the displacement - voltage gain of the throttle valve are critical to on the system performance. The proposed new riser flexible hang-off system casts light on an alternative compensation for drilling platform to avoid typhoon.