Research on a Mechanical Model of Subsea Christmas Tree During Lowering Stage in Deepwater Based on Sea Trial

To explore the mechanical characteristics of the Christmas tree lowering system and the sensitivity of influencing factors under typical deepwater lowering conditions., based on the self-improved mechanical model of the subsea Christmas tree lowering system., the parameter sensitivity analysis of the subsea Christmas tree lowering process in the deepwater lowering stage is carried out., to establish the mechanical characteristics of Christmas tree dropping system under this condition. The analysis results show that the deepwater lowering stage is mainly affected by the combined action of wave force and current force. With the increase of surface current velocity and wave height., the lateral displacement., stress., and bending moment increase. The increase caused by surface current velocity is the largest., followed by the influence of wave height., and the change caused by period and wind speed is not obvious. Deepwater lowering causes too much lateral displacement of the Christmas tree. The main reason for the docking failure is the current force., and the maximum lateral displacement is determined to be 2.7 m by converting the current velocity into the lateral displacement.