Abstract: Due to the many scattered pile pits of different shapes formed in the same area by double or multiple pile insertion of jack-up platform， the topographic relief changes greatly in the area of repeated insertion and removal of the pile. When the jack-up platform takes its place once again， there are many misunderstandings in the calculation of the initial mud depth of the jack-up platform， resulting from the seabed relief， pile shoe difference， and nonuniformity in the soil body. We summarize several common misunderstandings， compare the existing calculation methods， combine the geophysical topographic data， the real-time water depth of the towing ship and the change of pressurized current in the control room of the jack-up platform， and propose a method for determining the initial mud depth suitable for the area of repeated pile insertion and removal. This method improves the accuracy of calculation of mud depth for jack-up platform insertion in the area of repeated pile insertion and removal.

Key words: jack-up platform, repeated insertion and removal of pile, initial mud depth, Shengli Chengdao Oilfield