Landing string design and strength check in ultra-deepwater condition

Landing string used in ultra-deepwater casing running operations sustains complicated loads, including axial load, slip crushing load, bending load and dynamic load. Landing string design methods based on tension load are presented in detail. In these methods, sufficient margin of over pull is taken into account for the extreme axial load during surface casing running operations and environment loads caused by wave, current and vessel offset and heave. Landing string strength check is discussed to evaluate the safety of landing string in harsh environment. According to the analysis, slip crushing capacity is one of the critical limitations for landing string; bending stress caused by currents is great at the top of landing string at the beginning of operations while it will decrease by adjusting the vessel position after setting the casing below mud line.