Design Method and Development Trend of Landing Strings in Deepwater Drilling

To solve the design and type selection of landing strings,an analysis of the loading characters of landing string and the main complexities the landing string potentially encountered in deepwater drilling were examined.As a result,a new mechanical model for landing string design was established,which was used in an analysis of model combined with actual drilling in deepwater environments.The results showed that the calculated maximum tensile load of φ168.2 mm and φ149.2 mm common landing string was 3 234 kN and 3 136 kN respectively with the recommended slip collapsing model,which was closer to the maximum allowable tensile load than that calculated by other design methods,which suggests that the new landing string design is safer.The safety factor of φ168.2 mm and φ149.2 mm landing string was calculated based on the ultimate tensile load model in the case of conductor sinking was 1.37 and 1.26 respectively,which meets the requirement for minimum safety factor of 1.10,and the larger the size,the higher the safety margin and safety factor of the landing string,while ordinary drill pipe cannot meet operational requirements.The research results demonstrate that in order to ensure operational safety,the design of deepwater landing string must consider both slip crushing and ultimate tensile load which act on the setting string when handling the conductor sinking.