Study on the static mechanics and control method of the tubular system during subsea wellhead construction in deep water

Subsea wellhead construction in deep water mainly includes surface conductor installation by jetting method, surface casing installation, and marine riser and LMRP-BOPs (Lower marine riser assembly and blowout preventer stacks) installation. The tubular combinations vary in the above three processes, and the lateral displacements near mudline under marine environmental loads are different. The mechanical models and governing equations are established according to the different tubular system properties in different operation stages, and the tubular mechanics in different installation processes were solved by coupling lateral displacement boundary conditions at different pipe string connections. The numerical simulation of ABAQUS software is given to verify the correctness of the theoretical derivation and solution. Besides, the parameters sensitivity analysis is carried out to reveal the influence of current velocity, lateral displacement of the platform, surface casing length, and LMRP-BOPs weight on the mechanical characteristics of the tubular system in different installation stages. Two control methods of platform drift and using the inner thickening drill pipe is proposed to reduce the differences in lateral displacement at different installation stages of the subsea wellhead based on the theoretical analysis. Field case study is carried out to provide guidance for subsea wellhead construction in deep water.