NUMERICAL ANALYSIS OF CONTACT FORCES AT THE TOUCHDOWN ZONE (TDZ) OF FLEXIBLE RISERS
Carlos Eduardo da silva1; Leandro Carlos Gazoni1; Mario Alfredo Vignoles2; José Luis Drummond Alves1; Marcus Vinicius Casagrande1
1 Programa de Engenharia Civil COPPE/UFRJ; 2 TechnipFMC Group
doi:10.20906/CPS/CILAMCE2017-1257
Resumo
In the oil and gas industry, current technology for flexible risers and flowlines technology for deep and ultra-deep-water operation requires more realistic simulation tools and calculation methods every day. This work addresses a topic that represent, among others, one of the critical bottlenecks currently faced for the application of the flexible riser solution in the pre-salt projects in ultra-deep waters, i.e., the analysis of cross section forces at the touchdown zone (TDZ) and touch down point (TDP). Dynamic simulations performed in state-of-the-art program, usually present good agreement and reliable results for sections away from the strongly dynamic riser and soil interaction region (TDP-TDZ region). Some simulations in the TDP region, present very high compression and very low bending radii and may, in some cases, render the flexible solution unfeasible. There is also a large difference in results between programs in this region. At present, global analyzes are performed considering the rigid soil, thus ensuring conservatism in the results, since there are no experimental models or results of real-scale measurements for flexible tubes to guarantee more realistic or less conservative results. This work presents a specially tailored model for the global and local dynamic simulation of riser soil interaction. The model accounts the nonlinear soil behavior modeled with 3D solid elements and contact impact interaction at TDZ with the riser structure, modeled with 3D beam elements. Soil behavior were calibrated with a set of tests in a centrifuge apparatus while riser dynamics was calibrated with reduced model tests carried out on an ocean tank at COPPE/UFRJ. A series of benchmark tests were performed for usual riser configurations. Results of the proposed approach are assessed in the light of state-of-the art codes with respect to curvature and compression at cross sections along the riser, deformation and stresses in the underlying soil mass. This work was partially supported by MCTI/FINEP, MCTI/CNPq an
Palavras-chave: Numerical Modeling; Touchdown point (TDP); Flexible Riser