Dynamic Behavior of a Vertical Riser and Service Life Reduction

Abstract

In the last years, the most of offshore oil and gas reserves discoveries in Brazil are placed in ultra-deep water depths. Petroleum production from these offshore fields needs developments with novel solutions in terms of necessary technologies and economical viability. The use of vertical rigid risers such as top tensioned risers (TTR) and others like combined systems as self standing hybrid risers and steel catenary risers for ultra-deep waters have shown viable from both, technical and economical aspects. However, there are needs for detailed studies on their dynamic behavior in order to improve, particularly, the understanding of influence of the environment as wave and current, and floating platform oscillations at the riser top. The present work presents studies on vertical top tensioned riser dynamic behavior through time domain simulations of its displacements and respective, bending moments and stresses. Influences of the vortex induced vibrations (VIV) and waves on the riser service life reduction are analyzed. Maximum and minimum envelops for displacements and stresses along riser length are shown.

On the selection of boundary conditions for top tensioned risers facing wave induced vibrations

“…To do this, a comparison was made between the present code and data of Morooka, et al [15]. The code shows good compatibility with their results.…”

“…5 is a comparison between the results of two works. Comparison between the present model and Morooka et al [15] Comparisons were made to visualize the RMS of stress in different boundary conditions and different sea states. This analysis was a try to rapidly acquire the difference of riser behavior in different boundary conditions.…”

Nonlinear dynamic analysis and fatigue damage assessment for a deepwater test string subjected to random loads

“…In this paper, the P-M spectrum is used. The loads on the deepwater test string system caused by waves are calculated using the Morison equation (Morooka et al 2005). Simulation of the motion of the floating platform is an essential part of the vibration analysis of the deepwater test string system.…”

Comportamento dinâmico de um riser captador de água do mar

“…A faixa de valores do diâmetro externo é determinada levando em conta o diâmetro externo de um riser de produção com 0,25 m (MOROOKA et al, 2005), e um modelo de captador de água do mar de 1 m (CAO et al, 2015). Aproximando o valor do riser de produção, as simulações são realizadas com o diâmetro externo variando de 0,3 a 1 m, com intervalos de 0,1 m.…”