Session: 08-06-01 non-presentations

Paper Number: 128360

128360 - Flow-Induced Vibration of Subsea Well Jumpers at High Gas Rate With Low Liquid Loading 

Subsea well jumpers are steel pipe sections that define a flow path between a subsea production tree and a subsea manifold. They are designed with bends to accommodate limited expansions due to variations in temperature and pressure. The change of flow direction in these bends induces unsteady fluctuating forces with broadband frequency content. If the fluctuating forces are of significant amplitude and/or induced in a frequency range that overlaps with the structural natural frequencies of the jumper, they may lead to flow-induced vibration (FIV) of the well jumper.  FIV poses a structural integrity concern of cyclic stressing of girth welds (and other stress riser features if they are present) and over time, a threat of fatigue failure. 

We consider subsea well jumpers operating at high gas rates and with low liquid loading. Fluid-structure interaction (FSI) simulations of high-pressure gas with low liquid loading in 9-inch well jumpers were performed to predict flow-induced vibration and stress. Computational fluid dynamics (CFD) was used to predict the unsteady flow in the piping and the flow-induced forces on the bends.  A structural finite element (FE) model of the well jumper was loaded with the CFD-predicted flow-induced loading to predict piping vibration and stress in time domain. A one-way FSI simulation approach was adopted, where the flow interacts with the structure, but it is assumed that the vibration of the structure does not affect the flow field. This approach to FIV screening has been validated and is actively used to quantify the FIV threat for subsea piping, such as well jumpers. 

We present results for a flow condition with 1.26% liquid content by volume and a mixture ρU² value of 109,246 Pa.  The industry practice for low liquid loading flows is to take the flow as multiphase once the liquid content by volume is above 1%, and this flow condition stands at the fringe of being considered multiphase flow with respect to FIV. In the FSI simulation, we consider the flow as multiphase and in a separate simulation, as single-phase gas flow adopting the mixture density. The FSI simulation results give very similar vibration responses, which reinforces the current industry practice of treating gas flows with liquid loading below 1% as single-phase gas flows. 

We also consider a flow condition with 2.06% liquid content by volume and a mixture ρU² value of 177,039 Pa.  We observe very different vibration behavior relative to the flow condition with 1.26% liquid content by volume, indicative of multiphase flow FIV behavior. 

Presenting Author: Juan Pontaza Shell

Presenting Author Biography: Dr. Pontaza joined Shell in 2006 and is currently a Principal Engineer and the Shell subject matter expert for Fluid-Structure Interaction and Computational Fluid Dynamics. He has BSc, MSc, and PhD degrees in Mechanical Engineering from Texas A&M University and the Massachusetts Institute of Technology. Dr. Pontaza has authored over 40 journal papers and conference papers on numerical methods for fluid flow and fluid-structure interaction. He was the recipient of the 2004 Robert J. Melosh medal for best paper on Finite Element Analysis. Dr. Pontaza appeared in the World’s Top 2% of the most-cited scientists list compiled by Stanford University in 2020.

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