סמינר מחלקה של אלכסנדר יוריסלב - זרימת גז-נוזל במגשר בצורת M של מערכות ייצור גז תת-ימיות

SCHOOL OF MECHANICAL ENGINEERING SEMINAR

Monday, 05.08.2024 at 14:00

Wolfson Building of Mechanical Engineering, Room 206

Gas-Liquid Flow in M-Shaped Jumper of Subsea Gas Production Systems

Alexander Yurishchev

Ph.D. student under the supervision of Prof. Amos Ullmann and Prof. Neima Brauner

School of Mechanical Engineering, Tel Aviv University, Israel

Two-phase flow with low liquid loads is common in high-pressure natural gas offshore gathering and transmission pipelines. During gas production slowdowns or shutdowns, an accumulation of liquid in the lower sections of subsea pipelines may occur. The liquid may originate from condensates, water from the reservoir, or from chemicals added to prevent hydrates formation. This phenomenon is observed in jumpers that connect different units in deep-water subsea gas production facilities. The displacement of the accumulated liquid during production ramp-up (or production start-up) induces temporal variations in pressure drop across the jumper and forces on its elbows, resulting in flow-induced vibrations (FIV) that pose potential risks to the structural integrity of the jumper.

The flow phenomena during the liquid displacement process were investigated via transient 3D numerical simulations using OpenFOAM software. The simulation results were validated by lab experiments conducted in a downscaled jumper prototype operating at atmospheric pressure. These simulations facilitated the development of a mechanistic model to elucidate the factors contributing to increased pressure and forces during the liquid purging process. The study examined the influence of gas pressure level, pipe diameter, initially accumulated liquid amount, liquid properties, and gas mass flow rate on the transient pressure drop and the forces acting on the jumper's elbows. The critical gas production rate required for complete liquid removal of the accumulated liquid was determined, and scaling rules were proposed to predict the effects of gas pressure and pipe diameter on this critical value. The dominant frequencies of pressure and force fluctuations were identified, with low-pressure systems exhibiting frequencies associated with two-phase flow phenomena and high-pressure systems showing frequencies attributed to acoustic waves.