Time-Dependent CFD modelling of a Stalling Pig Wall Shear Stress in a Subsea Riser at 45°, 60°, and 90° Inclinations

Subsea oil and gas operations rely on extensive pipeline networks to transport crude oil efficiently, economically, and safely. Pigging a critical pipeline maintenance technique uses devices known as “pigs” to clean, inspect, and manage pipelines. However, operational challenges such as pig stalling, where pigs become lodged and disrupt flow, can lead to significant downtime and costs. This research employs transient CFD modeling to investigate the effects of a partially stalled bi-directional pig on wall shear stress and axial force in subsea pipeline risers at angles of 45°, 60°, and 90°. The study specifically aims to identify gaps in understanding flow characteristics and pig motion under stalling conditions, which can pose severe operational risks in subsea environments. Simulations conducted in ANSYS Fluent, with a single-phase flow velocity of 0.744 m/s, indicate stalling velocities of 0.45 m/s (45°), 0.3 m/s (60°), and 0.25 m/s (90°). Correspondingly, wall shear stress increased from 15 kPa at 45° to 35 kPa at 90°, highlighting the significant impact of pig orientation on flow dynamics and pipeline integrity.