Title: Impact of Riser Inclination on Multiphase Flow Performance and Production Rate Stability
Authors: Isaac Eze Ihua-Maduenyi, Kingsley Chidiebere Okwu, LoveGod Anthony Eke
Volume: 10
Issue: 4
Pages: 79-90
Publication Date: 2026/04/28
Abstract:
Multiphase flow behaviour in offshore production systems is highly sensitive to riser inclination. Improper riser geometry can lead to excessive pressure drops, flow instabilities, and reduced production efficiency. Understanding the impact of riser angle on flow performance is therefore essential for optimizing offshore pipeline design and operation. This study investigates the impact of riser inclination on multiphase flow performance and production rate stability, with the aim of identifying the inclination that minimizes flow instabilities while enhancing production efficiency. A multiphase pipeline network was modelled in PIPESIM software, incorporating a flowline and riser system under four inclination angles: 15°, 30°, 60°, and 90°. Simulations were performed for the different inclination on oil and gas flow rates, pressure distribution, liquid holdup, flow patterns, density variation, and temperature profiles along a 40,000 ft pipeline. The results show that shallower risers (15°) maintained higher oil flow rates and pressure stability but promoted liquid holdup and flow regime transitions that increase slugging risks. Steeper risers (60°-90°) reduced liquid accumulation and promoted gas-dominated regimes but incurred higher pressure drops and accelerated gas expansion. Thermal analysis further indicated that shallow risers experienced greater temperature losses, while vertical risers retained higher temperatures due to reduced residence time. Riser inclination exerts a significant influence on multiphase flow dynamics, with shallow angles supporting more efficient oil transport and pressure retention, and steeper angles favouring gas expansion but at higher hydraulic cost. The optimum inclination must therefore balance hydraulic efficiency and flow stability, supported by operational strategies such as slug management and thermal control.