Geomechanics and Geoenergy Journal

Geomechanics and Geoenergy Journal

Numerical Analysis of SPAR Rig Performance via Vortex

Document Type : Original Article

Authors
Sajjad Jokari 1
ARMIN HOSSEINIAN 2
Ali Esfandiari Bayat 3
1 Master's degree, Department of Petroleum Engineering, Faculty of Petroleum, Chemical, and Polymer Engineering, SR.C., Islamic Azad University, Tehran, Iran
2 Department of Science and Engineering, Faculty of Petroleum, Mining and Materials Engineering, CT.C., Islamic Azad University, Tehran, Iran
3 Department of Petroleum Engineering, Faculty of Petroleum, Chemical, and Polymer Engineering, SR.C., Islamic Azad
10.22107/ggj.2026.579483.1262
Abstract
Among the various types of offshore rigs, single-point anchor reservoir (SPAR) rigs are notable as exceptional engineering accomplishments. A challenge faced by SPAR rigs is the impact of vortex effects from the surrounding environment. The helical strakes positioned on the body of the SPAR rig serve to reduce these effects. This research aims to examine the vortex phenomenon along with the forces generated by environmental flow waves (specifically lift and drag forces) that act on offshore SPAR rigs through numerical analysis. For the computational fluid dynamics (CFD) simulations, laminar flow conditions were chosen, eliminating vibration and oscillation around a modeled SPAR rig. The simulation was carried out using STAR-CCM+ software to analyze the vortex effects around the SPAR rig both with and without the presence of spiral rings. The results from the numerical simulation suggest that a carefully designed array of helical strakes can significantly impact the reduction of the vortex effect and the direct influence of waves on the rig’s structure. Moreover, the water velocity can greatly influence the dynamics of lift and drag forces depending on whether helical strakes are incorporated or not. Consequently, the behavior of lift and drag on the spar structure varied based on the performance of the vortex effects across different components of the spar rigs. Additionally, water velocities of 0.5, 0.75, 1.00, 1.25, and 1.5 m/sec at depths ranging from 1.7 to 2.7 m can significantly impact lift and drag forces, whether strakes are present or not.
Keywords
Offshore Rigs
SPAR Rig
Environmental Factors
Vortex Effect
Lift and Drag Forces
Helical Strakes
Subjects
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Geomechanics and Geoenergy Journal
Volume 8, Issue 3
Autumn 2025
Pages 19-30