Session: 06-01-01 Computational Mechanics and Design Applications

Submission Number: 179692

Root Cause Analysis and Rectification of Seabed Erosion Near a Wellhead Platform in the Arabian Gulf 

Seabed erosion poses significant challenges to the integrity and operational readiness of offshore infrastructure, especially in shallow water regions subject to complex hydrodynamic forces. This study presents a detailed investigation into a localized seabed erosion event identified near a wellhead platform in the Arabian Sea. The erosion compromised seabed stability and hindered safe access for a mobile offshore drilling unit (MODU), posing risks to both operation and structure itself.

The root cause assessment was initiated following the identification of unexpected seabed depressions during a routine pre-rig move survey. A multi-disciplinary technical team conducted a comprehensive evaluation incorporating multibeam bathymetric mapping, sub-bottom profiling and detailed soil investigation, historical as-built data, and analysis of tidal and current regimes. The investigation concluded that the erosion was primarily driven by localized scouring due to wake effects from subsea structures caused by drilling operation

To remediate the affected area and reinstate operational readiness, a site-specific mitigation plan was developed. The solution involved engineered rock filling designed to restore seabed elevation, provide geotechnical stability, and create a safe bearing surface for MODU leg spud cans or anchors. Rock placement was performed using dynamically positioned vessels to ensure accurate deposition and thickness control. Key design parameters, including rock size gradation, layer thickness, and extent of coverage, were defined based on geotechnical and hydrodynamic modeling.

Following completion of the rectification works, verification surveys confirmed that the seabed profile had been restored within tolerance, with adequate bearing capacity for the planned drilling operations. No further signs of erosion were observed post rectification, and any future rig mobilization will further demonstrate the integrity.

This project demonstrates the importance of proactive monitoring, root cause analysis, and rapid implementation of engineered solutions to address seabed instability. The lessons learned are particularly relevant for offshore developments in dynamic marine environments such as the Arabian Gulf, where seasonal conditions and seabed mobility must be carefully considered in the design and maintenance of subsea infrastructure.

Presenting Author: Nawin Singh McDermott International Inc.

Presenting Author Biography: Graduated in Mechanical Engineering and master in Energy. Registered chartered engineer with engineering council, United Kingdom. I am having more than 25 years of experience covering conceptual studies, detailed feasibility studies, front end engineering & design, detailed engineering including procurement support, EPRS study, advance analysis etc. for subsea pipeline and associated system. Currently leading the Subsea Engineering team of McDermott Middle East.

Authors:

Nawin Singh McDermott International Inc.
Muhammad Asif Saudi Aramco
Krishna Chaitanya McDermott Middle East
Abdullah S. Joaib Armaco