OGIC Project Case Study: Xodus Group with University of Dundee
Analysis methods and design guidance for the removal of subsea structures
Xodus Group offers engineering and advisory support for oil and gas upstream operators and renewable energy developers worldwide. Recognising the need to develop new processes and technology for the emerging decommissioning market, Xodus sought to explore approaches to the efficient recovery of subsea structures.
Xodus’ development of analysis methods and design guidance for the removal of subsea structures reduces uncertainty in the execution of decommissioning removal operations. More accurate prediction of the breakout/recovery loads informs the decommissioning engineering, vessel selection, scheduling and gives increased confidence in decommissioning cost estimates. This informed forecasting combines with safety benefits with a reduced risk to equipment, vessels and personnel during recovery lifting operations if breakout loads can be predicted and properly planned for.
Xodus engaged with OGIC and selected the University of Dundee’s School of Science and Engineering to carry out the research in a controlled laboratory environment to produce data which would be challenging to gather in the field.
“Civil engineering activity within the offshore oil and gas sector has seen a growth in the emphasis placed on decommissioning in recent years, but extracting foundations from the seabed poses major engineering challenges due to the number of variables on which recovery loads depend. By performing a series of small-scale model tests, we understand better how each of these variables controls the process and hence improve the efficiency of foundation extraction in the future.”
Dr Andrew Brennan
Senior Lecturer in civil engineering, University of Dundee
The University carried out a series of small-scale model tests of uplift operations in a controlled environment. These tests investigated a range of variables including the effect of on-bottom time and skirt configuration on the required recovery loads for subsea structures.
“Decommissioning of subsea structures presents significant challenges for engineers. The potential for overall project cost increases due to unknowns is high, especially with regard to seabed uncertainty. This research produced invaluable knowledge and understanding of the recovery process and associated risks and will likely result in significant cost savings and operational efficiencies for future decommissioning projects. The transfer of knowledge and experiences through projects like this is crucial to enable the industry to continue to develop efficient and effective decommissioning practices.”
Principal Geotechnical Engineer, Xodus
Improved future subsea structure designs could be realised from this research by incorporating a “designed for decommissioning” philosophy, ultimately resulting in more efficient structure removal and reduced future decommissioning costs.