DASH7 in collaboration with French Consultant was engaged by TFMC to undertake the FEED Upheaval Buckling Analysis for the 6" gas lift pipeline for the BRASSE project in the Norwegian North Sea Sector.

Project Background

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BRASSE is an oil and gas field located in the Norwegian North Sea within the license area PL 740 (Block 31/7). The current Ownership of the block is DNO and Vår Energi, shared 50/50. The field will be tied-back to Oseberg. The water depth in the BRASSE field is between 99 m to 120 m MSL.

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Problem Definition​

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Upheaval buckling (UHB) is a major design concern for a trenched and buried pipeline operating at high temperature and pressure. Out-of-roundness (OOS) imperfection are formed at the bottom trench profiles during post installation trenching activities. For a buried pipeline, expansion is restrained by the surrounding soil causing the pipeline to be in compression, coupled with imperfection prop curvature, the pipeline will tend to buckle upwards to relieve these forces causing major bending overstress failure. The BRASSE GL pipeline has a max. operating pressure and temperature of 252Bar and 90°C. 

Scope of the Studies:

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• FEED UHB analysis to DNV-GL-F110

• Minimum backfill cover design for undetectable survey features

• UHB mitigation design – rockdump height requirement for prop imperfection 0.1m to 0.5m

• UHB mitigation rock quantity estimation

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