Statpipe landfall approach solves rocky shore problems
The irregular seabed conditions encountered during the Statpipe project included rocky subsea shore areas at the pipeline's landfall. Part 1 focused on subsea irregularities along the Norwegian Trench. Traditional pipeline landfall is on a sandy beach, into which a trench is excavated for subsequent pull-in of the pipe from the lay-barge. Excavation of a trench, although not in sand but in solid rock, was also considered for the Statpipe landfall at Kalsto. The seabed is mostly rocky for about 900 m from the coastline along the selected landfall route, with large local variations in water depths. Further out, to about 1,200 m, is a steep slope down to soft sediments at about 100-m water depth. The area is directly exposed to wind and waves from the North Sea, which significantly affects design and installation criteria. The topography as well as the exposure to the environment made this shore approach a challenge. A trench through the rocky shore approach zone would require more than 40,000 cu m of rock to be blasted and removed. This trench would at some spots be more than 12 m deep. Blasting would have to be performed to a water depth of 40-50 m. After pipeline installation, the trench would have to be completely backfilled in order to stabilize and protect the pipeline. This backfill would again require a thick protective layer of large stones in the wave-breaking zone. The trench excavation was found to be entirely feasible with some modification to existing equipment. The schedule was uncertain, however, because of the exposure of the landfall area to winds and waves.
- Research Organization:
- Den norske stats, oljeselskap A.S. (Statoil), Stavanger
- OSTI ID:
- 5515846
- Journal Information:
- Oil Gas J.; (United States), Journal Name: Oil Gas J.; (United States) Vol. 84:19; ISSN OIGJA
- Country of Publication:
- United States
- Language:
- English
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03 NATURAL GAS
032000 -- Natural Gas-- Transport
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ATLANTIC OCEAN
BACKFILLING
BARGES
COMMINUTION
DEPTH
DEPTH 1-3 KM
DIMENSIONS
DIRECTIONAL DRILLING
DRILLING
DYNAMIC LOADS
ENERGY SOURCES
EXCAVATION
EXPLOSIVE FRACTURING
FLUIDS
FOSSIL FUELS
FRACTURING
FUEL GAS
FUELS
GAS FUELS
GASES
HOISTING
INSTALLATION
MARINE RISERS
MATERIALS HANDLING
NATURAL GAS
NORTH SEA
OFFSHORE OPERATIONS
PETROLEUM
PIPELINES
PIPES
POSITIONING
ROCKS
ROUTING
SEA BED
SEAS
SEDIMENTS
SHORES
SURFACE WATERS
TOPOGRAPHY
TRANSPORT
WAVE FORCES
WIND LOADS