Subsea Pipeline Engineering Challenges in Sand Wave Area: The Lufeng Feed Project

Abstract Lufeng oilfields are located in the Pearl River Mouth Basin, South China Sea, where significant sand wave is located. The water depth of the area is 140 to 330 m. Sand waves are present around LF15-1. A study on the sand waves is required to assess the impact of the sand waves on the pipeline design. Due to its special seabed characteristic, it is challenging for the subsea pipeline engineering. This paper presents the Lufeng sand wave pipeline project on general basis. Collect and review available information including metocean, bathymetric data and soil data and carry out general morphological analysis for the project area including seabed erodibility assessment and analysis of sediment transport potential. Identify morphological features and bed forms in the project area and analyze characteristics of the sand waves. Sand wave migration and mobility are predicted and the pipeline route (least dredging/trenching and least free spans) is optimize considering on-bottom stability, in-place strength, global buckling and installation. Determine burial (dredging/trenching) requirements assuring pipeline stability/integrity. The main challenges faced are summarized, some preliminary results are also presented. Discussions about the solutions are also included, which may shed light to similar projects.

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Study of sand wave migration over five years as observed in two windfarm development areas, and the implications for building on moving substrates in the North Sea

Earth and Environmental Science Transactions of the Royal Society of Edinburgh ◽

10.1017/s1755691015000110 ◽

2014 ◽

Vol 105 (4) ◽

pp. 241-249 ◽

Cited By ~ 3

Author(s):

Ken P. Games ◽

David I. Gordon

Keyword(s):

Case Studies ◽

Large Scale ◽

Oil And Gas ◽

Sand Wave ◽

Sand Waves ◽

Migration Rates ◽

The North ◽

The North Sea ◽

Wave Migration ◽

The Impact

ABSTRACTSand waves are well known indicators of a mobile seabed. What do we expect of these features in terms of migration rates and seabed scour? We discuss these effects on seabed structures, both for the Oil and Gas and the Windfarm Industries, and consider how these impact on turbines and buried cables. Two case studies are presented. The first concerns a windfarm with a five-year gap between the planning survey and a subsequent cable route and environmental assessment survey. This revealed large-scale movements of sand waves, with the displacement of an isolated feature of 155 m in five years. Secondly, another windfarm development involved a re-survey, again over a five-year period, but after the turbines had been installed. This showed movements of sand waves of ∼50 m in five years. Observations of the scour effects on the turbines are discussed. Both sites revealed the presence of barchans. Whilst these have been extensively studied on land, there are few examples of how they behave in the marine environment. The two case studies presented show that mass transport is potentially much greater than expected and that this has implications for choosing turbine locations, the effect of scour, and the impact these sediment movements are likely to have on power cables.

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