Applications and Performance of Trenching Technologies in Asia-Pacific

Brunning, P. (Subsea 7) | Machin, J. (Geomarine)

OnePetro 

This paper was selected for presentation by an OTC program committee following review of information contained in an abstract submitted by the author(s). The material does not necessarily reflect any position of the Offshore Technology Conference, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Offshore Technology Conference is prohibited. The abstract must contain conspicuous acknowledgment of OTC copyright. Abstract Burial of submarine pipelines and cables is common practice in the North Sea where potentially damaging threats such as fishing gear interaction and dragged anchors are high, or where burial is required for flow assurance. Whilst the requirement to bury pipelines in Asia-Pacific has not had the same imperative as in the North Sea, there is now a growing requirement for pipelines to be trenched, particularly to increase mechanical protection and improve on-bottom stability. Trenching is considered to be one of the offshore activities that carry most commercial risk. It is therefore important to ensure that the correct tool is selected for the anticipated field conditions and to establish realistic performance criteria based on regional experience in the prevailing seabed soils. This paper compares the primary differences between seabed sediments of the North Sea to those that prevail in Asia-Pacific and discusses where differences in these conditions can affect the choice of burial equipment and tool performance when planning trenching in this region. Performance benchmarks for most trenching systems are based on experience and empirical relationships developed for seabed soils typically found in more northern latitudes. Consequently, the main body of burial performance data does not account for the carbonate rich seabed sediments for example that are prevalent in the Asia-Pacific region. Carbonate cemented soils and weak rocks pose a significant challenge to burial and trenching experience in these materials remains very limited. A trenching case study is presented which highlights the challenges of designing an appropriate protection and burial strategy for this region and provides indications of actual performance that can be expected in some of the carbonate sediments typically found in an Asia-Pacific location. It is hoped that this paper will go some way to address the gaps associated with performance predictions in carbonate sediments and will provide a reference point on which to plan trenching work in Asia-Pacific region.