Overtrawling of protection structures and umbilicals

When developing a new field, one of the factors to consider is the impact it may have on fishing within the area, and vice versa. Fishermen and oil companies have shared common ground in the North Sea and other regions for a number of years, and the experience and knowledge gained during this time can be used to ensure that projects are planned to incorporate the needs of both parties.

The objectives of this study were to investigate two main factors:

• The feasibility of providing protection to a control umbilical from fishing gear, using
  an adjacent flowline
• The interaction of fishing gear with protection structures within the field development

Jee has considerable experience of fishing gear interacting with both pipelines and subsea structures.  This has been gained from running both scale model and full-scale tests on a variety of projects and joint-industry projects, and also by maintaining close relationships with the relevant fishing organisations.

For this project, scale model tests of trawl gear and nets were completed on both the protection structures and the umbilical laid adjacent to the flowline.  The tests were videotaped to provide a record and also to allow a more detailed examination of trawl gear behaviour as it passed over the various structures.

Benefits to the client included:

• Access to extensive information and knowledge on trawl gear interaction
• Clear visual and analytical results from scale model trials, including an accurate representation of the trawl gear used in the area of the field development
• Flexibility throughout the project, enabling a fast turn-around of design modifications to maintain the target schedule
• Derivation of peak pullover loads and impact energies on the proposed protection structures