Pipeline installation in deep water involving very irregular seabed topography may cause major free spans along the route. In order to document sufficient pipeline integrity in such areas throughout the design lifetime, excessive amounts of seabed intervention may be required.
This paper presents the work related to seabed intervention design performed for the Ormen Lange Field Project (OLFP) pipelines, in particular for the deep water area with water depths ranging from 250m to 875m. The Ormen Lange field is characterized by extremely irregular seabed including steep slopes where the water depth drops rapidly 2-300 meters, with inclinations of above 30 degrees. An overview of the work leading to the final route selection and selected installation methodology was given in the ISOPE paper 2005-HM-02 "Routing and Cost-effective Seabed Preparation" /1/.
This paper will focus on the design process involving selection and optimization between the different available methods for seabed intervention, including application of novel intervention technology developed within the Ormen Lange Project, and experiences drawn from application of such tools.
The field was discovered by Hydro in 1997. The reservoir is around 40 km long and 8 km wide, approximately 3000 m below the surface of the sea. Hydro is the operator for the development phase and Shell will be the operator for the operational phase.
The well stream from Ormen Lange will be transported in two 30-inch multi-phase pipelines to the process plant on land at Nyhamna. The development of the field by subsea tie-back to shore requires two 6 5/8" MEG injection pipelines and two control umbilicals to the Ormen Lange field. The processed gas will be exported to Easington on the east coast of England through a 1200 km long export pipeline, see Figure 2.
