Pre-lay mooring systems

21st February 2013

IOS Offshore provides Pre-Lay Mooring solutions such as: safe mooring installations in all water depths; cost effective mooring installations using a single vessel; efficient rig moving results increasing drilling time; reducing risk of waiting on weather; pre-tensioning of anchors up to 300tons.

Within the past two years IOS Offshore has supplied 10 pre-lay mooring systems to oil companies operating offshore Norway and working in water depths from 300 to 1300 metres.

The concept normally consists of the following equipment: eight each 15ton Stevpris MK6 high holding power anchors; eight each seabed mooring chains 76mm or 84mm diameter NV R4 quality  of 1000 to 1800 meter length depending on water depth; eight each 800 meter lengths of fibre rope with 800 Ton MBL for connection between seabed chain and rig's mooring chain; installation and recovery system for the anchors, chain and fibre rope.

All equipment is prepared before deployment on the IOS Offshore chain base in Averøy, near Kristiansund.  An 8000sq metre asphalt chain storage and inspection base with a deep water quay for mobilisation of such pre-lay projects.

This base facility enhances the mobilisation and demobilisation of such large mooring projects that require a large area for handling so much equipment.

IOS Offshore provide the total package for Pre-Lay mooring projects. Starting with field data from the oil company such as water depth, seabed conditions, location, and infield seabed obstructions, IOS Offshore engineers design a mooring system to suit the field criteria.  All mooring equipment, installation and retrieval equipment required to perform the work is also provided by IOS Offshore. The company can also write the installation procedures for the pre-lay mooring installation and pre-tensioning of the mooring lines and the eventual hook-up of the drilling rig when it is towed to the location.

Offshore supervisors from IOS Offshore are available for assistance on the anchor handling vessels during installation to ensure correct reporting of all identification numbers on the equipment. Following the installation detailed line drawings showing each component are produced.  These drawings are available to clients via the IOS Offshore website with hyperlinks to the corresponding certificate for each item. The documentation package meets the requirements from the regulatory authority.

IOS Offshore has developed a detailed animation film of a pre-lay mooring project which illustrates all the phases of mobilisation, deployment, pre-tensioning, rig hook up, documentation package and demobilisation of equipment back to storage base. 

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IOS Offshore AS is based in Stavanger, Norway.


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