The Q4000: A Dynamically Positioned, Semi Submersible, Multi Service Vessel for Working in 10,000 Feet of Water
Authors: Strong Wm. H. , Michel Richard 
Published: October 2008

A new generation of support vessel for providing non-drilling services in 10,000 feet of water is under construction and scheduled for delivery in mid 2001. A multitude of state-of-the-art features has been incorporated in the design to enable this vessel to work economically and efficiently in the developing deep water arenas of the Gulf of Mexico, West Africa, Brazil and other international locations. This dynamically positioned, semi submersible vessel is a hybrid version of a column stabilized vessel design with the elimination of the lower hull's cross bracing. This design provides extraordinary transiting and station keeping characteristics for conducting operations in deepwater including geotechnical investigations, pre-installation of well bore structure pipe and suction piles, setting of sub sea trees, templates and manifolds, pipelines and umbilicals, IRM activities and field decommissioning.

Introduction

The Q4000 was designed to have a deck load capacity of 4,000 tons, hence the current name designator. Major features include a number of items that are not currently found on any other vessel and add significantly to the uniqueness as well as the capability of the vessel to work in very deep water. The most profound of those features is the absence of structural cross bracing, which ordinarily secure the pontoon and column on one side to the pontoon and column on the other side. Transit speed of the vessel is currently calculated to be 13.5 knots. A girder beam Multi Purpose Tower (MPT), the first of its kind in the world, will sit adjacent to the moon pool. Redundant heave compensation and winches as well as a unique split block feature, enable this 600 ton capacity tower to support a variety of tasks including J-lay of pipe lines, well completion and well intervention. A 360 ton revolving crane positioned on the port, aft quarter will be complemented with a 210 ton capacity traction winch capable of delivering a package weight of 110 tons in 10,000 feet of water utilizing 3½ inch non-rotating wire rope on a single fall. As of this writing, there is no other known crane/traction winch capability equal to this task. Supplementing the surface support equipment will be a Remotely Operated Vehicle (ROV) of the heavy work class variety, capable of working in 10,000 feet of water with an impressive array of onboard apparatus.

Description of Concept

The Q4000 is a column stabilized twin-hull semisubmersible design specialized by the absence of any cross bracing. This, plus four streamlined columns improve hydrodynamic and dynamic positioning performance. It is configured to work in all water depths and to carry out construction and well servicing in extreme depths worldwide.

A methodical design approach, sea keeping model test program, state-of-the-art materials, equipment, and systems, and innovative building techniques are the bases on which the Q4000 was developed.

Design Criteria.

The Q4000 has various operational design criteria that are satisfied by the design.