Deepwater Intervention and Connection Systems
Authors: MacKinnon Calum 
Published: October 2008

The development of hydrocarbon fields in very deepwater poses a number of technical and environmental challenges that have to be addressed and resolved. To be able to operate in deep water Installation Contractors will have to upgrade existing vessels, ROV systems and intervention equipment and also progress the development of new technologies and methods of operation.

This paper identifies some of the challenges being addressed in the field of Remote Intervention Technology and describes how some of these challenges were overcome during the design of the FLEXCONNECT® Pull-in and Connection system.

Introduction

This paper identifies some of the challenges being addressed in the field of Remote Intervention Technology. It considers the status of existing equipment and the new technology required as field developments move into deep water.

The definition of "deep water operations" varies depending on whom you talk to and their perception ofthe subsea intervention industry. Deep water can range from 1000 m through to full ocean depth. The impact that working in deeper water has, will depend on the type of workscope involved i.e. exploration, installation, production etc.

The Coflexip Stena Offshore Group is involved indeep water developments as an Installation Contractor, a Product supplier, an ROV Manufacturer and more importantly, and more importantly as the most integrated and accomplished deepwater solutions provider. This broad range of involvement in both Products and Services has provided the opportunity for the CSO Group to seriously address the environmental challenges and technical hurdles that have to be overcome. In order to fully service these new fields, the operational requirements for deepwater works have to be fully understood and then the support equipment and procedures developed to suit.

The CSO target for deepwater has currently been defined as operations in 2500 MSW. This is based on experience of working in Brazil down to 1709 m and also based on the range of Field Developments in deeper water currently under discussion. This target will undoubtedly be revised in the future as fields are discovered in increasing water depths.

For deepwater operations, the performance and specification of the ROV System, and the associated intervention tooling required, are critical to the success of the operation. To work efficiently in this environment the current equipment will have to undergo major upgrading in terms of specification, operations and reliability.

Deepwater Equipment

ROV Systems Challenges

Most Workclass ROV systems are rated for operations in 1500m to 2000m, however, the majority generally only work at about the 500 m level or shallower. In the UK Sector, prior to the development of the West of Shetland Basin (WOS), most ROV operations were at less than 200 m. ROV support work WOS in 500 metres has proven to be difficult in terms of the harsh weather environment and the extreme current regimes.

While operations at 500 m are now reasonably well understood, and a number of deepwater fields have been installed worldwide, the new challenge of continual working in 2500m involves a factor of 5 increase in the water depth operating duty. This not only requires the ROV systems to be upgraded at component specification level, it also means that the methods of operation and the efficiency of operations have to be fully considered.

The main challenges for Remote Intervention in deep water are the physical extremes i.e. Suspended Weight, Hydrostatic Pressure and the fact that the operating site is totally remote from the surface.