Background

Tension Leg Platforms have proven their abilities for moderate water depths and are now planned for deep water. A number of issues in design, operation and inspection however need to be resolved:

• Actual wind (hurricane), wave and (loop) current
• Platform motions
• Tensions in tendons and risers
• VIV behavior of tendons and risers
• Extreme loads and fatigue life of the platform

In order to collect data to resolve the above issues, the partners in Marco Polo (GulfTerra, Anadarko, MODEC and SEA) have equipped the TLP which is located in 4300ft of water with a monitoring system.

Since June 2004 this system provides data on:

• Effects of the large natural periods in heave, pitch and roll
• Damping in the stiff modes of motion
• Platform behavior in loop current
• Effect of strakes on risers and fairings on tendons to restrict VIV
• Platform in hurricane conditions
• Fatigue life consumption

Monitoring System

The monitoring campaign comprises the following:

• Wave frequency motions
• Low frequency motions
• Riser & tendon tension & vibration
• Hull strains
• Current profile
• Wave condition
• Wind

In total 170 signals are recorded continuously and stored for post processing.

Joint industry project

The analysis of the Marco Polo data to derive the dynamic behavior of TLP’s in operational and survival conditions and to verify design methods and numerical analysis, is the objective of a Joint Industry Project. In this JIP the partners in Marco Polo will co-operate with other operators interested in the optimization of deep water operations and the extension to ultra deep water which requires focus on calibration with in service observed behavior. The main tasks in the project are the monitoring campaign, the data analysis and the verification of design methods.