The Marlin TLP uses an extensive monitoring system to measure the environment and platform responses. These measurements are used as an aid in platform operations and are also important for use in verifying analytical models of platform global performance. Marlin's measurements include a comprehensive, high quality dataset recorded during Hurricane Ivan, an intense hurricane that passed through the Gulf of Mexico in September 2004. The eye of Ivan passed directly over Marlin resulting in wind and wave conditions substantially greater than the 100-year design hurricane. Measured response data are presented. These measured data are compared to both the design level responses and to predicted responses from a fully coupled frequency domain simulation of the TLP, including all tendons and risers, using hindcast environmental conditions as input.
The Marlin tension leg platform (TLP) was installed in the Gulf of Mexico in 1999 on Viosca Knoll Block 915. Marlin was designed for BP (Amoco) by ABB (1997) using an uncoupled, frequency domain numerical solution, with tendons modeled as springs, incorporating a number of empirical factors derived from model tests.
The water depth at the platform site is approximately 3,250ft. The TLP consists of a four column hull connected by ring pontoons and is moored using two tendons per corner. The TLP has a displacement of approximately 52,000kips. Table 1 summarizes the principal hull and tendon dimensions. Figure 1 is a photo of the platform. A plan view showing the position of tendon porches and riser orientation is given in Figure 2. Note that Platform North is 45deg CCW from True North.
Understanding how a floating production system (FPS) such as Marlin responds to the environment is critical for protection of personnel, the environment and the facility, for operations, and for future expansion. It is important to verify that analytical tools and corresponding assumptions used for the design and analysis of these systems represent the true response of the floating production system. This requires real time field monitoring of the FPS. To this end, BP has extensively monitored the motions and tendon tensions of the Marlin TLP along with the wind, wave, and current environment.
A fully coupled model of Marlin including detailed models of the floater, tendons, top tensioned risers, steel catenary risers, and flexibles was developed. A goal of this work was to compare the analytically derived motions and tendon tensions with field measurements for various environments. A number of winter storm and tropical cyclone datasets were used for the verification. The most significant dataset in terms of accuracy, completeness and severity was for Hurricane Ivan, and the model's performance for this storm is the focus of this paper.
Table 1: Marlin Principal Hull and Tendon Dimensions (Available in full paper)
Figure 1: Marlin TLP (Available in full paper)
This paper gives a brief overview of the Marlin instrumentation system. This is followed by a description of the methodology used for analysis of the data recorded during Hurricane Ivan as well as the methodology for the coupled global analysis model.