This paper describes the cause of failure of BP's Eugene Island 322 'A' (EI-322 A) Drilling platform during Hurricane Lilli and BPâ??s response to this event. BP's project team planned and implemented temporary strengthening of the platform so that well decommissioning could take place in a safe and environmentally sound manner during the peak of the 2003 hurricane season. Well decommissioning was successfully completed by November 2003. BP's health, safety, and environment (HSE) values were strictly adhered to throughout the project with zero injuries or environmental events.
Hurricane Lilli passed through the Gulf of Mexico in early October 2002. At its peak, the storm reached Category 4 on the Safford-Simpson scale with maximum sustained winds exceeding 140 mph. The stormâ??s eye passed through the Eugene Island 322 block. In the days immediately following the storm, BP learned that the EI-322 A Drilling platform was leaning and had sustained severe damage to the deck and bridge.
The EI-322 'A' platforms are typical of TAMPA complex (Hancock and Peavey, 1975) that was widely used by Amoco from the late 1960s until the early 1990s. The TAMPA concept consists of two, adjacent, four pile platforms linked by a relatively large bridge. The main function of the TAMPA was to replace one large 8-pile platform, which was typical of that time, with two significantly lighter platforms. One of the TAMPA platforms serves as a drilling/quarters platform with on-board rig capability while the other platform provided tender support during drilling operations. Post drilling, the tender platforms were converted into the production facility. The bridge supported the production flow lines as well as several small buildings.
The EI-322 'A' platforms were installed in 235 feet of water by Amoco in 1978. The primary design criteria for the facilities were a 70-foot 13-second wave, zero current, and a 125 mph wind. The design drag (Cd) and inertial (Cm) coefficients for the Morison equation were 0.65 and 1.35 respectively. These design values are more conservative than the API RP2A 9th Edition recommended Cd, Cm values of 0.6 and 1.5 respectively thereby exceeding the design basis check in API RP 2A Section 17. A preliminary wind-wave-current hindcast of Hurricane Lilli indicated that the storm generated a 56-foot maximum wave (Driver, 2002) in the EI-322 block, which is significantly lower than the original design criteria.
Figure 1 is a photograph of EI-322 'A' drilling before Hurricane Lilli. Figure 2 shows the complex after the hurricane. The top deck translated approximately 85 feet from its original position causing extensive structural damage to the deck and deck legs. Figure 3 shows a closer view of the buckled A-1 leg (NW location). For reference, Figure 4 shows the orientation of the EI-322 'A' complex as well as the leg nomenclature. The B-1 leg almost totally separated from the deck as is shown in Figure 5.
