This paper describes the development, implementation and performance of a comprehensive typhoon emergency response plan (ERP) utilized during 1995 by Arco China Inc (ACI) for their offshore Hainan Is. South China Sea development. An important component of the enhanced plan is a new system to forecast winds and sea stales generated by tropical cyclones (TC) built around known uncertainties in forecasts of cyclones and well proven numerical models of the TC surface wind field and (he spectral wave field. The forecast system provides specification of time histories of the winds and waves at the site for the nominally predicted track as well as the probabilities of exceedance of critical evacuation Thresholds of wind speed and sea slate. The ERP and forecast system were operated throughout the 1995 typhoon season and evaluated at the Yacheng development, which was seriously threatened by 15 tropical cyclones between June and November. The response to these threats in terms of interruption of operations, partial or total evacuation of offshore personnel and average downtime is describe and compared to previous experiencewhich used more conventional forecast services evaluation has shown [he new system to provide significant benefit in terms of safety, efficiency and cost savings. The wind and sea slate forecast histories provided year-round by the forecast system are also of significant benefit to the management of floating production systems.
The intensity and track of tropical cyclones are notoriously difficult to predict accurately. Faced with such uncertainties offshore operators in areas affected by cyclones (e.g. South China Sea, Gulf of Mexico, NW Australia) typically base response decisions on the predict entry of a tropical cyclone into a large watch circle, without regard to knowledge of quantifiable factors such as the uncertainty and confidence in the predicted track of a particular system, and the surface wind speed and wave height history to be expected at the offshore work site for the specific event, Such a strategy could lead tounnecessary false alarms resulting in risks to life and equipment caused by the evacuation and shutdown process, and costly downtime. Conversely, simple distance-to-site weighted decisions fail to account for the sometimes significant winds and seas generated by large but distant storms or storms with anomalous circulations, such as typhoon-northeast monsoon hybrid events in the South China Sea. This paper describes the development, implementation and performance of an enhanced emergency response plan (ERP) of Arco China Inc. (ACI), whose operations were greatly expanded in 1995 in terms of construction and drilling activities and the number of offshore personnel. The update of the ERP was considered necessary because past experience raised serious concerns that previous practices might entail considerable risk when they lead to unnecessary evacuations of large numbers of offshore personnel.
