Development and verification of computer simulation models for evaluation of siting strategies and evacuation procedures for mobile drilling units in hurricanes

Experience with Mobile Offshore Drilling Units (MODUs) in recent hurricanes in the Gulf of Mexico (GOM) has indicated the need to reassess where and how these units are sited. During hurricane Andrew (1992), several of these units moved significant distances from their original locations. In several instances there were collisions with platforms and pipelines. Also, in the case of hurricanes weather conditions can deteriorate rapidly, and timely decisions are critical to allow proper securing and evacuation of MODU's. This is particularly crucial in areas with high storm intensity and low predictability.;The primary objective of this research was to develop an analytical model to evaluate MODUs' movements in response to the combined load effects of hurricane winds, waves and currents, then use a Monte-Carlo simulation process to evaluate the probability of collisions between the MODU and surrounding large facilities. The computer simulation program MODUSIM was developed, and has been used to investigate alternative siting strategies.;The strategies investigated include location of the MODU relative to nearby facilities, capacities of the mooring systems, and incorporation of intentional 'weak links' in the mooring system to cause either the mooring to the anchor connections to break, or the anchors to drag. The results of the parametric studies of alternative siting and mooring strategies are summarized.;The second objective of this research was to use probabilistic risk analysis techniques to develop a computer model to help evaluate operation and evacuation systems for MODUs. Results from the evacuation simulation model are intended to assist in developing decision criteria for securing and evacuating MODUs.;This research is believed to be of interest to the offshore engineering community, including platform owner/operators, regulatory agencies, and engineering consulting firms.