Abstract
This paper presents a study to collect and analyze position loss incidents on dynamically positioned (DP) mobile offshore drilling units (MODUs) on the Norwegian Continental Shelf (NCS). These MODUs are of DP class 3 according to the requirements from the Norwegian Petroleum Safety Authority (PSA) and perform offshore operations with major accident risk potentials if position loss occurs. A definition of position loss is formulated in this study with considerations of capability and excursion. A method for position loss incident data collection and analyses is developed. Twenty-six (26) DP class 3 MODUs have worked on the NCS from 2000 to 2022. Among them, 31 position loss incidents were reported. Position loss incidents and associated DP operational time data are collected and estimated from multiple public sources and several databases in Equinor. Position loss scenarios and their common patterns of event development are analyzed. A historical frequency of position loss for DP class 3 MODUs on the NCS is derived, and uncertainties are discussed. The results in this paper provide useful knowledge of position loss incidents and insight into the safety of DP operations on MODUs on the NCS.
