Improved Methodology on the Safe Design of Offshore Exploration and Production Facilities for Accidental Collisions
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Date
2015
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Mary Kay O'Connor Process Safety Center
Abstract
Accidental loads constitute the great majority of potential and actual fatalities in offshore drilling operations. An unplanned HSE (Health, Safety, and Environment) event has a great potential to cause permanent disablement or death to onboard personnel. Therefore, it is highly desirable to minimize or prevent the accidental incidents rather than risking an unexpected event. Among all types of accidental collisions, dropped objects can pose the highest risks to the personnel, equipment, and structures on an offshore platform. Other types of accidental collisions, such as ship impact, helicopter collisions etc., can also endanger the safety of offshore platforms, however, these scenarios are often underreported. In order to prevent human loss and for a safe design of an offshore platform, the risks of these accidental collisions should be quantified, in terms of probability/frequency and consequence aspects. The risk assessment quantifies the risk caused by accidental collisions including dropped objects on potential targets from topsides to seabed, helicopter transport risk for inflight crash and for take-off/landing crash on the platform, and a passing vessel collision based on influence factors for severe structural damage and loss of hydrocarbon. This paper addresses the human and asset risk assessments against accidental collisions including dropped objects, helicopter collision, and ship impact in offshore operations. A new perspective on safe design of offshore structures for accidental collisions is outlined to estimate the associated risk to potential targets such as human personnel as well as platform decks, helidecks, jacket legs, risers, electrical cables, and pipelines. The frequencies and consequences of each modelled event are estimated to measure the overall risk to life in terms of IRPA (Individual Risk Per Annum), PLL (Potential Loss of Life), and WEV (Weighted Expectation Value). A risk matrix is utilized in mitigation decision as high impact frequency and high consequential events require mitigation strategies. The proposed assessment methodology will contribute towards identifying the mitigation measures and safety-critical procedures and equipment.
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Keywords
offshore operations