Barrier-Based Approach in Monitoring Risk Reduction Measures Associated with Major Accident Scenarios

摘要

This paper describes an approach adopted in monitoring Safety Critical Barriers (SCBs) associated with oil and gas production in Total's AKPO Floating Production and Storage Offloading (FPSO) facility located in OML 130 offshore Nigeria. The scenario-based Technological Risk Assessment study of AKPO FPSO provides a catalogue of major risks, with risk reduction measures developed into standard safety barriers and in some cases incorporated into existing barriers to improve their reliability. There are a total number of 366 SCBs being monitored using the approach described in this paper. The status of SCBs described as"Very Good", "Good", "Fair"or "Poor"is determined by systematically aggregating the test and maintenance results of relevant equipment items (functional locations), as well as results from audit checks of operational and management activities of the SCBs. The status of SCBs, so determined, is quantified and used to determine the risk portrait of the installation. Over 8,500 functional locations are linked to barriers based on their potential to contribute towards the control of one or more of the fourteen major accident scenarios identified from the major risk study. Test and maintenance records from UNISUP (Unified Information System for Upstream) are exported to a visual risk assessment tool for aggregation, based on a pre-set logic, to determine the status of SCBs that are dependent on equipment items. The application of this methodology enables the timely identification of barrier defects at the level of functional locations for a given safety critical equipment. The visual risk management tool deployed for the implementation of this process has proven to be of great benefit: i) diagrammatic view of potential accident path; ii) quick identification of failing barriers; iii) estimation of extent of failures in barriers; iv) understanding of the criticality of barriers in relation to a potential accident path; v) dynamic profiling of risks based on changes in barrier status. The implementation of this methodology contribute to savings in resources spent on safety inspections and audits by leveraging the information provided on the status of the barriers to determine the best approach and areas to assess during such exercises. In addition, records such as number of unavailable barriers per period, frequency of barrier failures etc can be obtained and used as metrics to determine Integrity Management performance on an operating facility.