(81n) Risk Based Design for a Gas Oil Separation Plant - An Industrial Case Study

Following the gas and oil market demand growth, the industrial upstream plants are becoming bigger and complex. Despite the continuous improvement in technologies in plant design and in plant operations, the accidental release of flammable gases or liquids due to loss of containments in gas/oil separation plants can not be avoided and can lead to accident escalation if not well managed. The management of such accidental scenarios shall begin at the early design stage in order to incorporate in the design evolution the possible scenario reductions or mitigation measures. The design philosophy traditionally applied in the gas/oil separation plants development is to reduce as much as possible the spatial extension of the plant in order to reduce earth movement and pipes, cables, piperacks length, containing CAPEX cost; however in this way the safety engineers are obliged to include into the design complex mitigation systems involving higher OPEX costs. This industrial case application summarises the risk/consequences based approach to an executive project carried out in 2006 to have a plant layout intrinsically safe against credible accidental events and fire reduction/mitigation measures tailored on expected consequences of the specific plant unit. After a brief presentation of the methodology implemented to identify credible leaks size used to develop the fire scenarios which will form the basis of the mitigations measures design, the articles focus on the determination of the minimum safety distances between equipment; on the assessment of the credible fire case in order to evaluate the total fire water request and on the assessment of sizing of drainage system to remove hydrocarbon spills and applied fire water to minimise fire spread in order to avoid possible escalation.