Well-specific Blowout Risk Assessment

Abstract

Abstract As oil and gas projects explore more and more challenging territories, and as public opinion is increasingly aware of risks from drilling operations, it is of furthermost importance to better understand and systematically manage these risks. For every well project on the Norwegian sector, the risks from a blowout are studied from the safety and the environmental perspective, through Quantitative Risk Assessments and Environmental Risk Analyses, respectively. The blowout characteristics (probability, flow rates, durations) are among the most influent input parameters for these analyses. Traditionally these parameters have been extracted from available historical statistics from blowout databases. These databases provide generic data with very limited consideration for the well and operation specific characteristics (e.g. exploration, development, HPHT). DNV has developed a methodology for the assessment of blowout risks in order to better understand them and to be able to provide a more realistic risk picture. A multidisciplinary approach is applied during the risk assessment process, assessing the drilling or well operations according to a set of predefined criteria or risk factors. This benchmarking analysis is used as a basis for assessing the probability of a leak or a blowout. Well flow simulations are used and adjusted in order to assess the well specific leak and blowout rates for the different operations. The potential leak and blowout durations are calculated using statistical models and taking into account the context of the drilling and well operations. This new method considers the field specific reservoir challenges, best available technology and best operational practices in order to generate a more field and operation specific risk exposure. The results are more accurate risk predictions. Traditional analysis may be too conservative and would typically not reflect the actual well conditions, barriers and operational steps. Relevant examples from the Norwegian sector are presented.