Many but not all Oil & Gas operators develop company rulesets for Quantitative Risk Assessments (QRAs). For those that do, it is to ensure a consistent and high standard approach across all company assets, aiming to achieve a balance between modelling simplification and complexity. A QRA ruleset has been developed for the Kashagan field in Kazakhstan by the North Caspian Operating Company NV (NCOC), with the purpose of addressing the specific challenges associated with quantifying the risk of toxic releases from high-pressure, high-H2S content pipelines. This paper summarises the analytical approach given in the ruleset, and explains how it was developed, by bringing together the most up-to-date guidance available in the industry.

The main themes presented in this paper are: methodologies used to assess H2S risks to the general public, including the effect of concentration fluctuations and the choice of averaging time; the choice of dispersion model for far-field dispersion; and defining appropriate 'source terms’ for the dispersion modelling in order to account for the effect of ground cover on buried pipelines and to allow the full-bore ‘crater’ releases to be characterised more realistically. Calculating the probability of releases, especially those for the largest full-bore releases, is another important consideration.

Keywords:
offshore pipeline, Production Chemistry, risk management, risk and uncertainty assessment, Corrosion Management, concentration, ruleset, risk assessment, frequency, qra ruleset
Subjects:
Production Chemistry, Metallurgy and Biology, Pipelines, Flowlines and Risers, Risk Management and Decision-Making, Offshore pipelines, Risk, uncertainty, and risk assessment, Corrosion inhibition and management (including H2S and CO2)
Copyright 2017, Society of Petroleum Engineers
You can access this article if you purchase or spend a download.