Publication Details

Technical Paper TP05


Improved Estimation of Failure Frequencies for Offshore Pipelines and Risers

Authors: Dr P Praks, VSB-Technical University of Ostrava, S Medonos, Petrellus Engineering Ltd. Proceedings of the European Safety and Reliability Conference ESREL 2011.

Abstract

Statistical failure frequencies of offshore pipelines and risers are relatively low, which would indicate good reliability. However, if a gas or oil leak occurs and it is ignited, the resulting consequences in the form of explosions and fires, harm to personnel, environmental damage, impairment of assets and financial losses may be very severe due to the high volume of leaking fluid. The relatively low number of observed failures causes uncertainties in statistical estimations of failure frequencies. This Paper deals with a probabilistic approach for analysing data based on counts of events (failures) during the fixed time period of monitoring (pipelines-years and risers-years). There is a problem with uncertainties of data resulting from observed failures because of i) limited number of observed failures and ii) restricted time-monitoring limitations. As point estimations of failure rates for pipelines and risers can underestimate or overestimate the computed risk, this Paper gives probabilistic estimates of lower and upper bounds of failure characteristics. Advantages of using these probabilistic estimations for practical risk analyses in the offshore oil and gas production are also discussed.

Figure 1

Figure 1

Typical fires from risers on offshore production installations.


Return to the Publications page.