Offshore North Sea Pipeline and Riser Loss of Containment Study (PARLOC)—Applications and Limitations in the Assessment of Operating Risks

Since the Piper Alpha disaster in 1988, there has been an urgent requirement to prevent such tragedies occurring by the introduction of higher safety standards and by improving the confidence in the statistical information available for the assessment of the risks of loss of containment associated with operation of North Sea pipelines. In order to achieve the latter, two databases have been compiled: 1) a pipeline database containing details of pipelines and risers installed in the North Sea; 2) an incident database containing details of reported “occurrences” (covering the period from 1975 to end 1993), which directly resulted or threatened to result in loss of containment from a pipeline or riser. The data has been compiled from information obtained from: U.K., Norwegian, Dutch and Danish Regulatory Authorities; Operators in the U.K., Dutch and Danish Sectors; reports from previous studies made available to the study; published sources. The databases have been used to perform assessments of factors affecting the frequency of incidents, such as: incident cause; part of pipeline or riser affected; pipeline or riser diameter, length, contents, age, type; whether the line is trenched or buried, piggy-backed or not; hydrotest pressure; location of pipeline or riser in the North Sea. The PARLOC study identifies potential hazards and provides an indication of likely loss of containment frequency associated with the operation of North Sea pipelines and risers. Furthermore, PARLOC provides a continually updated key reference for comparative risk assessment and ultimately for the implementation of risk control as part of an overall risk management program.