Yards Moving Forward - GL Group

How to predict the lifetime risks
Advanced analysis techniques are being utilized to evaluate the full range of risks
encountered in oil and gas pipeline operations and to target the inspection of pipeline
systems in the most cost-effective way possible.
Oil and gas pipelines are the world’s major energy
arteries. Pipelines not only transport the majority of oil
and gas traded internationally, they also perform a key
role in gathering supplies from the wellhead and in distributing
the product through local grids to the final customer.
As is the case with the tankers engaged in the carriage of
oil and gas, the design, construction and operation of pipeline
systems are governed by their own regime of safety and environmental
protection regulations. Effective rulemakings, in turn,
are dependent on a full understanding of the risks involved.
As has already happened in a number of other industries,
pipeline operators are becoming aware of the advantages of
risk-based assessment methods over traditional deterministic
approaches for investigating the probability and consequences
of failure and implementing remedial measures in
the most cost-effective way possible. This is particularly
important for ageing pipelines due to the risk of corrosion
and fatigue failure as a result of cyclic loads encountered over
a long service life. Pipeline failures can have dire consequences
in terms of environmental damage and through fires
and explosions involving escaped product.
Recent Incidents
In addition, from a commercial point of view, oil and gas
pipelines represent a capital-intensive means of transporting
energy and their closure can have a far-reaching impact on
the market. With supply and demand in the global energy
market now so finely balanced, a single incident can severely
disrupt product flows and prices, as evidenced by the August
2006 decision to shut down part of the BP-operated Alaskan
North Slope (ANS) crude oil pipeline system to enable repairs
to a number of corroded gathering lines.
The ANS incident has effectively cut the 400,000 barrel per
day (bpd) flow from the Prudhoe Bay oil fields in northern
Alaska by one-half and repairs will take several months to
complete. The decision to curtail operations followed the discovery
of internal corrosion in a pipeline from an oil processing
plant in the eastern part of the field.
In March 2006 a spill, which was caused by corrosion in an
oil transit pipeline, in the western part of the Prudhoe Bay
gathering system disrupted operations. The ANS pipeline
system is now 29 years old. A further notable pipeline was closed
in August 2006 due to a corrosion incident. The 42 year-old
Druzhba 1 line, which carries approximately 250,000 barrels
per day of Russian crude oil to Lithuania’s Mazeikiu refinery
58 nonstop 3/2006
and Butinge export terminal, was shut down after Transneft,
the Russian pipeline operator, discovered a leak in the line.
There are doubts as to whether Druzhba 1 will be reopened.
Holistic Approach to Risk
As part of the effort to utilize advanced analysis techniques
in enhancing pipeline safety, Germanischer Lloyd (GL)
has developed a risk-based assessment methodology for
pipelines to provide pipeline operators with an overview of
the integrity and safety performance of their existing networks
and to help them optimize their inspection efforts. The
new methodology has equal applicability to both onshore
and offshore pipelines.GL has extensive experience with the
development and use of risk assessment methodologies in
the marine and other industrial sectors. In addition,
Germanischer Lloyd Oil & Gas (GLO) provides certification
services for the pipeline industry and the company’s reference
list includes onshore projects in the North Africa, Mexico
and Germany and offshore pipeline systems in North Sea, the
Mediterranean, North Africa, West Africa, the Middle East
Gulf, South East Asia and Germany. The society’s work on the
development of a risk-based evaluation and inspection (RBI)
program for offshore and onshore pipeline systems began
back in 2001 and has encompassed several projects. In spring
2004 GLO’s Kuala Lumpur office initiated an RBI-database
system with a user-friendly interface called GALIOM, which
was previously intended for process units and gas plants.
Following establishment of the database, a methodology specific
to pipelines was developed including a specification for
the programming.
Semi-quantitative Evaluation
The risk associated with a system or a process is generally
defined as the product of the likelihood of an event happening
and the consequences of failure. In establishing its holistic
approach to assessing pipeline risks, GL was aware that
the methodology would have to adequately evaluate the probability
and consequences of failure and make an accurate
assessment of the risk level in order to ensure that the recommended
remedial actions represent the most appropriate
response. A semi-quantitative method was chosen as the
most appropriate for assessing the risks associated with
existing pipeline networks. Quantitative analysis requires
more effort than qualitative approaches, but provides more
accurate results. By taking into account the cost-benefit
implications of the risk assessment effort, the quantitative
risk analysis can be targeted at the most important subsystems