Oil and gas production handbook An introduction to oil ... - ABB Group

• Production allocation, which ensures that producers are able to deliver
their contractual volumes into the network.
• Leak detection, which compares actual measured data against dynamic
data predicted by the model. A discrepancy indicates a leak (or a failing
measurement). Simple liquid systems only calculate basic mass balance
(in-out), while an advanced modeling system can give more precise data
on size and position of the leak within a certain response time.
• Pig or scraper tracking is used to track the position of the pig within the
pipeline, both from pig detection instruments and the pressure drop
caused by the pig in the pipeline.
In case of liquid pipelines transporting batches of different products, a batch
transfer system is needed. Based on information on when each product is
injected into the pipeline, and gravity measurement at the receiving end, it is
possible to sequentially transfer different products, such as gasoline and
diesel in the same pipeline. Depending on product characteristics, there will
be an interface section between the two products that widens as the product
moves along the line. This “off spec” product must be discarded at the
receiving end to avoid product degradation. It is often disposed by mixing
with larger volumes of low grade fuel products. This system is often used
with countrywide refined product distribution to terminals.
Safety systems are used, as for other process plants, to ensure that the
systems shut down in case of malfunctions and out-of-bounds conditions. Of
particular importance is the high integrity pressure protection system
(HIPPS). This is a highly reliable system that is needed to maintain
protection against overpressures, and manage shutdowns. The strategy
used by normal safety system to isolate and depressure, or simply fail to
safe condition, often cannot be applied to pipelines due to the large volumes
of product in the pipelines. Simply opening or closing a valve would
potentially cause overpressure conditions or overload safety devices such as
flares HIPPS monitors and executes these responses in a specific
sequence.
5.5 LNG
LNG is a gas transport product. The gas, which is primarily methane (CH 4 ),
is converted to liquid form for ease of storage or transport, as its volume is
about 1/600th the volume of natural gas in the gaseous state. It is produced
close to the production facilities in an LNG liquefaction plant, stored,
transported in cryogenic tanks on an LNG carrier, and delivered to an LNG
regasification terminal for storage and delivery to a pipeline system.
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