Page 419 - Compression Machinery for Oil and Gas

398 SECTION III Applications

Gas chromatographs and other instrumentation are used at these custody
transfer points to measure or calculate various gas properties such as calorific
value (energy content), moisture content, concentrations of sulfur compounds,
dew points, etc.
It is also frequently necessary to include some type of pressure regulation
facilities at each custody transfer point to reduce maximum operating pressures
based on the design pressures of each individual pipeline. Pressure regulator
valves can be a source of noise and vibration and should be carefully sized based
on the full range of anticipated flows. It is occasionally necessary to install nat-
ural gas heaters in the system (to keep the gas temperature above the dew point)
to prevent the formation of hydrates or liquid hydrocarbons, particularly during
pressure reduction.
When the gas is transferred into smaller distribution networks, an odorant is
added to the gas so that any leaks can be more easily detected by smell.

Gas Storage/Withdrawal

Storage Reservoirs
Underground reservoirs are sometimes used as peaking storage locations for
natural gas transmission and distribution systems. They are used to provide
additional capacity at various locations where peak demand can exceed capa-
bility of existing pipelines to provide the necessary product at the required pres-
sure levels. Typical compression equipment consists of both reciprocating and
centrifugal compressors that are used to inject the gas into the storage formation
and to boost the pressure during removal to meet pipeline pressure
requirements.
Typical storage facilities include depleted oil and gas reservoirs, depleted
aquifers, underground salt caverns, etc. Natural gas can also be converted to
liquefied natural gas (LNG) and stored in large, aboveground tanks.
Underground storage by the numbers:
l Approximately 400 active storage facilities in 30 states, made up of depleted
natural gas or oil fields (80%), depleted aquifers (10%), and salt caverns
(10%).
l Approximately 20% of all natural gas consumed during the winter is sup-
plied by underground storage.
l Underground storage capacity increased 18.2% between 2002 and 2014.
l Approximately 4 trillion cubic feet of natural gas can be stored underground,
or enough to meet an average states residential natural gas consumption for
more than 20years.
REF: http://www.ingaa.org/File.aspx?id¼27272&v¼49766f72.