Page 19 - Oil and Gas Production Handbook An Introduction to Oil and Gas Production

Associated hydrocarbons, known as 'natural gas liquids' (NGL) are used as
raw materials for oil refineries or petrochemical plants, and as sources of
energy.

2.2.5 Metering, storage and export

Most plants do not
allow local gas storage,
but oil is often stored
before loading on a
vessel, such as a
shuttle tanker taking oil
to a larger tanker
terminal, or direct to a
crude carrier. Offshore
production facilities
without a direct pipeline
connection generally
rely on crude storage in
the base or hull, to
allow a shuttle tanker to offload about once a week. A larger production
complex generally has an associated tank farm terminal allowing the storage
of different grades of crude to take up changes in demand, delays in
transport etc.

Metering stations allow
operators to monitor
and manage the natural
gas and oil exported
from the production
installation. These
employ specialized
meters to measure the
natural gas or oil as it
flows through the
pipeline, without
impeding its movement.

This metered volume
represents a transfer of ownership from a producer to a customer (or another
division within the company) and is therefore called Custody Transfer
Metering. It forms the basis for invoicing the sold product and also for
production taxes and revenue sharing between partners and accuracy
requirements are often set by governmental authorities.

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