Oil and gas production handbook - Process Control and ...

4.2 Separation
As described earlier, the well-stream may consist of Crude oil, Gas, Condensates,
water and various contaminants. The purpose of the separators is to split the flow
into desirable fractions.
4.2.1 Test Separators and Well test
Test separators are used to separate the well flow from one or more wells for analysis
and detailed flow measurement. In this way, the behavior of each well under
different pressure flow conditions can be determined. This normally takes place
when the well is taken into production and later at regular intervals, typically 1-2
months and will measure the total and component flow rates under different
production conditions. Also undesirable behavior such as slugging or sand can be
determined. The separated components are also analyzed in the laboratory to
determine hydrocarbon composition of the Gas oil and Condensate.
The test separator can also be used to produce fuel gas for power generation when
the main process is not running. In place of a test separator one could also use a three
phase flow meter to save weight.
4.2.2 Production separators
The main separators are gravity type. On the right you see the main components
around the first stage separator.
As mentioned the production
choke reduces will pressure to
the HP manifold and First
stage separator to about 3-5
MPa (30-50 times atmospheric
pressure). Inlet temperature is
often in the range of 100-150
degrees C. On the example
platform, the well stream is
colder due to Subsea wells and
risers.
The pressure is often reduced
in several stages; here three
stages are used, to allow
controlled separation of
volatile components. The
purpose is to achieve
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