Page 81 - Petroleum and Gas Field Processing

The first modified method of separation implies adding several stages
of gas compression to recompress the separated gas from each flash stage.
Liquids from interstage vessels between the compressors can be collected
and processed as liquid natural gas (LNG) stock. Natural gas will be
delivered at the desired pressure depending on its usage. The second
modified method of separation is different in concept from the
conventional (flash) separation. It makes use of crude stabilizer columns.
Normally, these columns have top feed trays with no rectifying section and
no condenser, but are provided with interstage reboilers and feed
preheaters. Crude stabilization systems are advantageous as GOSPs if
space is critical, as may be encountered on an offshore platform, because
they occupy less space than conventional GOSPs.

3.5 GAS–OIL SEPARATION EQUIPMENT

The conventional separator is the very first vessel through which the well-
effluent mixture flows. In some special cases, other equipment (heaters,
water knockout drums) may be installed upstream of the separator.
The essential characteristics of the conventional separator are the
following:
1. It causes a decrease in the flow velocity, permitting separation of
gas and liquid by gravity.
2. It always operates at a temperature above the hydrate point of
the flowing gas.
The choice of a separator for the processing of gas–oil mixtures
containing water or without water under a given operating conditions and
for a specific application normally takes place guided by the general
classification illustrated in Figure 8.

3.5.1 Functional Components of a Gas–Oil Separator

Regardless of their configuration, gas–oil separators usually consist of four
functional sections, as shown in Figure 9:
1. Section A: Initial bulk separation of oil and gas takes place in
this section. The entering fluid mixture hits the inlet diverter.
This causes a sudden change in momentum and, due to the
gravity difference, results in bulk separation of the gas from the
oil. The gas then flows through the top part of the separator and
the oil through the lower part.

Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.