Page 79 - Petroleum and Gas Field Processing

Table 2 Comparison Between Mechanisms of Separation
Parameter Differential separation Flash separation
Process arrangement

Losses of hydrocarbon Low High
No. of stages Too many (can reach 100 stages) Few (2–4 stages)
Commercial application Not applied Applied

which consists of a series of flash separators operating over a pressure
range from wellhead pressure to atmospheric pressure. However, with the
increased desirability of recovering natural gas and natural gas liquids
(NGLs), other methods have been proposed as modification to the basic
flash separation technique [2].
Separation methods could be broadly classified as follows:
1. Conventional methods
2. Modified methods

(a) Adding vapor recompression unit to the conventional
methods
(b) Replacing the conventional methods by a stabilizer and a
recompression unit

The conventional method is a multistage flash separation system and
is recommended for comparatively high-pressure fluids. Several stages
operated at successively lower pressures affect the separation of oil
from gas, thus increasing the oil recovery. In general, the number of stages
in a multistage conventional separation process is a function of the
following:

1. The API gravity of the oil
2. The gas–oil ratio (GOR)
3. The flowing pressure
Consequently, high-API-gravity oils with high GOR flowing under
high pressure would require the greatest number of stages (from three to
four), as depicted in Figure 7.

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