Page 209 - Petroleum and Gas Field Processing

separated from the separator are collected using a VRU. This approach is
recommended for small-size oil leases handling small volume of fluids to
be processed. The principles underlying the stabilization process are the
same as for gas–oil separation covered in Chapter 3.

7.2.2 Stabilization by Stripping
The stripping operation employs a stripping agent, which could be either
energy or mass, to drive the undesirable components (low-boiling-point
hydrocarbons and hydrogen sulfide gas) out of the bulk of crude oil. This
approach is economically justified when handling large quantities of fluid
and in the absence of a VRU. It is also recommended for dual-purpose
operations for stabilizing sour crude oil, where stripping gas is used for
stabilization. Stabilizer-column installations are used for the stripping
operations.

7.3 TYPES OF STABILIZER EMPLOYING ENERGY AS A
STRIPPING AGENT

Two basic types of trayed stabilizer are commonly used:
Conventional reflux types normally operate from 150 to 300 psia.
This type of stabilizer is not common in field installations. It is
more suitable for large central field processing plants.
Nonrefluxed stabilizers generally operate between 55 and 85 psia.
These are known as ‘‘cold feed’’ stabilizers. They have some
limitations, but they are commonly used in field installations
because of their simplicity in design and operation.

7.4 NONREFLUXED STABILIZERS
7.4.1 Introduction
When hydrocarbon liquids are removed from the separators, the liquid is
at its vapor pressure or bubble point. With each subsequent pressure
reduction, additional vapors are liberated. Therefore, if the liquids were
removed directly from a high-pressure separator into a storage tank,
vapors generated would cause loss of lighter as well as heavier ones. This
explains the need for many stages in a GOSP. Nevertheless, regardless of
the number of stages used, some valuable hydrocarbons are lost with the
overhead vapor leaving the last stage of separation or the stock tank.

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