Page 13 - Petroleum and Gas Field Processing

present serious safety and corrosion problems. In such cases, another
treatment known as the sweetening process is needed to remove hydrogen
sulfide or reduce its content to acceptable limits.
A quick comparison between the properties of a typical crude oil
produced from a field in the Middle East before and after treatment
illustrates the role of field processing the crude oil [1].
Raw crude oil has the following materials present:
Water: present in two forms: emulsions (10%) and free water (30%)
Salt: 50,000–250,000 mg/L formation water
Gas: dissolved gas (600 scf/bbl crude oil)
H 2 S: 1000 ppm

Treated crude oils have the following final specifications:
Water content: 0.3 vol% maximum
Salt content: 10 lbs (as NaCl) per 1000 barrels of oil
H 2 S: 70 ppm
Vapor pressure: 10 psig (4–5 psi RVP)

II. FIELD PROCESSING OF NATURAL GAS
Nature gas associated with oil production (associated gas) or produced
from gas fields generally contains undesirable components such as H 2 S,
CO 2 ,N 2 , and water vapor. Field processing of natural gas implies the
removal of such undesirable components before the gas can be sold in the
market. Specifically, the gas contents of H 2 S, CO 2 , and water vapor must
be removed or reduced to acceptable concentrations. N 2 , on the other
hand, may be removed if it is justifiable. Gas compression is usually
needed after these treatment processes. In addition, the gas undergoes
separation and fractionation for the recovery of some hydro-
carbon components that are utilized as a feedstock for the petrochemical
industry.
Several schemes can be recommended for field processing and
separation of natural gas, but the specific solution is usually a function of
the composition of the gas stream, the location of this source, and the
markets available for the products obtained. Saudi Arabia’s master gas
system (MGS), as illustrated in Fig. 2, is a good example.
Nonassociated gases, including gas condensates, are also a potential
source of hydrocarbons for many oil-producing countries. The processing of
the gas condensates, however, involves a low-temperature technique to be
described later in the text.

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