Page 268 - Petroleum and Gas Field Processing

increased liquid product (NGL) recovery above that obtained by
conventional separation.

10.2.3 Types of Gas Reservoir
It is of interest in this chapter to comment briefly on the types of gas
reservoir that supply us with natural gas. It is misleading to infer that few
well-known types can rigidly describe reservoirs producing natural gas.
At one end, some fields produce saturated associated gas (gas
associated with crude oil); on the other end, a dry gas (free gas) is produced
from some fields. In between these two ends, one can find numerous types of
reservoir in which the hydrocarbons vary in composition and, hence, the gas
produced. Some of the factors contributing to these changes are as follows:
1. The contents of heavier components
2. The percentage of acidic gases
3. The presence of inert gases
The type of processing operations recommended for any specific operation
will, consequently, depend on the kind of gas under consideration along
with the distribution of the hydrocarbons found in the gas. For example,
natural gas separated via a GOSP to be transmitted for distribution
imposes specific duties on the field processing operations that are not
justified if the gas were to be diverted for gas injection application in oil
recovery.
For discussion purposes, Figure 2 illustrates some diversified
processing operations involved in the treatment of natural gas produced
by different reservoirs.

10.2.4 Gas Specifications and Standard Conditions
Market sales of natural gas require some specifications set by the
consumers regarding the maximum contents allowable for the following:
acidic gases and sulfur, oxygen and carbon dioxide, water vapor, and
liquefiable hydrocarbons. The thermal heating content of the gas sets
another value to be met as a minimum. These specifications are given in
the Introduction of the book.
As for the standard conditions used in the gas industry for reporting
the volumetric properties of the gas, two common standard conditions of
temperature and pressure are used:

1. Universal scientific, reported at 32 F and 760 mm Hg

2. Natural gas industry, reported at 60 F and 14.7 psia

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