Page 265 - Petroleum and Gas Field Processing

10

Overview of Gas Field Processing

10.1 PLANNING THE SYSTEM

Part IV of the book is devoted to field treatment and processing operations
of natural gas and other associated products. These include dehydration,
acidic gas removal (H 2 S and CO 2 ), and the separation and fractionation of
liquid hydrocarbons [known as natural gas liquid (NGL)]. Sweetening of
natural gas almost always precedes dehydration and other gas plant
processes carried out for the separation of NGL. Dehydration, on the other
hand, is usually required before the gas can be sold for pipeline marketing
and it is a necessary step in the recovery of NGL from natural gas.
For convenience, a system involving field treatment of a gas project
could be divided into two main stages, as shown in Figure 1:
1. Stage I, known as gas treatment or gas conditioning
2. Stage II, known as gas processing
The gas treatment operations carried out in stage I involve the removal of
gas contaminants (acidic gases), followed by the separation of water vapor
(dehydration), as explained in Chapters 11 and 12, respectively. Gas
processing, stage II, on the other hand, comprises two operations: NGL
recovery and separation from the bulk of gas and its subsequent
fractionation into desired products. The purpose of a fractionator’s facility
is simply to produce individual finished streams needed for market sales.
Fractionation facilities play a significant role in gas plants, as given in
Chapter 13.
Gas field processing in general is carried out for two main objectives:
1. The necessity to remove impurities from the gas
2. The desirability to increase liquid recovery above that obtained
by conventional gas processing

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