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1. EFFECT OF IMPURITIES ON GAS
INDUSTRY
PREPERED BY:-
- OSAMA SHEREEF ABBAS
- ALI HUSSEIN TALI
- WALAA KHAIRI OBAID

2. What Is Natural Gas?
Natural gas is the gas obtained from
natural underground reservoirs either
as free gas or gas associated with crude
oil. It generally contains large
amounts of methane (CH4) along with
decreasing amounts of other
hydrocarbons. Impurities such as H2S,
N2, and CO2 are often found with
the gas. It also generally comes saturated
with water vapor

3. Effect of Gas Type in Field Processing
The gas composition of the field is the most important
issue in choosing a processing scheme. In other words,
depending on the type of reservoir and the composition
of the produced gas, the gas processing plant may
contain extensive facilities for the processing of the
associated liquefiable
hydrocarbons. Typically, associated gas is very rich in
liquefiable hydrocarbons and must undergo NGL and
condensate recovery to meet hydrocarbon dew point or
minimum heating value requirements. The gas
processing scheme will also be dictated by the format of
the sales contract and its specifications. The contract
may be totally different for each customer depending on
the composition and amount of gas, plant recoveries,

4. Why Field Processing?
The principal market for natural gas is achieved via
transmission lines , which distribute it to different
consuming centers, such as industrial , commercial,
and domestic . Field processing operations are thus
enforced to tre at the natural gas in order to meet the
requirements and specifications set by the gas
transmission companies. The main objective is to
simply obtain the natural gas as a main product free
from impurities. In addition, it should be recognized
that field processing units are economically justified by
the increased liquid product (NGL) recovery above that
obtained by
conventional separation.

6. Types of Gas Reservoir:-
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

7. 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.

9. 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 760mmHg
2. Natural gas industry, reported at 60 F and 14.7 psia

10. EFFECT OF IMPURITIES FOUND IN NATURAL GAS
Field processing operations of natural gas, which is
classified as a part of gas engineering, generally
include the following:
1. Removal of water vapor, dehydration
2. Removal of acidic gases (H2S and CO2)
3. Separation of heavy hydrocarbons
the effect each of these impurities has on the gas
industry, as end user, is briefly

12. Sour Gas Treating
Natural gas usually contains some impurities such as
hydrogen sulfide (H2S), carbon dioxide (CO2), water
vapor (H2O), and heavy hydrocarbons such as
mercaptans. These compounds are known as ‘‘acid
gases.’’ Natural gas with H2S or other sulfur compounds
(such as COS, CS2 and mercaptans) is called ‘‘sour gas,’’
whereas gas with only CO2 is called ‘‘sweet gas.’’ It is
usually desirable to remove both H2S and CO2 to
prevent corrosion problems and to increase heating
value of the gas. Sweetening of natural gas is one of the
most important steps in gas processing for the
following reasons:

13. 1. Health hazards. At 0.13 ppm, H2S can be sensed by
smell. At4.6 ppm, the smell is quite noticeable. As the
concentration increases beyond 200 ppm, the sense of
smell fatigues, and the gas can no longer be detected by
odor. At 500 ppm, breathing problems are observed and
death can be expected in minutes. At 1000 ppm, death
occurs immediately.
2. Sales contracts. Three of the most important natural
gas pipelinespecification are related to sulfur content,
as shown in Table 1.Such contracts depend on
negotiations, but they are quite strictabout H2S
content.

14. 3. Corrosion problems. If the partial pressure of
CO2 exceeds 15 psia , inhibitors usually can only be
used to prevent corrosion . The partial pressure of
CO2 depends on the mole fraction of CO2 in the gas
and the natural gas pressure. Corrosion rates will
also depend on temperature. Special metallurgy
should be used if CO2 partial pressure exceeds 15
Pisa . The presence of H2S will cause metal
embrittlement due to the stresses formed around
metal sulfides formed.

15. Gas that contains CO2 or other acidic gases such as
hydrogen sulphide , is referred to as sour gas, and
always puts up the cost of field development

16. REFERENCE
- Saied - Handbook of Natural Gas Transmission &
Processing.
- Natural Gas Hydrates, Elsevier (2002), 0750675691
- H. K. Abdel-Alal and Mohamed A - Petroleum and Gas
Field Pro

17. THANK YOU