SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEERING
Natural Gas Processing Engineering
Professor Dr Ahmad Zuhairi Abdullah
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
OVERVIEW OF NATURAL GAS
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Natural Gas Production and Consumption
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Natural Gas Consumption
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Info on Natural Gas
• Naturally occurring hydrocarbon gas mixture
• Consists primarily of methane, but commonly includes varying amounts
of other higher alkanes and even a lesser percentage of carbon dioxide,
nitrogen, and hydrogen sulfide
• Natural gas is an energy source often used for heating, cooking, and
electricity generation
• Also used as fuel for vehicles and as a chemical feedstock in the
manufacture of plastics and other commercially important organic
chemicals
• Natural gas is found in deep underground rock formations or associated
with other hydrocarbon reservoirs in coal beds and as methane
clathrates.
• Petroleum is also another resource found in proximity to and with
natural gas.
• Most natural gas was created over time by two mechanisms: biogenic
and thermogenic. Biogenic gas is created by methanogenic organisms in
marshes, bogs, landfills, and shallow sediments. Deeper in the earth, at
greater temperature and pressure, thermogenic gas is created from
buried organic material.
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Associated and Non-associated Natural Gas
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EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Natural Gas Formation
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Associated and Non-associated Natural Gas
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Overview of Field Processing of Natural Gas
Pg viii Fig 1
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Overview of Field Processing of Natural Gas
•Natural gas associated with oil production (associated gas) or produced
from gas fields generally contains undesired components-H2S, CO2, N2,
H2 O
•H2S, CO2 and H2O need removal or reduced to acceptable
concentrations before the gas can be sold
•N2 may be removed if it is justifiable
•Gas compression is needed after these treatment processes
•The gas should also undergo separation and fractionation to recover
some HC components that are utilized as a feedstock for petrochemical
industry
•Several schemes can be recommended for field processing and
separation of natural gas
•Non-associated gases including gas condensates are also potential source
of HC for many oil producing countries
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Typical Natural Gas Composition
Pg x Fig 2
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Typical Natural Gas Composition
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Typical Natural Gas Composition
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
•Field processing of natural gas is carried out for two main reasons
1) The necessity to remove impurities from the gas
2) The desirability of increasing liquid product recovery above that
obtained from conventional gas processing
•Field gas processing units usually include the following
1) Removal of water vapor: Gas dehydration represents the most
common needed unit. Liquid and solid phase water are troublesome
especially when the gas is compressed and cooled. Water accelerates
corrosion of pipelines and other equipment. It reduces pipelines
capacity as it can accumulate in low point regions. Solid hydrates
can plug valves, fittings and the pipes itself
2) Acid gas separation: Acid gases basically imply H2S and CO2 and
they need to be removed. H2S is extremely toxic and when
combusted, it produced sulfur oxides. Both gases are corrosive
especially in the presence of water. Once removed, H2S could be
commercially utilized to produce sulfur
3) Heavy HC separation: HC heavier than methane can be removed for
fuel gases. C3+ tend to condense, forming two-phase flow and create
pipelines problems
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Pg xi Table 1
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Pg 256 The Table
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
•Irrespective of the source of natural gas, the typical final specification
set for market sales requirements are usually as the following;
H2 S
Total sulfur
Oxygen (air)
Carbon dioxide
Liquefiable HC
Water content
0.25-0.30 grain per 100 ft3 (one grain=64.799 mg)
20 grains per 100 ft3
0.2 % by volume
2 % by volume
0.2 gal per 1000 ft3
7 lbs/MMSCF (in a 1000 psia gas line)
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Gas Field Processing
•For convenience, field treatment of gas project could be divided into 2
main stages;
1) Stage 1: Gas treatment or gas conditioning
2) Stage 2: Gas processing
Pg 252 Figure 1
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
Pg 255 Figure 2
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
•Stage I involves the removal of gas contaminants (acidic gases) followed
by the separation of water vapor (dehydration).
•Stage II comprises 2 operations i.e. NGL recovery and separation from
the bulk of gas and its separation into desired products
•The purpose of fractionator’s facilities is to produce individual finished
streams needed for market sales
•Natural gas field processing and removal of various components
involves complex and expensive processes
•Sour gas leaving a gas-oil separation plant (GOSP) might first require
the use of an amine unit to remove acidic gases, a glycol unit to
dehydrate it and a gas compressor to compress it
•It is desirable to recover NGL in the gas that usually include C3+
•Ethane C2 could be separated and sold as petrochemical feedstock
•To recover and separate NGL from the bulk of a gas stream require a
change in phase i.e. a new phase has to be developed for separation
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING
•NGL separation and recovery can be achieved through the use of;
1) An energy-separating agent: Examples are refrigeration for partial
or total liquefaction and fractionation
2) A mass-separating agent: Examples are adsorption and absorption
(using selective HC, 100-180 molecular weight)
•The second operation in Stage II is concern with the fractionation of
NGL product into specific cuts such as LPG (C3/C4) and natural gasoline
•Most important factors to be considered in the design of a system for
gas field processing are such as;
1) Estimated gas reserve (both associated and free)
2) The flow gas rate and composition of the feed gas
3) Market demand, both local and export
4) Geographic location and methods of shipping of finished products
5) Environmental factors
6) Risks involved in implementing the project and its economics
SCHOOL OF CHEMICAL ENGINEERING, UNIVERSITI SAINS MALAYSIA
EKC 483/3 PETROLEUM & GAS PROCESSING ENGINEEERING