Enerproject supplied five associated gas recovery modules to this station in West Siberia.
ASSOCIATED GAS RECOVERY MODULES
Global Environmental Protection Issues Bring Growth in
Enerproject’s Associated Gas Recovery Module Business
By Roberto Chellini
Recent environmental protection directives prohibit flaring of associated
natural gas coming out of oil wells.
This practice is still widely used, but
in many nations national legislation
makes it illegal and controls are getting progressively stricter.
The problem, especially in remotely
located oil fields, is what do we do
with associated gas? It must be collected, treated and then used in the
most convenient way.
Enerproject of Switzerland is engineering and manufacturing associated
gas recovery modules.
For years the company has specialized in fuel skids supplying natural gas
for gas turbine operation. Designing of
an associate gas module is substantially
different from a turbine fuel gas module because of the type of gas to be
handled. While the fuel gas is practically pure methane — well over 80%
— clean and dry, the associated gas
coming out of an oil well is dirty and
unstable. Its composition can vary
from well to well and also vary over
time from the same well.
It is important to separate all components that could be absorbed by the
compressor lube oil, which could be
diluted and thereby lose its lubrication
characteristics. All the materials of piping,
valves, etc., have to be selected so as
to avoid the corrosive effect of the gas.
Usually the gas is received after a
first separation stage at 29 to 43 psi ( 2
to 3 bar) pressure, or after the second
separation stage at atmospheric pres-
sure (or even slightly below). At the
module inlet, high-performance filters
and separators are placed before the
compressor to avoid entraining of sand,
as well as to reduce water and other
impurities. After compression, the gas
is cooled down in a heat exchanger to
separate residual condensate and then
heated up again using the heat recov-
ered from the compressor lube oil to
go away from the dewpoint in order to
avoid condensation. It is delivered in
stable condition of pressure and tem-
perature so that its state is 36° to 54°F
( 20° to 30°C) away from its dewpoint.
The West Siberia station was constructed in 2008. Gas delivery pressure is 232 psi ( 16 bar). Gas
flow for each of the five Enerproject-supplied units is 247,202 cfh (7000 Nm3/hr).
