Hydrocarbon Processing - February 2022 - GP-17

SPECIAL FOCUS: TREATING SOLUTIONS
TABLE 1. GT-1 amine analysis
Sample 1,
MDEA, wt%
PZ, wt%
TEG, wt%
Lean loading, mol/mol
August 2016
55.3
4.4
1.08
0.0005
TABLE 2. GT-2 amine analysis
Sample 1,
MDEA, wt%
PZ, wt%
TEG, wt%
Lean loading, mol/mol
August 2016
40.4
4.6
-
0.003
gas and remove the water content below
7 lb/MMsft3
to protect the pipelines from
water condensation. The TEG contactor
is operating at 140°F, where the expected
TEG vaporization losses are relatively high.
High acid gas contents in feed gas.
The authors' company's lab and a thirdparty
vendor lab conducted extensive
work to perform complete analysis of the
sour gas from the four GOSPs plant outlet
and the Plant A inlet. The measurements
were conducted between November 2016
and October 2017. In addition, a plant
simulation was performed using crude
and gas samples representing the whole
field (north and south sections) to verify
and compare with actual measurements.
The simulation results were validated by
the field sample analysis. The following
were practiced during field sampling:
* Samples were collected from four
GOSPs outlets and the two AGRU
inlet headers
* Two samples per day representing
day and night conditions were
collected for each location
* Samples were collected for at least
one week. More than 100 samples
were collected in total, representing
summer/winter and day/night
compositions of the sour gas.
Based on the samples analyses and actual
simulation of GOSPs operation using
the updated compositions:
* The measurements and simulations
confirmed a significant increase
of acid gas content in the feed gas
stream (FIG. 3) from the design of
1.21 mol% to 1.8 mol%-2.1 mol%.
Sample 2,
December 2016
49.7
3.4
2.55
0.0013
Sample 3,
February 2017
53.15
3.27
3.54
0.0009
Sample 4,
April 2017
51.2
2.7
3.9
0.0008
Sample 5,
August 2017
51.2
2.7
3.9
-
Sample 6,
Sample 7,
September 2017 November 2017
50.4
6
2.86
0.0025
46.7
7.2
3.9
0.0025
Sample 2,
December 2016
42.7
3.9
1.8
0.0019
Sample 3,
February 2017
49.9
5
2.29
0.001
Sample 4,
April 2017
46.8
4.6
2.8
0.0018
Sample 5,
August 2017
46.8
4.6
2.8
-
Sample 6,
47.4
6
2.9
Sample 7,
September 2017 November 2017
48.1
6.7
3.9
0.0034
0.0017
FIG. 3. Acid gas content in feed gas.
* The C6
+ hydrocarbon increased
from 0.68 mol%-0.71 mol%.
* A significant BTEX (benzene,
toluene, ethylbenzene and xylene)
of more than 1,000 ppm was
measured. The BTEX measurement
was not a typical analysis during the
design phase, therefore it was not
considered. BTEX has a significant
impact on promoting foaming in
the amine contactor. Although
the unit is operating at a relatively
high temperature (140°F-145°F),
which reduces BTEX absorption,
the solvent-rich loading is relatively
low (0.2 mol/mol-0.25 mol/mol),
which promotes BTEX absorption.
Since the AGRU was designed for
1.21% mole acid gas (equivalent to
37 MMsft3
than 600 MMsft3
study are:
d acid gas volume), the new
acid gas content of 1.8%-2.1% limits the
plant processing capacity to less than
1.8 Bsft3
The main conclusions from the
d, which is a reduction of more
of processing capacity.
* The plant feed gas composition
that was used to design the AGRU
did not represent the actual
composition of the feed gas to the
plant-mainly the acid gas content
and heavy C6
+ components, which
had significant impact on AGRU
capacity. The actual sour feed gas
acid content is more than 50%
compared to the original design.
* Heavy hydrocarbons frequently
collected inside the AGRU amine
contactor. These hydrocarbons
were the main cause for the
frequent foaming in the unit.
* The topography of the plant area
resulted in unstable feed conditions
(temperature and liquid carryover)
to the plant. Diurnal impact
was evident were the feed gas
temperature fluctuated significantly
between day and night, especially
from nearby GOSPs (2 and 3)
* The oil field has unique
characteristics: the south part
cap gas contains less acid gas
Gas Processing & LNG | JANUARY/FEBRUARY 2022 17
Hydrocarbon Processing - February 2022

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