slides focus on how to reduce H2S in oil and gas field using (non recovered) H2S Scavenger (triazine base).

1. H2S TREATMENT IN
OIL AND GAS FIELD
BONY BUDIMAN
2021

2. COMMON QUESTIONS
• What is H2S ?
• Why H2S become a problem?
• How to control ?
• Field cases !

3. OBJECTIVES
• Know how to identify problems caused by H2S
• Get knowledge of H2S Scavenger mechanism

4. OUTLINES
• INTRODUCTION
• MONITORING
• CONTROL
• TREATMENT METHOD
• DOSAGE
• FIELD APPLICATION
• SUMMARY

5. INTRODUCTION TO H2S
• Natural oil and gas well streams often contain hydrogen sulfide (H2S) and carbon dioxide
(CO2).These two gases are called acid gases because in the presence of water, they form
acids or acidic solutions.These gases, particularly H2S, are very undesirable contaminants,
and unless they are present in very small quantities, they must be removed from a natural
gas well stream.
• H2S could be present at gas phase, hydrocarbon phase and also in water phase as well

6. CHARACTERISTIC OF H2S
• Hydrogen Sulfide is Toxic, Colorless Gas
• Rotten Egg Odor
• Detectable at >10 ppb
• LC50 = 713 ppm
• Weak Acid

7. LIMITATION OF H2S CONTENT
• Most pipeline specifications limit H2S content to 0.25 gr. per 100 cu ft of gas
• The maximum concentration of H2S in water is 400 ppm
• Wells with only 10 ppm or above can be labeled sour.
• Partial pressures of only 0.05 H2S are considered corrosive.

8. OUTLINES
• INTRODUCTION
• MONITORING
• CONTROL
• TREATMENT METHOD
• DOSAGE
• FIELD APPLICATION
• SUMMARY

9. MONITORING
• H2S may dissolved in water, in oil or mixture with others gasses
• To monitor H2S content we may used :
• Chemetric ampule to check H2S dissolved in water
• Using reference of ASTM D5705 to check H2S dissolved in crude oil
• Using a detector tube such as Kitagawa kit, Draeger or Gas Tech.
• Potentiometric titration refer to UOP-Method 163-05

10. TUBE
DETECTOR
POTENTIOMETER
ANALYSIS

11. OUTLINES
• INTRODUCTION
• MONITORING
• CONTROL
• TREATMENT METHOD
• DOSAGE
• FIELD APPLICATION
• SUMMARY

12. CONTROL
• H2S may be controlled using two ways :
• Mechanical for high content of H2S (usually combine with recovered chemical)
• (Non recovered) Chemical for relatively low concentration
Chemicals
Mechanical

13. H2S SCAVENGER
• There are two type of H2S Scavenger : Recovered and Non
Recovered Scavenger
• Recovered Scavenger
These solutions undergo reversible reactions with acid gases
and can be regenerated in a cyclic process to remove rather
large amounts of sulfur. Some of chemicals are :
o Monoethanolamine (MEA)
o Diethanolamine (DEA)
o N-methyldiethanolamine (MDEA)
o Diglycolamine (DGA)
• Non recovered Scavenger
This type effective and efficient to remove
H2S at relatively low concentration, such as
below 1% since the used chemicals will be
discharged with the treated fluid. Some of
chemicals are :
o ZnO
o NaClO2
o Aldehyde (formaldehyde and
glutaraldehyde)
o Triazine

14. TRIAZINE
• Triazine is most popular H2S Scavenger.Triazine
mostly made from formaldehyde.
• Water soluble.The reaction with H2S create water
soluble salt as well even there are some reports that
at excessive of salt will create inorganic deposit
• Low-toxicity characteristics and are usually
biodegradable
• Cost effective treatment.

15. Desulphurization by the use of H2S scavenger
 Process diagram for H2S removal by scavenger (see
on the right)
 The most commonly used scavengers are based on
triazines
 The chemicals are injected in the gas or liquid
pipeline,
 Conventionally, the scavenger is injected through a
nozzle, Framo mixer or just an open pipe, and at
some installations there is a static mixer
downstream the injection point.
 The scavenger is water-soluble and the main fraction
of the scavenger is discharged to the sea.

16. WORKING MECHANISM (I)
• Reaction of triazine with H2S forms water soluble reaction products, there are no solids
to clog up systems
• Reaction products thermally stable so the H2S is permanently removed
• Triazines can be used in flowline or towers
• Triazine has an excellent cold handling properties and can be stored outdoors

17. WORKING MECHANISM
THE CHEMISTRY
N
N N
NH
N
N S
N
N
R1
R1
R1
1. H+
2. S2-
S-
R1
R1
R1
R1
R1
+ R1NH2
H+
S
N
N S
N
NHR1 S
N
S
1. H+
2. S2-
H+
R1
R1
S-
R1 R1
+ R1NH2

18. KINETICS OF H2S SCAVENGER (TRIAZINE)
0.00001
0.0001
0.001
0.01
0.1
1
10
100
1000
10000
100000
4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0
pH
Half
life
time
triazine
(s)
22°C
60°C
 Half time of triazine is time consumed
for H2S scavenger to react 50% from
initial weight
 Less half time means the reaction is
faster. For example at pH 6.0. The half
time at 60oC (red line) is around 0.001
second meanwhile at 22oC (blue line)
is near 1 second. Means the reaction at
60oC faster 1000x than in 22oC.
 Reaction will be faster at higher
temperature and more acid (lower pH)
of treated fluid

19. OUTLINES
• INTRODUCTION
• MONITORING
• CONTROL
• TREATMENT METHOD
• DOSAGE
• FIELD APPLICATION
• SUMMARY

20. TREATMENT METHOD
• H2S Scavenger mechanism is refer to Stochiometric Law  simple mean : if
H2S content increase twice then the we need 2x dosage of H2S scavenger.
• Some treatment method that usually used are :
- One way injection
- Circulating injection

21. ONE WAY INJECTION
• Injection of scavenger upstream the let down
station, and removal of the scavenger in the filter
separator
• The injection point for the scavenger is upstream
the choke valve at the letdown station, to give a
good mixing of the scavenger and the gas.The
pressure drop at the choke valve will create small
droplets of the scavenger, and this will give a fast
mass transfer of H2S into the droplets which in
turn gives a high efficiency of the scavenger.

22. CIRCULATING INJECTION
• In this process the spent
scavenger separated in the
filter separator will
contain partly unreacted
scavenger and partly
scavenger reacted with
H2S.
• The spent scavenger will
be mixed with fresh
scavenger and re-injected
into the pipeline.

23. OUTLINES
• INTRODUCTION
• MONITORING
• CONTROL
• TREATMENT METHOD
• DOSAGE
• FIELD APPLICATION
• SUMMARY

24. DOSAGE
• Refer to SPE 71541 : Scavenging of H2S from 40 ppm(v) to the required <3 ppm(v) required a
scavenger dosage of approximately 10 L/kg H2S.
• Based on some field experience it could be 12 – 20 ppm H2S scavenger needed to treat 1
ppm H2S
• The dosage will very dependent to the :
• Active content of H2S Scavenger
• pH
• Temperature
• Contact time / retention time
• Contact style

25. OUTLINES
• INTRODUCTION
• MONITORING
• CONTROL
• TREATMENT METHOD
• DOSAGE
• FIELD APPLICATION
• SUMMARY

26. FIELD APPLICATION
• Romeo Gas Plant
• Charlie Oil Plant
• Tiger Gas Plant

27. ROMEO GAS PLANT
• Romeo Gas Plant is a plant to collect gas from gas well and oil-gas separation
• Some equipment allowed by gas are leaking
• H2S content in Romeo Gas Plant is more than 200 ppm

28. GAS SCRUBBER
(Black Sept).
GAS COMP.
CLARK
GLY
CNT
LTS
V3 V2 V1
Reboiler
VRU
Gas comp
AJAX
V1
Flare
DS GT
CONTROL
ROOM
PROD.SEPT
GAS BOOT
GAS & AUX
COOLER
GAS COOLER
GAS COOLER
FLO-BOSS
AUX.COOLER
Rest room
FLO-BOSS
Sludge
Catcher
RX # 8
Trafo
Trafo
Fencing
H2S
Sampling
H2S 300/200 ppm
Sampling
H2S 400 ppm
New
Candidate
Injection
Point
Sampling
H2S 125 ppm
Sampling
H2S 205 ppm
H2S Content

29. Field Trial Procedure
1. Prepare injection point at inlet separator 2, inlet
separator 5 and outlet separator (see flow diagram
below)
2. One of the monitoring point is at outgoing HCT
3. Check H2S before trial as baseline
4. Start at injection rate total 20.5 GPD.
5. Increase injection rate if no significant changes of
H2S content
6. Change or shut off injection point if necessary.

30. GPO
Separator 1
Separator 2
Separator 5
Separator 6
7
6
5
4
2
1
A
B
C
injection point
To HCT
Proposed H2S Scavenger
Injection Point

31. FIELD TRIAL RESULT
Step
No
Date
Injection Rate ( Gpd) H2S
(ppm)
inlet
Separator 2
inlet
separator 5
Outlet
Separator
1 7-Mar 0 0 0 370
2 7 Mar 7.5 8 5 320
3 7 Mar 7.5 8 7 330
4 8-Mar 0 0 25 190
5 8 Mar 0 0 12 280
6 9-Mar 0 0 0 350

32. TABLE OF FIELD TRIAL RESULT
H2S
Concentration
(ppm)
Injection rate (GPD)
Field trial Literature (SPE No
71541)
370 0
333 5 7
297 10 14
187 25 36
150 30 43
40 45 64
4 50 71
0 51 72
Field Trial H2S Scavenger
0
100
200
300
400
0 20 40 60
Injection Rate (GPD)
H2S
Content
(ppm)
Field Trial Data
Extrapolation

33. CHARLIE OIL PLANT
Inj. Point H2S
Scav
• Charlie Oil Plant has 3Well
Plant areas which areWell
Plant A (WPA),Well Plant B
(WPB), andWell Plant C
(WPC).
• H2S in crude oil before
treatment : 70 – 125 ppm and
target treatment : < 10 ppm
• H2S Scavenger injected outlet
SeparatorV-235

34. H2S SCAVENGER PERFORMANCE
0.00
10.00
20.00
30.00
40.00
50.00
60.00
520
540
560
580
600
620
640
660
1-November-…
(14:00)
4-November-…
(14:00)
7-November-…
(14:10)
10-November-…
(15:30)
13-November-…
(20:20)
(8:15)
17:00
(20:15)
(8:30)
(20:15)
(9:15)
(20:15)
(8:30)
(20:15)
(9:00)
(20:15)
H2S
Content
(ppm)
&
M.BOPD
(Bbls)
H2S
Scavenger
Dosage
(ppm)
H2S SCAVENGER PERFORMANCE
H2S Scav. Dosage (ppm) H2S Content (ppm)
H2S Content Target (ppm) M.BOPD
• Target : to decrease 70-125
ppm H2S to < 10 ppm (to
remove 60 – 115 ppm H2S in
crude oil).
• Dosage of H2S Scavenger =
580 – 640 ppm).
• Field dosage equivalent to 5-
11 ppm H2S scavenger / ppm
H2S in crude oil.

35. TIGER GAS PLANT
• Gas rate 20 mmscfd and
H2S content 30 ppm
• H2S Scavenger injected
60 GPD at Gas Plant
• H2S at Monitoring point
1 near the plant : 15
ppm
• H2S at Monitoring point
2 located 9.2 km from
gas plant : < 5 ppm
H2S Scav

36. OUTLINES
• INTRODUCTION
• MONITORING
• CONTROL
• TREATMENT METHOD
• FIELD APPLICATION
• DOSAGE
• SUMMARY

37. SUMMARY
• H2S is a harmful gas due to health of human, caused corrosion at metal facilities and
decrease selling price of oil and gas.
• One of common method to reduce H2S content is by inject H2S Scavenger
• H2S Scavenger should be inject at enough dosage, enough contact time and good contact
style in order to get optimum performance
• The performance of H2S Scavenger also depends on H2S content, temperature, pH and
active content.