This document summarizes the results of a field work investigation and chemical testing program to address acidic corrosion at the Tangga Barat Central Processing Platform in Malaysia. Key findings include: - Produced water from 12 of 13 active wells was acidic, with pH below safe limits of 6-8. - Total iron levels increased significantly throughout the production and processing system, indicating corrosion. - Chemical testing showed an engineered neutralizing filming additive was able to neutralize the acidic water and provide 25% additional corrosion protection. - Recommendations included installing injection pumps and points for the additive to provide long-term corrosion mitigation for the platform's produced water systems.

1. CLIENTPREPARED BY
REVIEWED BY
APPROVED BY
APPROVAL DATE
SMA
HBN
FEBRUARY 10-2015
CLIENT
CONTRACT NO.
WORK ORDER NO.
COSM REFERENCE NO.
PCSB - Tangga Barat
NA
NA
NA
DOCUMENTRELEASEDATE
REVISION NO.
DISTRIBUTION LIST :
OIM/PS - TBC - PCSB
Operations Engr. - PCSB
APC Manager - PCSB
Tech. Manager - COSM
REFERENCES :
1. Hach Digital Titrator 16900 Manual
2. Rohrback Cosasco Systems Corrosion Note
3. Draeger Gas Pump Manual
4. J Phys. Chem. Ref. Data, Volume 20, No 6
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FEBRUARY 10-2015
2
ARY
PCSB - PMO TANGGA BARAT ACIDIC WATER RECONFIRMATION & REASSESSMENT PROGRAM
TECHNICAL REPORT
5. Engineered NFA Injection Program
• Injection Method :chemical is injected continuously at 0.4 to 0.7% based on total
produced fluids volume.Estimated usage is 300 to 540 L/day (based on 119 kL/d).If
2 injection points are set-up,then this volume will be split between the two injection
locations.Note that dosage is calculated based on lab data.Based on previous work,
actual field dosage is a multiplier of 2 to 2.5.This will need to be confirmed during
actual injection in the plant.
• Injection Pumps :the chemical in itself is high pH (11),hence is corrosive.The
injection pump specification (all wet contact surfaces and seals) must be able to
withstand high pH exposure.RECOMMEND SPECIFIC PUMP HERE.
• Injection Points :upstream HP Production Header (line number 350-PG- 04064-
63420X) and LP Production Header (line number 450-PG-04065-63420X) at TBDR.
Since the chemical is water-based,no losses is expected when injecting at the
headers with no carryover of the chemical to the gas offtake line.
• Injection Quills :Since the available injection points are at a 12 o’clock position,
installation of injection quills at both points are mandatory to ensure the chemical is
injected into the mid-stream of the flow,thus to avoid corrosion at the injection point.
Proper selection of quill metallurgy is critical to ensure no failure at injection point.
• Chemical Storage :To minimize chemical handling onsite,it is recommended the
chemical is delivered in tote tanks (nominal capacity 2040 liters) or ISO tanks
(nominal capacity 7,500 liters).
Picture 3: Complete PPE are
used during fluid sampling,
and recycled plastic bottle
for flushing as well as to
prevent spillage.
Note: Due to no available
sampling point for each
wells at TBDR-A, individual
well is diverted to test
header for fluid sampling at
outlet Multiphase Flowmeter
(MPFM).
0
10
20
30
40
50
60
70
80
90
100
LP
&
HP
header
Inlet
V2020
Outlet
V2020
Inlet
V2030
Outlet
V2030
Outlet
V3020
Inlet
PWTS
Outlet
PWTS
Percent
Increase
in
Total
Iron
(%)
Sample
Point(s)
Chart 3: Percent Increase In Total Iron Through TBC Process
Total Iron increases by 48% from early stage of process up to 78% at PWTS (furthest downstream of water process)
%
Increase
In
Total
Iron
0
100
200
300
400
500
600
0
1
2
3
4
5
6
7
8
9
10
LP
&
HP
header
Inlet
V2020
Outlet
V2020
Inlet
V2030
Outlet
V2030
Outlet
V3020
Inlet
PWTS
Outlet
PWTS
Chloride
Content/Alkalinity
(mg/L)
Total
Iron
(mg/L)
Sample
Point(s)
Chart 2: Water Analysis for TBC Process System
Total Iron increases (accumulated) while Chloride Content & Alkalinity are consistent further downstream of TBC process
Total
Iron
Count
(mg/L)
Chloride
Content
(mg/L)
Alkalinity
(mg/L)
4. Chemical Test
The test findings are as follows:
• Chart 4 shows the effectiveness of the engineered NFA fluid to neutralize the acidic
liquid to within the“safe zone”of pH 6 to 8.There is no changes in water appearance
after being dosed with the engineered NFA.The performance of the NFA is also
further tested with adding the acid inhibitor in the acidic liquid prior to titration,to
ensure that there is no negative impact.The essential pH is about 6,but to ensure
better protection and maintain the safe pH ranges it is recommended to obtain and
control it between 7 to 8.
• Corrosion weight loss calculation based on soak test showed that the NFA is able to
provide additional corrosion protection of 25% reduction in corrosion (compared to
untreated acid liquid).This represents a secondary protection of the piping by the
formulated buffer.The different protection level is plotted above for different dosage
of acid inhibitor treatment (see Chart 5).
0
1
2
3
4
5
6
7
8
9
10
Blend
1
Blend
2
Blend
3
Blend
4
Blend
5
Engineered
NFA
Volume
per
160
mL
sample
(mL)
/
pH
Engineered
NFA
with
varia@on
in
Acid
Inhibitor
content
Chart 4: Acid Base Titration Analysis
Engineered NFA neutralizes acidic fluids to safe pH range (6 - 8) while providing additional 25% corrosion protection
Titrant
Volume
(mL)
Final
pH
0
5
10
15
20
25
30
X1
X4
%
Corrosion
Protec-on
Engineered
NFA
%
Ac-ve
(ppm)
Chart 5: Corrosion Coupon Soak Test
Engineered NFA provides Additional Corrosion Protection at 25% Inhibition
X1
X4
1 2 3 4 5 6
Picture 4: Image of corrosion coupons after 12 days exposure time. Coupon number 5 (minimal
discoloration & most visible coupon number) had the lowest corrosion with a percent protection in
corrosion of 23%.
X1 - 10 ppm (4 hours soak)
X2 - 20 ppm (4 hours soak)
X3 - 40 ppm (4 hours soak)
Blank X1 X2 X3 X4 X5
X4 - 10 ppm (4 hours soak) & 10 ppm (12 days immerse)
X5 - 10 ppm (4 hours soak) & 20 ppm (12 days immerse)
Most corrosive zone
4.TBC Acidic Water Study
The following are key findings from the field work conducted:
Tangga Barat Produced Water Properties
Average Produced Water 119 kL/d
Average pH of Water 4.1
Lowest pH of Water,partial pressure 3.6, 2134 kPa
• Presently,production at TBCP-A are from Tangga Barat Drilling/Riser Platform (TBDR),
where 13 wells are online (out of 18 wells).The wells are segregated into HP and
LP wells where well A-7 is the only HP well with a very significant water cut of 62%.
Compared to the previous visit,current produced water has increased by 82% (A-7
not flowing).The two satellites for Tangga Barat Field,Melor and Laho,are offline.
• The lowest pH is from well A-9L (3.6) while the highest pH is from well A-4S (7.6).
The flowing wells pH and dissolved CO2
profile are categorized into two categories;
low and high level of corrosive wells respectively.Low corrosive wells (pH within
the safe zone of 6-8 and very low dissolved CO2
) is only A-4S while the other 12
remaining (pH below the safe zone of 6-8 and very high dissolved CO2
) flowing
wells are considered to be acidic and corrosive as shown in Chart 1.Therefore TBC
environment is concluded to be 95% acidic because only well A-4S appeared to be
in the safe zone and have the lowest dissolved CO2
.
• For the acidic liquid profiling at process system,samples are taken from seven
different sample points,namely V-2020 condensate inlet & outlet (production
separator),V-2030 water inlet & outlet (condensate degasser),V-3020A water outlet
(media coalescer),S-4230B water inlet (particle filter) and V-4250B water outlet
(deoiler vessel).The pH of the process system liquid samples are 100% acidic.As
shown in chart 1,the pH of the samples are observed to be consistent within the
range of 3.9 - 4.3 (acidic environment).
• From flowing wells to process system,there is quite a significant increase of 46% on
average in dissolved CO2
.This would be due to the significant drop of temperature
(50%) from the wells to the process system.Based on studies of solubility of CO2
,
it tends to be more soluble in water at lower temperature.However,there is only a
small percentage drop by 11% of pH from flowing wells to process system due to the
variation of pH (3.6 to 7.6) from the flowing wells.
• Other water analysis (total Iron,Chloride content and Alkalinity) are also conducted
during the visit. Chart 2 shows the trending where Chloride content and Alkalinity
are very consistent.However,there is a significant increase in total Iron accumulated
further downstream of the process system.The baseline (average) of total Iron
reading for the flowing wells is 0.3 mg/L. As the liquid flows to the process system,
total Iron increased significantly by 48% from early stage of process up to 78% at
PWTS (leaked and corroded facility).
• There are no individual sampling point for each wells at TBDR-A.During sampling,
only one well diverted into MPFM with 1-4 hours stabilization/flushing period.
Corrosion coupon access point is also not in-place currently.
• Onboard TBCP-A there is no available chemical injection facility yet for engineered
NFA.
2. Scope of Work
The scope of work (SOW) for this field work are as follows:
STAGE 1:Program Start-up
• To compile current produced water data,operating parameters & well test data.
STAGE 2 :Acidic Water Total System Survey & Analysis (Water & Gas Properties)
• To determine readiness for chemical solution deployment (availability of chemical
injection point(s),sampling point(s),injection facility,chemical storage layout);
• To perform various water analysis based on pH,dissolved CO2
,Total Iron,Chloride
Content & Alkalinity for all flowing wells at TBDR-A and throughout the process
system at TBCP-A; and
• To perform gas analysis based on CO2
& H2
S content for all flowing wells at TBDR-A.
STAGE 3 :Chemical Test (Performance & Consumption)
• To re-conduct acid titration test with various engineered Neutralizing Filming Additive
(NFA) to deduce the best blend and dosage requirement; and
• To re-quantify corrosion protection provided by the formulated NFA through corrosion
coupon soak/exposure test.
1. Background & Objectives
Due to the high CO2
levels in the gas produced at Tangga Barat,the discharged liquid has
a very low pH (safe operating pH ranges from 6 to 8) caused by the high concentration of
carbonic acid in the liquid.The impact of the corrosive acidic environment in the process
system is the incident of numerous leaks at various parts of the liquid handling system.The
biggest challenge of handling the acidic liquid is at the Produce Water Treatment System
(PWTS) within the Tangga Barat Central Processing Platform (TBCP-A).
Although the leaked pipings for PWTS have been fully replaced,for the longer term
solution Petronas Carigali has requested for Clariant to investigate and develop system
specific chemical solution to rectify and mitigate the corrosion problem.The first field work
is completed on July 2014.To focus more on the low pH stream from TBC flowing wells,
the second field work are executed on January 20 and completed on January 28,2015
with two CLARIANT technical personnel accompanied with one PCSB representative from
Production Chemistry department coming onboard.
Picture 1: Outer visual of severely corroded
carbon steel piping at PWTS for TBCP-A. Leakings
occured at most of the wellments.
Picture 2: Inner visual of corroded carbon steel
piping at PWTS for TBCP-A. Corrosion attack
usually happens at the weakest part.
References (Rohrback Cosasco Systems Corrosion Rate Application Note) :
Calculations of Corrosion Rate:The corrosion rate is calculated for each coupon using the diffrence in value of the
initial and final weight,control weight loss,coupon surface area (5.25 in2
),density of the alloy (7.86 g/cm3
),and
exposure time (12 days) in the formula
C.R(mpy)= 22300*[Weight Loss]
A*t*d
Where:
A = surface area of coupon,in2
t = exposure time,days
d = density of the alloy,g/cm3