Paper No.
2221
Chemical Inhibitor Field Trial in Effluent Water Treatment Facilities
Abdul Wahab Al-Mithin
TL(S&E) Inspection & Corrosion Team
Kuwait Oil Company, Ahmadi, Kuwait
Amer Jarragh
Snr. Corr.Engr, Inspection & Corrosion Team
Kuwait Oil Company, Ahmadi, Kuwait
Sandip Kuthe
Corrosion Engr, Inspection and Corrosion Team
Kuwait Oil Company, Ahmadi, Kuwait
Sharad Londhe
Corrosion Engr, Inspection and Corrosion Team
Kuwait Oil Company, Ahmadi, Kuwait
ABSTRACT
Chemical inhibitor field trial was conducted in one of the main companies in the field of exploration,
production and transportation of crude oil and gas in the region. Effluent water, which is a byproduct of
crude oil separation and processing from the gathering centers, was disposed of in evaporation pits. In
the past few years, two effluent water disposal plants were constructed and commissioned is east and
south Kuwait fields, for treating the effluent water collected from several gathering centers and dispose
it by re-injecting in the disposal/injection wells. Effluent water is known for its high corrosivity and high
content of chloride which could lead to premature failures at the EWDP facilities and injection lines.
Various types of chemicals are used to control corrosion, scales and microbial growth in these facilities.
In an effort to select proper inhibitor chemicals, a field trial had been carried out for five chemical
vendors for various chemical formulations (corrosion inhibitor, scale inhibitor, oxygen scavenger, and
biocide). This paper will focus on the methods used to evaluate the performance of the corrosion
inhibitor and biocide.
Key words: Effluent water, inhibitor chemicals, field trial methodology
INTRODUCTION
Chemical inhibitors are widely used to reduce corrosion and scaling in the upstream oil and gas
production facilities and pipelines. The selection of inhibitors can be done by evaluating their
performance at the laboratory or field conditions or both.
Different types of chemicals are used by the Kuwait Oil Company( †) to control corrosion in their
operating facilities. In an effort to select/optimize treatment chemicals in the facilities handling effluent
†
Trade name
©2013 by NACE International.
Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to
NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084.
The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association.
1
water, field trials were conducted using products from different vendors in the EWDP(Effluent water
disposal plant) including injection lines.
As per company protocol, it is stated that “suitable treatment chemicals necessary to achieve effective
corrosion and/or scale control under the prevailing process conditions, shall be identified through a step
process comprising of documentary evidence, laboratory tests and field trials, with nomination for use
subsequently being determined on a cost performance basis.”1 Accordingly, chemical vendors were
short listed based on the results of laboratory screening tests performed in synthetic brine matching the
composition of effluent water. These laboratory tests were conducted for EWDP water quality by a third
party laboratory.2
This paper presents the methods used in conducting the field trials in EWDP including
injection/disposal pipelines using products from chemical suppliers namely (1) A (2) B (3) C (4) D and
(5) E. The products consisted of corrosion inhibitors and Biocide A and Biocide B from each vendor.
EXPERIMENTAL PROCEDURE
Field Trial
The facilities participating in the chemical field trial includes the effluent water treatment systems
(EWTS) of gathering centers (GCs) 09, 10, 20 and 22, and the EWDP including injection/disposal
pipelines. At each GC, the waste water is conveyed to an effluent water tank, which is further pumped
to EWDP as shown in the process flow diagram (Figure 1). The effluent water from GC-09 and GC-10
are combined before the common inlet manifold (CIM) at EWDP. The effluent water from GC-20 is
pumped directly to the CIM; while water from GC-22 is combined with waste waters from the North
Tank Farm (NTF) and the South Tank Farm (STF) before the CIM. The locations of chemical injections,
corrosion coupons, corrosion probes and fluid sampling points are also shown in Figure 1.
Prior to the start of the chemical trial, all existing chemical treatments in the EWTS of the various GCs
and in EWDP was stopped and the systems were allowed to run for about 6 weeks without treatment in
order to generate baseline data for corrosion rates, water chemistry and bacteria levels.
Materials
1. Treatment chemicals, namely corrosion inhibitor (CI), Biocide A and Biocide B from five vendors
were used in this study. The treatment scheme and dosage levels of the chemicals were based
on vendors’ recommendations.
2. Standard carbon steel corrosion coupons and standard linear polarization resistance flush type
(LPR) probes were used for corrosion monitoring.
3. UV-visible spectrophotometer was used for chemical residual analysis in EWDP fluids.
4. Bacteria growth media was used to evaluate the microbial proliferation.
Methods
1. The treatment chemicals were received in drums from various chemical suppliers and stored at
EWDP under appropriate storage conditions. The chemical injection day drums were flush
cleaned prior to each trial.
2. General corrosion rates (CR) were obtained from coupon analysis retrieved from several
locations at EWDP and injection/disposal pipelines. The coupon locations have duplicate strip
coupons. Prior to the start of the field trials, a blank trial without chemical treatment for 6 weeks
was conducted and all coupon locations were used to establish “baseline” corrosion rate. The
©2013 by NACE International.
Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to
NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084.
The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association.
2
3.
4.
5.
6.
7.
coupons used in the trial were removed at the end of the trial after 90 days and processed as
per ASTM G1.3
LPR probes were installed at the pig launcher, injection well (MG-108) and at disposal wells
(MG-204/MG-205). Probe readings were obtained on a continuous basis via remote data
collection (RDC) units during the course of the trial. LPR probe elements were cleaned or
changed as needed during the course of the trial.
Fluid samples were collected twice a week at the common inlet at EWDP, common outlet
(downstream of chemical injection) and at the Wellhead of the farthest disposal well (MG-204).
The chemical residuals for CI were determined by using the procedures provided by individual
vendors.
Fluid samples for planktonic sulfate reducing bacteria (SRB) analysis were collected from
• SC-0701- common inlet before chemical injection
• SC-0711- common outlet from EWDP plant
• Pipeline to Wellheads - MG-204/MG-205/MG-108
Serial dilution media specific to SRB was used for culturing and the bacterial growth analysis
was conducted as per NACE TM0194-2004.4
As per the company protocol1 the target values for general corrosion rate and planktonic
bacteria levels is as follows:
General corrosion rate < 1 mpy.
Corrosion Inhibitor residual at the farthest well – as per vendors’ specified limits
Bacterial proliferation, for planktonic SRB was targeted to be nil in the fluid samples.
RESULTS AND DISCUSSION
Corrosion Monitoring Analysis
Historically, it was observed that the incoming effluent water to EWDP plant was known to cause
severe general corrosion in carbon steel equipment/piping. Hence it was decided to assess the
chemicals on the basis of their effectiveness in reducing the general corrosion.
The general corrosion rate for each coupon was calculated by using the standard procedure.3 As stated
earlier, prior to the start of trial, blank run (without any chemical treatment) was conducted for about 6
weeks and baseline corrosion rates were obtained from the representative locations like effluent water
common outlet and pipelines to injection (MG-108)/disposal (MG-205, MG-204) wellheads. The
common outlet coupon location (CC-006) is on the inlet of the pig launcher and it is nearest to the plant
and coupon location (CC-011) is on farthest wellhead MG-204. It was presumed that the corrosion
inhibitor should be able to form a sustainable film up to the farthest well head MG-204 so as to provide
adequate corrosion protection in the upstream locations including the EWDP plant. In view of the
above, for assessment purpose, comparative weightages were given for the above mentioned coupon
locations; highest for the farthest wellhead location (MG-204) and lowest for the common outlet
location. Subsequently, weighted score was calculated for each location for each vendor by taking into
account the reduction in corrosion rate as compare to the blank rate and location weightage. The final
score for each vendor was calculated by adding the weighted scores for all the locations and tabulated
in Table 3.
Table 3
Corrosion Rate Analysis
©2013 by NACE International.
Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to
NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084.
The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association.
3
Vendor
A
B
C
D
E
Common outlet
Well head MG-108
Well head MG-205
(Weightage 30%)
(Weightage 40%)
(Weightage 60%)
Wtd
Wtd
Wtd
BCR CR Redn
BCR CR Redn
BCR CR Redn
Scr
Scr
Scr
29.4
9
20.4 6.12
6
8
-2 -0.8 20 42 -22
-13
29.4
7
22.4 6.72
6
5
1
0.4 20 33 -13 -7.8
29.4
5
24.4 7.32
6
5
1
0.4 20
3
17 10.2
29.4
6
23.4 7.02
6
4
2
0.8 20
8
12
7.2
29.4 102 -72
-22
6 13 -7 -2.8 20 12
8
4.8
Well head MG-204
(Weightage 70%)
Wtd
BCR CR Redn
Scr
14.4 22 -7.6 -5.3
14.4 8
6.4 4.48
14.4 3 11.4 7.98
14.4 13 1.4 0.98
14.4 18 -3.6 -2.5
Total
Scr
-13
3.8
25.9
16
-22
BCR: Blank corrosion rate
CR: Actual corrosion rate after coupon exposure for 90 days during trial
Redn: Reduction in corrosion rate (BCR - CR).
Wtd Scr: Weighted score (Redn x location weightage)
Total Scr: Addition of weighted scores for each vendor.
It is observed that, based on the overall score, Vendor C has performed best among the lot followed by
Vendor D. However, none of the vendors could reduce the corrosion rate within company target of <1
mpy.
LPR probe data was found to be highly erratic probably due to presence of sulfides and/or conductive
corrosion products. Though LPR probes gave some indication of occurrence of ongoing corrosion, the
corrosion rate obtained from the LPR probes was not considered for evaluation. The residual analysis
of the corrosion inhibitors for all the vendors was found to be within the vendors’ specified limits at the
farthest well.1
Bacterial Analysis
The aim of biocide treatment was to eliminate/reduce the bacterial contamination in the effluent water.
For assessing the biocides, planktonic SRB proliferation was considered as the main factor.
Figures 2 through 6 shows planktonic SRB levels for each vendor. It is observed from the figures that
the planktonic SRB levels were consistently high in the fluid sample from common inlet before chemical
injection in the order of 1000-100000 counts/mL. Biocide injection was carried at the common inlet and
the biocide efficiency was evaluated in terms of bacterial counts observed at the common outlet and
the three injection/disposal well heads.
For Vendor A, it is clearly seen that the bacteria levels were within 10 counts/mL at common
outlet/wellheads during most of the trial period.
For Vendor B, it can be clearly seen the bacteria levels were within our target of Nil count/mL at the
common outlet and farthest well head for most of the trial period.
For Vendor C, the planktonic SRB levels were not controlled in the initial period, which showed some
improvement at the later stage of the trial.
For Vendor D, the SRB levels were reduced by significant levels during the later period of the trial.
For Vendor E, the planktonic SRB levels were found to be controlled within 10 counts/mL only at the
later stage of the trial.
©2013 by NACE International.
Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to
NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084.
The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association.
4
FILTER
EWDP-CC-006B-EFW
FILTER
EWDP-CC-006A-EFW
EWDP-SC-0709-EFW
EWDP-CC-007-EFW
BALANCE
TANK
EWDP-SC-0711-EFW
20” GRP LINE
EWDP1-CI-0708 (Biocide)
24” CS LINE
To Wells
Pig
Launcher
To Flare
FILTER
EWDP-SC-0716-EFW
10” GRP LINE
24” PIPELINE (±14 KM)
EWDP1-CI-0706 (Corr. Inh.)
Back Wash
EWDP1-SC-0704-EFW
EWDP1-SC-0701-EFW
12” GRP LINE
To Flare
BALANCE
TANK
20” GRP LINE
FILTER
MG-108
EWDP-SC-0710-EFW
16” GRP LINE
MG-206
MG-203
GC-9 (EFW Dispatch Pump Inlet)
RECOVERED
OIL DRUM
GC-10 (EFW Dispatch Pump Inlet)
GC-20 (EFW Dispatch Pump Inlet)
MG-205
SEPARATOR
GC-22 (EFW Dispatch Pump Inlet)
NTF
STF
MG-204
10” CS LINE
Pig Receiver
LEGENDS
SAMPLING LOCATION
LP WET CRUDE
EFFLUENT WATER
LP GAS
CHEMICAL INJECTION
LOCATION
RETRIEVABLE COUPON
LOCATION
RETRACTABLE
COUPON
LOCATION
PROBE LOCATION
EWDP
Effluent Water Disposal Plant PFD
Figure 1: Process Flow Diagram of EWDP Plant
100000
10000
Counts/mL
1000
100
10
109
100
91
82
73
64
55
46
37
28
19
10
1
1
Days
SC-0704
SC-0711
WH MG-204
Figure 2. Planktonic SRB levels for Vendor A
©2013 by NACE International.
Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to
NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084.
The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association.
5
100000
10000
Counts/ml
1000
100
10
1
Days
SC-0704
Sc-0711
WH MG-204
Figure 3. Planktonic SRB levels for Vendor B
10000000
1000000
Counts/mL
100000
10000
1000
100
10
12
8
11
9
11
0
10
1
92
83
74
65
56
47
38
29
19
10
1
1
Days
SC-0704
SC-0711
Wellhead
Figure 4. Planktonic SRB levels for Vendor C
©2013 by NACE International.
Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to
NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084.
The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association.
6
10000000
1000000
100000
Counts/mL
10000
1000
100
10
110
101
91
82
73
64
55
46
37
28
19
10
1
1
Days
SC-0704
SC-0711
WH MG-204
WH MG-206
Figure 5. Planktonic SRB levels for Vendor D
10000000
1000000
100000
Counts/mL
10000
1000
100
10
109
100
91
82
73
64
55
46
37
28
19
10
1
1
Days
SC-0704
SC-0711
WH MG-204
WH MG-205
WH MG-206/-108
Figure 6. Planktonic SRB levels for Vendor E
©2013 by NACE International.
Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to
NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084.
The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association.
7
CONCLUSIONS
In the above trial, the authors found that the corrosion coupon data analysis was the most effective
method in assessing the chemical inhibitor effectiveness in preventing general corrosion in effluent
water stream, whereas, the corrosion probe data analysis and the residual analysis could not deliver
meaningful results in the assessment.
Based on corrosion monitoring results it appears that the maximum reduction in corrosion rate that any
chemical could achieve at the farthest well location was 78% compared to the blank corrosion rate.
However, none of the vendors could reach the company target value of <1mpy.
In case of biocide trials, method of analyzing the planktonic SRBs proliferation trends for assessing the
efficacy of biocide was found to be satisfactory. During the trial, few vendors’ chemicals were found to
control the bacteria population within company target of zero counts/mL as per the sampling results
from some locations.
ACKNOWLEDGEMENTS
Authors would like to thank Kuwait Oil Company for support in publishing this paper.
REFERENCES
1. KOC-ICM-001, “Chemical Selection Strategy for Internal Corrosion and Scale Control” (Kuwait,
[2005]).
2. KISR Report, “General Assessment of Chemicals for Biocide and Corrosion Inhibition” (Kuwait,
[2009]).
3. ASTM G-1, “Standard Practice for Preparing, Cleaning and Evaluating Corrosion Test
Specimens” (West Conshohocken, P: ASTM International, [2003]).
4. NACE Standard TM0194-2004, “Field Monitoring of Bacterial Growth in Oil and Gas Systems”.
(Houston, TX: NACE, 2004).
©2013 by NACE International.
Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to
NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084.
The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association.
8