Paper No. 3749 - Corrmagnet · 2020. 4. 29. · were prepared in a Postgate B medium (PGB) containing 16,000 mg/L of chlorides according to the procedures described in NACE TM0194.24

Synergistic Effect of Sulphate-Reducing Bacteria and CO2 on the Corrosion of Carbon Steel and Chemical Treatment to Control it

Antonio De Turris Universidad del Zulia / Centro de Estudios de

Corrosión Avenida Universidad

Maracaibo, Estado Zulia, 4001 Venezuela

Sankara Papavinasam

CANMET Materials Technology Laboratory 183 Longwood Road South Hamilton, Ontario L8P 0A1

Canada

Matilde de Romero

Universidad del Zulia / Centro de Estudios de Corrosión

Avenida Universidad Maracaibo, Estado Zulia, 4001

Venezuela

Lisseth Ocando Universidad del Zulia / Centro de Estudios de

Corrosión Avenida Universidad

Maracaibo, Estado Zulia, 4001 Venezuela

ABSTRACT The combined effect of sulphate-reducing bacteria (SRB) and CO2 on the corrosion of carbon steel in produced water were investigated using a rotating cage. During the experiment, pH, planktonic SRB, and concentrations of sulphide, sulphate, iron, calcium and magnesium ions were monitored. After the experiment, the sessile SRB were enumerated by serial dilution and optical microscopy, scanning electron microscopy, mass loss and laser profilometry were used to identify corrosion products, bacterial cell and corrosion rate. Both mass loss and localized pitting corrosion were two and three times higher in solutions containing 10 % SRB and 10 % CO2 respectively compared to solutions containing either 10% CO2 or 10% SRB alone. Higher CO2 concentrations killed SRB which indicates that production water with CO2 concentrations higher than 10%, where the pH drops below 5.5 and can down until 4.3, the potential risk of MIC by SRB decreases. A commercial package of treatment based on quaternary ammonium salts as filmic corrosion inhibitors, glutaraldehyde with quaternary ammonium salts as biocide and polyepoxysuccinic acid as scale inhibitor decreased corrosion rate by 96%, controlled the SRB lower than 102 cells/cm2 and reduce the risk of scales. Keywords: Sulphate-reducing bacteria, CO2, scale, corrosion products, corrosion morphology, chemical treatment synergistic effect

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Paper No.

3749

©2014 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.

INTRODUCTION Internal uniform and pitting corrosion is a major problem in pipelines and equipment made of carbon and low-alloy steels in the oil and gas industries due to flow, pressure, temperature, acid gases (CO2, H2S) and SRB 1-2. This problem of internal corrosion is managed using appropriate chemical treatments3-5. Several studies show that annual costs for corrosion at the industry ranged from 1-5% of each nation’s GDP and from those costs, between 15-30% are associated with microbiologically induced corrosion (MIC )4-6. A basic characteristic of MIC is the formation of a biofilm on the metallic surface with sessile microorganisms. The kinetics of sessile SRB growth is different from that of planktonic microorganisms and the incubation period for sessile bacterial growth is relatively long. Once the biofilm is formed, the metal surface is susceptible to MIC by SRB and other bacteria such as acid producing bacteria and methanogens. 7-14 Several investigations have been made to understand the influence of acid gases and SRB individually7-14 but studies to investigate their combined effect are minimal. According to several studies14-18, there is no consensus on the combined effect of corrosion inhibitors, biocides and scale inhibitors on corrosion, bacteria, and scales. Busch19 et al in 2010 reported that many of the tested corrosion inhibitors increased the pitting corrosion rate associated with MIC when compared with untreated controls, despite reducing the concentration of SRB. In contrast, some less toxic inhibitors to the SRB caused a less severe pitting. Amir20 et al in 2010 studied the performance of corrosion inhibitors used in petroleum product pipelines prone to the risk of microbial corrosion; it was observed that the corrosion inhibitors used showed adequate performance, but in the presence of corrosive microorganisms, the effectiveness of protection against corrosion was reduced. Al Hashem21 and Carew in 2005, found out that a biocide and scale inhibitors decreased the efficiency of a corrosion inhibitor in two brines tested, both at atmospheric pressure as the operating pressure. Prasad22 in 2003 carried out several studies to find a suitable chemical treatment for water used in hydrostatic testing, protect pipelines against corrosion, comply with environmental guidelines regarding the disposal of these waters and also decrease the costs of chemical treatment. Special mixtures were made to attain protection against corrosion and scaling, which were used in combination with low doses of biocides based on aldehydes and quaternary ammonium salts. Freiter23 in 1992 evaluated the effect of a corrosion inhibitor on the growth of planktonic and sessile bacteria and found in most of the tests performed that the presence of corrosion inhibitor had no effect on the populations of sessile and planktonic bacteria. In some cases, planktonic growth was higher where the corrosion inhibitor was injected and in other cases there was greater growth in the absence of the inhibitor. The field requires chemical treatment to help protect the carbon steel infrastructure. Therefore, in this research the relative interaction between SRB, CO2 and the effect of a commercial inhibitor package consisting of scale inhibitors, corrosion inhibitors, and biocides was evaluated.

EXPERIMENTAL PROCEDURE

Activation of the mixed culture and growth curve of SRB. A sample of mixed culture of SRB was obtained from the produced water from an oil field in western Venezuela. Several inocula

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were prepared in a Postgate B medium (PGB) containing 16,000 mg/L of chlorides according to the procedures described in NACE TM0194.24 The inocula were activated before use by replacing the Postgate B with fresh medium and incubating at 37°C for 48 h to obtain 108 cells/mL of planktonic bacterial concentration. Then the growth curve was determined using 10% of inoculum and 90% of SPW during 96 hours to evaluate the behavior of this mixed culture and confirm the sessile bacterial growth fixed previously in 106 cells/cm2. Preparation of synthetic produced water (SPW). This water was prepared similar to natural produced water following the general guidelines prescribed in the ASTM(1)-D114125, but using sodium lactate as an organic source for the growth of the SRB as recommended in the NACE standard TM0-19424. Corrosion Tests. All corrosion tests were performed in a rotating cage apparatus26 as per the procedures described in ASTM G170,27 ASTM G18428 and ASTM G202.29 All tests were performed in duplicate using a rotation of 100 rpm under atmospheric pressure conditions at

37C. The rotating cage rate simulated the wall shear stress equivalent to the flow rate of an oil production pipeline. In each test, 8 coupons of carbon steel with a surface area of 34.14 cm2 were used, which were prepared according to the procedures described in ASTM G0130 and ASTM G31.31 The experiments without SRB were carried out in 4 L of solution, and with SRB were carried out using 3.6 L of synthetic produced water with 0.4 L of SRB inoculum (10%). All tests were realized by 96 hours, time where the sessile SRB growth was similar to the field (106 cells/cm2). The synthetic produced water and the rotating cage apparatus was de-aerated with argon gas before the tests as per the procedure described in ASTM G 20229. CO2 and argon gas mixture at the following ratios: 100/0, 50/50, 25/75 and 10/90 was used on the solution during the test to evaluate the effect of CO2 on the bacterial growth and the synergistic effect of CO2 and SRB on the corrosion of carbon steel. During the experiments, samples of test solution were withdrawn every 24 hours to determine planktonic bacteria count, pH, and concentrations of sulphide, sulphate, calcium, magnesium and iron. After testing, one coupon was sonicated (energy equivalent 2880 J) to detach the sessile SRB and measure the sessile bacteria growth using the serial dilution method24 and other seven coupons were cleaned in an ultrasonic bath for 1 min to remove soft corrosion products. The coupons were cleaned as per ASTM G 0130 and ASTM G 3131. The mass loss of the coupons was determined according to the procedures described in ASTM G 1632 and ASTM G 46.33 Chemical treatment influence. To study the influence of chemical treatment on the corrosion rate a commercial package used individually in the field was evaluated, measuring mass loss, planktonic and sessile SRB growth as well as the increase in the calcium and magnesium solubility. Table 1 presents the main characteristics of chemical package and Table 2 present the experimental design used in this research to evaluate the efficiency of the products. This table shows the equations used to calculate the synergistic effect of chemicals used for treatment, considering a percentage of each characteristic problem of the system which is minimized by the use of appropriate chemical treatment. The benefits generated by the chemicals used can be classified as: mass loss reduction (MLR), planktonic SRB reduction (PBR), sessile SRB reduction (SBR) and increase in calcium (CSI) and magnesium (MSI) solubility.

(1) ASTM International, 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959.

3


Morphological attack. The surfaces of the cleaned coupons were also examined using an optical microscope (photomicrographs were taken at 5X magnifications), scanning electron microscope (SEM) and laser profilometer to determine the corrosion morphology.

RESULTS AND DISCUSSION

Synthetic produced water. Table 3 presents the composition of both natural produced water (NPW) and synthetic produced water. The compositions of both were similar, with both having high chloride concentrations. The total dissolved solids (TDS) were within the range normally found in oil field natural produced water, i.e., between 10,000 mg/L and 350,000 mg/L.3 The presence of cations such as calcium (Ca2+) and magnesium (Mg2+) indicates that the synthetic produced water had a high tendency to form scale. SRB planktonic concentrations with 10 % inoculum. Table 4 and Figure 1 present the planktonic SRB growth under dynamic conditions with 10% of inoculum, along with the variation in the concentrations of iron, sulphides and sulphates in tests with and without CO2. The planktonic bacterial growth remained constant at 108 cells/mL in both assays approximately, indicating this high bacterial concentration. However at 48 hours showed a slight increase to 109 cells/mL corresponding with an increase in average sulphide production of 10.1 and 7.1 mg/L for both trials. Then, sulphide levels showed a decrease to 8.2 and 5.6 mg/L without and with CO2 respectively due to the high consumption of these ions when the ferrous ions increase too due to metal corrosion, being this higher in the presence of CO2. On the other hand, the sulphate concentration decreased rapidly from 163 mg/L to 1.5 mg/L in tests without CO2 and from 192.5 mg/L to 1.3 mg/L in tests with CO2, being this reduction most dramatic in the presence of CO2 where at 48 hours the sulphate content low to 1.3 mg/L, while without CO2 this reduction was at 72 hours, which may be associated with the lower pH (5.7-5.8) in the medium with CO2. With the development of this growth curve was confirmed that after 96 hours a sessile SRB growth of 106-107 cells/cm2 (Table 5) was obtained similar to the field. Effect of CO2 and chemical treatment on SRB growth. Table 5 presents the effect of CO2 and chemical treatment on planktonic and sessile growth, sulphide production and sulphate consumption. In this table is shown that when the CO2 concentration is 10% the growth of planktonic and sessile SRB is 108 cells/mL and 106 cells/cm2 respectively but as the CO2

concentration increased from 25 to 100 % the population of planktonic SRB decreased and no sessile SRB formed. At 100 % CO2 neither planktonic nor sessile bacteria survived, due to the pH under 5.5, this value is the lower limit for the growth of SRB. Some SRB grow below pH 5.5 but it is not very common. So, these assays confirm that the risk of MIC by SRB is minimal when the CO2 concentration is higher than 10%, but the risk of sweet corrosion increases. Tests with corrosion inhibitor indicate that this product had some biocide effect as it reduced the planktonic and sessile growth between one and two order of magnitude, due this inhibitor has quaternary ammonium salts which are tensioactive products, but an increase in sulphide production and sulphate consumption were also noted indicating that bacteria were active. Test with biocide neither planktonic nor sessile SRB growth was observed, and no sulphide production in the medium and just small sulphate consumption was noticed, due to this product consists of a mixture of glutaraldehyde and quaternary ammonium salts which oxide the bacterial cell.

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Tests with scale inhibitor based on polyepoxysuccinic acid showed that this product had no biocide effect because planktonic bacteria remained at a high level (there was high sulphide production and sulphate consumption in the media due to the bacterial growth obtained), but the sessile bacterial growth was 104 cells/cm2 approximately two order lower than the blank, associated with a scattering effect of the scale inhibitor which caused a lesser sessile growth. Due to all these individual effects of the chemical products; when they were used together both planktonic and sessile bacterial activity completely ceased, without sulphide production and with low sulphate consumption. Effect of chemical treatment on scales and iron. Table 6 presents the final pH and change of calcium, magnesium and iron content and precipitated iron. It can observe that the worst condition is at 100% CO2 with the lower pH (4.3), highest iron concentration (Fe++: 36.9 mg/L), and moderate precipitation of calcium and magnesium. The better condition is when the SPW + 10% SRB + 10%CO2 is treated with a commercial package of chemical treatment where the pH is acid (5.7). Under this condition was obtained the highest calcium and magnesium solubility due to the action of scale inhibitor. In general the pH in the others tests was kept within an acid range (5.7-5.8), due to the continuous addition of CO2 to the medium in order to maintain anaerobic conditions in the reactor, and to simulate plant conditions related to the coexistence of SRB and CO2. Iron in the medium was reduced as the mass loss of coupons was decreased by the use of different chemical treatments. However, a higher amount of iron in the medium was observed in tests with scale inhibitor compared to the untreated test. This effect is associated to the dispersing effect of the inhibitor of scales and deposits which permitted to maintain the ferrous ions in solution. The highest precipitation of calcium and magnesium is observed in the tests without chemical treatment or using corrosion inhibitor alone, due to the scaling trend of produced water by the high content of calcium and magnesium ions combined with the continuous addition of CO2, which makes these ions precipitate as carbonates or sulphate5. Tests with scale inhibitor showed an increase in calcium and magnesium ions in solution, associated with the dispersing effect of the polyepoxysuccinic acid, which avoid the scales despite the high content of calcium, magnesium, sulphates and carbonate ions in the produced water. It should be noted that sulphate reduction in the medium was mostly associated with the sulphate dissimilation process carried out by SRB during growth. However, a part of sulphate also precipitates with the calcium in the medium. This explains why in tests with scale inhibitor alone, the sulphate content was slightly higher than in other tests with bacterial growth. Tests with biocide showed that this product (glutaraldehyde and quaternary ammonium salts) also kept a larger amount of calcium and magnesium ions dispersed in the medium, due to its surfactant effect. Effect of SRB, CO2 and chemical treatment on corrosion of carbon steel. Table 7 presents the effect of SRB, CO2 and chemical treatment on mass loss, it standard deviation and increase in pit density of carbon steel. In the absence of CO2 and SRB both general and localized mass loss was low (5.4 mg) and 0 pits/mm2 respectively but in the presence of CO2 or SRB it can be seen that both mass loss and localized pitting corrosion increase; however, with SRB the susceptibility to localized pitting corrosion was higher than that in the presence of CO2 alone. The simultaneous presence of both SRB and 10% CO2 synergistically increased both mass loss and localized pitting corrosion of carbon steel at 23.9 mg and 3.5 pic/mm2 respectively. Mass

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loss was 17.3 mg lower than the blank, associated with the protective effect of the inhibitor. The biocide reduced the mass loss in 13.1 mg due to the elimination of planktonic and sessile SRB, and with the scale inhibitor the mass loss was 4.3 mg lower than the blank, confirming the low function of this product as a corrosion inhibitor. The lowest mass loss was obtained in the tests where the chemical products were used together by the synergistic effect of them. Efficiency of the chemical treatment. Table 8 presents the efficiency of the chemical treatment in synthetic produced water with SRB and CO2. Comparing with tests without chemical treatment (Test A) the findings show that:

Tests with corrosion inhibitor (Test B) showed that this product had the following efficiencies: 72% of reduction in mass loss, 19% in control of SRB planktonic and 25% in control of SRB sessile, 10 % in control of calcium scales and 29% in control of magnesium scales. This behavior showed a low global efficiency (35%) of all the problems in the medium.

Tests with biocide (Test C) showed that this product had the following efficiencies: 55% of reduction in mass loss, 100% in control of planktonic and sessile SRB, 50% in control of calcium scales and 65% in control of magnesium scales. This behavior showed an intermediate global efficiency (72%) of all the problems in the medium.

Tests with scale inhibitor (Test D) showed that this product had the following efficiencies: 18% of reduction in mass loss, 6% in control of planktonic SRB, 33% in control of sessile SRB, 93% in control of calcium scales and 93% in control of magnesium scales. This behavior showed a low global efficiency (48%) of all the problems in the medium.

Tests with corrosion inhibitor and biocide (Test E) showed a synergistic effect with the following efficiencies: 86% of reduction in mass loss, 100% in control of planktonic and sessile SRB, 50% in control of calcium scales and 54% in control of magnesium scales. This behavior showed an intermediate global efficiency (78%) of all the problems in the medium.

Tests with corrosion inhibitor, biocide and scale inhibitor together (Test F) showed a synergistic effect with the following efficiencies: 90% of reduction in mass loss, 100% in control of planktonic and sessile SRB, 97% in control of calcium scales and 99% in control of magnesium scales. This combination of products showed higher global efficiency (96%) to control all the problems in the medium.

The product with a higher contribution to the Integral Chemical Treatment Efficiency (CTE) is the biocide.

Morphological attack. The maximum pitting density was observed in tests without chemical treatment and the average pitting depth detected with a laser profilometer was 48 µm in test without chemical treatment and 41 µm in test with scale inhibitor equivalent to a maximum pitting corrosion rate of 172 and 147

mpy respectively, which represents a severe pitting corrosion ( 15 mpy). Photomicrographs with an optical microscope at magnifications of 5X and secondary electron (SE) images taken with a scanning electron microscope (SEM) at magnifications of 200X showed the type of corrosion damage and was used to determine the average diameter of pits formed by the different tests (Figure 2). The most extensive damage by pitting occurred in tests where a significant growth of SRB was obtained; the pitting density was also higher.

CONCLUSIONS

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1. Simultaneous use of quaternary ammonium salts working as film amines, a mixture of glutaraldehyde and quaternary ammonium salts and polyepoxysuccinic acid at 30, 200 and 10 ppm respectively can minimize the aggressiveness of a produced water with 108 cells/mL of SRB and 10% CO2.

2. The presence of 10% CO2 or 10% SRB in produced water can increase mass loss in 2 and 3 orders of magnitude respectively, whereas CO2 and SRB together increase mass loss in 5 orders of magnitude, which shows a synergistic effect of these two additive factors.

3. In the laboratory was confirmed that the aggressiveness of the produced water appears as pitting with average diameter of 50 µm and 48 µm of depth (172 mpy) generated mainly by SRB, with a mass loss of 23.9 mg (3.2 mpy) and further showed precipitation of calcium and magnesium salts and high presence of sessile SRB (106 cel/cm2) similar to the field.

4. CO2 concentration above 10% which produced pH≤ 5.5 inhibits the growth of planktonic and sessile SRB, so the risk of MIC by SRB is minimal when the CO2 concentration is greater than 10%, but increases the risk of sweet corrosion.

5. The exopolymer generated by SRB may decrease initially uniform corrosion rate of carbon steel but once the biofilm is established and the interaction of H2S (biotically generated by the bacteria) is initiated, the mass loss is increased due to pitting corrosion.

6. Planktonic SRB Growth related to the sulphides production and sulphates consumption established that these bacteria may be kept in a stationary phase of high growth with minimal sulphate concentration.

REFERENCES

1. M.B. Kermani, L.M. Smith, A Working Party Report on CO2 Corrosion Control in Oil and

Gas Production: Design Considerations, (London, GB: European Federation of Corrosion Publications, Number 23, 1997), p. 6-17.

2. S. Papavinasam, A. Doiron and R. W. Revie, Corrosion 66, 3 (2010): p. 035006-035006-11.

3. F. Kemmer, J. McCallion, Manual del Agua su Naturaleza, Tratamiento y Aplicaciones, (Nalco Chemical Company, Tomo III, Edición McGraw Hill, 1989), p. 43-1 – 43-19.

4. J. K. Fink, Oil Field Chemicals, (Burlington, MA: Elsevier Science, 2003), p. 67-107.

5. P.R. Roberge, Corrosion Inspection and Monitoring, (Hoboken, NJ: John Wiley Sons, 2007), p. 233-301.

6. M. Kutz, Handbook of Environmental Degradation of Materials, (Norwich, Connecticut: William Andrew Publishing, 2005), pp 3-22.

7. M.J. Hernández, G. Zabala, N. Ruiz, C. Juarez, R. Garcia, A. Padilla, Electrochimica Acta 49, (2004): p. 4295-4301.

8. M. Rzeczycka, M. Blaszcyk, Polish Journal of Environmental Studies 14, 6 (2005): p. 891-895.

9. H.A. Videla, Manual of Biocorrosion, (Boca Ratón, FL: CRC Press, 1996), p. 1-254. 10. S. Watkins Borenstein, Microbiologically influenced corrosion handbook, (Abington,

Cambridge: Woodhead Publishing Ltd, 1994), p. 1-26. 11. R. Javaherdashti, Microbiologically Influenced Corrosion: An Engineering Insight,

(Springer, 2008), p. 29-155. 12. J. G. Stoecker, A practical Manual on Microbiologically Influenced Corrosion, Second

Edition, Volume 2, (Houston, TX: NACE International, 2001), p. 1.1-1.7. 13. G. Kobrin, A practical Manual on Microbiologically Influenced Corrosion, (Houston, TX:

NACE International, 1993), p. 1-111.

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14. R. W. Revie, H. H. Uhlig, Uhlig’s Corrosion Handbook, Third Edition, (Hoboken, NJ: John

Wiley Sons, 2011), p. 229-243, 589-599, 1021-1032. 15. V.S. Sastri, Corrosion Inhibitors Principles and Applications, (Baffins Lane, Chishester:

John Wiley & Sons, 1998), p. 25-191. 16. B.P. Boffardi, Corrosion Inhibitors in the Water Treatment Industry, In: Corrosion

Fundamentals, testing, and Protection, ASM Handbook, Vol. 13A (Materials Park, OH: ASM International, 2003), p. 891-906.

17. A.G. Ostroff, Introduction to Oilfield Water Technology, 2nd Edition (Houston, TX: NACE International,1979), p. 17.

18. D.P. Pope, Pipe Line & Gas Industry, (1997): p. 23-25. 19. J. Busch, R. Webb, G. Jenneman, “Evaluating corrosion inhibitors as a means to control

MIC in produced water”, CORROSION 2010, paper no. 10256. (Houston, TX: NACE International, 2010), p. 1-15.

20. Q. Amir, M. Upreti, M. Singh, S. Dubey, “Performance of corrosion inhibitors used in underground petroleum product pipeline under microbial influenced corrosion risk”, CORROSION 2010, paper no. 10222. (Houston, TX: NACE International, 2010), p. 1-6.

21. A. Al Hashem, J. Carew, “The synergistic / antagonistic effect of water treatment chemicals on corrosion inhibition of carbon steel in the water injection system of west Kuwait oil fields”, CORROSION 2005, paper no. 05279. (Houston, TX: NACE International, 2005), p. 1-15.

22. R. Prasad, “Chemical treatment options for hydrotest water to control corrosion and bacterial growth”, CORROSION 2003, paper no. 03572. (Houston, TX: NACE International, 2003), p. 1-14.

23. Freiter E.R., Corrosion 48, 4 (1992): p. 266-276. 24. TM0 194-04, “Standard Test Method. Field Monitoring of Bacterial Growth in Oilfield

Systems” (Houston, TX: NACE International, 2004). 25. ASTM D1141-98, “Standard Practice for the Preparing of Substitute Ocean Water” (West

Conshohocken, PA: ASTM International, 1998). 26. S. Papavinasam, R.W. Revie, M. Attard, A. Demoz, K. Michaelian, Corrosion 59, 10

(2003): p. 897-912. 27. ASTM G170-06, “Standard Guide for Evaluating and Qualifying Oil Field and Refinery

Corrosion Inhibitors in the Laboratory” (West Conshohocken, PA: ASTM International, 2006).

28. ASTM G184-06, “Standard practices for Evaluating and Qualifying Oil Field and Refinery Corrosion Inhibitors Using Rotating Cage” (West Conshohocken, PA: ASTM International, 2006).

29. ASTM G202-09, “Standard Test Method for Using Atmospheric Pressure Rotating Cage” (West Conshohocken, PA: ASTM International, 2009).

30. ASTM G1-03, “Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens” (West Conshohocken, PA: ASTM International, 2003).

31. ASTM G31-72, “Standard Practice for Laboratory Immersion Corrosion Testing of Metals” (West Conshohocken, PA: ASTM International, 2004).

32. ASTM G16-95, “Standard Guide for Applying Statistic to Analysis of Corrosion Data” (West Conshohocken, PA: ASTM International, 2010).

33. ASTM G46-94, “Standard Guide for Examination and Evaluation of Pitting Corrosion” (West Conshohocken, PA: ASTM International, 2005).

34. TM0374-2007, “Item No. 21208. Laboratory Screening Tests to Determine the Ability of Scale Inhibitors to Prevent the Precipitation of Calcium Sulphate and Calcium Carbonate from Solution for Oil and Gas Production Systems” (Houston, TX, NACE International, 2007)

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Average values in Tests with SRB

Average values in Tests with SRB+CO2

FIGURE 1: Correlation between SRB growth curve and sulphide, iron and sulphate content in synthetic produced water with 10 % inoculum under dynamic conditions

with and without CO2

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A. Photomicrograph with an optical

microscope at magnifications of 5X B. Secondary electron (SE) image with

SEM at magnifications of 200X

FIGURE 2: Photomicrograph with optical microscope and scanning electronic microscope

TABLE 1 Chemicals used for treatment of synthetic produced water with SRB and CO2 Product Active Ingredient Recommended

Dosage (ppm)

Used Dosage (ppm)

pH

Corrosion Inhibitor Quaternary ammonium salts acting as film amine

5 - 30 30 7.5

Biocide Glutaraldehyde with quaternary ammonium salt

20 - 200 200 4.3

Scale Inhibitor Polyepoxysuccinic acid 1 - 10 10 12.8

Table 2

Equations used to calculate synergistic effect of chemicals used for treatment of synthetic produced water in the presence of SRB and CO2

Mass Loss Reduction - MLR (%) Planktonic SRB Reduction - PBR (%)

Sessile SRB Reduction - SBR (%)

Calcium solubility Increase (CSI) Magnesium solubility Increase (MSI)

36

,

,1100*

ChemicalNo

ChemicalChemicalNo

X

XXXR

45

,max,

,2100*

ChemicalNoChemical

ChemicalNoChemical

YY

YYYI

X: Mass loss (ML), Planktonic SRB (PB) and Sessile SRB (SB) Y: Calcium (C) and Magnesium (M) concentration R: Reduction I: Increase

CTE (%) = Y MLR *MLR + YPBR*PBR + YBSR*BSR + YCSI*CSI+YMSI*MSI (3) CTE (%): Chemical Treatment Efficiency YMLR (Fraction): Mass Loss Reduction Fraction= 0.28 YPBR (Fraction): Planktonic SRB Reduction Fraction = 0.13 YBSR (Fraction): Sessile SRB Reduction Fraction = 0.22 YCSI (Fraction): Calcium solubility Increase Fraction = 0.19 YMSI (Fraction): Magnesium solubility Increase Fraction = 0.18 Classification Criteria for chemical treatments: CTE < 70%: Low Efficiency 70% < CTE <90%: Media Efficiency CTE ≥ 90%: High Efficiency

0.5 mm

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Table 3 Water composition

Parameter Average field

Produced Water (mg/L)

Synthetic Produced Water (mg/L)

pH 6.9 6.9 0.1

Sulphate 191 205 11

Calcium 11920 11770 423

Magnesium 1522 1614 95

Iron 1.8 <1.1

Chloride 36873 37872

SRB planktonic (cells/mL) 106 – 10

8 10

6 – 10

8

SRB sessile (cells/cm2) 10

4 10

4-10

6

TABLE 4

SRB growth and sulphide, iron and sulphate content in synthetic produced water with 10 % inoculum under dynamic conditions with and without CO2

Average values and standard deviation in Tests with SRB

0 24 48 72 96

Valor Valor Valor Valor Valor

Sulphate (mg/L) 163.0 12.7 145.5 0.7 67.0 2.8 1.6 0.2 1.5 0.2

Sulphide (mg/L) 6.6 0.0 11.2 4.8 16.7 1.8 10.6 3.3 8.2 4.0

Iron (mg/L) 1.1 0.0 2.1 0.3 2.4 0.2 4.2 1.8 14.2 0.4

Average values and standard deviation in Tests with SRB + CO2

0 24 48 72 96

Valor Valor Valor Valor Valor

Sulphate (mg/L) 192.5 2.1 49.5 17.7 1.3 0.0 1.3 0.0 1.3 0.0

Sulphide (mg/L) 12.9 5.0 15.2 3.4 19.9 6.4 7.9 3.0 5.6 3.4

Iron (mg/L) 1.1 0.0 4.3 0.2 9.9 2.9 18.5 2.1 26.4 4.7

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TABLE 5 Effects of CO2 and Chemical Treatment on Planktonic and Sessile Growth, sulphide production and sulphate consume

Test ID

% SRB*

% CO2**

Chemical Treatment

(mg/L) Inoculum (cells/mL)

Average Planktonic SRB (cells/mL)

Sessile SRB

(cells/cm2)

Average

Sulphide Production

(1) Average

Sulphate Consume

(2) Average

CI B SI Initial Average Final Average Final (mg/L) (mg/L)

1 0 0 0 0 0 0 0

0 0

0 0

0 0

0 0

3 3

2 0 0 0 0 0 0 0 0 0 0 3

3 0 10 0 0 0 0 0

0 0

0 0

0 0

0 0

3 5

4 0 10 0 0 0 0 0 0 0 0 7

5 10 0 0 0 0 10 9

10 8 -10

9

10 8

10 7 -10

8

10 8

10 7 -10

8

10 6

10 6 -10

7

11.4 10.1

153 162

6 10 0 0 0 0 10 8 10

7 10

7 10

7 8.8 170

7 10 100 0 0 0 10 8 10

8 10

7 10

7 0 0 0 0 na na 5 5

8 10 50 0 0 0 10 10

10 10

10 8 10

8 10

5 10

5 0 0 na na 16 16

9 10 25 0 0 0 10 8 10

8 10

7 10

7 10

6 10

6 0 0 na na 14 14

10 10 10 0 0 0 10 9

10 9

10 8

10 7 -10

8

10 8

10 8 10

6 10

6

6.1 7.1

194 193

11 10 10 0 0 0 10 9 10

7 10

8 8.0 191

12 10 10 30 0 0 10 9

10 9

10 8

10 7 -10

8

10 5

10 5 -10

7

10 5

10 4 -10

5

4.5 4.3

170 157

13 10 10 30 0 0 10 9 10

7 10

7 10

4 4 144

14 10 10 0 200 0 10 9

10 9

10 8

10 7 -10

8

0 0

0 0

0 0

19 19

15 10 10 0 200 0 10 9 10

7 0 0 0 18

16 10 10 0 0 10 10 9

10 9

10 8

10 8

10 7

10 7 -10

8

10 3

10 3 -10

5

3.7 5.2

95 104

17 10 10 0 0 10 10 9 10

8 10

8 10

5 6.7 112

18 10 10 30 200 0 10 9

10 9

10 8

10 7 -10

8

0 0

0 0

0 0

16 10

19 10 10 30 200 0 10 9 10

7 0 0 0 3

20 10 10 30 200 10 10 9

10 9

10 8

10 8

0 0

0 0

0 0

8 12

21 10 10 30 200 10 10 9 10

8 0 0 0 15

CI: Corrosion Inhibitor B: Biocide SI: Scale Inhibitor * % volumetric of inoculum added into the medium in liquid phase used in the test **% volumetric of CO2 added on the medium in gas phase mixed with argon

12


TABLE 6 Final pH and change of calcium, magnesium and iron content and precipitated iron

Test ID

% SRB*

% CO2**

Chemical Treatment

(mg/L) Final pH

Average

Calcium Average

Magnesium Average

Iron Average

Precipitated Iron Average

CI B SI (mg/L) (mg/L) (mg/L) (mg/L)

1 0 0 0 0 0 6.9 7.0

-180 -190

-30 -24.5

7.6 7.8

2.1 1.8

2 0 0 0 0 0 7.0 -200 -19 8.0 1.5

3 0 10 0 0 0 5.2 5.3

-792 -666

-49 -41

26.3 24.3

3.8 6.1

4 0 10 0 0 0 5.3 -539 -33 22.2 8.3

5 10 0 0 0 0 6.7 6.6

-232 -215

-37 -32

12.8 13.1

6.5 8.5

6 10 0 0 0 0 6.4 -197 -27 13.3 10.4

7 10 100 0 0 0 4.3 4.3 -465 -465 -46 -46 36.9 36.9 1.0 1.0

8 10 50 0 0 0 5.2 5.2 -343 -343 -48 -48 25.8 25.8 6.7 6.7

9 10 25 0 0 0 5.4 5.4 -447 -447 -56 -56 12.8 12.8 12.3 12.3

10 10 10 0 0 0 5.9 5.8

-751 -836

-96 -113

22.0 25.3

23.7 21.9

11 10 10 0 0 0 5.7 -921 -130 28.6 20.1

12 10 10 30 0 0 5.8 5.8

-696 -705

-71 -71

10.2 9.7

2.3 2.4

13 10 10 30 0 0 5.8 -714 -70 9.2 2.5

14 10 10 0 200 0 5.7 5.8

-239 -187

-19 -18

19.3 19.8

0 1.0

15 10 10 0 200 0 5.8 -135 -16 20.2 1.9

16 10 10 0 0 10 5.7 5.7

455 384

17 24

35.8 33.6

2.9 4.5

17 10 10 0 0 10 5.7 313 31 31.3 6

18 10 10 30 200 0 5.7 5.7

-153 -181

-29 -34

6.7 7.2

0 0.2

19 10 10 30 200 0 5.7 -208 -38 7.7 0.4

20 10 10 30 200 10 5.7 5.7

474 429

30 32

4.9 3.9

0 0.0

21 10 10 30 200 10 5.7 384 34 2.9 0 CI: Corrosion Inhibitor B: Biocide SI: Scale Inhibitor * % volumetric of inoculum added into the medium in liquid phase used in the test **% volumetric of CO2 added on the medium in gas phase mixed with argon

13


14

TABLE 7 Effect of SRB, CO2 and Chemical Treatment on Mass Loss and Localized Pitting Corrosion

Test ID

% SRB

% CO2

Chemical Treatment

(mg/L) Mass Loss*

Average Standard Deviation

Average Change in Pit density

Average

CI B SI (mg) (mg) (pits/mm2)

1 0 0 0 0 0 5.4 5.4

0.9 0.7

0 0.0

2 0 0 0 0 0 5.3 0.5 na

3 0 10 0 0 0 15.6 15.2

0.5 1.2

0.7 0.7

4 0 10 0 0 0 14.8 1.9 na

5 10 0 0 0 0 9.3 10.7

1.5 1.4

2.6 2.6

6 10 0 0 0 0 12.0 1.3 na

7 10 100 0 0 0 19.5 19.5 0.8 0.8 na na

8 10 50 0 0 0 16.8 16.8 1.8 1.8 na na

9 10 25 0 0 0 13.1 13.1 1.1 1.1 na na

10 10 10 0 0 0 22.9 23.9

0.3 0.9

3.5 3.5

11 10 10 0 0 0 24.9 1.5 na

12 10 10 30 0 0 6.8 6.6

0.6 0.9

0 0.0

13 10 10 30 0 0 6.4 1.1 na

14 10 10 0 200 0 9.9 10.8

0.4 1.0

0 0.0

15 10 10 0 200 0 11.6 1.5 na

16 10 10 0 0 10 19.9 19.6

1 0.8

2.5 2.5

17 10 10 0 0 10 19.2 0.5 na

18 10 10 30 200 0 3.6 3.6

1.1 1.1

0 0.0

19 10 10 30 200 0 3.2 1 na

20 10 10 30 200 10 3.0 2.5

0.1 0.4

0 0.0

21 10 10 30 200 10 2.0 0.7 na

na: Not Available

14


15

Table 8 Efficiency of chemical treatment in synthetic produced water with SRB and CO2

Test ID

Chemical Treatment

(mg/L)

Mass Loss (mg)

Reduction in mass loss

(mg)

Planktonic SRB (cel/mL)

Reduction in

Planktonic SRB

Sessile SRB

(cel/cm2)

Reduction in Sessile

SRB Ca

(mg/L)

Calcium Solubility Increase

Mg (mg/L)

Magnesium Solubility Increase

Chemical treatment Efficiency

IC B II Final RML (%) Inicial Final RPB (%) Final RSB (%) CSI (%) MSI (%) CTE (%)

A 23.9 - 108 10

8 - 10

6 - -836 - -113 - -

12 30 0 0 6.8 72 108 10

5 38 10

5 17 -696 10.7 -71 28.6 36

13 30 0 0 6.4 73 107 10

7 0 10

4 33 -714 9.3 -70 29.3 35

14 0 200 0 9.9 59 108 0 100 0 100 -239 45.6 -19 63.9 72

15 0 200 0 11.6 51 107 0 100 0 100 -135 53.5 -16 66.0 71

16 0 0 10 19.9 17 108 10

7 13 10

3 50 455 98.5 17 88.4 52

17 0 0 10 19.2 20 108 10

8 0 10

5 17 313 87.7 31 98.0 43

18 30 200 0 3.6 85 108 0 100 0 100 -153 52.1 -29 57.1 79

19 30 200 0 3.2 87 107 0 100 0 100 -208 47.9 -38 51.0 78

20 30 200 10 3.0 87 108 0 100 0 100 474 100.0 30 97.3 96

21 30 200 10 2.0 92 108 0 100 0 100 384 93.1 34 100.0 96

Average

Test ID

Chemical Treatment

(mg/L)

Mass Loss (mg)

Reduction in mass loss

(mg)

Planktonic SRB (cel/mL)

Reduction in

Planktonic SRB

Sessile SRB

(cel/cm2)

Reduction in Sessile

SRB Ca

(mg/L)

Calcium Solubility Increase

Mg (mg/L)

Magnesium Solubility Increase

Chemical treatment Efficiency

IC B II Final RML (%) Inicial Final RPB (%) Final RSB (%) CSI (%) MSI (%) CTE (%)

B 30 0 0 6.6 72 107-10

8 10

5-10

7 19 10

4-10

5 25 -705 10 -71 29 35

C 0 200 0 10.8 55 107-10

8 0 100 0 100 -187 50 -18 65 72

D 0 0 10 19.6 18 108 10

7-10

8 6 10

4 33 384 93 24 93 48

E 30 200 0 3.4 86 107-10

8 0 100 0 100 -181 50 -34 54 78

F 30 200 10 2.5 90 10 8 0 100 0 100 429 97 32 99 96

15


Documents

Paper No. 3749 - Corrmagnet · 2020. 4. 29. · were prepared in a Postgate B medium (PGB) containing 16,000 mg/L of chlorides according to the procedures described in NACE TM0194.24