Comparison of sulphide corrosivity of sulphate-and non-sulphate

Materials and Corrosion 2011, 62, No. 9999

DOI: 10.1002/maco.201106298

Comparison of sulphide corrosivity of sulphate- and non-sulphate-reducing prokaryotes isolated from oilfield injection water ´ and D. A. Moreno* Z. Duque, J. R. Ibars, M. I. Sarro The microbiologically influenced corrosion (MIC) of water injection systems by sulphate-reducing prokaryotes (SRP) has caused many problems in the oil industry. These prokaryotes produce H2S, which reacts aggressively with steel and is thus widely considered to be the main cause of bacterial corrosion of industrial oil equipment. However, current microbiological treatments and controls have not taken into account other groups of sulphidogenic prokaryotes, which also produce H2S or its derivatives and with the same adverse effects of MIC. In the present work, sulphidogenic prokaryotes were isolated from water injection systems and identified by DNA sequencing. The identified species included sulphate-reducing Desulfovibrio termitidis and non-sulphate-reducing Escherichia coli. Biocorrosion tests were carried out on API 5L grade X65 carbon steel. Electrochemical impedance spectroscopy, polarisation resistance, open circuit potential and weight loss were carried out. Steel corrosion resulting from the production of the metabolite H2S by SRP and non-SRP was observed, with sulphide generation by SRP much greater than that by non-SRP. These results confirm the need to investigate and consider the role of not only SRP but also non-SRP in order to improve the control over bacterial corrosion of oil-industry equipment.

1 Introduction In the 1980s, microbiologically influenced corrosion (MIC) was internationally recognised as the cause of serious problems in the oil industry [1], accounting for 50–90% of all localised corrosion and 30% of the total cost of corrosion. In MIC, the culprit microorganisms are mainly sulphate-reducing prokaryotes (SRP), but efforts aimed at their control have been largely unsuccessful and MIC continues to be a recurrent problem. Magot et al. [2] and Crolet and Magot [3] detected H2Sproducing non-SRP strains in the corrosion products found in crude-production water pipelines in Africa, highlighting the capacity of these microorganisms to produce significant amounts of H2S and organic acids from thiosulphate and peptides, which ´, D. A. Moreno Z. Duque, J. R. Ibars, M. I. Sarro ćnica de Madrid, Departamento de Ingenierıá y Universidad Polite ćnica Superior de Ingenieros Ciencia de los Materiales, Escuela Te ´ Gutie ´rrez Abascal 2, E28006 Madrid (Spain) Industriales, Jose E-mail: [email protected] ´ M. I. Sarro ń Sobre la Evolucio ń Humana (CENCentro Nacional de Investigacio IEH), Paseo Sierra de Atapuerca s/n, E-09002 Burgos (Spain)

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for some bacterial species are the only source of carbon and energy. Additionally, H2S is responsible for souring (increased sulphide concentrations) in oil reservoirs. The importance of sulphide generation in MIC by non-SRP strains was also described by Lie et al. [4]. These results point to the relevance of identifying H2Sproducing anaerobic groups (non-SRP) and assessing their influence, together with that of SRP, on corrosion processes. However, to date, there have been few published studies on nonSRP strains as agents of MIC and thus their importance to the control of this type of corrosion has been largely ignored. Here we present the results of a study of MIC by strains of SRP and nonSRP isolated from the injection water used in secondary crude recovery processes. Conventional microbiological, molecular biological, electrochemical and gravimetric techniques were applied to determine the relative influence of these strains on MIC.

2 Materials and methods The study was divided into three phases: 1) sampling of oil-related water and detection of H2S-producing prokaryotes; 2) isolation

ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1

2

´ and Moreno Duque, Ibars, Sarro

and identification of SRP and non-SRP; and 3) determination of the corrosivity of carbon steel exposed to the isolated strains. 2.1 Sampling of oil-related water and detection of heterotrophic mesophilic H2S-producing prokaryotic groups H2S-producing strains were isolated in samples of oil-related water used in secondary crude recovery processes in the state of Zulia (Venezuela). These water samples were collected from two of the industry’s largest plants in western Venezuela, both of which receive water from different oil production wells. Microbiological analysis was carried out by incubating the water in selective culture media allowing the detection of H2Sproducing strains, using modified Postgate B [5] (KH2PO4 0.5 g/L, NH4Cl 1.0 g/L, CaSO4 1.0 g/L, MgSO4 7H2O 2.0 g/L, sodium lactate 50% 5.5 mL/L, yeast extract 1.0 g/L, ascorbic acid 0.1 g/L, thioglycollic acid 80% 0.1 mL/L, FeSO4 7H2O 0.5 g/L) for SRP and a peptone/meat extract medium (peptone 3.0 g/L, NaCl 1.5 g/L, meat extract 5.0 g/L) for heterotrophic non-SRP, according to the NACE TM0194-2004 standard test method [6]. The use of a peptide-rich medium without compounds useable in SRP respiration (sulphate and lactate) guaranteed the differential metabolic activities of these bacterial groups. Media de-aerated with high-purity N2, in order to generate anoxic conditions, and with the pH adjusted to 7.3 0.2 were separately dispensed into anaerobiosis vials. A carbon steel nail was then placed inside the culture vials. The attack of bacterial H2S on steel generates black-coloured FexSy products [7], thus allowing visual detection of H2S formation. In addition, the nails are important for bacteria cultured in peptone/meat extract medium, since it does not contain ferrous salts. The culture vials were sterilised in an autoclave at 121 8C for 15 min. 2.2 Isolation of SRP and non-SRP strains and identification by DNA sequencing Once H2S-producing bacteria were detected in the vials, they were isolated by dilution and on poured plates. The culture media were modified Postgate E [5] (KH2PO4 0.5 g/L, NH4Cl 1.0 g/L, Na2SO4 1.0 g/L, CaCl2 6H2O 1.0 g/L, MgSO4 7H2O 2.0 g/L, sodium lactate 50% 5.5 mL/L, yeast extract 1.0 g/L, ascorbic acid 0.1 g/L, thioglycollic acid 80% 0.1 mL/L, FeSO4 7H2O 0.5 g/L, agar 15.0 g/L) for SRP and peptone/ferric citrate (peptone 20 g/L, NaCl 1.5 g/L, K2HPO4 1.0 g/L, ferric citrate 0.5 g/L, agar 15.0 g/L) for non-SRP. As redox indicator, resazurin (1g/L) was added to modify Postgate E medium. Media adjusted to pH 7.0 were purged with high-purity N2 for 15 min and then autoclaved at 121 8C for 15 min. The samples were incubated under anoxic conditions at 37 8C for 21 days. The isolated black colonies were subsequently inoculated in peptone/meat extract broth for non-SRP and modified Postgate B for SRP [5]. Sodium molybdate (NaMoO4 0.01 M) was used to determine whether the black colonies were SRP [8]. 2.2.1 PCR amplification of 16S rDNA fragments Genomic DNA of the isolated prokaryotes was extracted using the commercial product PrepMan Ultra (PE Applied Biosystems), in



Table 1. Primers used in amplification of DNA fragments for sequencing

Primers 5F 531R 385F 907R

Sequence 50 -TGGAGATTTGATCCTGGCTCAG-30 50 -TACCGCGGCTGCTGGCAC-30 50 -CGGCGTCGCTGCGTCAGG-30 50 -CCGTCAATTCCTTTGAGTTT-30

accordance with the manufacturer’s protocol. Polymerase chain reaction (PCR) was carried out in a GeneAmp PCR system 2400 (Perkin Elmer). Fragments corresponding to different nucleotide positions of the Escherichia coli 16S rDNA sequence were amplified with the forward primers 5F and 385F and the reverse primers 531R and 907R (Table 1). All reactions were carried out in 25-mL volumes and consisted of 5 mL of DNA (ca. 10–30 mg/mL), 12.5 mL of PCR Master kit 1T (1.5 mM MgCl2, 50 mM KCl, 10 mM Tris–HCl, 1.25 U Taq DNA polymerase, 0.2 mM dNTPs; Roche Diagnostics), 25 pmol of each primer, and 0.4 mM MgCl2. All PCR products were checked by electrophoresis in 1% (wt/v) agarose gels in a 1T TBE buffer (0.09 Tris–borate, 0.002 M EDTA) containing 0.5 mg ethidium bromide/mL. PCR was performed with the following thermocycling program: 7 min denaturation at 94 -C followed by 35 cycles of 1 min denaturation at 94 -C, 1 min annealing at 54 -C and 2 min extension at 72 -C, with a final extension step of 10 min at 72 -C. 2.2.2 Sequencing of 16S rDNA fragments The PCR product was purified through Microcon1 centrifugal filter devices (Millipore) and then used as template for the second PCR, carried out using the BigDye1 Terminator v1.1 cycle sequencing kit (L-7012; Applied Biosystems) with the same primers as in the first PCR. The final product was sequenced using an ABI PrismTM 310 DNA genetic analyser. Desulfovibrio desulfuricans (DSM no. 642) and Desulfotomaculum nigrificans (DSM no. 591) served as the positive controls. The obtained sequences were compared with those deposited in the European Molecular Biology Laboratory (EMBL, www.embl.org) and National Center of Biotechnology Information (NCBI, www.ncbi.nlm.nih.gov) databases using the Fasta3 and Blastn programs, respectively. Sequences were aligned using Clustal_X software v. 1.81 [9]. Phylogenetic and molecular evolutionary analyses were conducted using Molecular Evolutionary Genetics Analysis (MEGA) v 2.1 [10]. Phylogenetic trees were constructed using the neighbourjoining and unweighted pair group method with arithmetic mean (UPGMA) methods with the Jukes–Cantor model [11]. A total of 1000 bootstrapped replicate re-sampling data sets were generated.

2.3 Assessment of bacterial activity and corrosivity on API 5L grade X65 carbon steel Bacterial corrosion of API 5L grade X65 carbon steel was studied with each strain (SRP and non-SRP) in a typical electrochemical corrosion test cell. None of the media contained iron, thus

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Sulphide corrosivity of sulphate- and non-sulphate-reducing prokaryotes

66 64 97 58 98

100

99

94 93

90 100

60

100

[AJ295678] Desulfovibrio sp. JG1 [AF273083] Desulfovibrio oryzae [Z24450] Desulfovibrio longreachii [AF418179] Desulfovibrio vulgaris [M34399] Desulfovibrio vulgaris [AY362360] Desulfovibrio vulgaris [AF053752] Desulfovibrio burkinabensis [AF373920] Desulfonatronum sp. C02 Desulfotomaculum nigrificans (DSM No 591) [AB035723] Pelotomaculum thermopropionicum [AB091323] Pelotomaculum sp. [AB076610] Sporotomaculum syntrophicum [AY340810] Desulfotomaculum ruminis C01 Desulfovibrio desulfuricans (DSM No 642) [AB026550] Desulfotomaculum nigrificans

[X98407] Desulfotomaculum aeronauticum [AF053933] Desulfotomaculum putei [AF053929] Desulfotomaculum putei [AB004755] Raoultella planticola [AY319393] Escherichia coli [AY664596] Escherichia coli [AF403733] Escherichia coli

100 100

[X93147] Desulfovibrio-termitidis [X87409] Desulfovibrio termitidis [AY664595] Desulfovibrio termitidis

[AY548777] Desulfotomaculum sp. [X62176] Desulfotomaculum nigrificans [U95951] Desulfotomaculum reducens

98

62

[Y12255] Desulfovibrio termitidis

53

59 56

79 94 100

100 75 76 100

99

[AB075769] Clostridium paraputrificum [AF320283] Clostridium bifermentans [AY458851] Clostridium bifermentans [AY664597] Clostridium bifermentans [AB064872] uncultured Clostridium sp. [AY458857] Clostridium butyricum [X77676] Clostridium algidicarnis [AF127023] Clostridium algidicarnis [AJ318906] Clostridium putrefaciens [X68188] Clostridium novyi [AF502398] Clostridium sp. V13 [AY167950] swine manure bacterium

50 54 97 74 97

76

[X96965] Shigella boydii [AB075685] Escherichia coli [AY444555] Photorhabdus luminescens [AF076038] Serratia marcescens [AY604562] Clostridium bifermentans

[AY664598] Clostridium sp. [AB064814] uncultured Bacteroides sp. [X83954] Bacteroides merdae [AY664599] Bacteroides sp. [AF157056] Bacteroides sp. ASF51 [AY571962] Bacteroidetes bacterium [AB074602] uncultured Bacteroides sp.

Figure 1. Phylogenetic relationship of bacteria based on partial 16S rDNA gene sequences from samples isolated from oilfield injection water and sequenced using the primers 5F and 531R

allowing an analysis of the corrosivity directly promoted by H2S and its derivative on the exposed steel. Electrochemical studies were carried out at the same temperature and under the same anoxic conditions noted above. A saturated calomel electrode was used as reference electrode, a high-density graphite rod as counter electrode, and API 5L grade

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X65 carbon steel (C: 0.21%, Mn: 1.20%, P: 0.014%, S: 0.009%) as the working electrode. The steel was embedded in epoxy resin with an exposed flat circular face of 0.67 cm2. The exposed steel surface was treated with grade 600 sandpaper, cleaned with 100% ethanol in an ultrasound bath for 15 min and then exposed to UV light for 12 h


3

4



[X87409] Desulfovibrio termitidis

3 Results and discussion

[AJ295679] Desulfovibrio sp. JG5 [AJ295677] Desulfovibrio vulgaris [AJ295669] Desulfovibrio sp. 63

[X93147] Desulfovibrio sp.

3.1 Isolation and identification of H2S-producing prokaryotes

[AY664600] Desulfovibrio oryzae [AJ295678] Desulfovibrio sp. JG1

99

[AY664601] Desulfovibrio oryzae [AF273083] Desulfovibrio oryzae

100

[Z24450] Desulfovibrio longreachii [AY362360] Desulfovibrio vulgaris 100

[AY664602] Desulfovibrio vulgaris [Y12254] Desulfovibrio intestinalis [AF192154] Desulfovibrio desulfuricans

Figure 2. Phylogenetic relationship of bacteria based on partial 16S rDNA gene sequences from samples isolated from oilfield injection water and sequenced using the primers 385F and 907R

in order to guarantee its sterility before it was placed in the electrochemical cell. The working electrode was positioned faceup, parallel to the horizontal plane, in the electrochemical cell. As electrolyte, a modified Postgate C medium [5] without ferrous salt (KH2PO4 0.5 g/L, NH4Cl 1.0 g/L, Na2SO4 4.5 g/L, CaCl2 6H2O 0.06 g/L, MgSO4 7H2O 0.06 g/L, sodium lactate 50% 9.5 mL, yeast extract 1.0 g/L, sodium citrate 2H2O 0.3 g/L) was used for the SRP strains and a peptone/meat extract medium for the non-SRP strains. Both media were adjusted to pH 7.3 0.2, de-aerated with high-purity N2, and sterilised in an autoclave. The culture media were then inoculated, and the activity of the cultures was evaluated for 60 h. The pH and total sulphide of the cultures were determined every 12 h of incubation. Sulphide were analysed following the iodometric method of standard methods [12]. The tests were performed in quadruplicate. A Gamry Framework PC4/300 potentiostat/galvanostat/ ZRA, version 4.10, was used for the electrochemical corrosion tests. Open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), at an initial frequency of 100 000 Hz and a final frequency of 0.01 Hz with 5 steps/decade and 5 mV rms, and polarisation resistance (Rp), applied at 10 mV versus OCP at 0.16 mV/s, were determined. EIS was modelled and fitted with Zview 2.6b software. The gravimetric weight loss method was applied according to ASTM G1-90 [13] after 720 h of exposure of the carbon steel coupons to bacterial activity.

The analyses of the selective cultures detected the presence of sulphate- and non-sulphate-reducing anaerobic bacterial groups (Figs. 1 and 2). SRP generated H2S by dissimilation of the sulphate present in the different Postgate media while in nonSRP H2S production was the result of proteolysis or anaerobic fermentation. The isolated and identified strains and their homology percentages are listed in Table 2. The identified SRP belong to the genus Desulfovibrio, which has commonly been associated with MIC in oilfields [14]. All the identified SRP species showed 99% homology with the related microorganism in the database. Among the non-SRP, participation of the Enterobacteriaceae family in H2S production by the reduction of either organic or inorganic sources has been documented in the literature. In the case of E. coli, both the use of citrate and H2S production are atypical, although this species has a number of variants and in some cases the capacity to produce H2S has been attributed to E. coli K-12 [15]. In this study, the groups identified and selected for the comparative assessment of corrosivity were Desulfovibrio termitidis and E. coli, since both were extracted as predominant species from the same sample of oil-related water, indicating that they coexist in this environment. These species also had the highest percentage of homology with the sequences of the databases.

3.2 Assessment of sulphides generated by the selected strains Figure 3 displays the average curves for sulphides and for pH in the cultures of the selected strains. Total sulphide production by D. termitidis was significant, increasing from an initial value in the inoculum of 134 mg/L to 1087 mg/L after 24 h of incubation, followed by a decrease to 821 mg/L after 60 h. In cultures of E. coli, the initial sulphide concentration of 645 mg/L present in the inoculum reached a maximum of 791 mg/L after 36 h, followed by a drop after 48 h and a further slight increase after 60 h to 801 mg/L. This variability and low concentration of sulphide indicate that proteolysis is a complex enzymatic process in which other products, including other sulphides, such as mercaptans,

Table 2. Bacteria isolated and identified with access number in Blastn database (NCBI) and percentage homology with related bacteria

Bacteria isolated Desulfovibrio termitidis Escherichia coli Clostridium bifermentans Clostridium sp. Bacteroides sp. Desulfovibrio oryzae Desulfovibrio oryzae Desulfovibrio vulgaris

Sequence lenght (bp)

NCBI number

Related bacteria in NCBI [access number]

Alignment, percentage homology

532 365 344 388 390 478 441 418

AY664595 AY664596 AY664597 AY664598 AY664599 AY664600 AY664601 AY664602

Desulfovibrio termitidis [X87409] Escherichia coli [AY319393] Clostridium bifermentans [AY458851] Clostridium sp. [AF502398] Bacteroides sp. [AY949860] Desulfovibrio oryzae [AF273083] Desulfovibrio oryzae [AF273083] Desulfovibrio vulgaris [AY362360]

507/510, 99 365/365, 100 327/334, 97 384/390, 98 386/388, 99 477/479, 99 441/442, 99 416/419, 99


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1600

9

1400

8 7

1200

6 1000 5 pH

Average Total Sulfide (mg/L)


800 4 600 3 400

Sulfide D. termitidis Sulfide E. coli pH D. termitidis pH E.coli

200

2 1

0

0 0

12

24

36

48

60

Time (h)

Figure 3. Average sulphide and pH curves in media containing Escherichia coli or Desulfovibrio termitidis

characteristic of anaerobic desulphurisation, are generated [16, 17]. The pH of the media for the two species of bacteria tended to be stable, remaining in a neutral range for E. coli and somewhat more alkaline for D. termitidis. This difference is typical of products generated by bacterial metabolism in selective media, as described by reactions (1) [18] and (2) [17]: SRP

4Fe þ SO2 þ 4H2 O ! FeS þ 3FeðOHÞ2 þ 2OH

(1)

non-SRP Peptides ! CO2 ; NH4 ; amines; H2 S; H2 O; RCOOH0 s

(2)

However, HS is the most abundant anion in the neutralalkaline range and is related to the H2S dissociation rate [12].

metabolic activity. By contrast, the resistance of SRP increased with time, dropping after 36 h possibly as a result of differences in the products generated. The CPE parameters indicated the capacitive tendency of the interface, which was greater in the case of D. termitidis, as a consequence of the developed biofilm on the exposed steel. By contrast, the surface irregularity parameter (CPE-P) showed a similar tendency for the two cultures although after 48 h this parameter was highest in the E. coli culture, a finding that was associated with the greater formation of layers comprising a less irregular product, as suggested by the OCP (Table 3). In general,

105

(A)

3.3.1 Electrochemical corrosion tests Figure 4 shows the Bode curves and Fig. 5 the equivalent circuit of EIS curves obtained from exposure of the steel to the bacterial cultures. The corrosive processes promoted by E. coli or D. termitidis were the activation. Rs represents the resistance of the electrolyte; Rct is the charge transfer resistance of a uniform corrosion process; CPE simulates the interfacial activity with the behaviour of an electrical double layer capacitor (parameter CPET) and the surface irregularities of the latter (CPE-P). Tables 3 and 4 present the results of the different electrochemical parameters corresponding to the bacterial cultures, as obtained by fitting the EIS curves derived at different evaluation times, along with the corresponding polarisation resistance, obtained in DC, and the corrosion potentials. As seen in these two tables, the behaviour of E. coli (Table 3) and of D. termitidis (Table 4) could be represented by the circuit associated with activation processes, indicating continuous dynamics at the interface. Regarding the parameters of the equivalent circuits, in the non-SRP cultures, Rs was seen to decrease with time, possibly due to the increase in ionic compounds and in products promoted by

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103 102 10 -2

10 -1

10 0

101

102

103

104

105

Frequency (Hz) -75

(B) -50

theta

3.3 Assessment of corrosivity of the selected strains

|Z|

104

-25 0 10-2

10-1

100

101

10 2

103

104

105

Frequency (Hz) Figure 4. Bode curves associated with the corrosion of steel exposed to bacterial cultures. (A) Bode modulus diagram. (B) Bode phase angle diagram


5



0,18 0,16

2

Inverse of Resistances (Rct and Rp) cm /Kohm

6

0,14 0,12 0,1 0,08 0,06

1/Rp D. termitidis

1/Rp E. coli

1/Rct D. termitidis

1/Rct E. coli

0,04 0,02 0 0

Figure 5. Representative equivalent circuit proposed for the corrosion of steel exposed to bacterial cultures

Table 3. Element values of equivalent circuit, Rp and OCP at different times on API 5L exposed to Escherichia coli

Time (h) 0 12 24 36 48 60

Rs (V) 301.9 270.80 219.55 182.60 163.50 163.25

Rct CPE-T CPE-P Rp OCP (kV/cm2) (F) (kV/cm2) mV/ECS 42.84 70.09 70.10 68.38 75.06 81.27

5.1E5 7.2E5 1.1E4 1.4E4 2.2E4 2.3E4

0.75 0.85 0.83 0.85 0.90 0.92

63.6 83.3 76.1 77.2 76.7 92.8

729.3 720.6 738.7 744.4 751.9 763.1

Table 4. Element values of equivalent circuit, Rp and OCP at different times on API 5L exposed to Desulfovibrio termitidis

Time (h) 0 12 24 36 48 60

Rs (V)

Rct (kV/cm2)

CPE-T (F)

CPE-P

36.73 52.95 57.15 55.10 48.05 62.23

10 37 88 67 98 95

8.33E5 5.77E4 3.50E4 6.10E4 3.90E4 1.12E3

0.80 0.86 0.76 0.80 0.85 0.84

Rp OCP (kV/cm2) mV/ECS 6.03 39.82 110.27 88.82 96.06 66.34

718 634 648 695 691 682

12

24

36

48

60

Time (h)

Figure 6. Inverse of resistances (Rct and Rp) of steel exposed to media containing Escherichia coli or Desulfovibrio termitidis

CPE-P showed an increasing tendency, reflecting the development of the bioorganic interface and the corrosion products formed on it. A similar increase was described by other researchers, in experiments carried out in media containing SRP, confirming the formation of products that are more compact in time [19, 20]. The Rct values were below the homologous DC value represented by Rp, due among other factors to the ability of EIS to discriminate between the different impedances that participate in the corrosive process. As shown in Fig. 6, the uniform corrosivity, associated with the inverse of Rct, tended to decrease asymptotically. It should be stressed that the main processes of interest in MIC are local developments, which are aggravated in the presence of a biofilm. Indeed, in our study, localised corrosion increased with exposure time due to the formation of a bioorganic layer with products that increased the local heterogeneity. This finding was consistent with the EIS analysis. 3.3.2 Gravimetric test The Vcorr of E. coli was slightly lower than that of D. termitidis (0.500 mm/year vs. 0.846 mm/year). For similar materials exposed to SRP (isolated from different oilfields), other studies (Table 5) reported a slightly lower or similar Vcorr (0.352– 0.500 mm/year) than obtained with E. coli (non-SRP). In the

Table 5. Corrosion rates of steel coupons obtained in laboratory tests with sulphate-reducing prokaryotes (SRP) isolated from oil and gas industry

Material

SRP

Isolation place

Corrosion rate (mm/year)

Test time (h)

Reference

API XL52

Desulfovibrio vietnamensis

0.500

500

Gayosso et al. [21]

Carbon steel ASTM a366

Sulphate-reducing bacteria

0.408

1728

Hubert et al. [22]

Low allow steel

Desulfotomaculum sp.

0.352

168

API 5L X65

Desulfovibrio termitidis

Residual products sample from a gas pipeline (Mexico) Water samples from an oilfield (Canada) Oil-water mixture from a production well (Turkey) Oil-related water from a production well (Venezuela)

0.846

60


Cetin et al. [23] This study

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present work, D. termitidis had the higher corrosion rate (0.846 mm/year).

4 Conclusions Different H2S-producing anaerobic and facultative anaerobic groups are known to coexist in oil-related water from geological formations. These groups include species of the genera Desulfovibrio, Escherichia, Clostridium and Bacteroides. In the present work, Desulfovibrio termitidis and Escherichia coli, isolated from the same water sample, were found to alter the corrosion resistance of API 5L grade X65 steel, with the differences between the respective strains decreasing as exposure time progressed, in terms of the production of sulphides and of causing uniform, localised corrosion. In view of the above, in natural environments, where steel is exposed to the development of biofilms comprising different bacterial groups, the severity of localised corrosion could be high, as was observed in the EIS tests. Accordingly, both SRP and nonSRP H2S-producing groups must be considered in the microbiological monitoring and control of MIC. Since bacterial diversity is complex, detection should be focused on the aggressive metabolites of these bacteria and on their final products (FexSy), which are ultimately the promoters of MIC. Acknowledgements: We are grateful to Comunidad de Madrid (Spain) (grant 07M/0003/99), and Fondo Nacional de Ciencias y Tecnologıá (Venezuela), headed by Centro de Estudios de Corrosioń (CEC) at Universidad del Zulia (LUZ) (grant G2000001606) for financial support. Furthermore, we give special thanks to Ciro Gutie´rrez of the SIMCO Consortium for his logistical support in sampling performed at oil industry facilities.

5 References [1] R. Prasad, CORROSION/00, Paper No. 390, NACE, Houston, TX 2000. [2] M. Magot, L. Carreaul, J.-L. Cayol, B. Ollivier, J.-L. Crolet, in: Proceedings of the 3rd International EFC Worshop on Microbial Corrosion, The Institute of Materials, London 1995, pp. 293– 300. [3] J. L. Crolet, M. Magot, CORROSION/95, Paper No. 188, NACE, Houston, TX 1995. [4] T. J. Lie, W. Godchaux, E. R. Leadbetter, Appl. Environ. Microb. 1999, 65, 4611.


[5] J. R. Postgate, The Sulphate-Reducing Bacteria, 2nd Edn., Cambridge University Press, Cambridge 1984. [6] NACE Standard TM0194-2004, Field Monitoring of Bacterial Growth in Oilfield Systems, NACE, Houston, TX 2004. [7] G. B. Farquhar, CORROSION/97, Paper No. 210, NACE, Houston, TX 1997. [8] B. F. Taylor, R. S. Oremland, Curr. Microbiol. 1979, 3, 101. [9] J. D. Thompson, T. J. Gibson, F. Plewniak, F. Jeanmougin, D. G. Higgins, Nucleic Acids Res. 1997, 25, 4876. [10] S. Kumar, K. Tamura, I. B. Jakobsen, M. Nei, Bioinformatics 2001, 17, 1244. [11] T. H. Jukes, C. R. Cantor, in: H. N. Munro (Ed.), Mammalian Protein Metabolism, Academic Press, Maryland Heights 1969, pp. 21–132. [12] APHA Method 450052, Iodometric method, in: L. S. Clesceri, A. E. Greenberg, A. D. Eaton (Eds.), Standard Methods for the Examination of Water and Wastewater, 20th Edn., American Public Health Association, American Water Works Association, Water Environmental Federation, Washington, D.C., USA 1998. [13] ASTM G1-90, Standard Practice for Preparing Cleaning, and Evaluating Corrosion Test Specimens, ASTM International, West Conshohocken, Pennsylvania, USA 1999. [14] M. Nemati, G. Voordouw, CORROSION/00, Paper No. 126, NACE, Houston, TX 2000. [15] N. Harnett, L. Mangan, S. Brow, C. Krishnan, Diagn. Micr. Infec. Dis. 1996, 24, 173. [16] M. T. Madigan, J. M. Martinko, P. V. Dunlap, D. P. Clark, (Eds.), Brock Biology of Microorganisms, Pearson-Benjamin Cummings, San Francisco, California, USA 2008. [17] R. M. Atlas, R. Bartha, Microbial Ecology: Fundamentals and Applications, 4th Edn., The Benjamin Cummings Publ. Co., Redwood City, California, USA 1998. [18] E. Heitz, in: E. Heitz, H-.C. Flemming, W. Sand (Eds.), Microbially Influenced Corrosion of Materials, Springer-Verlag, Berlin, Heidelberg, New York 1996, pp. 27–38. [19] J. L. Mora-Mendoza, A. A. Padilla-Viveros, G. Zavala˜ ez J. L. Moreno-Serrano, Olivares, M. A. Gonzalez- Nuń CORROSION/03, Paper No. 3548, NACE, Houston, TX 2003. [20] F. Mansfeld, B. Little, Corros. Sci. 1991, 32, 247. [21] M. J. H. Gayosso, G. Z. Olivares, N. R. Ordaz, R. G. Esquivel, Mater. Corros. 2005, 56, 624. [22] C. Hubert, M. Nemati, G. Jenneman, G. Voordouw, Appl. Microbiol. Biot. 2005, 68, 272. [23] D. Cetin, S. Bilgic, S. Donmez, G. Donmez, Mater. Corros. 2007, 58, 841. (Received: July 27, 2011) (Accepted: September 16, 2011)

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