Paper No. 3879 - storage.dow.com.edgesuite.netstorage.dow.com.edgesuite.net/dow.com/microbial/C2014-3879_J... · test, the heat-aged samples were challenged with oil and gas field

Determining Effective Antimicrobial Treatments for Long-Term Protection of Hydrocarbon Reservoirs

Jon Raymond Dow Microbial Control 1500 E. Lake-Cook Rd Buffalo Grove, IL 60089

USA

Earl Parnell Baker Hughes Inc.

3100 State Hwy 135 N Kilgore, TX 75662

USA

Jennifer Fichter Encana Oil & Gas (USA) Inc. 370 17th Street, Suite 1700

Denver, CO 80202 USA

ABSTRACT Conventional antimicrobial treatments for hydraulic fracturing fluids, flow-back water, and produced water include chemistries such as glutaraldehyde, tetrakis-(hydroxymethyl)-phosphonium sulfate (THPS), and quaternary ammonium compounds (quats). While the rapid microbial kill efficacy of these biocides in top-side water sources are effectively demonstrated by traditional microbial enumeration methodologies, such as “bug-bottles”, the long-term potential for protection of the oil and gas reservoirs from microbial-induced damage has received limited attention. A stringent two-stage laboratory method has been developed to assess rapid and long-term biocide efficacy, ranging from the mild, top-side conditions of water sources in drilling and fracturing operations to the harsh conditions of downhole environments. Specifically, water sources used in stimulation and fracturing operations were treated with various concentrations of biocide combinations and incubated at elevated temperatures during the course of the laboratory experimental procedure. At predetermined time points during the two-month test, the heat-aged samples were challenged with oil and gas field microbial contaminants (acid-producing and sulfate-reducing bacteria) to evaluate extended biocide performance in water chemistries and temperatures that mimicked downhole environments. This paper discusses a summary of effective biocide treatments for the holistic protection of hydraulic fracturing operations from microbial contamination. Key words: hydraulic fracturing, biocides, high temperature, bacteria, downhole

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Paper No.

3879

©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

Hydraulic fracturing plays a large role in recovering energy reserves from subterranean environments and is one of the key methods used to improve and stimulate production of natural gas and hydrocarbons from unconventional and conventional oil and gas plays with very low permeability, such as tight sands and shale formations. In designing and planning a hydraulic fracturing treatment, several factors are considered for the type of fluid systems that will be used to help initiate the fractures for proppant placement within the formation. In the case of hydraulic fracturing of low permeable reservoirs, it has become prevalent in the stimulation design to use large volumes of water to obtain area coverage of the formation and increase fracture length. The water used can come from many sources and is typically obtained from water wells, rivers, lakes, ponds, chlorinated city water, flowback water and recycled produced water. Because of the large volumes required these water sources are often stored in portable frac tanks, permanent water storage tanks, lined or unlined storage ponds (pits) or inflatable storage bladders. In the majority of the scenarios, either the water used or the containment in which the water is stored is contaminated with problematic bacteria which can lead to operational issues downhole or in the surface equipment. These operational issues can include reservoir souring, microbiologically induced corrosion (MIC), iron sulfide deposition, near wellbore or surface equipment plugging and degradation of polymer frac fluid additives. In an attempt to prevent these operational issues from occurring, hydraulic fracturing fluids are commonly treated with biocides.1 Typically, the frac water biocide treatment is implemented either during the water storage process or “on the fly” at the frac equipment blender as the water is pumped downhole. The biocides most commonly used for frac water treatment are those chemistries possessing moderately fast to rapid microbial kill properties such as sodium hypochlorite, chlorine dioxide, glutaraldehyde, glutaraldehyde/quaternary ammonium compound (quat) blends, tetrakishydroxymethyl phosphonium sulfate (THPS), 2-2-dibromo-3-nitrilopropionimide (DBNPA), 2-bromo-2-nitropropane-1,3-diol (Bronopol), or 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT). While these chemistries provide good bacterial control under most surface conditions, many often have difficulty performing under the more severe physical and chemical environment encountered downhole. Specifically, the high temperatures, high salinity, low pH and high sulfide environment often encountered downhole can significantly impair or neutralize the performance of the majority of these chemistries. In addition, it is not uncommon to recover only a small percentage of the frac fluid during the flowback process, resulting in the need for thermally stable, sulfide-tolerant antimicrobial treatments that will provide long-term control over bacteria introduced during the fracturing process and the indigenous bacteria often present in the connate water from production reservoirs. In addition to the need for longer lasting biocide chemistries, the industry also requires new methodologies for biocide selection and bacterial monitoring. Currently the industry relies largely on ambient temperature kill studies where the planktonic bacteria present in the frac waters are exposed to the aforementioned biocides at various concentrations. After a distinct exposure time, bacterial culture media is inoculated to determine the relative kill performance of each antimicrobial treatment. The testing does not mimic the severe conditions encountered downhole and often results in the illusion that commonly used oilfield biocides are effective choices for the holistic protection of water/fluids used in hydraulic fracturing or other oilfield processes. This paper demonstrates a new methodology for biocide selection where the stringent downhole conditions are more closely emulated. Using the more stringent testing methodology, it was determined that a synergistic combination of a quick kill, traditional biocide with a slow-acting, long-term control biocide was required to maintain control over the bacterial populations under both surface and downhole conditions.

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EXPERIMENTAL PROCEDURE Materials Biocides The following biocide chemistries were utilized for the studies described within this document: pentane-1,5-dial (glutaraldehyde, GDA); tetrakis-(hydroxymethyl)-phosphonium sulfate (THPS); 2-hydroxymethyl-2-nitropropane-1,3-diol (THNM); cis/trans 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride (CTAC); di-n-decyl-dimethylammonium chloride (DDAC quaternary ammonium compound, DDAC quat); N-alkyl-N,N-dimethyl-N-benzylammonium chloride (ADBAC quaternary ammonium compound, ADBAC quat). Water Samples Multiple water sources were utilized as the matrices to conduct bacterial kill analyses and determine biocide performance. The water samples were obtained from distinct hydraulic fracturing operations in the United States and represent water sources commonly used to formulate fluids utilized in stimulation and shale fracturing. Microorganisms and Growth Media Bacterial species utilized in the biocide efficacy studies were isolated directly from the water samples obtained from the various hydraulic fracturing operations. The water samples (1 mL), as received in the laboratory or directly in the field, were dispensed in anaerobic microbial growth media (9mL) and incubated under anaerobic conditions at 20°C to 35°C to culture individual field consortiums of acid producing bacteria (APB) and sulfate reducing bacteria (SRB). Each organism consortium was sub-cultured (1:50) anaerobically in fresh growth media and stored under anaerobic conditions at 4°C for the duration of the study. Growth media used included Phenol Red Dextrose (PRD) for the cultivation of APBs and Modified Postgate’s B (MPB) for the cultivation of SRBs. Sample Preparation Water and Biocide Samples Following organism isolation, water samples were steam sterilized (121°C, 20 minutes) to eliminate bacterial endospores that could potentially interfere with viable microbial count measurements in subsequent steps of the evaluation. The sterilized water samples were depleted of oxygen via nitrogen bubbling and stored under anaerobic conditions for the duration of the laboratory study. Biocide stock solutions were prepared the day antimicrobial efficacy evaluations commenced. Normalized volumes (200 µL) of the various stock solutions were applied to aliquots (20 mL) of each sterilized, deoxygenated water sample to achieve the desired end-use concentration of each biocide or biocide combination. The 20 mL biocide/water samples were mixed in glass serum vials containing an air-tight septum/metal clamp to prevent sample exposure to oxygen and evaporation upon transfer to 75°C for the heat-aging portion of the experimental method. Bacterial Inoculum For antimicrobial efficacy evaluations, fresh anaerobic bacteria cultures were prepared from the field consortium stocks previously stored at 4°C. APB and SRB cultures were sub-cultured in PRD and MPB media prior (typically one day) to a required microbial challenge date (see schedule below) and

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grown to saturation at 35°C. On the day of bacterial challenges the saturated cultures were sub-cultured in fresh media and grown to late exponential growth phase. Once the desired cell count was achieved (~107 – 109 Colony Forming Units [CFU]/mL) the individual cultures were centrifuged and washed/resuspended once in an equal volume of buffered, salt solution. The washed APB and SRB cultures were then mixed together (1:1) to form a pooled APB/SRB inoculum. Antimicrobial Efficacy Evaluations Stage 1: Rapid Microbial Kill Biocide Performance (Day 0) In an anaerobic chamber, 1 mL aliquots were removed from each of the freshly prepared 20 mL water/biocide samples and challenged with the pooled inoculum of freshly prepared APB and SRB cultures (10 µL) to achieve a final bacterial concentration of ~105 to 107 CFU/mL. Rapid-kill biocide efficacy was determined by incubating the water/biocide/bacteria mixtures at room temperature (~21°C) and assessing microbial viability/kill following a contact time of 1 hour. Bacterial viability/kill counts were assessed, in triplicate, by standard serial dilution (1:10) technique in separate 96-well microtiter-plates containing PRD medium (for APB viability/kill analysis) and MPB medium (for SRB viability/kill analysis). Microtiter-plates were incubated at 35°C for 48 - 72 hours and viable microbial counts (log10) were estimated utilizing a modified most probable number (MPN) enumeration method. Stage 2: Long-term Microbial Kill Biocide Performance (Days 1 – 64) Immediately following the 1 mL aliquot removal during stage 1 of the antimicrobial efficacy evaluation, the remaining anaerobic biocide/water samples (19 mL) were transferred to a 75°C oven for heat-aging. To measure the longevity of biocide protection following exposure to high temperature, the water/biocide samples were periodically transferred (days 1, 8, 15, 22, 36, 50, and 64) from 75°C to an anaerobic chamber where aliquots (1 mL) were removed and acclimated to room temperature (~21°C). Upon aliquot removal the remaining water/biocide samples were immediately returned to 75°C heat-aging. The acclimated water/biocide aliquots (~21°C) were challenged with the pooled inoculum of freshly prepared APB/SRB cultures (10 µL) to achieve a final bacterial concentration of ~105 to 107 CFU/mL. Long-term, high-temperature biocide efficacy was determined by incubating the water/biocide/bacteria mixtures at room temperature (~21°C) and assessing microbial viability/kill following a contact time of 5 days. Bacterial viability/kill counts were assessed, in triplicate, by standard serial dilution (1:10) technique in separate 96-well microtiter-plates containing PRD medium (for APB viability/kill analysis) and MPB medium (for SRB viability/kill analysis). Microtiter-plates were incubated at 35°C for 48 - 72 hours and viable microbial counts (log10) were estimated utilizing a modified MPN enumeration method. Scoring Scale Viable APB and SRB were scored on a scale of 0 to 8 and represent the average value of triplicate experiments. Individual scores correspond to the approximate surviving population (log10 CFU/mL) of bacterial cells (i.e. a score of 4 indicates that ~104 CFU/mL viable bacterial cells were detected in a particular sample). A score of 0 indicates few to no surviving bacteria.

Score Approximate CFU/mL

0 < 50

1 5 x 101 - 5 x 102

2 5 x 102 - 5 x 103

3 5 x 103 - 5 x 104

4


4 5 x 104 - 5 x 105

5 5 x 105 - 5 x 106

6 5 x 106 - 5 x 107

7 5 x 107 - 5 x 108

8 > 5 x 108

Antimicrobial Efficacy Evaluation Setup

RESULTS

Water composition can significantly affect the microbial kill performance of biocides due to a variety of factors such as pH, salinity, metal/anion, sulfide, amine and organic content. To determine optimized biocide treatments for particular shale plays, water samples from vastly different geographic locations and sources (Table 1) were obtained and utilized in the two-stage laboratory test methodology described within the Experimental Procedures section.

Table 1 Water Sample Overview

Water sample Location Composition/Source

A United States

(Western) Blend of produced (~90%) and fresh (~10%) water sources

B United States

(Western) Blend of produced waters (water treatment facility processed)

C United States (Mid-western)

Blend of fresh (~95%) and produced (~5%) water sources

D United States 100% fresh water (river)

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(Eastern)

Non-traditional oilfield biocide combinations were selected for antimicrobial evaluations by pairing chemistries which typically demonstrate enhanced performance under conditions that mimic either the topside or downhole environment of shale fracturing operations (Table 2A). Specifically, CTAC and THNM biocide chemistries, which have traditionally been utilized for the long-term protection of water-based materials2 and are capable of maintaining antimicrobial efficacy in high temperature environments, were chosen as complementing chemistries to conventional oilfield biocides such as glutaraldehyde, quaternary ammonium compounds and THPS which display robust and rapid microbial kill in topside water sources while providing moderate to limited performance under conditions reflected in the downhole environment/hydrocarbon reservoir. To further understand the potential for non-traditional biocide combinations to provide both top-side and prolonged downhole antimicrobial protection, various ratios and concentrations of the active ingredients in each combination were evaluated (Tables 2A and 2B). Of particular interest was evaluating and determining the appropriate ratio of rapid kill (topside) and long-term protection (reservoir) biocide chemistries required for providing maximal antimicrobial protection to the water sources throughout the course of the laboratory tests. An example of the specific concentrations and ratios of GDA/CTAC and GDA/Quats utilized in the two-stage laboratory method are displayed in Table 2B. Similar concentrations and ratios were evaluated for the GDA/THNM, THPS/CTAC, and THPS/THNM combinations.

Table 2A Overview of Biocide Combinations Evaluated

Biocide 1 Biocide 2 Treatment Strategy Ratios Evaluated

GDA Quats (ADBAC/DDAC) Traditional 2:1

GDA CTAC Non-traditional 1:1 and 1:2

GDA THNM Non-traditional 1:1 and 1:2

THPS CTAC Non-traditional 1:1 and 1:2

THPS THNM Non-traditional 2:1 and 1:2

Table 2B

Examples of Biocide Ratios and Concentration for GDA/CTAC and GDA/Quats Combinations

Biocide combination (ratio)

Biocide concentration (total a.i. ppm)

Biocide concentration (individual a.i. ppm)

GDA CTAC ADBAC DDAC

GDA/CTAC (1:1)

150 75 75 0 0

200 100 100 0 0

300 150 150 0 0

400 200 200 0 0

GDA/CTAC (1:2)

150 50 100 0 0

225 75 150 0 0

300 100 200 0 0

450 150 300 0 0

GDA/Quats (2:1)

94 62.5 0 12.5 19

188 125 0 25 38

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The two-stage experimental method described in the Experimental Procedures section was utilized to determine the potential of specific biocide combinations, ratios and concentrations to rapidly decontaminate water sample A at typical top-side temperatures and provide prolonged antimicrobial activity within the water at an elevated temperature resembling the downhole environment (Figures 1 – 5). For reference, each biocide treatment was tested against APB (left columns) and SRB (right columns). Additionally, within each figure, charts A and B represent stage 1 of the test procedure (topside/surface, one hour rapid-kill analysis), whereas charts C – F represent heat-aged, prolonged (up to 64 days) antimicrobial performance (stage 2). Values in each chart depict the surviving bacterial population at particular time points and represent the average of triplicate MPN analyses.

Figure 1: Performance of various GDA/CTAC treatments for the antimicrobial protection of water sample A. MPN analysis is given following rapid-kill assessments (charts A – B) and heat-aged,

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long-term protection evaluations (charts C – F). Charts A,C,E represent evaluations against APB whereas charts B,D,F represent evaluations against SRB.

Figure 2: Performance of various GDA/THNM treatments for the antimicrobial protection of water sample A. MPN analysis is given following rapid-kill assessments (charts A – B) and heat-aged, long-term protection evaluations (charts C – F). Blue charts represent evaluations against

APB whereas red charts represent evaluations against SRB.

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Figure 3: Performance of various THPS/CTAC treatments for the antimicrobial protection of water sample A. MPN analysis is given following rapid-kill assessments (charts A – B) and heat-aged, long-term protection evaluations (charts C – F). Blue charts represent evaluations against


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Figure 4: Performance of various THPS/THNM treatments for the antimicrobial protection of water sample A. MPN analysis is given following rapid-kill assessments (charts A – B) and heat-aged, long-term protection evaluations (charts C – F). Blue charts represent evaluations against


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Figure 5: Performance of various GDA/Quat (ADBAC, DDAC) treatments for the antimicrobial protection of water sample A. MPN analysis is given following rapid-kill assessments (charts A

– B) and heat-aged, long-term protection evaluations (charts C – D). Blue charts represent evaluations against APB whereas red charts represent evaluations against SRB.

Summarized results of the antimicrobial evaluations conducted in water sample A for the 1:2 ratios of the non-traditional oilfield antimicrobial treatments and 2:1 traditional GDA/quat treatment are shown in Table 3. In accordance with the two-stage test methodology, the performance of each biocide combination/concentration was assessed by its ability to (1) rapidly decontaminate and (2) retain antimicrobial activity within the water source over a prolonged time period (64 days) at high temperature. Complete microbial kill (< 1 log10 bacterial survival), at a short contact time (i.e. 1 hour) is a typical biocide efficacy measurement used to demonstrate rapid microbial decontamination of top-side water sources and is indicated utilizing a “+/-“ scoring scale in Table 3. Due to the stringency associated with biocide heat-aging at a temperature mimicking downhole environments and the slow-acting characteristics of long-term protection chemistries such as CTAC and THNM the use of complete kill at 1 hour as the measure of success for biocide performance is not suitable for stage 2 of the test methodology. To facilitate differentiation and interpretation of stage 2 biocide efficacy, > 4 log10 bacterial kill was utilized to indicate successful long-term, heat-aged biocide performance. The bacterial challenge day where > 4 log10 bacterial kill was no longer attained is listed in Table 3. Although higher concentrations of several non-traditional biocide combinations at a 1:1 or 2:1 ratio demonstrated effective rapid microbial kill and long-term protection in water sample A (Figures 1A-D, 4A-D), the 1:2 ratios generally displayed enhanced performance at lower concentrations especially in stage 2 of the test methodology. Laboratory evaluations utilizing the two-stage antimicrobial test method were additionally conducted in water samples B, C, and D (data not shown). With the exception of water sample D, where slightly

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modified biocide concentrations were tested, the test method parameters and data analyses were identical to those conducted in water sample A. Summarized results are shown in Tables 4 – 6.

Table 3 Summary of Rapid and Prolonged Microbial Kill in Water Sample A

Biocide Treatment (ratio)

Concentration (total a.i. ppm)

APB SRB

Rapid Kill in 1 hr

Prolonged Kill (days)

Rapid Kill in 1 hr


GDA/CTAC (1:2)

150 + ≥ 64 + ≥ 64

225 + ≥ 64 + ≥ 64

300 + ≥ 64 + ≥ 64

450 + ≥ 64 + ≥ 64

GDA/THNM (1:2)

150 + 22 + 22

225 + 36 + 22

300 + 64 + 50

450 + 64 + ≥ 64

THPS/CTAC (1:2)

150 + ≥ 64 + ≥ 64

225 + ≥ 64 + ≥ 64

300 + ≥ 64 + ≥ 64

450 + ≥ 64 + ≥ 64

THPS/THNM (1:2)

150 - ≥ 64 + 50

225 + ≥ 64 + ≥ 64

300 + ≥ 64 + ≥ 64

450 + ≥ 64 + ≥ 64

GDA/ADBAC/DDAC (2:1)

94 + < 1 - < 1

188 + < 1 - < 1

Table 4

Summary of Rapid and Prolonged Microbial Kill in Water Sample B



APB SRB

Rapid Kill in 1 hr


Rapid Kill in 1 hr


GDA/CTAC (1:2)

150 + 64 + ≥ 64

225 + ≥ 64 + ≥ 64

300 + ≥ 64 + ≥ 64

450 + ≥ 64 + ≥ 64

GDA/THNM (1:2)

150 + 36 + ≥ 64

225 + 36 + ≥ 64

300 + ≥ 64 + ≥ 64

450 + ≥ 64 + ≥ 64

THPS/CTAC (1:2)

150 + 36 + ≥ 64

225 + ≥ 64 + ≥ 64

300 + ≥ 64 + ≥ 64

450 + ≥ 64 + ≥ 64

THPS/THNM (1:2)

150 + 36 + ≥ 64

225 + 36 + ≥ 64

300 + 50 + ≥ 64

450 + ≥ 64 + ≥ 64


94 + 8 + 15

188 + 8 + 15

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Table 5 Summary of Rapid and Prolonged Microbial Kill in Water Sample C



APB SRB

Rapid Kill in 1 hr


Rapid Kill in 1 hr


GDA/CTAC (1:2)

150 - 8 + 8

225 + 64 + 50

300 + ≥ 64 + ≥ 64

450 + ≥ 64 + ≥ 64

GDA/THNM (1:2)

150 + 64 + 64

225 + 64 + 64

300 + 64 + ≥ 64

450 + ≥ 64 + ≥ 64

THPS/CTAC (1:2)

150 + 64 + 15

225 + ≥ 64 + ≥ 64

300 + ≥ 64 + ≥ 64

450 + ≥ 64 + ≥ 64

THPS/THNM (1:2)

150 + 8 + 8

225 + 64 - 8

300 + ≥ 64 + 8

450 + ≥ 64 + 8


94 + 8 + 8

188 + 8 + 8

Table 6

Summary of Rapid and Prolonged Microbial Kill in Water Sample D



APB SRB

Rapid Kill in 1 hr


Rapid Kill in 1 hr


GDA/CTAC (1:2)

100 + 22 - 22

150 + ≥ 64 + 36

225 + ≥ 64 + 36

300 + ≥ 64 + 36

GDA/THNM (1:2)

100 - ≥ 64 - 50

150 - ≥ 64 - ≥ 64

225 - ≥ 64 - ≥ 64

300 + ≥ 64 - ≥ 64

THPS/CTAC (1:2)

100 - 22 - 8

150 + 64 - 36

225 + ≥ 64 - 50

300 + ≥ 64 - 64

THPS/THNM (1:2)

100 - 22 - 22

150 - 36 - 22

225 + 22 + 22

300 + 36 + 22


94 - 22 - 22

188 + 22 + 64

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CONCLUSIONS Established test methods utilized to determine oilfield biocide efficacy commonly assess the speed of kill and inability of the bacterial population to recover (i.e. complete kill) following antimicrobial application.3 While these evaluations are a critical step in the establishment of baseline information regarding the effectiveness of specific biocide chemistries in particular oilfield applications, many times the environmental conditions of the system of interest do not necessarily match the experimental test conditions resulting in false positive or negative antimicrobial efficacy results. To address these concerns for hydraulic fracturing operations, a two-stage laboratory method was designed to provide insight regarding biocide efficacy in water sources used to formulate stimulation and shale fracturing fluids throughout the water’s life-cycle from short-term, top-side containment to long-term performance in downhole environments. The first stage of the test method fundamentally replicates traditional oilfield biocide efficacy tests by determining complete bacterial kill over a relatively short time frame (1 hour) and provides a reasonable estimate of the biocide’s ability to effectively decontaminate top-side water sources/fluids prior to downhole injection. To further understand the efficacy of biocides in shale fracturing operations, the antimicrobial chemistries were subsequently subjected to prolonged heat-aging during the second stage of the laboratory test method in an attempt to reproduce an environmental condition (downhole high temperature) that can significantly impact the efficacy of biocide chemistries. Specifically, a traditional oilfield biocide treatment (glutaraldehyde plus quaternary ammonium compounds) and non-traditional biocide combinations (glutaraldehyde or THPS plus CTAC or THNM) were applied to water sources obtained from various hydraulic fracturing operations to assess biocide performance in this modified test methodology. The glutaraldehyde/ADBAC/DDAC traditional biocide treatment was generally effective at rapidly decontaminating all samples regardless of the water source/composition and the microorganisms applied under ambient temperature, surface conditions. However, the ability to protect the water samples over an extended time frame at high temperature was highly variable and greatly reduced as compared to the non-traditional biocide combinations. The combination of traditional oilfield biocide chemistries (glutaraldehyde or THPS) with traditional long-term protection chemistries (THNM or CTAC) demonstrated the best overall performance from rapid microbial kill under conditions mimicking the mild top-side environment to long-term protection from recurrent bacterial challenges under a high temperature reflective of the downhole environment. Furthermore, enhanced performance was observed with ratios weighted toward the long-term biocide in all water samples evaluated. However, the data does not imply that one particular non-traditional oilfield biocide combination, ratio and/or concentration will necessarily be the most effective treatment for application to all water sources utilized in the formulation of hydraulic fracturing and stimulation fluids. For example, whereas a combination of glutaraldehyde/CTAC or THPS/CTAC displayed the best performance in water samples A and B (Tables 3 and 4), a combination of glutaraldehyde/THNM was more effective in water samples C and D (Tables 5 and 6) which likely resulted from a variety of complex factors ranging from water source composition to the native microbial populations inhabiting a particular geographic region. These results underscore the necessity of performing in-depth biocide efficacy evaluations to optimize and customize designed antimicrobial treatments for particular water sources, microbial populations and geographical locations.

ACKNOWLEDGEMENTS

The authors would like to acknowledge Seth Rindner for his support in performing the laboratory tests and generation of data described in this paper.

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REFERENCES 1. Fichter, J.K., K. Johnson, K. French, and R. Oden, “Use of microbiocides in Barnett Shale gas well fracturing fluids to control bacteria related problems”, Proc CORROSION 2008, Paper No. 08658 (Houston, TX; NACE International, 2008). 2. W. Paulus, Microbicides for the Protection of Materials: A Handbook, 1st ed. (London, UK: Chapman & Hall, 1993), p. 68 and 85 3. NACE TM0194 (latest revision), “Field Monitoring of Bacterial Growth in Oil and Gas Systems” (Houston, TX: NACE).

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Paper No. 3879 - storage.dow.com.edgesuite.netstorage.dow.com.edgesuite.net/dow.com/microbial/C2014-3879_J... · test, the heat-aged samples were challenged with oil and gas field