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ISocietyof Petroleumnginee

SPE 29735

Biocide and Corrosion Inhibition Use in the Oil and Gas industry: Effectiveness and.—--

Potential Environmental Impacts

D.M. Brandon, J.P. Fillo, ENSR Consulting and Engineering; A.E. Morris,

B~o~n~~~trial Technologies, inc., and J.M. Evans, Gas Research InstituteCopyr tght 1995, SOc$ety o f Pet ro leum Engineers, Inc .

Thi s paper was prepared for pr esent ati on at t ha SPE/EPA Explor at ion & Product I on Enwronmental Conf erence held m Houst on, TX, U .SA. , 27-29 March 1995

Thm paper was sel ect ed for pr esent ati on by an SPE Progr am Commit tee f oll owi ng review of reformati on contai ned m an abat ract submit ted by tha aut hor (s) . Content s of t he paper ,

as pr esent ed, have not baen raviewed by the Soci et y of Petr ol em Engi neers and are subject t o cor rect ion by the author( s). The materi al, as pr asent ed, does not necessar il y r ef lect any

posdi on of t he Society of Petr oleum Engi neer s, !ts of fi cers, or members. Papers pr esent ed at SPE meetmgs are subj ect t o publi cat ion review by Edi tor ial Commit tees of the Soc#et y

of Petro leum Enginears . Permlss lon to copy is res tr ic ted to an abstrac t o f not more than 300 words. I llus trat ions may not be cop!ed. The abstrac t should mntain conspicuous acknowladgmant

of where and by whom the paper IS pr esent sd. Writ s Li br ari an, SPE, P.0, Box 833836, Richar dson, TX 75083-3636, U. S.A .,Tel ex, 163245 SPEUT

ABSTRACT

Treatment chemicals are used in all facets of thenatural gas industry (NGI) from well development

through transmission and storage of natural gas. Themultitude of chemicals used, combined with thedn.nnc nf eh~mic%l manufacturers and/or SUPPkrSUu-”1 ! “ “. w... . .. ---- . ..has lead to the availability of hundreds of possible

chemical products. Because of the widespread use ofchemical products and their numerous sources, theNGI needs access to consistent data regarding their

effectiveness and potential environmental impacts.

The objective of this work was to evaluate the

effectiveness and potential environmental impacts of

chemical products used in the NGI. This assessment

was initially focused on biocides and corrosioninhibitors and their use in the gas production, storage

and transmission facilities, The overall approach wasto obtain the necessary data on chemical use and

effectiveness directly from the oil and gas industry,supplemented with data/information obtained fromthe published literature. Five case histories of

chemical use were documented and evaluated to

assess the effectiveness of these chemicals. Potential

environmental impacts were addressed by performing

a screening environmental assessment on the use ofglutaraldehyde, a widely used biocide. Prototype

discharge scenarios were formulated and modeled toevaluate potential impacts to groundwater and surface

water.

The paper describes the basis for the study, provides

an overview of chemical use with a focus on biocides

and corrosion inhibitors, describes and assesses thespecific uses of chemicals, and presents the results ofthe environmental assessment. It was found thatvarious chemicals can be effective in treating

microbiologically influenced corrosion and souring,

but that the effectiveness of specific chemicals isdependent on the operational scenario and the site-specific conditions. Resuits of the screening

environmental assessment indicated that surface andgroundwater impacts were not significant for the

scenarios evaluated.

INTRODUCTION

Background

As natural gas wells are developed, chemicals are

applied during drilling, fracturing, completion, and

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2 BIOCIDE AND CORROSION INHIBITION USE IN THE OIL AND GAS INDUSTRY:EFFECTIVENESS AND POTENTIAL ENVIRONMENTAL IMPACTS SPE 2973

often throughout years of service. In addition,

chemicals are applied in numerous locations withinthe network of pipelines that ultimately connect theproducers to the end users. If one considers that allfacets of the NGI are subsets of a much largersystem, there is a large and diverse group ofchemical products being added to the system[l ].

The multitude of chemical ingredients used, combinedwith the literally dozens of chemical manufacturers

and/or suppliers, has lead to the availability ofhundreds of possible chemical products for use in the

NGI. Generally, the operator is concerned about

effectiveness in the intended use, potentialenvironmental and human health impacts, and cost.I- X-.—-A:-- -.. :l-L..A+- +h ~1~-1hat -e4Arne ne thaeaIrlwrrlwuuri dvalldul= w LIIf) IWUI u laL ~uul ~=%= LI ,==-

primary concerns in a concise, single-source formatis limited.

Currently available data are often incomplete and canbe contradictory, depending on the site-specific

details cf a chemical product’s use. An effmt tostandardize assessments of effectiveness andassociated impacts of various chemicals wouldprovide the NGI with a consistent basis for making

decisions about future use of these chemicalproducts.

GRI Research Program

The GRI is sponsoring a research program to assess

the issues and needs associated with the use ofchemicals in the NGI. This program is designed todetermine what chemicals are used, their properties,where and how they are used, their effectiveness, and

environmental issues associated with their use, if any.In so doing, information and data needed by the NGI

can be identified, and products to benefit the NGI canbe developed. Information on current chemical use

and practices is being oti~ained through directparticipation of NGI personnel. The initial focus of thework in this program is biocides and corrosioninhibitors.

Scope of Investigation

The overall objective of this assessment is to evaluatthe effectiveness and potential environmental impactof chemical products used in NGI operations. Thassessment was initially focused on biocides ancorrosion inhibitors, due in part, to the interest ithese topics expressed by GRI’s membership. Thprogram was also limited to storage and transmissionfacilities to take advantage of GRI’s ongoing biologica

souring research in microbiologically influenced

corrosion (MIC), microbiologically influenced souring(MIS) and microbiologically influenced fouling

(MIF)[2]. Limited toxicological information anpublished exposure limits on glutaraldehyde weracidrsccd fnr ~h~ p~~p~~~~ ~f the enVirQnrnent--”,””””” s-,impact assessment.

CHEMICAL USE IN THE NGI

The NGI is comprised of various operations from th~Alhaad tn tha wd I lStarthat p~QJ~~~pip~!ilT&~Ua!~.. ”!!! !“-” .- .,,” w,,- - -. .... .natural gas as a primary product. These operationsinclude exploration, wellhead production,

conditioning, processing, transmission/compression,storage, and distribution. The final products from thindustry, aside from pipeline-quality natural gasinclude natural gas liquids such as liquefied petroleum

gases (LPG) and natural gasoline, and byproductssuch as sulfur. The following sections of this reporprovide an overview of NGI operations.

Wellhead Production

Production operations begin with natural gas wellsDuring gas production, hydrocarbon liquids anformation water mixtures are withdrawn from

subsurface reservoirs through completed wellsIndigenous liquids and impurities found in the natura--- -, ,-a= ,11U=4-. .A.-nA.Ja~;- -.dm- tfi -,,A;A Aiffiet,ltiac iLUGIGIIIUVGU Ill Ulucl tu avulu UIIIIVUILIGQ 1

handling and processing gas and to meet pipelinespecifications. Separation of wellhead gas from freliquids such as crude oil, hydrocarbon condensatesand/or produced water is the first and most common

of the field processing operations. A fieici gatinerini. Jallh AaA -“ fi~~d

SjiSkTi tEiilS~Wk ~EiS tiCN17k WGIII i-au UI

processing facilities to a central point fo

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SPE 29735 D.M. Brandon, J.P. Fillo, A.E. Morris, and J.M. Evans 3

compression, further processing, or entry into atransmission or distribution system.

Natural Gas Conditioning

Natural gas conditioning involves the removal of

contaminants from and the addition of desirableconstituents to the natural gas stream. This includesprocesses such as gas/liquid separation, filtration,dehydration for the removal of water vapor,sweetening for the removal of sour gas constituents,and addition of methanol for hydrate pointdepression. Gas/liquid separation operations canoccur at the wellhead and at central gathering,

processing, and storage facilities. Water vapor mustbe removed from natural gas in order to preventhydrate formation and the associated blockage ofpipelines, to avoid accelerated corrosion, and to meet

a water dew point specification for a gas salescontract. Dehydration of natural gas is accomplishedby absorption (e.g., glycol contacting), adsorption

(e.g., ~~iid bed dehydi=ti~ti), and/m injecticn andrecovery of dehydration media (e.g., glycol injection).Acid-gas removal or “sweetening” is the removal ofhydrogen sulfide (HZS), or other sulfur compounds

(e.g., mercaptans, carbonyl sulfide, carbon disulfide),

and carbon dioxide (COZ) from the natural gas.Dehydration and sweetening operations, can belocated either at the wellhead or at a central facilitysuch as a aas cwocessing plant or an underground_.– ,–storage facility.

Natural Gas Processing

Natural gas processing plants are usually designed toH?-K?Ye ~n~ ~~~~v~~ ~~i~a~t~ pWdUCtS over and

above those needed to make the gas marketable.These products can include ethane, propane,

butanes, natural gasoline, and other natural gas liquidmixtures. Gas/liquid separators at the wellhead can..---..” -As -* db. k -s :- A-- -mea Adt Cenar=+innRXAJV’er rrlo~l UI 11W I leaVIGl WI I Gl I=C4 G. w PU1-LWS D

of the products into the various components ispossible through a variety of processes includingabsorption, refrigerated absorption, refrigeration,compression, adsorption, and cryogenics.

Gas processing piEi~% rK%ary ahvays ifi~cip~~ate----

-=fi,, Af th earn= nm rdinne I Ie@ at ficdfi faci!iti~eI I lal Iy UI LI 1~ ~a14& Wpel CILIWI w W“ - M. ..u. - -- . . . . ‘-,

including dehydration and sweetening processes. Thedegree to which these processes take place in the

field (near the wellhead) or at a central processingfacility is principally a matter of economics.

Transmission/Compression

Natural gas transmission systems transport natural

gas via pipeline from a processing plant or source ofsupply to one or more distribution centers or largevolume customers. These pipelines, constructedprimarily of steel, may be as large as 48 inches in

diameter and are operated at pressures up to 1,300psig. Compressor stations in natural gas transmission

systems are generally located from 40 to 130 milesapart.

Transmission lines include a number of valves for

controlling flow and may include equipment forremoving water and hydrocarbon condensates. Drips(or drip traps) can be used and are usually located ati~$.~p~~~?~~~ t~~ 9iPeii~e. p~p~i~n~~?h~? ~~n ~~

cleaned with pigs or scrapers may not include drips,but must include full-opening valves and piglaunchers/receivers. The collected liquids from drips

and scraper traps are either processed at a refinery or

processing plant or are disposed. Water andcondensates collected from inlet and/or interstageseparators at compressor stations are managed in asimilar fashion.

Underground Storage

The primary functions of natural gas storage facilities

are to equalize pressures and meet peak demandsplaced on pipelines and delivery systems.Underground storage of natural gas ‘involves theinjection of natural gas into natural rock or sandreservoirs that have suitable connected pore spaces.These are usually depleted oil and/or gas fields,

h~~e~er, water bearing sands that have never heid

hydrocarbons and salt cavities have also been

used[3].

Surface operations associated with an undergroundgas storage field may include gas/liquid separation,=fiiA- == F rnmtf I da~udrdinrlaulu-ga= Ielllwval, WV,, =,=.,”,,, gas processing, ad

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compression. These processes were previously

discussed.

OVERVIEW OF CHEMICAL USE

Chemical products are used in a wide variety of NGIoperations. Examples of chemical products used andtheir specific applications are provided in Table 1.

The majority of chemical products reported in this

study fall into the category of biocides and corrosioninhibitors. Biocides are chemical formulationsintended to kill organisms. Corrosion inhibitors are

formulations that retard corrosion processes. Someproducts contain chemicals or mixtures of chemicalsthat fall into both categories.

Chemicals that were less frequently reported includedscale inhibitors, scale removers, demulsifiers andviscosity reducers. The information on scale inhibitorswas very limited; however, it is anticipated that

additional information wiii be obtained fmml NG1sitesin the future. Also, limited information on demulsifiers,viscosity reducers and scale removers was obtainedas part of a larger treatment program involving

biocides and corrosion inhibitors.

Biocides

In the NGI, biocides are applied to prevent or mitigateMIC, MIS, and MIF. These problems occur as aconsequence of specific types of microbial

colonization on surfaces. Most biocides reduce theoverall microbial population with little specificityregarding which organisms are targeted.

MiC is a form Q?pitting-type corrosion that can result

from microbial colonization of metal sutiaces. Theproblem can occur on internal or external surfaces ofpipelines, separators, and well components.

Component failures due to MIC, unlike those fromgeneral corrosion, are often not anticipated becausethe material loss can be highly localized. The mostreliable strategy for preventing MIC is to takemeasures to prevent microbial growth. Although

treating external surfaces of buried pipelines is difficult

and subject to environmental restrictions, the internal

surfaces can be treated with biocides with minim

difficulty. Monitoring for MIC is often done using metcoupons suspended in the pipeline or sidestream teloop. Coupon retrieval and inspection for pit initiatioand microbial colonization is done on a regular basto determine if MIC is occurring in the system.

MIS is the production of H$ by viable bacteriaMicrobiologically influenced souring can result fromsulfate reduction, a metabolic process th

characterizes a broad group of bacteria referred to asulfate-reducing bacteria (SRB), or other microbiaprocesses that either reduce sulfur or degrad

biomass containing suifur. in addition, Ri$corrosive to steel at low levels (0.001 to 400 ppm) anproduces offensive odors when released to thatmosphere. As in the case of MIC, MIS ha

traditionally been mitigated using biocides to controthe offending microbes. Microbiologically influencesouring often occurs in subsurface environments sucas gas storage or production reservoirs wher

+ anaarnhi~ and amnb CI lnni@s~~~lditi~ri~are weK,al l==!uu~w,=,~=~,, .P.” *-FY. --soluble sulfate and organic carbon are present. Sinctreating subsurface geological environments involvemuch greater surface areas than in enclosed systems

the costs are higher and the success rates tendto be lower.

MIF is the accumulation of undesirable materiresulting from microbial colonization. Th

accumulated mass can consist of metal oxide

organic polymers (e.g., polysaccharides), metsulfides, sulfur, cell mass, and other productsmicrobial growth. Bacterial cells have a tendencymaintain a negative electrical charge whenenvironments of adequate nutrition, which facilitate

attachment to surfaces. When nutrient conditions alow, the charge may be reversed, which allows thorganism to mobilize to a more favorable growtenvironment[4]. This process of growth, mobilizationand reattachment can result in extensive microbiacolonization within a system or subsurfacenvironment. The resulting mass accumulation caplug or significantly reduce the flow capabilitypipelines or reduce the permeability of subsurface ga

storage or production reservoirs. AS in MIIC md Mi

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SPE 29735 i3.M. i5ranaon, J.P. Fiiio, A.E. Morris, and J.M. E;ans !5

MIF has traditionally been treated using biocides thattarget the overall microbial population.

Corrosion Inhibitors

Corrosion inhibitors are chemical additives used forreducing corrosion on internal surfaces of equipment.In the NGI survey, pipeline and well components werefound to be the primary points of application forcorrosion inhibitors. External surfaces are alsoprotected using coatings and paints, but thesemeasures also fall into the category of corrosioninhibitors as previously defined.

The most predominant form of internal corrosion ofwell and pipeline components is “wet” or

electrochemical corrosion. This form of corrosion canonly occur when there is metal in contact with anelectrolytic solution, and when simultaneous oxidationand reduction (cathodic and anodic) reactions arepossible. This type of corrosion can resuit in both

----

uniform material loss and pitting. The rate at whichmetal will corrode is dependent on the rates at which

oxidation and reduction reactions can occur in theenvironment[5]. Therefore, the fundamental strategiesfor corrosion inhibition include: 1) isolation of the

metal surface from the electrolyte, oxygen, bacteria,etc, using a film, coating or scale accumulation; or 2)limiting the rate of oxidation (and therefore, reduction)in the environment by removing the oxidant.

Biocide and Corrosion Inhibitor Case Histories

Upon review of information reeeiwd froml participantsin this investigation, it was obvious that information

had been documented to demonstrate the successorfailure of individual treatment programs, but that itshould be considered only site-specific. The most

common perception encountered was that the use ofa given product provided “some good” and to havenot used it would have allowed the situation tobecome worse. In many instances, the decision toinitiate, continue, or even discontinue a treatment

strategy was based entirely on the recommendationsof the chemical vendor. When this issue was

discussed with individual operators, it was found thatthere was a great interest in integrating case historyinformation, when possible, into the database. This

would provide objective evaluation of individualtreatment programs in terms of the conditions before

treatment, how treatment was carried out, andconditions after treatment. A prevalent opinion amongoperators was that information on strategies that donot achieve the treatment objective are equally asimportant as those that do. However, for reasons ofliability, most publishable case histories document

success rather than failure.

Two approaches were taken for compiling casehistory information. The first approach was to reviewtechnical literature and identify case histories relevantto chemical treatment in the NGI. The second

approach was to work with operators in the NGI toacquire the data necessary to develop new casehistories. The information acquired to date ispresented in this report. It is anticipated that

additional case histories will be available fordocumentation in the future.

Background and Technical Literature

A review of technical literature revealed that the vastmajority of information on efficacy of individualchemical treatment strategies was limited to

laboratory testing. While this information was helpfuland was utilized in general discussions on chemicals,only the information pertaining to actual field

applications was selected for case historydocumentation. Relatively few articles were found thatwere focused on field-documentation of thesephenomena. Five ~rtki~~ were retiiewed from theteeh~;~a! i~tera?~rethat reiate tQ field dQC!JrnQn@tkI~

of MIC and MIS and represent a small fraction ofthose which address issues generally related to MICand MIS. These five cases are summarized inTable 2.

Case i+kWk%3 Obtained FiGiil

Field Site Interactions

While investigating a variety of microbiologicallyrelated problems in the NGI opportunities to

document facts regarding the nature of problems andtreatment approaches uses w-ere encountered. in

---1

some instances, the operators have permitted theinformation to be compiled in generic format, with

company identity confidential, so that information on

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the problem, treatment, and outcome could be shared

with others. These five cases are summarized in Table3.

ENVIRONMENTAL IMPACT ASSESSMENT

Treatment chemicals are used routinely in oil and gasmng~a~i~n~.Depending on the specific chemical and

~nction, they can be applied at the wellhead, in gasprocessing/conditioning plants, in gas

transmission/compression operations, and in

underground gas storage reservoirs. Chemical usecan be in contained systems or, by design, chemicals

can be added into the system so that they migrate toachieve their intended purpose. Because chemicalresiduals can come in contact with environmentalmedia, their potential environmental impacts are ofinterest. Thus, a screening environmental assessment...!.-- --1 A-A -L.--:--l- h., a“us]rl~ =ele~l=u ~11=1ll~al= UYGAi% 1 lplG VWUIU PI WVIUU

mnla mfni Ild nrnuidta

relevant information and an overall methodology forthe evaluation of chemical use in the NGI.

In order to assess these impacts, the fate andtransport of glutaraldehyde was modeled using

anaiythi and S~rnF=~l~iytik~i 1a , ,+:mneau ULIUI la

,v.+~~~~

incorporate mechanisms such as dispersion andfirst-order degradation. The results were then used to

calculate the concentration of glutaraldehyde withinan aquifer as a function of position and time. A variety

of solutions were evaluated for their applicability tothis study; however, only those which are extensively

cited in literature or are non-proprietary were chosen.

Flow and transport of glutaraldehyde were modeledfor selected scenarios from the following three

industry segments:

.....~....m.~.-d -+fi.m-fi V ~~n,fiire= UIIUGIUIUUIIULulay= Ie==l VW=

q production and transmission operations. produced water treatment and discharge

Model output from each impact scenario (i.e.,downgradient concentrations of glutaraldehyde afterinput to the subsurface) was evaluated by comparing

concentrations to drinking water concentrationguidance criteria developed in this section.

Development of Comparison Criteria

In order to evaluate the potential environmentaimpact of glutaraldehyde, itwas necessary to developcomparison criteria for the model. Currently, th

USEPA has not established a maximum contaminanlevel (MCL) for glutaraldehyde[6]. The MCL refers tthe maximum permissible level of a contaminantwater which is delivered to any user of a public wate

system. The following describes how publishedtoxicological and risk data were used to developdrinking water guidance criteria for glutaraldehyde.

Based on referenced toxicity data for glutaraldehydeand the drinking water concentration guidance limitfor acrolein and formaldehyde, a preliminar

concentration limit for glutaraldehyde may bestimated. The OSHA PELs for acroleinf~~rna!~~hy~~, ~n~ ~fut~~~fd~h~~~ We On the Same

order of magnitude and are based on their irritaneffects on humans. The acute aquatic toxicity rangefor glutaraldehyde are two orders of magnitude highethan acrolein. The risk-based concentration guidancefor drinking water for formaldehyde is one order om=fimi+ida hinhnr than amnlain If th~S~e~~~~ip~tt~mIllayl ,,. ””Q , ,,~, ,“, ., ,Mr, W“, V,”,, ,. ,,

of order of magnitude comparison is extended foglutaraldehyde, a reasonable range of concentrationin water would be two orders of magnitude highethan acrolein. This broad range would be 10 to 9mg/L. In order to narrow the range, a risk-base

estimate using the same order of magnitudeapproach may be used. The oral reference dose (i.ean estimate of a daily exposure level for the humapopulation that is likely to be without an appreciable

risk of deleterious effects in mg/kg/day) for acrolei

and ~ormaidenyue is 0.02 and 0.1 rng/kg/d,respectively[7]. Formaldehyde is five times higher o

appro~irnateiu a nna.half nrrie~ Of ~~(pi~u~~ inc~eaSe,, s ”. .- ..=-----

Assuming a one-half order of magnitude increase fothe glutaraldehyde oral reference dose is appropriatethe proposed value would be 0.5 mg/kg/d. ThUSEPA uses the oral reference dose to calculataction levels for hazardous constituents

groundwater.

if the estimated value of 17 mg/L is considered

mid-range of the concentration guidance range, the

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the range of concentration values based on this order

of magnitude approach would be S to 26 mg/L. This

range of estimated values for drinking waterconcentration guidance will be used in this study toevaluate impact scenario modeling of glutaraldehydereleases.

Model Selection and Results

Due to the lack of site-specific data, the resultspresented in this report are intended as a screeningtool to determine if glutaraldehyde releases for

specific scenarios warrant further evaluation to assesspotential environmental impacts. Model results would

be compared to site-specific data to provide a basisfor decision making. This comparison would include

both model calibration and sensitivity analysis. Modelcalibration would be performed by varying inputparameters within their expected or observed range ofvalues to arrive at a better fit between the calculated

and observed results. Ideally, the calibration stepwould attempt to simulate more than one set ofresults over time, so as to gain confidence in themodel’s ability to correctly predict the behavior of thegroundwater flow and transport under changing

conditions. Calibration would be considered complete

when the calculated results meet a statisticalAmnee.nf-fi+ tad finqnarnrl tn the nhcwvd data.

gooul IGQC7-VI-11, .s/-. ““J{ p-l ““ .-., ,“ -“--- --- -----

After model calibration is achieved, the model would

be run where important parameters such as hydraulicconductivity and recharge are systematicallyincreased and decreased from their calibrated values

to assess the sensitivity of the model. Predictable and

reasonable response to these changes would

demonstrate that the model is a good representationof site conditions, and a unique solution has beenfound, thus raising confidence in the use of the model

for predictive simulations.

Because of the variability in the glutaraldehydeinjection/input scenarios, three models were selectedto calculate the distribution of glutaraldehyde ingroundwater and surface water. A description of the

industry segment, source parameters and potential

source impacts are presented in Table 4. Modelm--,m-n+imne .,aa=ul I I pLIWI m pertammg

to anl Iifar andwy”, rwl -. .- ~QUrcR. --

~~~ia~!~~ were Sirn.il~r for each scenario.

Case 1: Slua Iniection of Glutaraldehvde into a Gas

A two-dimensional, analytical solution developed byHunt, 1978[8] and Wilson and Miller, 1975[9] wasused to simulate the migration of a glutaraldehydeslug injected instantaneously into an aquifer.Glutaraldehyde solutions are injected into gas storagewells to reduce the potential for sour gas production.

Mechanisms by which glutaraldehyde may beintroduced into a drinking water aquifer include

leakage along the injection well casing or through

direct discharge into a gas storage reservoir, whichalso may serve as a drinking water source.

Case 1: Discussion

The results indicate that given the most conservative

scenario (i.e., lower end of the comparison, 10percent leakage factor, six-week reaction half-life, andthe distribution of the slug seven days after injection),

the maximum glutaraldehyde concentration within theflow field is 48.3 mg/L. The peak concentration

occurs at a distance of 38 feet from the source area.With an increase in time after injection, the

concentration of glutaraldehyde decreases within the

aquifer and is attributed to spreading of the slug aswe!! as degradation. Thirty days after injection, the

maximum concentration decreases to 8 mg/L and

occurs at a distance of 150 feet from the source area.At this distance and time, the modeled concentrations

are below the lower end of the comparison criteriarange (i.e., 9 to 26 mg/L).

The results of this exercise indicate that elevatedlevels of glutaraldehyde associated with the sluginjection may occur in areas immediately adjacent tothe gas storage well and at early times after injection.

r:--- -.-1-. A--”-A-.:--t-lrs~-cxaeruegrmkuw[ I appears tc pkiy ~ minor rolein attenuating glutaraldehyde concentrations,particularly during early injection periods. This is dueprimarily to the relatively small initial leakageconcentration. For example, given the conservativescenario previously discussed, the maximum

concentrallOn reporl~U dllW / Ud)k WcRi vt.2 ~~/~, ~. . ! -- -- -- A--l ~u-. 7 4-. - ... -- CA

relative difference of approximately 10 percent.

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~~~~ ~: pr~~~~~~ w~t(y ~~~~~g~ (~~nt~~n~nfl

Glutaraldehvde) to Soil

The USEPA Multimedia Exposure Assessment Model(MULTIMED) Version 1.01[10] was used to simulateglutaraldehyde impact for Case 2. MULTIMED isavailable as shareware from the USEPAEnvironmental Research Laboratory, Office ofResearch and Development; or a re-compiled version

can be purchased from private software companies.It is the intent of the USEPA to release an updatedversion in late 1994.

Similar to Case 1, input parameters typical of adrinking water aquifer were assumed. Specifically, thiscase simulated 17 different scenarios of producedwater leakage to soil with subsequent transport to a

downgradient drinking water well.

Case 2: Discussion

The results indicated that leakage of produced water,which migrates from the unsaturated zone to the

saturated zone while undergoing degradation,nrndl Itme a ml I ltaralAah\~An finnfiantratinn nn +ha nD.Am PPIUUUU-- = ylULUl UIU=I IYU= WWl IVGI lLlaLIWl I WI I LI IQ WI UCZI

of 1.8 to 1014 mg/L at drinking water wells locatedapproximately 1/2 through 3 miles downgradient.These concentrations are well below the lower end of

the comparison criteria of 9 mg/L.

C se 3: Laaoon Fluid Leakaae (ContainingGfitaraldehvde) Throuah a Liner Under HiahGroundwater Elevation Conditions

The same input parameters were used for Case 3 asin Case 2 except the liner of the lagoon is in direct

contact with the saturated aquifer (i.e., no unsaturatedzone exists) and a slug input source of glutaraldehydewas used to simulate steady-state leakage through a

hole or stressed area of the liner, directly to the

saturated zone and to a downgradient drinking waterwell.

Cae3 : Discussion

Similar to Case 2, the results for Case 3 yieldedglutaraldehyde concentrations on the order of 10°4 to

j Q-14rng/~ ~t ~ dnwrmrar-brat chinking water w?V . . . m~.uw.w, ,.

Even at a drinking water well distance of 1/2 milfrom the source, the glutaraidehyde concentrationwas approximately 4 orders of magnitude lower thathe lower end of the comparison criteria of 9 mg/L.

Case 4: Laaoon Fluid Leakaae (ContaininGlutaraldehvde) Throuah a Liner Under Lo

Groundwater Elevation Conditions

The same input parameters were used for Case 4 ain Cases 2 and 3 except that an additiona

unsaturated zone was placed beneath the liner t

simulate fluid leakage through an unsaturated zoninto the saturated aquifer.

Case 4: Discussion

The results for Case 4 were identical to Case 3.

Case 5: Slua Iniection of Glutaraldehvde intoSurface Water Body

During the withdrawal season, produced waters ar,i#i+hA.a,.#fi ,.,;+h..I-.+,.-1 ,U-A<.-- A -+----- “---...,-:.VVILI Iulavvl I VVILI I I la~ulal yaa llulll a alul aye lGat21vul

and may be managed through treatment andischarge to a surface water body under propeNPDES permit. These produced fluids may contain

residual concentrations of glutaraldehyde resultingfrom glutaraldehyde-containing solutions injected intthe storage reservoir during the injection season.

Near-field mixing associated with a glutaraldehyde

slug injected instantaneously into a surface wate

body was estimated using three dilution factors: 10100, and 1,000. The degree of mixing is a function o

the geometry and flow characteristics of the surfacewater body (e.g., depth and flow velocity), as well athat of the alutaraldehvde stream..—.-..—.—_-- -.. -—....

Case 5: Discussion

Assuming an initial glutaraldehyde concentration o200 mg/L exists in a produced water stream,dilution factor of 10, 100, and 1,000 would yielglutaraldehyde concentrations in surface water of 2mg/L, 2 mg/L, and 0.2 mg/L, respectively. Th

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highest of these values is in the upper end of the

comparison criteria range; a dilution factor for asurface discharge would typically be well in excess of10times. Note that ifthe glutaraldehyde concentrationwere 10 ppm, the resulting surface water

concentration would be 1, 0.1, and 0.01 mg/L,respectively. These are all well below the lower end ofthe comparison criteria range. It should be noted that

additional dilution will occur as the slug is transportedfrom the initial discharge point (i.e., far-field mixing).As a result, based on these dilution factors, directdischarge of glutaraldehyde does not appear to havea significant impact on water quality.

FINDINGS AND CONCLUSIONS

information on efficacy is important in screerung. --—:-_

potential products for biocide treatment; however, it isimportant for the user to have a systematic and

on-going approach to evaluating and optimizing thetreatment program on site. This is exemplified by thefact that conflicting, although often legitimate,conclusions are found in the technical literatureregarding efficacy, due to varying conditions underwhich the products were tested. For example,

isothiazolin was shown to be an effective biocide incooling water environments, but relatively ineffectivein produced water.

Chemical use case histories were presented from theliterature and field data obtained from NGI participants

in the study. The operational scenarios for the

different case histories were substantially different,and therefore the approaches to mitigation varied.Fundamentally, the treatment approach for each casewas dictated by the nature of the problem, perceivedprobability for success, environmental constraints

imposed at the site, and costs for treatment, support,and waste disposal. For example, treatment for MISin three different operational scenarios wasaccomplished using three different chemical

approaches: glutaraldehyde, iodine and nitrate. Theuse of glutaraldehyde was acceptable in the gasstorage reservoir, but would not have been allowablein produced water storage tanks that discharge to thepublic sewer system, where nitrate was used. The use

of dissolved iodine was an attractive alternative in the

produced water evaporation ponds because itprovided for microbiological control and sulfide

scavenging at concentrations nontoxic to higherforms of life.

Because biocides and corrosion inhibitors are used inways that may result in their contact with the

environment (i.e., either directly or through disposal ofwastes containing residual levels of these chemicals),

a screening environmental assessment wasperformed. This conservative assessment was

conducted to determine whether significantenvironmental impacts may occur under conditions

representative of those seen in NGI operations.

In general, the modeled scenarios predicted that

significant surface and gioiindwder knpx!s either didnot occur or that short-term peaks in predicted

concentrations were short lived and near the originalpoint of impact. In most cases, predicted

glutaraldehyde concentrations were well below thelower end of the comparison criteria range. Becausesite-specific data were not available to calibrate themodels used, the overall predictive capability of theevaluation was limited to the assumed general

operational and impact scenarios.

The wide diversity in use of chemical productsthroughout the NGI necessitates having knowledge of

whether, and to what extent, these chemicals may

impact the environment. The screening environmental

assessment presented in this report indicated that

significant impacts did not occur for glutaraldehyde inthe scenarios evaluated. Thus the need for moredetailed evaluation is not warranted. The assessmentalso provides a methodology that may be used forassessment of the use of other chemical products in

their specific uses. As is the case with any predictivemodeling of environmental impacts, the procurementand use of field data to calibrate the models andcorroborate the predicted results is essential.

REFERENCES

1. Hudgins, C.M., Chemical Treatments and Usagein Offshore Oil and Gas Production Systems, Journal

of Petroleum Technology, pp 604-611, May, 1992.

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2. Morris, E.A. Ill and Pope, D.H., “Field andbkidol”j !fW@j~tkriS MC) the Persistence d

Glutaraldehyde and Acrolein in Natural Gas StorageOperations,” CORROSION/94, paper no. 270,(Houston, TX: NACE International, 1994).

3. Petroleum Extension Service, Field Handling ofNatural Gas. 3rd cd., (Austin, TX: University of Texasat Austin, 1972).

4. Cullimore, D.R., Practical Manual of Groundwater

Microbiology, (Chelsea, Ml: Lewis Publishers, 1993).

5. Fontana, M.G., Corrosion Engineering, 3rd ed,(San Francisco, CA:McGraw-Hill, Inc., 1967).

6. United States Environmental Protection Agency,Drinking Water Regulations and Health Advisories,

EPA 622-R-94-001, Office ofWater, Washington, D.C.,4nfiA

I YY4.

7. United States Environmental Protection AgencyRisk-Based Concentration Table, Third Quarter, 1993.

8. Hunt, B., Dispersive Sources in UniformGroundwater Flow, Journal of the Hydraulics Division,ASCE. 104 (HY1), pp 75-85, 1978.

9. Wilson, J.L. and Miller, P.J., Two-DimensionalPlume in Uniform Groundwater Flow, Journal of the

Hydraulics Division, ASCE. 104 (HY4). pp 503-514,1978.

10. Salhotra, A.M., Mineart, P., Sharp-Hansen, S.,

and Allison, T., Multimedia Exposure AssessmentModel (MULTIMED) for Evaluating the Land Disposal

of Wastes--Model Theory, Environmental ResearchLaboratory Office of Research and Development, U.S.Environmental Protection Agency, 1990.

11. Pope, D.H., Zintel, T.P., Aldrich, H., andDuquette, D.: “Laboratory and Field Tests of Efficacy

of Biocides and Corrosion Inhibitors in the Control ofMicrobiologically Influenced Corrosion, ”

CORROSION/90, paper no. 334, (Houston, TX NACE,1990).

12. Jones, D.S., O’Rourke, P.C., and Caine, C.W.

“Detection and Coniroi of ihiicrobioiogicaiiy-influencedCorrosion in a Rocky Mountain Oil Production system- A Case History,” CORRQS!ON/93, paper no. 311(Houston, TX: NACE, 1993).

13. Agostini, R.A., and Young, R.D.: “A Case History

of Microbially Influenced Corrosion in a West TexasWaterflood,” CORROSION/90, paper no. 1999(Houston, TX:NACE, 1990).

14. Pope, D.H., Cookingham, B.A., Day, R.A.Pogemiller, G.E, Zintel, T.P., Morris, G.R., Howard, D.

and Frank, J.R.: “Mitigation Strategies foMicrobiologically Influenced Corrosion in Gas IndustryFacilities,” CORROSION/89, paper no. 192 (Houston,TX: NACE, 1989).

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TABLE.NPES OF TREATMENT CHEMICALS AND THEIR USES IN NQI OPERATIONS ‘u

FI mt?llnn thrnose I tiOlkwOn/Uae I Chemlcelype or Chemlcet b’. ... ... ... . -. r . .

Biocides q Prevent biological corrosion/fouling of wells and q Glutaraldehyde

production equipment q Acrolein

q MitigaIe biological souring of oii/gas production and q Cluaternary ammonium compounds (QAC)

gas storage resewoim

.-.l’ --—----,wmmamums

= m-A.. -A 4--. .. ,..” , - , ., -*a. . . . -.1!e.,e*anl .“-”v= ,“-, ,,,! ,g !rr ..-,=. “1 “,, .,,.7,=!! !“ * Dnhmhmnl Dctorc. -., =.,--- ------

q Slllcones

Coagulants/Flocculants q Enhance separation of oil/water mixtures q Polyamine esters

q Enhance separation of suspended solids from WSder q Polyamine quaternary ammonium salts

——.—L. . . . .Corrosion mrmmors

... -, —,-- ,-. --”, A“--”,. ,- . . . ... . . . . a“,+ ..,,. a ,,”a.G wwmuze IvIIWIIUI ucu,,agww .squ,p,,m,, mw p,p=mr-o ~ AIIAJI =nd sim#nrmnin#m cslk

“J.. y, “!, , “!!,, ,,”, ,,”, ,, . . . .

q Amides/imidazolines

q Qualernary amines

q Suifonates

q Fyridine salts

Emuision/ q Enhance removai of oil dropiets from produced water q Oxyalkyiated dipropylene giycols

Reverse Breakers q Phenol formaldehyde resins

q Polyamine QAC~ M.+s.l .-hlnridac (s. hwnmotm iron 7inr)

,.,-.-, -, !,”,.--” ,-. ”,, ,,. .”..., . . . ...! -. ..-,

Gas Conditioning q Dehydration of natural gas q Ethylene glycol

q Triethyiene glycol

q Acid gas (H2S, C02) removal q Dlethanol amine

q Monoethanol amine

q Hydrate inhibitors q Methanol ‘d

q Ethyiene glycol

Paraffin Treating q Controis accumulation of solid hydrocarbons q Vlnyi poiymer

q Sulfonate salts

q Aliphatic or aromatic solvents

Scale inhibitors q Reduce deposition of suifate and C&WbOf)ateSCdfX q Phosphates

q Amine phosphate esters

q Acrylic poiymers

Surfactants q Cleaning of equipment q Alkyl aryl sulfonates

q Ethoxylated alkyl phenols

(a) Information was parfiatly derived from Hudgins (1992) ‘“.

(b) Examples of chemicals or chemical types are provided; additional chemicals may also be used in specific applications.

(c) Methanoi is atao used to prevent freezing in equipment/piping carrying production waters.

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. .

12 BIOCIDE AND CORROSION INHIBITION USE IN THE OIL AND GAS INDUSTRY:

EFFECTIVENESS AND POTENTIAL ENVIRONMENTAL IMPACTS SPE 2973

cftation

Morris and Pope,

(1994) [2]

Pope, Zintel,

et et., (1990)[11]

Jones, et al.,{I aomr+ 91, ..---,,,-,

Agostini and Young,

(1990) [13]

Pope, Cookingham,

et al., (1989) [14]

TABLE 2. SEf.ECTED CASE HISTORIES FOUND IN TECHNICAL LITERATURE

Description

A gas storage field that produced iow levels of H2Swas

diagnosed as having MIS using an analylicat strategy based on

relative ievels of SRB, sulfides, sulfate, and phosphate.

Discussion is provided on approaches to and eftecthrenees of

biocide treatment.

Glutareidehyde, cocadiamine and a corrosion inhibitor were

tested at three field snes for effectiveness in controlling MIC-

type bacteria md prevention of corrosion plffing.

MIC was mitigated in a water injection system of an oil f ie ld onUI**C.*flfwwi I ,eimft I-.iaeiAa *yp-.a-* C-s,- .-, b.i--L-L-.,... -, , ,“”” “e,, ,~ “owe,”= ,, = u , ,=, ,$. -“G, a, “,”V, UC

formulations were tested to determine which would be most

effective under the conditions at the site.

A study was done at a waler flood injection system to

investigate the effectiveness of an organic amine-type biocide

for reducing MIC end loss of injectivity due to microbial fouling.

A study was done to investigate the effectiveness of

commercially available biocides and corrosion inhibitors for

controlling MlC-type organisms.

Mefor Findings

The diagnostic strategy was effective for early

detection of MIS.

Treatment of profuse-stage MIS by conventional

methods may not be effective.

Glufaraldehyde consistently equaled or

outperformed cocodiamine under the conditions

tested.

Siocide performance varies according to conditions

where applied.

The corrosion inhibitor had little effect on the

organisms or the prevention of corrosion pitting.

Biocide formulations containing glutaraldehyde,

~i~i il ir le S~ifS ~ilCi G,K ivt%~ ii i.S rmeSi &f@~~~ Of

those tested.

Giutaraldehyde was administered at 500 ppm

concentration, foilowed by diamine salts and QAC.?h~ ~~ff~~~~!~i~~j~~~ ~~ra sflAaA mmal~ar-=fa., ..””-” “, , “, =I,,alc

weeks to prevent the possibility of interference.

The treatment program significantly improved the

water qualify end resuited in lower corrosion rates,

The most effective approach to microbial control

was the addition of high concentrations of biocide

over short time periods.

The biocides and corrosion inhibitors tested were

iargely ineffective in controlling the organisms on

surfaces, under the conditions tested.

Concentrated doses of biocide were more effective

than continuous iniection of biocide,

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E 29735 D.M. Brandon, J.P. Fillo, A.E. Morris, and J.M. Evans 13

TABLE 3. CASE HISTORIES OBTAINED FROM FIELD SITE INTERACTIONS

case I Oaacrlntlon I Treatments I Outcome—- -. I-.

#l: Profuse-stage Souring in A subsurface natural gas storage reservoir Oownhole biocide treatment The trend of

an Aquifer-storage Reservoir was developed in the 1950’s wtth gas InjectIon was done using organic increasing H$ was

initiated in 1954. H2S was detected In this emlnes. n w as initiated in not reversed during

reservoir in 19S4. Oownhole biocide treatment 1965 and continued through the 30 years of

was Initiated in 1965; however, Hz.s 1977. In 1977, and treatment. An on-site

production in the reservoir increased. Twenty- subsaquent years, different amine-based H2S

ftve years iafer, the H2S levels had increased bicrddes were applied, scavenging plant wee

by over 1,000 percent. implemented to reduce

HgS to iess than 4 ppm

to meet pipeline

specifications.

IP2: Earty-stage Souring in a A natural gee storage facility has produced Of 24 wells diagnosed es Treatment was

Naturei Gas Storage HIS In gas from a few wells since 1990. The having MIS, 12 were treated

Reservoir

concluded 10 be

souring mechanism was found to be MIS. The with gluteraidehyde and 12 ineffective because: 1)

H2S concentration at Individual wells ranged were reserved as non-treated the treafment was

from O -100 ppm. Many of the sour welis controls, Monitoring data done too late in the

were in close proximity to sweet welis, which showed no significant summer gas injedon

Indicated that the MIS community was Iocai to differences in mean levels of season, 2) the

the wellbores. sulfides nor H2S in the overflush was

treafed and non-treated weiis. inadequate in 10 of 12

wells, and 3) the

volume of gas injected

after treatment was!fi~fi~q~c!~.

#3: Sourtng In AkIove- A natural gas storage facillty disposes Commercially available Souring in the effluent

ground Produced Water produced waler to a sanitary sewer. The water bloc ides were inetiecfive.

Tanks

water was eliminated

treatment plant requires soluble suifldes to be Some of the wells would after treating with

less than 0.1 mg/L In the wastewater. One gas continually supply viable nitrate, Microbiological

storage well, which discharges water to the bacteria to the tanks, and tests were run on

produced water tanks k geochemically sour, recolonization would occur water samples from

producing gee of up to 4,000 ppm H2S. This shortly after biocide various points in the

well Is treated with iron chlorfde to convert treatment. The microbial system. The presencegaseous and eoiuble H,S to Insoluble Iron community was shifted from of organisms in the

sutfide. Other walls which also discharged Into sulfate reduction to nitrate system strongly

the produced water tanks had MiC, and es a reduction by supplying the support the concept

result, continuity input viable APB and SRB system with sodium nitrate. thal biological

into the tanks. Mer the addition of nitrate, oxidation of H2S is a

solubie sulfides in the effiuenf key factor in

feil below detectable levels. sweetening of the

sysfem.

#4: Above-ground Souring A naturai gas storage facility disposes of The problem was miligated The water quality was

in Produced Water producad water using evaporation pa?ds. The using elemenfal iodine. Soiid

Evaporation Ponds

improved by the

ponds racelve water containing viable bacteria pellets of iodine were added treatment. H,S

from waits and piping. Produced water to the evaporation ponds and emissions were

disposal is accomplished solely through allowed to settle on the reduced to ievels

evaporation and is never discharged to bottom. The iodine slowly beiow the odor

surface water. Microbial colonizat ion in the dissolved, oxidizing soluble threshold.

ponds resutted in H2S emissions to the su~ldes to elementai sulfur,

atmosphere at ievels unacceptable to Ihe piant whiie apparently controlling

operators. sulfide production.

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#5: MIC In a Produc8dWater Dlstrbuflon System

Pftting-type comosion due to MIC hadoccurred in llquid/gae separator units and

piping of a gathering system at a natural gas

storage facilHy. Sampling of the pipes end

wPSrSfOfS revealed high levels of bacteria and

biofilm accumulation, In conjunction with pits

and corroetan products on the metal surfaces.

Tredltional biocide and treatment strategies

had been applied, unsuccessfully, for over

eight yeare.

The conventional strategyinvolved using a solution of

200 ppm gluteratdehyde In a

50:50 mixture of

methsnol/isopropanol. The

innovative strategy involved

using only the alcohol

mixture, Sections of fhe

affected pipe were blocked

oft, filled with the treatment

solwlon and allowed fo sosk

for seven days. Liquid

samples were taken from the

treated systems and analWed

for viable bacteria.

The results showed

that all solutions

resulted in biological

control within four

hours of application.

Pipe samples were cut

out of the system and

inspected for fouling.

In all cases, significant

corrosion was noted

before treatment;

however, the systems

were clean after

treatment.

TABLE 4. REPRESENTATIVE SCENARIOS FOR ENWRONMENTAL IMPACTS ASSESSMENT

Industry Segment I source parameters I Potential Source and Impact

IJnderground Storage

Reservoir

Chemical treatment

q 2,000 gal. treatment dawnhole at 1-2% active

glutaraldehyde

q 10,000 ppm glutaraldehyde

q 5,000 ppm glutareldehyde + 2,400 ppm alcohol

(iscmrorwl or methanol)

Production/

Transmission

Treatment/

Discharge

Produced water

q glutaraldehyde concentration of 200 ppm and 10,000

ppm

q alcohol concentration at 100 ppm

q prcduced water release of 1,000 gallons or 10,000

@ens

Prcduced water

q 10 and 200 ppm glutaraldehyde

q 5 and 100 ppm akohol

Treaiment cnemicai ieakage to uauw ~c,ase I), --.., ,---- .\

Produced water leakage to soil (Case 2)

1) Lagoon fluid leakage through liner, high and

low groundwater table (Cases 3 and 4)

2) Fluid discharge (Case 5)

q surface stream dlscharae

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