prediction of corrosion inhibitor performance using simulated co2h2s environmental autoclave and...

7/25/2019 Prediction of Corrosion Inhibitor Performance Using Simulated CO2H2S Environmental Autoclave and Flowloop Tests - I

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Prediction of Corrosion Inhibitor Performance Using Simulated CO2/H2SEnvironmental Autoclave and Floloo! "ests # I

Abstract:

The hot topic series describes a test program and the result targeted towards evaluating corrosion inhibitor performance in

CO2/H2S environments. After preliminar screening of the inhibition characteristics and performance of ! corrosion inhibitors

"designated A#$#C#% & '( under simulated CO2/H2S environment in a high temperature# high pressure flowing autoclave# the best

two corrosion inhibitors "corrosion inhibitors A & $( were selected for further flow loop testing under simulated )orth Sea

pipeline service conditions.

Overview"his hot to!ic series describes a test !rogram and the results targeted toards evaluating corrosion inhibitor !erformance in CO2/H2Senvironments$ After !reliminar% screening of the inhibition characteristics and !erformance of & corrosion inhibitors 'designated A( )( C( *( +E, under simulated CO2/H2S environment in a high tem!erature( high !ressure floing autoclave( the best to corrosion inhibitors 'corrosioninhibitors A + ), ere selected for further flo loo! testing under simulated -orth Sea !i!eline service conditions$"he orst case !i!eline service conditions '.0 s%nthetic field brine/10 h%drocarbon 'de!olaried 3erosene, environment ith H2S '!artial!ressure $4& !sia 5$& 6Pa7, and CO2 '!artial !ressure 4& !sia 5$& 8Pa7, ere simulated at 9 F$ '1:. C$, in a laborator% floloo! and the!erformance of the selected corrosion inhibitor formulations A + ) on API &; , and eight loss techni?ues$"he test results indicated the folloing@

Provided the !ro!er concentration of corrosion inhibitor is a!!lied continuousl%( carbon steel can be satisfactoril% inhibited under

laborator% test conditions that simulate !i!eline orst case corrosion conditions$

Corrosion inhibitor ) as not as effective as corrosion inhibitor A re?uiring about 2$& times as much ) as A to accom!lish the


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same level of corrosion control under these simulated laborator% test conditions$

"he results of this corrosion inhibitor evaluation !rogram do not su!!ort the use of $& Cr e%nolds number '>e */G viscosit% of the li?uid$,"he effect of flo rate on the inhibitor film as studied using the flo loo! a!!aratus at u! to nine '., flo rates corres!onding to :0( =0(0( 10( 120( 990( :&=0( ==0 and =&0 of the maBimum '10, antici!ated -orth Sea !i!eline all shear stress value using avelocit% of 1 ft/sec '"able 9,$ Other floloo! test !arameters included ere@ 9 F$ '1:. C$,G !! CO2of 4& !siaG !! H2S of $4& !siaG .0S%nthetic -orth Sea Pi!eline brine '"able :,G 10 de!olaried 3erosene$ "hese test !arameters re!resented orst case senario for the!ro!osed -orth Sea !i!eline$Prior to initiation of the Phase 2 stud%( flo loo! a!!aratus !erformance as tested using the )P Protocol Calibration "est$ "he flo loo! testa!!aratus encountered no !roblems !assing the re?uire calibration test criteria$"he chemical su!!lier of the to corrosion inhibitors to be evaluated in the flo loo! test( !rovided !reliminar% floloo! test data develo!ed in
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their laborator%$ "he test !arameters used ere@ 1 F$ '2 C$,G !! CO 2of 4 !siaG


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Table 2HT-H Autoclave TestsCorrosion *nhibitors 'valuations


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Table 3North Sea Pipeline Flowloop TestCorrosion Inhibitor Evaluation - Flow Regime Data


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*nput %ata - ield

RHO[kg/cu.m.]

I.D.[cm]

Velocity[m/s]

MU[poise]

ReynoldsNo

Re

Roughnesse/D

Fiction!"cto

[!]

#"u$"

#"u%&s/s' !t

691.04 36.2 3.05 0.001626 4692357 0.00014 0.013 41.78 0.872

-ote@ "au 5all shear stressJ value calculations based on a velocit% of 1 ft/secCalculated %ata - lowloop Apparatus

PercentTAU

TAUPa

TAULbs/sq/ft

RHO[!/c".#.$

%.&.[c#$

'e()c*t+[#/s$

,U[-)*se$

Re+n)(s). Re

r*ct*)nfact)r [f$

'e()c*t+[ft/sec$

()Rate

[!-#$

100 41.78 0.872 967.61 1.27 2.13 0.002825 92738 0.019 6.99 4.28

40 16.71 0.349 967.61 1.27 1.28 0.002825 55790 0.021 4.21 2.58

60 25.07 0.523 967.71 1.27 1.61 0.002825 70016 0.02 5.28 3.23

80 33.42 0.698 967.71 1.27 1.91 0.002825 82947 0.019 6.26 3.83

120 50.14 1.047 967.71 1.27 2.4 0.002825 104373 0.018 7.87 4.82

Table 4SNT!ETIC "RINE C#$P#SITI#NNorth Sea S%ntheti& "rine Composition

Constituent Desired Mixture - mg/L Actual Mixture - mg/L


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)*"# a 20000 20835.30

a(c*"# a 2000 2000.00

,a!nes*"# ,! 1500 1500.4

ar*"# a 50 50

()r*e ( 40000 39994.90

"(fate O4 20 20

*carb)nate HO3 100 100.3


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lowloop Test ApparatusAs a result of budget and !ersonnel restraints( it as necessar% and more economicall% attractive to contract the floloo! testing to an outsidelaborator% than to design and construct the floloo! test a!!aratus re?uired as ell as commit the number of !ersonnel necessar% to !erform thetesting$ "he consulting laborator% that did our earlier high !ressure#high tem!erature floing autoclave testing as selected to !erform thefloloo! testing$ "he a!!aratus used as theirs and is diagramed in Figure 1$"he a!!aratus test !arameters included@ 9 F$ '1:. C$,G !! CO2of

4& !sia '$& 8!a,G !! H2S of $4& !sia '$& 6!a,G 1 !ercent de!olaried 3eroseneG . !ercent S%nthetic )rine$"he floloo! as designed to !roduce the same magnitude of all shear stress in the !i!eline due to laminar flo and in the turbulent flo regionof the im!ingement electrode for a given li?uid flo rate in the !i!eline$ Additionall%( it !rovides for simulation of com!leB miBed brine fluids and theeffects of dissolved acid gas at !artial !ressures similar to those in the !i!eline$"he diagram indicates the location of the test electrodes in the floloo! a!!aratus$ In all cases linear !olariation resistance ';P>, !robes ereused and instantaneous corrosion rates ere determined using electrochemical techni?ues 'AS"8 K&., and the average corrosion rate usingeight loss techni?ues 'AS"8 K,$ "he t%!e and metallurg% of the ;P> are located in the a!!aratus as indicated in Figure 1@;ocation ;P> Probe *escri!tion 8etallurg%1$ ;aminar Flo Electrode


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Figure 1 Consulting ;aborator% Flo ;oo! A!!aratus

Table !Allo Analses of 01 'lectrode aterials for low 0oop TestChemical roperties


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A00O3 H'AT Al C Cr Cu Fe Mn Mo Ni P S Si Ti other

!l45! d,67 8.89 ,.25 8.8,7 8.8,, 8.27 Cb-8.866 ;-8.87

!08.!Cr


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Corrosion *nhibitors"he to corrosion inhibitors 'designated A and ), selected for floloo! testing ere evaluated at concentrations of 1 and 2& !!m b%volume$Corrosion inhibitor A as a !ro!rietar% formulation of sulfonated fatt% acid al3%l amide !ol%amine al3%late and iso!ro!anol in h%drocarbonsolvent$ "he h%drocarbon solvent s%stem contained the folloing@ heav% aromatic solvent(( eth%lbenene( na!hthalene and B%lene$

Ph%sical characteristics of corrosion inhibitor A include@Form@ ;i?uidColor@ O!a?ue to amber Solubilit% in Later@ InsolubleLater dis!ersibilit%@ Highl% ater dis!ersibleS!ecific Kravit%@ $.9 M = F$ '1&$= C$,Niscosit% 'AS"8 *#::&,@ :9 cst M 4& F$ '29$. C$,Pour Point 'AS"8 *#.4,@ #9 F$ '#9:$: C$,P8CC Flash Point 'AS"8 *#.9,@ &. F$ '1& C$,Na!or Pressure 'AS"8 *#929,@ =1 mm Hg '1$9= !si, M 1 F$ '94$ C$,Corrosion Inhibitor ) as a !ro!rietar% green formulation$ Kreen formulated !roduction chemicals are formulated to be more environmentall%f riendl%$ Corrosion inhibitor ) is an a?ueous blend containing an al3%l amino acid and eth%lene gl%col$Ph%sical characteristics of corrosion inhibitor ) include@Form@ ;i?uidColor@ Clear( bron li?uidOdor@ KeraniumLater Solubilit%@ Later soluble!H 'M10,@ :$ M 2 C$ '= F$,)oiling Point >ange@ 1 C$ '212 F$,Freeing/8elting Point@ #1 C$ '1: F$,*ensit%@ 1$&= gms/cm9 M 1& C$ '&. F$,Niscosit% 'Cannon#Fens3e,@ ==$9 cst M C$ '92 F$,2$: cst M 2 C$ '= F$,Flash Point 'P8CC,@ D1& C$ '221 F$,Na!or Pressure@ $& mm Hg '$1=& !si, M 1 F$ '94$ C$, "hese are onl% indicative values su!!lied on the 8S*S sheets b% the chemical su!!lier$Test rocedures"he test s!ecimens ere !olished to a = grit finish( degreased and dimensions and eights ere recorded$ "he degreased s!ecimens eremounted carefull% in the flo loo! test a!!aratus$ "he deaeration of the test fluids ere carried out in se!arate reservoir containers$ "he autoclaveand the flo loo! ere also deaerated ith ultra high !urit% nitroben !rior to starting the test$ "he test solution 's%nthetic seaater orbrine/3erosene miBture, as introduced into the autoclave b% !um!ing$ Once the autoclave as !ercent full 'a!!roBimatel% : liters of fluid,stirring in the autoclave and floing in the loo! as started$ "he gassing and measurement !rocedures for calibration test and for inhibitorevaluation tests are given belo$"he Calibration "est

At room tem!erature( CO2as introduced slol% into the autoclave and stabilied at 2& !sig$ "he autoclave as then heated to test tem!erature(


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& C$ '122 F$, "he !ressure as adusted to !sig at & C$ '122 F$, "he li?uid flo in the loo! as adusted to give a flo rate of 1$& g!m hich!roduced a all shear stress of 4 Pa '$1:= lbs/ft 2,$ "he corrosion rates of 11 steel s!ecimens ere measured in the reservoir and laminarregions em!lo%ing linear !olariation resistance ';P>, techni?ue !er AS"8 K#&.$ "he measurements ere continued for a duration of three da%s'=& hours,$"he Inhibitor Evaluation "ests

"he autoclave as heated to test tem!erature of 1& C$ '92 F$, and the test gas as floed into the autoclave to achieve the test conditions@$4& !sia '$& 3Pa, H2SG 4& !sia '$&: 8Pa, CO2$ "he !ressure and li?uid flo through the autoclave ' 9 ml/min, ere maintained using a bac3!ressure regulator on the outlet of the autoclave and metering !um!s at the inlet$ *uring the last three test series '1 !!m corrosion inhibitor A(2& !!m and 1 !!m corrosion inhibitor )( the deaerated brine/3erosene miBture as saturated ith the test gas '$1 !ercent H 2S and thebalance CO2, before !um!ing into the autoclave$Once the environment as established( the flo rate in the loo! as adusted to !roduce a all shear stress value that corres!onded to 1 ft/sec'9$& m/sec, li?uid flo in the 1:$2& inch '9=$2 cm, !i!e in the field based on flo modelling !erformed 'see "able 9,$ "he corrosion rates in theuninhibited environment ere measured on s!ecimens '


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RHO

[kg/cu.m.]

I.D.

[cm]

Velocity

[m/s]

MU

[poise]ReynoldsNoRe

Roughness

e/DFiction!"cto[!]

#"u

$"

#"u

%&s/s' !t

691.04 36.2 3.05 0.001626 4692357 0.00014 0.013 41.78 0.872

-ote@ "au 5all shear stressJ value calculations based on a velocit% of 1 ft/sec

Calculated Data - Flowloop Apparatus

PercentTAU

TAUPa

TAULbs/sq/ft

RHO[!/c".#.$

%.&.[c#$

'e()c*t+[#/s$

,U[-)*se$

Re+n)(s). Re

r*ct*)nfact)r [f$

'e()c*t+[ft/sec$

()Rate

[!-#$

100 41.78 0.872 967.61 1.27 2.13 0.002825 92738 0.019 6.99 4.28

40 16.71 0.349 967.61 1.27 1.28 0.002825 55790 0.021 4.21 2.58

60 25.07 0.523 967.71 1.27 1.61 0.002825 70016 0.02 5.28 3.23

80 33.42 0.698 967.71 1.27 1.91 0.002825 82947 0.019 6.26 3.83

120 50.14 1.047 967.71 1.27 2.4 0.002825 104373 0.018 7.87 4.82

prediction of corrosion inhibitor performance using simulated co2h2s environmental autoclave and...

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