H2S Inhibition By Nitrate Injection On The Gullfaks Field

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H 2S I n h i b i t io n B y N i t r a te I n j e c t i o n O n T h e G u l l f a k s F i e l d

Egil Sunde

Statoil,

N- 4035 Stavanger , Norway .

Bente-Lise P. Lillebo,

Gunhild B odtker and Ter je Torsvik.

UNIFOB Pe t ro leum,

Microbiology sec tion.

N-5020 Bergen, Norway.

Tore Thors tenson

Statoil,

N-5020 Bergen, Norway.

A B S T R A C T

Injection water on all Gullfaks platforms have been treated with nitrate to reduce H2S production caused

by Sulfate Reducing B acter ia (SRB). Resul ts f rom Gullfaks B (GFB) and Gullfaks C (GFC ), which have

had the most stable injection and production during the treatment period, show a decrease in BS

production, when the treated injection water reaches the producers. In the water injection systems the

change from biocide treatment to nitrate treatment resulted in more than 1000-fold reduction in SRBnumber and 10-20-fold reduction in sulphate respiration activity. Following nitrate injection, the SRB

popula t ion w as replaced with an equal ly la rge popula t ion o f NRB in the biof i lm and corros ion level in

the water injection system dropped by more than 50%. This result corresponds well with the

observations from a similar water injection treatment at Veslefrikk.

Keyw ords: H2S, reservoir souring, corrosion, G ullfaks, nitrate, bacteria, SRB, NR B.

Paper No. CORROSION2004 04760

1

Copyright

2004 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 77084-4906. The material presented and the views expressed in this paper are

solely those of the author(s) and not necessarily endorsed by the Association. Printed in U.S.A.



I N T R O D U C T I O N

T h e p r o c e s s o f r e s e r v o i r s o u r in g , c a u s e d b y t h e g r o w t h o f Su l f a t e Re d u c i n g B a c t e r i a ( SRB ) i n

o i l reservo i rs , rep re sen t s a m ajo r p rob lem fo r the o i l i ndus t ry .

In t rodu ct ion o f n i t ra t e as e l ec t ron ac cep to r fo r anaerob ic resp i ra t ion i s an a l t e rna t ive to b ioc ide

t r e a tme n t . T h e i d e a h a s b e e n th a t s t i mu l a t i o n o f n i t ra t e r e d u c i n g b a c t e r i a ( N R B) c o u l d i n h i b i t g r o w t h o f

SRB1, 2, 3. N i t ra t e has bee n use d succe ss fu l ly to inh ib i t m icrob ia l su l f ide p ro duc t ion in o i l -con tam ina ted

w a s t e w a t e r 4, 5. L a b o r a t o r y e x p e r i me n t s w i t h o i l r e s e r v o i r mo d e l c o l u m n s h a v e s h o w n t h a t i n j e c ti o n o f

n i t ra t e inh ib i t s su l f ide p roduct ion 6 , 7 . Tela ng e t a l . 8 show ed tha t n i t ra te in j ec t ion in wa ter in j ec t ion we l l s

l e d t o e n r i c h me n t o f s u lf i d e - o x i d i z i n g , n i t r a te - r e d u c i n g b a c t e r i a i n t h e r e s e r v o i r. J e n n e m a n e t a l. 9

s h o w e d r e d u c e d HzS p r o d u c t i o n f r o m i n j e c ti o n a n d p r o d u c t i o n w e l l s a f te r t r e a t me n t o f in j e c t io n w a t e r

w i t h 4 0 0 m g / L o f N H 4 N O 3 .

M y h r e t al . 7 s h o w e d i n la b o r a t o r y e x p e r i me n t s t h a t m i c r o b i a l H z S- p r o d u c t i o n i s in h i b i te d b y n i tr a t e , i n

conc en t ra t ions tha t i s app l i cab le to o f fshore o i l f i e lds. As a resu l t o f th i s the in j ec t ion w ater a t t he

V e s l e f r i k k f i e l d ( N o r t h S e a ) w a s t r e a te d w i t h n i t ra t e . Mi c r o b i o l o g i c a l mo n i t o r i n g o f t h e w a t e r i n j e c t io n

s y s t e m s h o w e d r e d u c e d g r o w t h a n d a c t i v i t y o f SRB i n t h e w a t e r i n j e c t i o n s y s t e m, a n d a c o n c o mi t a n t

reduc t ion in microb ia l i nduced cor ros ion (MIC) in C-s t ee l t ops ide seawater in j ec t ion sys t ems ~0 .

O n t h e b a s i s o f r e s u l ts o b t a i n e d f r o m t h e mo d e l e x p e r i me n t s 7 a n d s u c c e s s f u l t r e a t m e n t o f th e w a t e rin j ec t ion sys t em a t Ve s le f r ik k ~0, severa l o i l fi e lds on the N orw eg ian Co n t inen ta l Sh e l f have be en t rea t ed

wi th n i t ra t e s ince 1999 , amo ng them a l l t he Gul l faks p l a t fo rms . In th i s pap er resu l t s f rom n i t ra te

t r e a t me n t o f th e w a t e r i n j e c ti o n s y s t e m a n d t h e e f f e c t o n H z S p r o d u c t i o n f r o m t h e r e s e r v o i r ( r e s e r v o i r

sour ing) a t Gu l l faks B and C are p resen ted .

M A T E R I A L S A N D M E T H O D S

T h e G u l l fa k s p l a tf o r m s G F B a n d G F C

T h e G u l l f a k s f i el d i s lo c a t e d o n b l o c k 3 4 / 1 0 i n th e n o r t h e r n p a r t o f th e N o r t h Se a , w e s t o f Be r g e n

c i ty in No rw ay . The p rod uct io n s t a r t up wa s in 1986 , 1988 and 1989 fo r the Gul l faks A , B, and C

p l a t f o r ms r e s p e c t i v e l y . T h e f i e l d u s e s g a s a n d s e a w a t e r i n j e c t i o n ( W A G ) a s p r e s s u r e s u p p o r t . T h e w a t e r

i n j e c t i o n v o l u me s h a v e , f r o m e a c h p l a t f o r m , b e e n v a r y i n g b e t w e e n a p p r o x i ma t e l y 3 0 . 0 0 0 m 3 and 70 .000

m 3. D u r i n g t h e l a te s t y e a r s , a p p r o x i ma t e l y 5 0 . 0 0 0 m 3 a n d 4 0 . 0 0 0 m 3 h a v e b e e n i n j e c te d o n G FB a n d C

r e s p e c t i v e l y . I n j e c t i o n p r e s s u r e d o w n s t r e a m o f t h e w a t e r i n je c t i o n p u mp s a r e c l o s e to 2 0 0 b a rs . T h e

s e a w a t e r i n t a k e d e p t h is 7 0 m o n G FA / B a n d 1 2 0 m a t G FC . O x y g e n i s r e m o v e d b y v a c u u m d e a e r a t i o n

i n c l u d i n g b i s u lf i te s c a v e n g e r , t o l e ss th a n 2 0 p p b . T e m p e r a t u r e d o w n s t r e a m o f th e d e a e r a t o r i s

a p p r o x i ma t e l y 2 5 °C . O n G F t h e w a t e r w a s o r i g i n a l l y f i l t e r e d t o l e s s t h a n 7 mi c r o n . T h e f i l t e r h a s s i n c e

1998 been bypassed on GFB. On GFC, the f i l t ra t ion i s con t inu ing , bu t f rom 2000 , wi thou t the s t r ingen t

f i lt e r s p e c if i c a t io n s . C h l o r i n e t r e a t me n t o f i n je c t io n w a t e r o n G u l l f a k s B a n d C w a s t e r m i n a t e d i n 1 9 9 7.

2



B i oc i de and n i t r a t e t r ea t m en t

The b i oc i de t r ea t m en t o f in j ec t ion w a t e r on Gu l l f aks has been e f f ec t ua t ed by u s i ng ba t ch

t r ea t m en t o f g l u t a ra l dehyde f rom f i e ld s t a r t up i n 1986 . Vary i ng dos i ng r eg i m es have bee n u s ed , bu t fo r

the l a tes t 5 years unt i l subs t i tu t ion by cont inuous n i t ra te in ject ion la te 1999, the in ject ion ra te impl ied

500 ppm (50% g l u t a ra l dehyde) , 1 h r / week . The n i t r a te s a l t is added con t i nuous l y a t a dos i ng r a te o f 30 -

4 0 p p m o f a 4 5 % Ca(NO3)2so lu t ion .

S a m p l i n g

Anaerob i c wa t e r s am p l es were t aken a f t e r deae ra t i on t ower and a t t he we l l head . S am pl i ng po i n t s

fo r GF B and GF C a re s how n i n f i gu re 1 . B i o f i l m and wa t e r s am p l es were co l l ec t ed dow ns t r eam o f

deae ra t i on t ower , and ad d i t i ona l wa t e r s am p l es a t we l l he ad fo r s e l ec ted we l l s . GF B has s up p l y o f t r ea ted

i n j ec t i on wa t e r f rom GF A v i a 4 km p i pe l i ne i n add i t i on t o s epa ra t e GF B i n j ec t i on wa t e r t r ea t m en t p l an t .

B i op robes and wa t e r s am p l es were co l l ec t ed a t t he wa t e r r ecep t i on f rom GF A, and add i t i ona l wa t e r

s am p l es a t we l l head m an i fo l d .

M i c r o b i o l o g i c a l m o n i t o r in g

Mi crob i a l m on i t o r i ng o f t he wa t e r i n jec t i on s y s t em fo l l owed the s am e p roc edu res a s p rev i ous l y

des c r i bed fo r t he Ves l e f r i kk f i e ld 10. The t o t al num ber o f bac t e r i a was de t e rm i ned wi t h ep i f luo res cence

m i c ros copy a f t e r f i l t e r i ng s am p l es on t o a 0 . 2 gm nuc l epo re f i l t e r and s t a i n i ng wi t h t he DNA s pec i f i c

f l uo res cen t dye DAP I ~ . S R B was de t e rm i ned by f l uo res cen t an t i body (F A) t echn i que a s des c r i bed by

Ni l se n e t a l. ~2. A m ixture of an t ibodie s spe ci f ic for SRB ut i l i s ing lacta te , aceta te an d long ch ained fa t ty

ac i d s was p repa red and u s ed fo r s pec if i c de t e rm i na t i on o f t hes e phys i o l og i ca l S R B g roups . The

an t i bod i es a r e po l yc l ona l and s pec i f i c fo r S R B p rev i ous l y i s o l a t ed f rom wa t e r i n j ec t i on s y s t em s a t t he

S t a t fj o rd and G u l l f aks f i e l d (Nor t h S ea ) .

V i a b l e c o u n t s o f S R B w e r e d e t e r m i n e d w i t h t h e " m o s t p r o b a b l e n u m b e r " m e t h o d ( M P N ) u s i n g a

m e d i um des c r i bed b y P os t ga t e 13, t a rge t i ng l ac ta t e ox i d i s i ng S R B . T he m ed i u m was d i s pens ed i n

a l i quo t s o f 9 m l i n t o n i t rogen - f l u s hed 10 m l s e rum bo t tl e s , and s ea l ed wi t h bu t y l rubber s t opper s and

a l um i n i um c r i m p s ea l s . C u l t u res were i ncuba t ed a t 30° C fo r 4 weeks and as s ayed fo r HzS p roduc t i on

and bac t e r i a l g rowt h .

S R B ac t i v it y was de t e rm i ned by r ad i o res p i r a t o ry m eas u rem en t u s i ng 35S l abe l l ed s u l f a t e a s des c r i bed by

Paulsen et al . ~4.

Ni t r a t e r educ i ng bac t e r i a (NR B ) were quan t i f i ed by M P N m et h od u s i ng a s u l f a te f r ee m i ne ra l m e d i um

des c r i bed by My hr e t a l . 7. The ca rbon s ou rces w ere a m i x t u re o f ( fi na l concen t r a t i on ) ; ace t a t e (20 m M) ,

bu t y ra t e (5 m M) , cap roa t e (5 m M) and l ac t a t e (8 .2 m M) . Lac t a t e was added t o t he m i ne ra l m ed i um

befo re au t oc l av i ng , t he r em ai n i ng s ubs t r a t e s were s t e r i l e f i l t e r ed and added a f t e r au t oc l av i ng . Two t ypes

o f N R B m e d i a w e r e u s e d. O n e m e d i u m t a r g e ti n g f a c u lt a t iv e l y a n a e ro b i c N R B w a s m a d e a n o x i c b yf l u s h i ng t he m ed i um wi t h n i t rogen gas . The o t he r m ed i um , t a rge t i ng ob l i ga t o ry anae rob i c NR B , was i n

add i t i on r educed w i t h 2 m M N azS (f i na l concen t r a t i on ) t o r em ove t r aces o f oxygen . T he m e d i a were

d i s pens ed i n a l i quo t s o f 9 m l i n to n i t rogen - f l u s hed 10 m l s e rum bo t t le s , and s ea l ed wi t h bu t y l rubber

s t opper s and a l um i n i um c r i m p s ea l s . C u l t u res were i ncuba t ed a t 30° C fo r 4 weeks and as s ayed fo r

bac t e r i a l g rowt h .

3



T h e d e t ec t io n l im i t f o r SRB an d NRB b y th e MPN m e th o d i s 6 ce l l s / cm 2 in b iof i lm sam ples an d 0 .3

ce l ls /ml in wa ter sam ples . T he de tec t ion l imi t o f SRB using the F A tec hniqu e is 105 ce l l s /cm 2 in b io f i lm

sam p le s an d 2 5 5 ce l l s /m l i n wa te r sam p le s .

E n r i ch m en t cu l tu r e s

Fo r en r i ch m en t cu l tu r e s o f SRB a m in e r a l m ed iu m d esc r ib ed b y W id d e l an d P f en n ig ~5 was u sed ,

to which d i f fe ren t carbon sources were added . Pa lmi ta te ( f ina l concen tra t ion 1 .5 mM) was used to enr ich

for SRB ab le to ox id ise long chained fa t ty ac id , benzoate ( f ina l concen tra t ion 0 .25 raM) was used to

en r i ch f o r SRB ab le to o x id i se a r o m a t i c s , an d ace t a t e ( f in a l co n cen t r a t io n 2 0 m M ) w as u sed to en r i ch f o r

ace t a t e o x id i s in g SRB. Gr o wth o f SRB was d e t e r m in ed b y su lp h id e p r o d u c t io n a s d e sc r ib ed b y Co r d -

Ru wis h 16. The m ethod was mo dif ied by add ing 0 .5 ml cu l tu re sam ple in 2 ml copper reagen t and

v i su a l ly d e t e r m in in g p o s i t i v e su l f id e p r o d u c t io n b a sed o n th e in t en s i ty o f co lo u r in g co m p ar ed to a b l an k

m ed iu m sam p le . Fo r en r i ch m en t cu l tu re s o f NR B n i t r o g en f lu sh ed an d red u ced m e d ia we r e m ad e u s in g

th e sam e m in e r a l m ed ia a s u sed f or NR B- M PN se ri e s , w i th p a lm i t a t e , b en zo a te an d ace t a t e a s c ar b o n

so u r ce s ( in t he sam e co n cen t r a t io n s a s u sed f o r SRB) . Gr o w th o f NR B was d e t e r m in ed a s i n cr ea se in

ce ll n u m b er s . 4 5 m l m ed iu m was in o cu la ted wi th 5 m l wa te r sam p le o r 1 m l b io f i lm sam p le an d

in cu b a ted a t 3 0 °C f o r u p to t h ree m o n th s an d a ssay ed f o r HzS p r o d u c t io n a n d /o r b ac t e r ia l g r o wth .

Co r r o s io n m o n i to r in g

Co r r o s io n m o n i to r in g in t h e wa te r i n j ec t io n sy s t em was p e r f o r m ed b y we ig h t l o ss co u p o n s , o n

GFB a t p o in t o f t r e a t ed in j ec tio n wa te r r e cep t io n f ro m G FA, an d d o w n s t r eam th e d eae r a to r o n GFC.

F lu sh m o u n ted C- s t ee l b io co u p o n s a r e a r r an g ed c lo se to t h e co r r o s io n m o n i to r in g eq u ip m en t . T h e

m e ta l lu r g y o f t he w a te r i n j ec t io n sy s t em d o w n s t r eam th e d eae r a to r i s C- s t ee l .

M e a s u r e m e n t o f H 2 S

H2S was measured wi th a Dr~eger tube appara tus in the gas phase f rom tes t separa tor (as ppm

HzS in the hydrocarbon gas phase) o r as ppm HzS in the sa les gas .

T he H2S data f rom Gul l faks a re based on s ing le wel l tes t separa to r measurements . The H2S

co n cen t r a t io n i s m easu r ed in t h e g a s p h ase an d m u l t ip l i ed wi th th e am o u n t o f g a s p r o d u ced . T h i s g iv e s

to t al k i lo s o f H2 S p r o d u ced . T h e k i lo s p r o d u ced a r e th en d iv id ed b y th e am o u n t o f p r o d u ced wa te r ;

which is main ly in jec ted seawater , to g ive a concen tra t ion in the water .

On ly we l l s , wh ich , d u r in g th e o b se r v a t io n p e r io d , h av e n o t b een r eco m p le t ed an d h av e h ad a wa te r

product ion h igher than 500 m3/day , have been inc luded in the survey . This was done because o i l and gas

h as a b ack g r o u n d l ev e l o f HzS an d b ack ca l cu la t in g th a t am o u n t i n to a sm a l l w a te r v o lu m e , w i l l g ive

e r r o n eo u s h ig h co n cen t r a t io n .

On th is b a s i s d a t a fr o m 1 4 we l l s o n GFB an d 11 we l l s o n GFC h av e b een in c lu d ed . Da ta f r o m G FA was

ex c lu d ed b ecau se o f f ew s t ab l e we l l s an d an ex ten s iv e W AG p r o cess .

4



R E S U L T S

Microb ia l ac t iv i ty in the water in j ec t ion sys t em pr io r to n i t ra t e in j ec t ion

A t t h e b e g i n n i n g o f t h e mo n i t o r i n g p e r i o d s t a rt i n g a t G FB i n 1 9 8 9 a n d G F C i n 1 9 9 2 , SRB

d o mi n a t e d t h e b a c t e r i a l c o mmu n i t y i n t h e b i o f i l m ( f i g u r e 2 a n d 4 ) , a s d e t e c t e d w i t h FA . L a c t a t e

o x i d i z i n g SRB , d e t e c t e d a s v i a b l e c o u n t s a s r e c o m me n d e d b y A PI R P- 3 8 ~7, w e r e o n l y s p o r a d i c a l ly

d e t e c t e d i n th i s p e r io d . S t a i n i n g w i t h s p e c i f ic F A i n d i c a t e d t h a t t he p o p u l a t i o n w a s d o m i n a t e d b y a c e t a te

a n d f a t t y a c i d o x i d i z i n g SRB, n o t a b l e t o g r o w i n t h e s t a n d a r d MPN me d i u m.

A t G FB , SRB ( a s e n u m e r a t e d b y MP N ) w e r e r e g u l a r ly d e t e c te d w i t h v i a b le c o u n t s f r o m A p r i l 1 9 9 4

(f igure 2 ) . Over the nex t two years a rap id increase in SRB v iab le coun t s was observed , un t i l t he v i ab le

c o u n t s m a t c h e d t h e FA c o u n t s a n d s t a b il i z e d a t 1 .1 0 6 t o 6 .1 06 S RB / c m 3, ma k i n g u p 1 t o 3 % o f t h e t o ta l

b a c t e r i a l p o p u l a t i o n . T h e i n c r e a s e i n v i a b l e c o u n t s w a s a c c o mp a n i e d b y a n i n c r e a s e i n s u l f a t e r e d u c i n g

ra te in the b io f i lm to an average o f 4 .6 gg HzS/cm2/day and increased co r ros ion ( f igure 3 ) .

A t G F C a s i m i l a r t r e n d w a s o b s e r v e d . B e f o r e n i tr a t e i n je c t i o n v ia b l e c o u n t s o f SRB r e a c h e d a ma x i m u m

o f 1 . 10 7 SR B/ c m 3, a n d m a d e u p 6 % o f t h e t o ta l b a c t e r i a l p o p u l a t i o n ( f i g u re 4 ) . T h e i n c r e a s e i n v i a b l e

coun t s w as ac com pan ied by an increase in su l fa te redu c ing ra t e to 11 .9 ~ tg H2S/cm2/day (averag e) in the

b i o f i l m a n d i n c r e a s e d c o r r o s i o n , b u t i n c o n t r a s t t o w h a t w a s o b s e r v e d o n G FB, t h e SRB a c t i v i t y

me a s u r e me n t s d r o p p e d t o a l o w l e v e l a f t e r r e a c h i n g a ma x i mu m i n J a n u a r y 9 6 ( f i g u r e 5 ) .

N RB w e r e p r e s e n t i n l o w n u mb e r s i n t h e w a t e r i n j e c t i o n s y s t e ms a t b o t h p l a t f o r ms p r i o r t o t h e s t a r t o f

t h e n i t ra t e t r e a t me n t ( 1 03 N R B/ c m 2 i n Ma y 1 9 9 9 a t G FB a n d 105 N R B/ c m 2 i n Se p t e m b e r 1 9 9 9 a t G FC,

f i g u r e 2 a n d 4 ) . E n r i c h me n t c u l t u r e s s h o w e d t h a t t h e N RB i n w a t e r a n d b i o f i l m s a mp l e s f r o m b o t h

p l a t f o r ms w e r e a b l e to u t i li z e a b r o a d r a n g e o f c a r b o n s o u r c e s i n c l u d i n g a c e t a te , p a l mi t a t e , b e n z o a t e a n d

lactate.

T h e t o t a l n u mb e r o f b a c te r i a i n th e b i o f i l m w a s c l o s e t o 1 0~ c e l l s /c m 2 t h r o u g h o u t t h e mo n i t o r i n g p e r i o d

( f i g u r e 2 a n d 4 ) a t b o t h G FB a n d G FC.

Microb ia l ac t iv i ty a f t e r n i t ra t e in j ec t ion

A t G FB n i t r a t e i n j e c t i o n s t a r t e d i n O c t o b e r 1 9 9 9 . T h e f i r s t r e d u c t i o n i n SRB w a s d e t e c t e d 1

month a f t e r n i t ra t e in j ec t ion , as a decrease in v i ab le coun t s in the b io f i |m. A fu r ther decrease in the

v i a b l e SRB c o u n t s w e r e o b s e r v e d d u r i n g t h e n e x t f e w mo n t h s u n t i l s t a b i l i z i n g a t a p p r o x i ma t e l y 1 0 3

SR B/ c m 2. T h e F A c o u n t s s h o w e d l a rg e f l u c t u a t io n s o v e r t h e n e x t tw o y e a r s , a n d h i g h v a l u e s ( mo r e t h a n

105 S R B / c m 2 ) w e r e o b s e r v e d , b e f o r e d r o p p i n g d r a ma t i c a l l y b e l o w t h e d e t e c t i o n l e v e l ( f i g u r e 2 ) .

N i t r a t e i n j e c t i o n r e s u l t e d i n a n e n r i c h me n t o f N R B i n t h e b i o f i l m ( f i g u r e 2 ) . A s i g n i f ic a n t r i s e in N R B

n u mb e r s w e r e d e t e c t e d , a n d a f t e r a p p r o x i ma t e l y 1 0 mo n t h s v i a b l e c o u n t s h a d i n c r e a s e d a b o u t 1 0 0 0 f o l d ,

and s t ab i l i zed a t 1 0 6 N R B / c m 2. T h e h i g h e s t v ia b l e c o u n t s o f N R B w e r e o b s e r v e d w i t h th e me d i u m

t a r g e t i n g f a c u l t a ti v e a n a e r o b i c N R B, w h i c h e n d e d u p a t 5 % o f t h e t o ta l b a c t e r i a l p o p u l a t io n . T h es u b s t r a t e d i v e r s i t y i n t h e N RB p o p u l a t i o n r e ma i n e d d i v e r s e a f t e r n i t r a t e i n j e c t i o n . N i t r a t e t r e a t me n t d i d

no t resu l t i n chan ges in the to t a l numb er o f bac te r i a in the b io f i lm.

A l s o a t G FC t h e f i r s t r e d u c t i o n i n SRB w a s d e t e c t e d a s a d e c r e a s e i n v i a b l e c o u n t s , w h i c h w e r e r e d u c e d

1000 fo ld f rom m ore than 105 to approx ima te ly 1 0 2 S R B / c m 2. FA c o u n t s c o u l d n o l o n g e r b e d e t e c t e d

5



a f t e r 1 6 mo n t h s n i t r a t e i n j e c t i o n . A s o b s e r v e d a t G FB t h e d e c r e a s e i n SRB n u mb e r s w e r e a c c o mp a n i e d

by a reduc t ion in su l fa t e resp i ra t ion ac t iv i ty ( f igure 5 ) . Dur ing n i t ra t e t rea tmen t , su l fa t e resp i ra t ion ra t e in

the b io f i lm d ropp ed and s t ab i l i zed a t 1 .3 l ag HzS/cmZ/day .

A s o b s e r v e d a t G F B, n i t r a te i n j e c t i o n r e s u lt e d i n 1 0 0 0 - f o l d i n c r e a s e i n N R B n u m b e r s i n t h e b io f i lm .

N R B n u m b e r s r e a c h e d a n a v e r a g e o f 2 .1 0 7 N R B / c m 2 a f te r a p p r o x i m a t e l y 1 0 m o n t h s , m a k i n g u p 1 0 % o f

the to t a l bac te r i a l popu la t ion .

Ba c t e r i a i n w a t e r s a mp l e s

T h e c h a n g e s i n t h e b a c t e r i a l c o mmu n i t y o b s e r v e d i n b i o f i l m s a mp l e s w e r e a l s o e v i d e n t i n t h e

w a t e r s a mp l e s , b u t l e ss p r o n o u n c e d . T h e n u m b e r o f v ia b l e c o u n t s o f SRB i n a n a e r o b i c w a t e r s a mp l e s

f r o m b o t h G FB a n d G FC b e f o r e n i tr a t e i n je c t i o n w a s g e n e r a l l y l o w , le s s t h a n 1 SR B/ m l w a s d e t e c t e d .

E n r i c h m e n t c u l t u r e s s h o w e d t h a t SRB a b l e t o g r o w o n la c t a te w e r e p r e s e n t i n s a mp l e s o f a n a e r o b ic

i n j e c ti o n w a t e r t h r o u g h o u t t h e g l u t a r a l d e h y d e t r e a t me n t p e r i o d . A f t e r t h e s ta r t o f n i t ra t e t r e a t me n t SRB

a b l e t o g r o w o n l a c t a t e , a c e t a t e , b e n z o a t e a n d p a l mi t a t e w e r e d e t e c t e d i n e n r i c h me n t c u l t u r e s .

E n r i c h me n t c u l t u r e s a l s o s h o w e d t h a t N RB w e r e a b l e t o u t i l i z e t h e s a me s u b s t r a t e s a s SRB, a n d t h a t t h e y

w e r e a l r e a d y p r e s e n t i n w a t e r s a m p l e s p r i o r t o n it r a te i n j ec t i on . T h e t o t a l n u m b e r o f b a c t e r ia i n w a t e r

s a mp l e s w a s c o n s t a n t a n d c l o s e t o 105 c e l l s /m l t h r o u g h o u t t h e mo n i t o r i n g p e r i o d .

C o r r o s i o n m e a s u r e m e n t s

Co r r o s i o n me a s u r e me n t s o n C- s t e e l c o u p o n s s h o w e d t h a t , d u r i n g t h e p e r i o d w i t h g l u t a r a l d e h y d e

i n j e c t i o n , w e i g h t l o s s i n c r e a s e d f r o m a n i n i t i a l l o w v a l u e t o 1 . 0 6 mm/ y e a r a t G FB a n d 0 . 7 6 mm/ y e a r a t

G FC. N i t r a t e t r e a t me n t r e d u c e d c o r r o s i o n r a t e s t o 0 . 4 mm/ y e a r ( G FB) a n d 0 . 2 8 mm/ y e a r ( G FC) ( F i g u r e

3 a n d 5 ) . I n c r e a s e d p i t ti n g w a s n o t o b s e r v e d .

H 2 S p r o d u c t i o n

A v e r a g e H2S c o n c e n t r a t i o n i n p r o d u c e d w a t e r ( s e a w a t e r c u t i s a p p . 8 0 % ) o n G F B a n d G FC w a s

un t i l 2000 increas ing , f rom an o r ig ina l va lue o f app . 0 .05 mg/1 , t o app . 2 and 4 rag /1 respec t ive ly befo re

b r e a k t h r o u g h o f n it r a te t r e a t e d s e a w a t e r i n th e p r o d u c e r s . S i n c e M a y 2 0 0 0 t h e H 2S c o n c e n t r a t i o n h a s

d r o p p e d t o a p p . 1 a n d 2 mg /1 a t G FB a n d G FC r e s p e c t iv e l y .

The resu l t s a re p resen ted in f igures 6 and 7 .

D I S C U S S I O N

M icrob ia l ac t iv i ty and cor ros ion in the water in j ec t ion sys t em

Pr io r to n i t ra t e in j ec t ion , a t bo th Gul l faks B and Gul l faks C, the water in j ec t ion sys t em con ta ined a

s t a b l e a n d d i v e r s e SRB p o p u l a t i o n , c o u n t i n g a p p r o x i ma t e l y 1 0 6 S R B / c m 2 (a s s h o w n b y b o t h F A a n d

v i a b l e c o u n t i n g ) . T h e a v e r a g e s u l fa t e r e d u c t i o n r a t e a t G FB a n d G FC w a s 4 . 6 a n d 1 1 .9 ~ tg HzS/cmZ/day

r e s p e c t i v e l y , a n d e n r i c h m e n t c u l t u r e s f r o m w a t e r a n d b i o fi l m s h o w e d t h e p r e s e n c e o f SRB c a p a b l e o f

6



u t i li z i n g a w i d e r a n g e o f c a r b o n s o u r c e s . N RB w e r e a l s o p r e s e n t , i n b o t h w a t e r a n d b i o f i lm , b u t i n l o w

n u m b e r s ( 1 03 N R B / c m 2 a t G F B a n d 104 N R B / c m 2 a t G F C ) . E n r i c h m e n t c u l tu r e s s h o w e d t h a t N R B

u t i li z e d t h e s a me r a n g e o f c a r b o n s o u r c e s a s SRB.

T h e c h a n g e f r o m b i o c i d e t r e a t me n t t o n it r a te t r e a t me n t r e s u l t e d i n mo r e t h a n 1 0 0 0 - f o l d r e d u c t io n i n SRB

n u m b e r a n d 1 0 - 2 0 - f o l d r e d u c t i o n i n s u l p h a t e r e s p i r a ti o n a c t iv i t y . O v e r a y e a r f o l l o w i n g n i t r a te i n j ec t io n ,

t h e SRB p o p u l a t i o n w a s r e p l a c e d w i t h a n e q u a l l y la r g e p o p u l a t i o n o f N R B a n d t o d a y N R B c o n s t it u t e

a p p r o x i ma t e l y 1 0 % o f t h e to t a l p o p u l a t i o n i n t h e b i o f il m . C o r r o s i o n r a t e s a t G FB a n d C w e r e n e v e r v e r y

h i g h , r e a c h i n g a ma x i mu m o f 1 . 0 a n d 0 . 7 mm/ y e a r a t G FB a n d G FC r e s p e c t i v e l y p r i o r t o n i t r a t e

t r e a t me n t . U p o n n i t r a t e t r e a t me n t t h e c o r r o s i o n l e v e l d r o p p e d b y mo r e t h a n 5 0 % . T h i s r e s u l t c o r r e s p o n d s

w e l l w i t h t h e o b s e r v a t i o n s f r o m a s i m i l a r w a t e r i n j e c t io n t r e a t m e n t a t V e s l e f r i k k 10. A t V e s l e f r i k k S RB

n u m b e r s w e r e r e d u c e d 2 0 0 0 0 f o l d a n d SRB a c t i v it y 5 0 f o ld a f t e r 3 2 mo n t h s o f n it r a te t r e a t me n t a n d

c o r r e s p o n d i n g t o t h e d e c r e a s e i n SRB , g r o w t h o f n i tr a t e r e d u c i n g b a c t e r i a ( N RB ) w a s s t i mu l a t e d .

Co r r o s i o n me a s u r e me n t s o n me t a l c o u p o n s s h o w e d a d e c r e a s e i n w e i g h t l o s s f r o m 0 . 7 mm/ y e a r t o 0 . 2

mm/ y e a r . T h e r e s u l t s f r o m G u l l f a k s c o n f i r m t h a t n i t r a t e t r e a t me n t c o u l d e f f i c i e n t l y i n h i b i t g r o w t h o f

S R B a n d c o nt r ol M I C .

Re s e r v o i r s o u r i n g

I n t h e e a r l y 1 9 9 0 s , t h e G u l l f a k s A p l a t f o r m e x p e r i e n c e d s e v e r e r e s e r v o i r s o u r i n g . S i n g l e w e l l s h a ds e v e r a l t h o u s a n d p p m HzS i n th e p r o d u c e d g a s , c o r r e s p o n d i n g t o a p p . 3 5 m g H z S /1 i n t h e p r o d u c e d

w a t e r . O n t h e b a s e s o f th e s e w e l l s a n d l a b w o r k , a r e s e r v o i r - s o u r i n g mo d e l w a s d e v e l o p e d 18. U s i n g t h e

b io f i lm op t ion in the model , a typ ica l HzS p roduct ion p ro f i l e as shown in f igure 8 , can be expec ted .

A l t h o u g h H2S genera t ion a t t he in j ec to r s t a r t s immedia te ly a f t e r seawater i s i n j ec t ed , t he b reak th rough o f

HzS i n the p roducers i s de layed by severa l po re vo lumes (p .v . ) . Th i s de lay in HzS b r e a k t h r o u g h i s c a u s e d

by adsorp t ion and equ i l ib r ium wi th rock and res idua l o i l i n the reservo i r .

T h e r e d u c t i o n i n H2S p r o d u c t i o n o b s e r v e d u p o n n i tr a t e tr e a t me n t o f i n j e c t io n w a t e r c o r r e s p o n d s w e l l

w i t h t h e r e su l t s o b t a i n e d f r o m l a b o r a t o r y e x p e r i me n t s . M y h r e t al . 7 s h o w e d t h a t i n j e c t i o n o f 0 .5 m M

n i tr a t e f o r 2 .5 - 3 . 5 m o n t h s l e d t o c o mp l e t e i n h i b it i o n o f H 2 S- p r o d u c ti o n f r o m a n o i l r e s e r v o i r mo d e l

c o l u mn . A s e x p e c t e d t h e o b s e r v e d e f f e c t o f n it r at e t r e a t me n t is d e l a y e d i n a f ie l d c o m p a r e d t o a mo d e l

s y s t e m d u e t o l o n g e r r e s i d e n c e t i me f o r w a t e r .

Even m ore imp or tan t i s t he fac t t ha t when s topp ing the H2S genera t ion , by us ing n i t ra t e , par t o f the

a d s o r b e d H 2 S w i l l f r o m e q u i l i b r i u m r e a s o n s , e n t e r t h e w a t e r o n i t s w a y t o t h e p r o d u c e r s , s o i t my t a k e a

long t ime to reach p re sour ing H2S va lues .

I t i s a l so im por tan t to no t i ce , t ha t when m easu r ing in the gas f rom tes t s ep ara to r , on ly a par t o f the to t a l

HzS i n the wel l s t ream i s acco un ted fo r . The s i ze o f the f rac t ion depe nds on the p ressu re in the t es t

s e p a r a t o r a n d a l s o t h e g a s / o i l / w a t e r r a t i o s . W h e n t h e p r e s s u r e i s l o w e r e d f u r t h e r t h r o u g h t h e s e p a r a t i o n

train , more HzS w i l l b e r e l e a s e d i n t o t h e g a s p h a s e . O n t h e G u l l f a k s p l a t f o r ms , t h e ~ S c o n c e n t r a t i o n i n

the sa l es gas (befo re s cave ng ing ) i s two to th ree t imes h igher than the t -IzS con cen t ra t ion es t im ated f romtes t s epara to r va lues .

7



C O N C L U S I O N S

H2S c o n c e n t r a t i o n s i n p r o d u c e d w a t e r h a v e d e c r e a s e d i n mo s t p a r ts o f t h e G u l l f a k s f i e l d a f te r

s t a r t ing wi th n i t ra t e in j ec t ion .

• I n t h e w a t e r i n j e c t io n s y s t e m n i t ra t e i n j e c ti o n l e d t o r e d u c t io n i n SR B n u m b e r s a n d a c t i v it y a n d a

c o n c o m i t a n t e n r i c h m e n t o f N R B .

• Co r r o s i o n m e a s u r e m e n t s o n me t a l c o u p o n s i n t h e w a t e r i n j ec t i o n sy s t e m s h o w e d a d e c r e a s e i n w e i g h t

l o s s o f mo r e t h a n 5 0 % a f t e r c h a n g i n g f r o m b i o c i d e t o n it r a te t r e a t me n t .

A C N O W L E D G M E N T S

T h e a u t h o r s w a n t t o th a n k Be n t e T h o r b j o r n s e n a n d R i k k e H e l e n U l v o e n f o r te c h n i c a l a s s i s t a n c e a n d t he

Gul l faks l i cense PL 050 fo r the oppor tun i ty to g ive th i s p resen ta t ion .

R E F E R E N C E S

1. Jenn em an , G .E . e t a l . 1986 . Ef fec t o f n i t ra t e on b iogen ic su l f ide p rod uct ion . App l . Env i ron .

Microb io l . 51" 1205-1211 .

2 . M a c I n e r n e y M . J . e t a l. 1 9 9 2 . E v o l u t i o n o f a m i c r o b i a l m e t h o d t o re d u c e h y d r o g e n s u l f id e l e v e ls

in a poro us roc k b io f i lm. J . Ind . M icrob io l . 11"53-58 .

3 . H i t z m a n , D . O . a n d G . T . Sp er l , 1 9 9 4. A n e w mi c r o b i a l t e c h n i q u e f o r e n h a n c e d o i l r e c o v e r y a n d

s u l f i d e p r e v e n t i o n a n d r e d u c t i o n . So c . Pe t r o l . E n g . SPE 2 2 7 5 2 : 1 7 1 - 1 7 9 .

4 . Su b l e t ti , K . L . e t a l. 1 9 9 4 . A f ie l d d e m o n s t r a t i o n o f so u r - p r o d u c e d w a t e r r e me d i a t i o n b y

mi c r o b i a l t r e a t me n t . SPE P r o d u c t i o n a n d Fa c i l i t i e s 9 : 1 8 3 - 1 8 7 .

5 . Lon dry , K .L . and J .M. S uf l i t a , 1999 . Use o f n i t ra t e to con t ro l su l f ide g enera t ion by su l fa te -

reduc ing bac te r i a as soc ia t ed wi th o i ly was te . J . Indus t . Microb io l . Bio tech . 22 : 582-589 .

6 . Rein se l e t a l . 1996 . Con t ro l o f micro b ia l sour ing by n i t ra t e , n i t r it e o r g lu ta ra ldehy de in j ec t ion in

a sands tone co lumn. J . Ind . Microb io l . 17 : 128-136 .

7 . M yhr , S . , B-L .P . L i l l ebo , J . Beed er , E . Sunde , and T . Torsv ik , 2002 . Ef fe c t o f n i t ra t e in j ec t ion on

HzS p r o d u c t i o n a n d mi c r o b i a l c o mm u n i t y c o m p o s i t i o n i n a n o il re s e r v o i r mo d e l s y s t e m. A p p l .

M i c r o b i o l . B i o t e c h n o l . 5 8" 4 0 0 - 4 0 8 .

8 . Te lan g , A .J . e t a l . 1997 . The e f fec t o f n i t ra t e in j ec t ion on the microb ia l co m m uni ty in an o il f i e ld

a s mo n i t o r e d b y r e v e r s e g e n o me p r o b i n g . A p p l . E n v i r o n . Mi c r o b i o l . 6 3 : 1 7 8 5 .

8



9. Jennem an, G.E. et al. 199 9. Sulfide removal in reservoir brine by indigenou s bacteria. SPE Prod.

& Facilities 14 (3)" 219-225 .

10. Tho rstenson, T., G. Bodtker, B -L.P. Lillebo, T. Torsvik, E. S unde an d J. Beeder, 2002 . Biocide

replacem ent by nitrate in seawater injection systems. In" Corro sion NA CE xp o 2002 57th Annual

Conference and Exposi t ion. D enver , Colorado, USA.

11. Porter, K.G. and Y .S. Feig, 19 80 . The u se of DAP I for identifying and counting aquatic

microflora. Limnol. Oceanogr. 25" 943-948.

12. Nilsen, R .K. , J . Beeder , T. Torsvik and T. Thors tenson, 199 6. Dis tr ibut ion of thermophil ic

marine sulfate reducers in North Sea oil f ield waters and oil reservoirs. Appl. Environ. Microbiol.

62" 1793-1798.

13. Postgate, J .R. 198 4. The sulfate-reducing b acteria, 2"ded. , Cambridge Univers i ty Press , London,

1984.

14. Paulsen, J .E. 19 86 . Radiorespirometr ic m easurement of sulfa te reduct ion in Desulfovibrio.

Thesis in Genera l Microbiology. Un ivers ity of Bergen. Norw ay. ( in Norwegian

15. W iddel, F. and N. Pfennig, 198 4. Dissim ilatory sulfate- and sulph ur-reducin g bacteria. In: Kieg,

N.R ., J .G. Holt, (eds.) Berge y's manual o f systematic bacteriology , vol. 1. W illiams & Wilkins.

Bal t imore , London, pp. 663-679.

16. Cord-Ruw ish, R. 1985 . A quick method for de terminat ion o f dissolved and prec ipi ta ted sulfides

in cultures o f sulfate-reducing bacteria. J . Micob iol. Meth. 4: 33-36.

17. API RP-38, 1975 . Recom men ded prac tice for biological ana lys is of subsurface injec t ion w aters .

Am erican Petroleum Ins ti tute .

18. Sunde, E., T. Thorsten son, T. Torsvik, J .E. V aag and M.S. Esped al, 19 93 . Field-Related

Mathematica l Model to Predic t and Reduce Reservoir Sour ing. Paper SPE 25197, presented a t

the SPE Interna t ional Symp osium on O ilfie ld Ch emistry in Ne w Orleans , LA, USA. M arch 2-5.

9



.................. S a n (f ff lt er

Ni t r ~ te

Vacuum

deaeration

tower - - )

W ate r s am p l e

W e U h e a d m a m f o l d

m

TS e awater re take

a t l 2 0 m ( G F C )

an d 70 I n ( ( ; ~ " B )

Bioprobe and watersample

W ate r s am p l e

Fi gure 1 . The water i n ject i on sys tem a t Gul l faks C . Water i s abs tracted a t 70 m eter a t GFB and a t 120

m e t e r a t G F C . B o t h n i tr a te a n d b i o c i d e ( b e f o r e O c t . 1 9 9 9 ) w e r e a d d e d b e f o r e d e a e r a t i o n t o w e r . T h e

a n a e r o b i c p a r t o f t h e w a t e r in j e c t i o n s y s t e m i s m a r k e d i n b l a c k . B i o f i l m a n d w a t e r s a m p l e s w e r e

c o l l e c t e d d o w n s t r e a m o f d e a e r a t io n t o w e r , a n d a d d i ti o n a l w a t e r s a m p l e s a t w e l l h e a d f o r s e l e c t e d

i n d i v i d u a l w e l l s .

10



1 , 0 E + 0 9

1 , 0 E + 0 8

1 , 0 E + 0 7

¢' ,1

1 , 0 E + 0 6

1,0E+05ca

1 , 0 E + 0 4

1 , 0 E + 0 3

1,0E+021 , 0 E + 0 1

1 , 0 E + 0 0

1 ,0 E + 1 0 ................................................................................ .............. I ...................................................

• ' ~ ~ ; 2 " : ~ ~ ~ ; ~ , . a ~ ~ " '

•~ "~ E = " E E = 5

T i m e ( m o n t h s )

B i o c i d e ( g l u t a r a l d e h y d e ) v - N i t r a te ( s t a r t o c t . 9 9 ) v -

SR B - F A

~ S R B - M P N

l. I NRBTotal bacteria

D e t e c t i o n l im i t F A m e t h o d : le+05 cells/cm2

D e t e c t i o n l i m i t M P N m e t h o d ' 6 cells/crn2

F i g u re 2 . N u m b e r o f b a c te r ia i n b io f i lm c o l l e c te d f r om b i o c u p o n s m o u n t e d d o w n s t r e a m o f d e ae r a ti o n

t o w e r a t G F B . C o l u m n m a r k e d N R B s h o w c e ll n u m b e r i n M P N s e r ie s t a rg e t in g b o t h f a c u lt a t iv e l y a n d

o b l ig a t o r y a n a e r o b ic N R B .

1 , 2 2 5 " ~

1 ,0> ,

EE o , a ~

i i i i i i ! i i ! i i i i i i i i i i ! i i ~ i ~ i ~ i ~ i ~i i i i i i i i i i i i~ i~ i i~ i i i ! i i i i i i i l

; i i ii i i ii ~ i i i i i i i i i i l - _ _ i i i ii i ii i !

i i i i ii i i , i i i ! i ~ : . . . . . .. . . . .. . . . . .. . . . . i i i i i i ii i i~ . . . . . . .

¢ ~ t - ~ t - . " . .~

t

N i t r a t e

0 ,6i_

C

. o 0 ,4

" 0 , 2oO

0 , 0

C o r r o s i o n r a t e

- - 0 - S R B a c t iv i ty ]J

B i o c i d e

%o

2 0

"1 -

15

10 ._~

5IDag

ofar)

F i g u r e 3 . S R B a c t i v it y a n d c o r r o s i o n r a te a t G F B .

11



1 , 0 E + 1 0

1 , 0 E + 0 9

1 , 0 E + 0 8

1 , 0 E + 0 7

E 1 , 0 E + 0 6r~

1 , 0 E + 0 5

1 , 0 E + 0 4

1 , 0 E + 0 3

1 , 0 E + 0 2

1 , 0 E + 0 1

1 , O E + O 0

r , ~ ~ ¢ t ~ , , - , ~ ~ " - - ~ ~ I

T i m e ( m o n t h s )

B io c id e (g lu tara ld e h y d e ) N i tra te ( s tar t n o v .99 )

SR B-FA

~ SR B-MPN

~NRB

Total bacteria

D e t e c t i o n l im i t F A m e t h o d : l e + 0 5 c e l l s / c m 2

D e t e c t i o n l im i t M P N m e t h o d 6 ce l l s / cm2

F i g u r e 4. N u m b e r o f b a c t er i a in b i o f i l m c o l l e c t e d f r o m b i o c u p o n s m o u n t e d d o w n s t r e a m o f d e a er a t io nt o w e r a t G F C . C o l u m n m a r k e d N R B s h o w c e l l n u m b e r in M P N s e r ie s t a rg e t in g b o t h f a c u lt a t i v e ly a n d

o b l i g a t o r y a n a e r o b i c N R B .

0,8 40

0 , 6 -

0 ,4

i 0 .2r,.)

0 , 0 2

!iii!iiiii iiiiiiil

i ! E ~~ ~~ ~!iiii !!i! ! ! !!

~i~!~{!{{{! .......

<:D '~ i ! ~ i !!! i i i i i iY :,,,.:,.,~!!iii!iii!!ii::i::iii::iii i:~:::~::~] !::.::.5..........

!i!)i!i!i! :~~!~ .....

Z~;NNNN~S~SNNNP~NNNmmm~NNNN888SS;;~N m m ~ ~ o o o

Time (months)

B ioc ide N i tra te

~ C or r os i on G F C

S R B a c t i v i t y

F i g u r e 5 . S R B a c t i v i t y a n d c o r r o s i o n r a t e a t G F C

%

3 0 e q

~z

: : 1 .

2 0

" j= l

1 0 ~ '

12



4

~D

• - 3

eq

Zz

~0 2E

6 ...........................................................................................................................................................................................................................

m J

~© ~ ~ ~ <> OO ~

n o v . 9 7 s e p . 9 8 j u l . 9 9 m a i . 0 0 f e b .0 1 d e s . 0 1 o k t . 0 2 a u g . 0 3

Da t e

Figure 6 shows the m e a n H 2 S concentrat ion for 14 producers and theoret i ca l I~S deve lopment on GFB.

• Theoret i ca l H2S deve lopm ent . 0 Measured H2S (mg) in produced water .

1 0 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

6

5rm o

4~0

3

2

1

0

n o v . 9 7

~ % ~

, I , f ~ i ,

s e p . 9 8 j u l . 9 9 m a i . 0 0 f eb . 0 1 d e s .0 1 o k t . 0 2 a u g . 0 3

Da t e

Figure 7 shows the mean H2S concentration for 11 producers and theoretical HzS development on GFC.

• Theoretical H zS development . 0 Measured H zS (mg) in produced water .

13



%

/

~ J0 2 ~

f/

1 0

T i m e ( p v ,)

F i g u r e 8" T h e a m o u n t o f H 2 S v s . d i m e n s i o n l e s s t i m e ( p . v . ) f o r a p r o d u c t i o n w e l l w i t h a d s o r p t io n .

14

H2S Inhibition By Nitrate Injection On The Gullfaks Field

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