MEOR: From an Experiment to a Model

Sidsel Marie Nielsen, Amalia Halim, Igor Nesterov, Anna Eliasson Lantz, Alexander Shapiro

Stavanger, 18 Nov 2014

RECOVERY MECHANISMS

Reduction of oil-water interfacial tension (IFT) by surfactant production and bacteria.

Fluid diversion by microbial plugging.

Reduction of oil viscosity.

Gas production.

2

EXPERIMENTS

3

CHALK ROCKNorth Sea Reservoirs are mainly chalk reservoirs

4

Chalk rock: Small pore throats, comparable to microbe sizes

Stevns Klint outcrop: Model study, pore throat size: 0.004-6.1µm

Bacterial sizes: 0.5x3µm

Scanning Electron Microscope of Cretaceous, Maastrictian M1b1 unit reservoir chalk (Maersk Oil, 2014)

SPORE PROPERTIESModel bacteria used in penetration test:Bacillus licheniformis 421 (spore-forming)Pseudomonas putida K12

Vegetative cellGrowing with metabolism.

Spore

Sporulation induced by stress.

Dormant (non-growing).Smaller size.

Different surface properties.

Reactivation.5

http://bio1151.nicerweb.com/Locked/media/ch27/endospore.html

Schematic Core Flooding Set-up

Injection cylinder

1 = brine/nutrient

2 = bacteria

3 = crude oil

Pressure tapped core holder

Fridge

P1 P2 P3

Fraction collector

dPi = differential pressure transducer= pressure tapped (0.5”, 1.5”, 2.5”)= thermocouple= valves= safety valves

Temperature controller

ISCO pump(injection)

dPi

ISCO pump

(Sleeve pressure)

Heating jacket1 2 3

Webcam

6

Methods

Spore-forming vs non-spore-formingBacteria penetration study/One phase liquid core flooding: Halim et. al., Transp. Porous Med. (2014) 101, 1–15. doi:10.1007/s11242-013-0227-x

• More cells were found in the effluents of core flooding with B. licheniformis 421 as compared to P. putida K12

• Survival/motion of bacteria can be mainly due to spores.

0123456789

1,E+00

1,E+02

1,E+04

1,E+06

1,E+08

1,E+10

In 2 3 4 5 6 7

viab

le c

ell (

cfu

/mL)

PVI

bacteria cell (core 2)

bacteria cell (core 10)B. licheniformis 421

0123456789

1,E+00

1,E+02

1,E+04

1,E+06

1,E+08

1,E+10

In 2 3 4 5 6 7

pH

viab

le c

ell (

cfu

/mL)

PVI

bacteria cell (core 5)bacteria cell (core 9)

P. putida K12

7

Penetrated bacteriaBacteria penetration study/One phase liquid core flooding: Halim et. al., Transp. Porous Med. (2014) 101, 1–15. doi:10.1007/s11242-013-0227-x

B. licheniformis 421 cells under DAPI staining (a) in growth media, before injection into a chalk core plug, cell size 0.5 x 3µm (b) in the effluent from a chalk core plug, spore formation

spore

ba

8

Flooding sequences

9

1. Injection of SS (2-3 PVI)2. Injection of crude oil until Swi

3. Injection of 1PV SS (1st SS)4. Injection of bacteria (1PV)5. Incubation (3 days)6. Injection of SS until Sor (2nd SS)7. Injection of nutrient (1PV)8. Incubation (7 days)9. Injection of SS (3rd SS)

Seco

nd

ary

1. Injection of SS (2-3 PVI)2. Injection of crude oil until Swi

3. Injection of SS until Sor (1st SS)

4. Injection of bacteria (1-3PV)5. Incubation (3 days)6. Injection of SS (2nd SS)

Tertiary

“Tertiary recovery” “Secondary recovery”

Core plug properties

Core ID

k

before

(mD)

k

after

(mD)

before

(%)

after

(%)

26_water 3.2 2.8 30.8 30.7

26_3rd m 3.2 3.1 31.1 30.7

26_2nd m 3.1 3.2 30.7 30.8

• Core 26 – homogenous reservoir chalk core

• No significant change in k and before and after experiment

• No fractures based on CT scan results before and after experiments

10

Results

Tertiary oil recovery method with production stopped at 11.5 PVI.

1 PV bacteria injected and incubated.

Additional oil: 2.3 % OOIP.

Core no Sor (% OOIP)

26_water 45.2

26_3rd method 44.2

Samples Viscosity (cP)

Crude oil 4.96

SS 0.55

SS+molasses+bacteria 0.55

11

0

20

40

60

80

100

0 2 4 6 8 10 12 14 16 18 20 22

cum

mu

lati

ve o

il p

rod

uct

ion

(%

OO

IP)

PVI

core 26_water_1st SS

core 26_water_2nd SS

core 26_3rd method_1st SS

core 26_3rd method_bacteria

core 26_3rd method_2nd SS

+ 1.4 %55.8% + 0.9 %

Do bacteria produce more oil?

Results

Secondary oil recovery method produces 3.3 % OOIP compared to tertiary method. 1 PV bacteria injected 1 PV after break-through.

12

Core no Sor-1PV (%)

26_2nd

method56.7

0

20

40

60

80

100

0 2 4 6 8 10 12 14 16 18 20 22

cum

mu

lati

ve o

il p

rod

uct

ion

(%

OO

IP)

PVI

core 26_water_1st SScore 26_water_2nd SScore 26_3rd method_1st SScore 26_3rd method_bacteriacore 26_3rd method_2nd SScore 26_2nd method_1st SScore 26_2nd method_bacteriacore 26_2nd method_2nd SScore 26_2nd method_nutrientcore 26_2nd method_3rd SS vs. 2nd method→ 3.3 % (at 18.3 PVI)

Secondary vs tertiary recovery?

Total oil recoveryWater : 54.8%Bacteria_3rd : 58.1%Bacteria_2nd : 61.6%

SIMULATIONS

13

1D MEOR SIMULATOR

▪ Generic model.

▪ Growth and other reactions.

▪ Bacterial surfactant reducing IFT.

▪ Bacteria attachment due to filtration or equilibrium adsorption.

▪ Plugging

▪ Application of spore-forming bacteria.

SIMULATOR OVERVIEW

14

1D MEOR MODEL

1 1

p pn n

ij j j ij j j i

j j

s v f qt x

= =

+ =

{ , , , , }, { , }i o w b s m j o w= =

15

Reaction

Bacteria, surfactant and substrate.

Sporulation

Attachment

Irreversible deep bed filtration.

Pore size vs. bacteria size.

16

( )·

( )

s w

b sb bw max

s s w

r Y rK

=

+ 0att bwr v =

00.1sp =

spa spwttr v =

( )s x xyij bs

r K a =

bacteria pore substrateb sp s

a s aa +⎯⎯→⎯⎯

SOURCE TERMS

SPORULATION

17

Sporulation▪ Sigmoid-shaped curve

for stress response in bio-systems

▪ Conversion releasessubstrate.

Reactivation▪ Triggered by good

conditions for survival10

-710

-610

-510

-310

-210

-1

0.0

0.1

0.2

0.3

0.4

0.5

Convers

ion r

ate

s

Kbs

Ksb

EFFECTS

Oil mobilization

Surfactant production

IFT reduction

Residual oil saturation

Relative permeability

Fractional flow

Option: Porosity reduction

Attachment

Microbial growth

Porosity reduction

Water relative permeability

Fractional flow

18

PROFILE CHARACTERISTICS

19

0.0 0.2 0.4 0.6 0.8 1.00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

sa

tura

tio

n

sw (0.21 PVI)

sor (0.21 PVI)

sw (0.30 PVI)

sor (0.30 PVI)

Two oil banks appear.

InjectionConstant rate.Continuous.

RISK OF INLET CLOGGING

Two bacteria peaks.

Surfactant effect.

Inlet clogging risk.

Increased recovery.

20

0.0 0.2 0.4 0.6 0.8 1.0

0.0

1.0x10-4

2.0x10-4

3.0x10-4

4.0x10-4

5.0x10-4

6.0x10-4

7.0x10-4

Volu

me fra

ction

Bac attached

Bac water

Metabolite water

0.32 PVI

0.0 0.2 0.4 0.6 0.8 1.0

0.0

1.0x10-4

2.0x10-4

3.0x10-4

4.0x10-4

5.0x10-4

6.0x10-4

7.0x10-4

0.48 PVI

Volu

me fra

ction

Bac attached

Bac water

Metabolite water

SLUG INJECTION SCHEME

21

0.0 0.2 0.4 0.6 0.8 1.0

0.0

1.0x10-4

2.0x10-4

3.0x10-4

4.0x10-4

5.0x10-4

6.0x10-4

7.0x10-4

0.48 PVI

Vo

lum

e f

raction

Bac attached

Bac water

Metabolite water

sub

stra

te+

spo

res

sub

stra

te

wat

er s

lug

t1 t2t

Slug injection scheme selected to avoid clogging and to concentrate attached bacteria in specific zones in the reservoir.

0.0 0.5 1.0

0.0

2.0x10-6

4.0x10-6

6.0x10-6

8.0x10-6

1.0x10-5

1.2x10-5

1.4x10-5

Volu

metr

ic c

oncen

tratio

n

Bacteria att

Bacteria water

Substrate

Metabolite water

Spores water

Spores att0.67 PVI

0.0 0.5 1.0

0.0

5.0x10-5

1.0x10-4

1.5x10-4

2.0x10-4

2.5x10-4

3.0x10-4

3.5x10-4

4.0x10-4

0.82 PVI

Volu

metr

ic c

oncen

tratio

n

Bacteria att

Bacteria water

Substrate

Metabolite water

Spores water

Spores att

0.0 0.5 1.0

0.0

1.0x10-4

2.0x10-4

3.0x10-4

4.0x10-4

5.0x10-4

6.0x10-4

7.0x10-4

8.0x10-4

0.86 PVI

Volu

metr

ic c

oncen

tratio

n

Bacteria att

Bacteria water

Substrate

Metabolite water

Spores water

Spores att

0.0 0.5 1.0

0.0

1.0x10-4

2.0x10-4

3.0x10-4

4.0x10-4

5.0x10-4

6.0x10-4

7.0x10-4

8.0x10-4

9.0x10-4

0.94 PVI

Volu

metr

ic c

oncen

tratio

n

Bacteria att

Bacteria water

Substrate

Metabolite water

Spores water

Spores att

RELEASING PROCESS

22

Water slug inducesconversion of attached bacteria to spores.

Rate of conversion is determined by released substrateand thus bacteriaconcentration.

REDUCTION OF CONVERSION RATE

23

0.0 0.2 0.4 0.6 0.8 1.0

0.0

5.0x10-5

1.0x10-4

1.5x10-4

Volu

me fra

ction

Bacteria att 0.6

Substrate 0.6

Bacteria att 0.5

Substrate 0.5

Bacteria att 0.4

Substrate 0.4

Waterslug

Waterslug

Waterslug

0.0 0.5 1.0 1.5 2.0

0.0

0.2

0.4

0.6

0.8

Recovery

t (PVI)

1e-3

2e-3

3e-3

4e-3

5e-3

Substrate concentration

Substrate slug 0.07 PVI

Water slug 0.13 PVI

SUBSTRATE AND SLUGS

24

HIGH SUBSTRATE INJEC-TION CONCENTRATION

Faster MEOR response

Spore injection and spore-forming bacteriainjection are similar

Waterflooding curvecorresponds to 1e-3 curve.

SPORE-FORMING BACTERIA

25

SLUGS

▪ Reduced clogging risk

▪ Larger surfactantproduction

▪ Improved utilizationof substrate

▪ Prolonged oilmobilization

0.0 0.2 0.4 0.6 0.8 1.0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Sa

tura

tion

sw NSP slug 0.20

sw SP slug 0.20

sor NSP slug 0.20

sor SP slug 0.20

second water front

SLUG INJECTION SCHEMES

26

High substrate injectionconcentration.

First slug is importantfor final recovery.

Improved utilization of substrate injected.

1.0 1.5 2.0

0.64

0.66

0.68

0.70

0.72

0.74

0.76

RF

(O

OIP

)

t (PVI)

1 x slug 0.15

1 x slug 0.20

2 x slug 0.12 wslug 0.30

5 x slug 0.07 wslug 0.30

5 x slug 0.07 wslug 0.20

1 x slug 0.20 NSP

0.20 sub, 0.95 water, 0.06 sub

0.20 sub, 0.85 water, 0.06 sub

CONCLUSION

❖ Spore-forming bacteria penetrate tight chalk better and may beused for MEOR.

❖ Experimental discoveries lead to new MEOR features to investigate numerically:

❖ Filtration type behavior (no biofilms)

❖ Spore formation

❖ Selective plugging

27

CONCLUSION

❖ Numerical simulations show that spore-forming bacteria have the potential to avoid clogging due to sporulation.

❖ High substrate injection concentration gives fast MEOR response.

❖ Prolonged oil mobilization with water slugs due to substraterelease from sporulation of attached bacteria.

❖ It is possible to optimize the recovery by selecting right slug sizesand sequences

❖ It is possible to deliver spores to a certain point at the reservoir and make them plugging there.

❖ The first slug is the most important for final recovery.

28

QUESTIONS?Thank you for your attention.

29

30

Measurement of k and , CT scan

Core Flooding Experimental Flow Chart

Core plug saturation under vacuum and high pressure

31

Methods

Core plug: Cleaning

Measurement of oil produced

Effluent

Bacterial counting

Methods

32

1. Injection of SS (2-3 PVI)2. Injection of crude oil until Swi

3. Injection of 1PV SS (1st SS)4. Injection of bacteria (1PV)5. Incubation (3 days)6. Injection of SS until Sor (2nd SS)7. Injection of nutrient (1PV)8. Incubation (7 days)9. Injection of SS (3rd SS)

Secon

dary

1. Injection of SS (2-3 PVI)2. Injection of crude oil until Swi

3. Injection of SS until Sor (1st SS)

4. Injection of bacteria (1-3PV)5. Incubation (3 days)6. Injection of SS (2nd SS)

Tertiary

Different studies:

1. Injection of SS (2-3 PVI)2. Injection of crude oil until Swi

3. Aging – 3 weeks4. Injection of crude oil (2-3 PVI)5. Injection of SS until Sor (1

st SS)6. Injection of bacteria (1-3PV)7. Incubation (3 days)8. Injection of SS (2nd SS)

Wettab

illity

Methods

33

Effluent (oil in brine)

Add 3ml toluene

Hand shake to dissolve the oil

Let the oil in tolueneand brine seperateinto two phases

Upper phase (oil in toluene) was decantedto a silica glass cuvette

Measure at UV-vis spectrophotometer at λ=750 nm

Oil Measurement ( Evdokimov et. al., 2002)

Results

• The UV/visible spectroscopy method relies on absorptivities of solid asphaltene aggregation in toluene solution.

• Fig. a shows good linear regression of the NO concentration vs. the absorbance data. The replicate samples showed similar linear regression trend line which means this method is quite stable and reproducible.

• This method can detect oil as low as 1 µl (Fig. b).

34

y = 4,1227x + 0,0112R² = 0,997

0

0,2

0,4

0,6

0,8

1

0 0,05 0,1 0,15 0,2 0,25

Op

tica

l De

nsi

ty (

75

0 n

m)

oil (ml)

200-1 µl fit

Lineær (200-1 µl fit)

0

0,5

1

1,5

2

2,5

3

3,5

4

0 0,2 0,4 0,6 0,8 1 1,2

Ab

sorb

ance

(λ

= 7

50n

m)

oil (ml)

NO

NO_Replicate 1

UV-vis methoda) b)

Results

Core ID

k before

(mD)

k after

(mD)

Before

(%)

after

(%)

26_water 3.2 2.8 30.8 30.7

26_3rd m 3.2 3.1 31.1 30.7

26_2nd m 3.1 3.2 30.7 30.8

26_aging 2.8 3.1 30.7 30.6

• Core 26 – homogenous reservoir chalk core• No significant change in k and before and after

experiment• No fractures based on CT scan results before and after

experiment

35

Core Plugs Properties

Results

• Experiment with an aged core gave 3.6% incremental oil, veryslightly higher than non-aged core

36

Core no Sor (% OOIP)

26_aging 48.6

Wettability alteration?

Total oil recovery: Aged core : 55.6%

0

20

40

60

80

100

0 3 6 9 12 15 18 21 24 27 30 33

cum

mu

lati

ve o

il p

rod

uct

ion

(%

OO

IP)

PVI

core 26_water_1st SScore 26_water_2nd SScore 26_3rd method_1st SScore 26_3rd method_bacteriacore 26_3rd method_2nd SScore 26_aging_1st SScore 26_aging_bacteriacore 26_aging_2nd SS

+ 0.4 % + 3.2 %52.0%

NUMERICAL SOLUTION

Tanks-in-series approach

Multivariable Newton iteration

Sequential procedure

37