Potential for Wettability Alteration in the LKC using Biosurfactants from Agricultural Waste

University of Kansas: Stephen Johnson, Mehdi Salehi, Karl Eisert and Jenn-Tai LiangIdaho National Laboratory: Gregory Bala and Sandra Fox

Seventeenth Oil Recovery ConferenceWichita, KS, USA, 4 – 5 April 2007

Outline

Introductionsignificance to Kansas productionwettability & spontaneous imbibition

Surfactin and benchmark surfactantsStatic and dynamic adsorptionAging procedure & wettability testsConclusionsFuture and ongoing workAcknowledgments

Why is this important to Kansas?

http://www.searchanddiscovery.net/documents/2006/06093watney/images/01.htm

WettabilityWettability is the tendency of a liquid to spread on a surfaceOn a PVC surface, mineral oil will spread out while water forms beads - PVC is said to be oil-wetWettability is a major factor in crude oil/brine/rock interactions

Mineral oil Water

Spontaneous imbibition and wettabilitySpontaneous imbibition of water is the main production mechanism in naturally fractured reservoirs (NFR)Secondary production is very low, especially if the fractures form a connected networkTraditional surfactant flooding uses high concentration to create ultra-low IFT

rarely economic in the field

Low-concentration surfactants can change the wettability of the reservoir rock to a more water-wet state, promoting the spontaneous imbibition of waterCheap biosurfactant may be an economical option

Imbibition in fractured reservoirs

Effectiveness of surfactant-based EOR depends on surfactant propagation through reservoirDilute solutions of biosurfactant assessed for:

adsorptioneffectiveness in changing wettability of carbonate rocks

Compared to benchmark chemical surfactant

BiosurfactantSurfactin

anionic cyclic lipopeptide surfactant and antibiotic properties

Bacillus subtilisgrow on high-starch medium (agro-industry waste stream)

O

N O

N

O

NO

N

ONO

N

O

N

OO

O

OO

OGlu

Leu

Leu

Val

Asp

Leu

Leu

Benchmark chemical surfactantsSimilar chargeComparable tail lengthPrior study and/or useCandidates:

sodium dodecylbenzene sulfonate (1C12LAS)sodium dodecyl sulfate (SDS)sodium laureth sulfate (SLS)

OSO

OO

Na+

SO

OONa

+O

O

O

O

SO

O

O

Na+

IFT between surfactants and Soltrol 130

0

5

10

15

20

25

30

35

40

0 500 1000 1500 2000

IFT,

mN/m

Concentration, ppm

Sodium laureth sulfateSodium dodecylsulfate

Sodium dodecylbenzene sulfonateSurfactin

MaterialsBenchmark surfactant: Sodium laureth sulfate (SLS)Biosurfactant: Crude surfactin (INL)Adsorbent :

Lansing-Kansas City oomoldic reservoir material (L7) from the Hall-Gurney Field in Russell County, KS.

Crushed (53 to 300 μm) for static adsorption1-inch core for dynamic adsorption test

Surfactant-ion selective combination electrode used to determine concentration of anionic surfactants in aqueous solution by potentiometric titration with Hyamine 1622

Potentiometric titration

mV

--

mV

--

++

mV

--

++

++

A: Before equivalence B: At equivalence C: After equivalence

Modified after DIN EN 14480

Surfactant electrode response

-20

0

20

40

60

80

100

120

140

160

0 1

0.05 M Hyamine 1622, ml

E, m

V

0

100

200

300

400

500

600

Der

ivat

ive

E, mV

First Derivative

A B C

AdsorptionRetention of surfactants on rock surface often exhibit a Type I adsorption isotherm

0

1

2

3

4

0 0.5 1 1.5 2 2.5 3

Concentration

Spec

ific

Ads

orpt

ion

(mg/

g)

I

II

IIIIV

After Tabatabai et al. (1993)

Explanation for regions of adsorption isotherms

After Somasunduran et al. in Sharma (1995)

Langmuir model

n* = adsorptionkH = Henry’s law coefficientnm = monolayer loadingCeq = equilibrium solution concentration

eqH

eqmH

CkCnk

n+

=1

*

Freundlich model

n* = adsorptionA, B = constantsCeq = equilibrium solution concentration

BeqCAn ×=*

Static adsorption procedure

2.0 g crushed rock30 ml surfactant solutionShake for 24 hCentrifuge @ 3000 rpm for 30 min.Measure surfactant concentration before and after equilibrating with crushed rockCalculate specific adsorption (mg/g)

Static adsorption of SLS and surfactin on LKC rock

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Ads

orpt

ion,

mg/

g

Initial concentration, mmol/l

SLSSurfactin

Static adsorption results

Specific adsorptionsurfactin > SLSmaximum adsorption density reached at a lower concentration

reflects the lower CMC of surfactin

Surfactin and SLS adsorption on LKC rock exhibits the four regions seen in a Type I isotherm

Dynamic adsorption procedure

One-inch diameter L7 core plug saturated with RO-water in a Hassler type core holderKnown mass and concentration of surfactant solution was circulated through the core for 24 h at 2 ml/minEquilibrium concentration (mg/g) of the solution determined by potentiometric titration for replicate samplesRepeated for several concentrations and adsorption plotted against equilibrium concentration

Dynamic adsorption of SLS and Surfactin (w/v) on LKC rock with fits to Langmuir model

.

0

0.5

1

1.5

2

2.5

3

3.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Ads

orpt

ion,

mg/

cm^3

Equilibrium concentration, mmol/l

SLS SLS Langmuir fit

Surfactin Surfactin Langmuir fit

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Ads

orpt

ion,

mg/

g

Equilibrium concentration, mmol/l

SLSSurfactin

Dynamic adsorption of SLS and Surfactin (w/w) on LKC rock

.

Dynamic adsorption of SLS and Surfactin (mol/w) on LKC rock

.

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Ads

orpt

ion,

mm

ol/g

Equilibrium concentration, mmol/l

SLSSurfactin

Dynamic adsorption resultsType I isothermSLS

Langmuir: nm = 1.676 mg/cm3, kH = 3.383 (R2 = 0.934)Freundlich: A =1.270, B = 0.327 (R2 = 0.833)

SurfactinLangmuir: nm = 3.636 mg/cm3, kH = 10.898 (R2 = 0.891)Freundlich: A =4.072, B = 0.358 (R2 = 0.810)

Neither model fits the data wellLangmuir model slightly better fit and is probably more descriptive of the processmore appropriate to model each region separately

Wettability change

Clean crushed rocksTHF, chloroform, methanol, waterstrongly water-wet

Age crushed rocks in crude oil two weeks at 90°C strongly oil-wet

Change in wettability due to surfactantscontact aged rock with surfactants assess wettability

Qualitative wettability tests

Two-phase separation(Somasundaran & Zhang 1997)

0.2 g of crushed rock20 ml RO-water 20 ml Soltrol 130shake for 1 min by hand and allow to settlematerial partitions between aqueous/non-aqueous phases

Flotation test (Wu et al. 2006)0.2 g of crushed rockRO-wateroil-wet material floats

LKC reservoir rock:Two-phase separation and flotation tests

Amott WettabilityQuantitative test of wettability

Core is flooded with oil to Swi

Placed in brine or a surfactant solutionOil collected to find water saturation after spontaneous imbibition, Sws

Flooded with brine to Swf

Amott wettability to water calculated:

)()(

wiwf

wiwsw SS

SSI−−

=

Spontaneous imbibition of surfactant solution into un-aged cores, Swi = 0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 2 4 6 8 10 12 14

Oil

prod

uced

, ml

Time, days

RO waterSLS

Surfactin

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 5 10 15 20 25

Oil

prod

uced

, ml

Time, days

SLSSurfactin

Spontaneous imbibition of water into surfactant-aged cores, Swi = Swr

Replace water with 700 ppm SLS

ConclusionsSodium laureth sulfate and surfactin exhibit typical adsorption isotherms with four distinct regionsSurfactin exhibits higher specific adsorption onto crushed LKC than does SLS

but comparable on a molar basis500 ppm surfactin more effective than SLS at changing wettability of crushed LKC material on both molar and weight bases

not seen in whole cores, possibly due to lower IFT or greater adsorptionbut is seen if core is flooded with surfactant and allowed to imbibe water

Surfactin seems to be more effective than SLS if the surface is oil-wet rather than mixed-wet

Ongoing and future work

OngoingDynamic adsorption/desorption experimentsAssess other chemical surfactantsSpontaneous/forced imbibition in cores

different concentrations

FutureIdentification of mode of action

adsorption onto oil wet surfaceEconomic analysis

Acknowledgements

Financial supportGrant # DE-FC26-04NT15523

United States Department of Energy (National Energy Technology Laboratory/Strategic Center for Natural Gas and Oil)

Co-authors:Mehdi Salehi (PhD candidate, KU)Karl Eisert (MS graduate, KU – now with Chevron)Jenn-Tai Liang (PI, KU)Gregory Bala (Co-PI, INL) Sandra Fox (INL)

Contact details

☺ Stephen J. JohnsonThe University of KansasTertiary Oil Recovery ProjectLearned Hall, Room 4165E 1530 W. 15th StreetLawrence, KS 66045-7609+1 (785) 864-3654+1 (785) 864-4967sjohn@ku.edu