Wettability alteration of carbonate rock mediated by biosurfactant produced from
high-starch agricultural effluents
University of Kansas: Mehdi Salehi, Stephen Johnson and Jenn-Tai Liang
Idaho National Laboratory: Sandra Fox and Gregory Bala
9th International Wettability Symposium
Bergen, Norway. 18-19 September 2006
Outline
Introduction Surfactin and benchmark surfactants Static adsorption Aging procedure Wettability tests Conclusions Future and ongoing work Acknowledgments
Introduction
Spontaneous imbibition of water is the main production mechanism in naturally fractured reservoirs (NFR)
NFRs are mostly oil-wet or mixed-wet (Roehl et al. 1985).
Secondary production is very low, especially if the fractures form a connected network (Allan et al. 2003)
Low-concentration surfactants can change the wettability of the reservoir rock to a more water-wet state, promoting the spontaneous imbibition of water
Cheap biosurfactant may be an economical option
Effectiveness of surfactant-based EOR depends on surfactant propagation through reservoir
Dilute solutions of biosurfactant assessed for:– effectiveness in mediating wettability of carbonate rocks– adsorption
Compared to similar benchmark chemical surfactant
Oil
Surfactant
Biosurfactant
Surfactin– anionic cyclic lipopeptide – surfactant and antibiotic
properties Bacillus subtilis
– grow on high-starch medium (agro-industry waste stream)
– centrifuge to remove cells– HCl to precipitate surfactin– centrifuge and freeze-dry– re-dissolve in RO-water as
required Characterized by Schaller et al.
(INL)
O
N O
N
O
NO
N
O
NO
N
O
N
OO
O
OO
OGlu
Leu
Leu
Val
Asp
Leu
Leu
Benchmark chemical surfactants
Similar charge Comparable tail length Prior study and/or use Candidates:
– sodium dodecylbenzene sulfonate (BIO-SOFT D40)
– sodium dodecyl sulfate (STEPANOL)
– sodium laureth sulfate (STEOL CS-330)
O
S
O
OO
Na+
S
O
OO
Na+
O
O
O
O
SO
O
O
Na+
Selecting the chemical surfactant
IFT between surfactants and Soltrol 130
Materials
Benchmark surfactant: STEOL CS-330 (Stepan Co.) Biosurfactant: Crude surfactin (INL) Adsorbents (53 to 300 m) :
– Miami oolitic outcrop (MI)– Bethany Falls oomoldic outcrop (BF)– Lansing-Kansas City oomoldic reservoir material (L7) from the
Hall-Gurney Field in Russell County, KS.
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
.
-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
De
riv
ati
ve
E, mV
First Derivative
A B C
Static adsorption
Procedure: – 2.0 g crushed rock– 30 ml surfactant solution– shake for 24 h– centrifuge @ 3000 rpm for 30 min.– measure surfactant concentration before and after
equilibrating with crushed rock– calculate specific adsorption (mg/g)
0
5
10
15
20
25
0 1 2 3 4
Rock Mass (g)
Sp
ec
ific
Ad
so
rpti
on
(m
g/g
)
0.37 mmol/l Surfactin on Miami
0.37 mmol/l Surfactin on BF
1.44 mmol/l STEOL on Miami
1.44 mmol/l STEOL on BF
Specific adsorption at various surfactant/adsorbent mass ratios
0
1
2
3
4
5
0 0.5 1 1.5 2 2.5 3
Initial Concentration (mmol/l)
Sp
ecifi
c A
dso
rptio
n (m
g/g
)
0.5 g
1.0 g
2.0 g
3.0 g
STEOL CS-330 isotherms on BF rock
STEOL and surfactin isotherms on 2.0 g BF and L7 rocks
.
0
1
2
3
4
5
6
0 0.5 1 1.5 2
Initial Concentration (mmol/l)
Sp
ecif
ic A
dso
rpti
on
(m
g/g
)
Surfactin & BFSTEOL CS-330 & BFSurfactin & L7STEOL CS-330 & L7
STEOL and surfactin (30 ml) adsorption isotherms on 2.0 g BF and L7 rocks
Adsorption results (I)
Higher adsorption on oomoldic material– higher specific surface area
Specific adsorption as rock mass – settling of crushed rock in the test tubes reduced contact with
surfactant? higher shaking rates adsorption
– mechanical scouring of surface
Adsorption results (II)
Specific adsorption– surfactin > STEOL CS-330– maximum adsorption density reached at a lower
concentration reflects the lower CMC of surfactin
Surfactin and STEOL CS-330 on both L7 and BF rocks exhibit the four regions seen in a typical adsorption isotherm
Four regions of adsorption isotherm
.
0
1
2
3
4
0 0.5 1 1.5 2 2.5 3
Concentration
Sp
ec
ific
Ad
so
rpti
on
(m
g/g
)
I
II
IIIIV
Regions of typical adsorption isotherm
After Tabatabai et al. (1993)
HMC
CMC
Explanation for regions of adsorption isotherms
After Somasunduran et al. in Sharma (1995)
Wettability change
Clean crushed rocks– THF, chloroform, methanol, water– strongly water-wet
Age crushed rocks in crude oil – two weeks at 90C – strongly oil-wet
Change in wettability due to surfactants– contact aged rock with surfactants – assess wettability
Qualitative wettability tests
Two-phase separation (Somasundaran & Zhang 1997)– 0.2 g of crushed rock– 20 ml RO-water – 20 ml Soltrol 130– shake for 1 min by hand and allow to settle– material partitions between aqueous/non-aqueous phases
Flotation test (Wu et al. 2006)– 0.2 g of crushed rock– RO-water– oil-wet material floats
LKC reservoir rock – two-phase separation and flotation tests
Bethany Falls oomoldic outcrop - two-phase separation and flotation tests
.
Wettability tests results
Two-phase separation and flotation tests agree Surfactin more effective than STEOL CS-330 in
reversing the wettability of oil-wet crushed carbonate rocks.
Conclusions
Standardize and report mass of rock and volume of surfactant solution used to develop adsorption isotherms
STEOL CS-330 and surfactin exhibit typical adsorption isotherms with four distinct regions
Surfactin has higher specific adsorption on carbonate rocks than STEOL CS-330
Surfactin is more effective than STEOL CS-330 in altering wettability of crushed BF and LKC carbonates from oil-wet to water-wet state.
– on both molar and w/w bases
Ongoing and future work
Ongoing– Assess other chemical surfactants– Spontaneous/forced imbibition in cores
Future– Dynamic adsorption/desorption experiments– Economic analysis
Acknowledgements
Co-authors:– Mehdi Salehi (PhD candidate, KU)– Jenn-Tai Liang (PI, KU)– Gregory Bala (Co-PI, INL) – Sandra Fox (INL)
Other team members– Karl Eisert (MS candidate, KU)– Vivian Lopez (Undergraduate, KU)
Financial support– Grant # DE-FC26-04NT15523
United States Department of Energy (National Energy Technology Laboratory/Strategic Center for Natural Gas and Oil)
Contact details
Stephen J. Johnson The University of Kansas
Tertiary Oil Recovery Project Learned Hall, Room 4165E 1530 W. 15th Street Lawrence, KS 66045-7609
+1 (785) 864-3654 +1 (785) 864-4967 [email protected]
Top Related