Presentation EOR updated on references-Wan

By: Wan Mohd Shaharizuan b. Mat Latif
831107115535 / MY131031
From SPE-159700
“A New Family of Anionic
Surfactants for Enhanced Oil
Recovery Applications”
Bo Gao, Upstream Research Company at
ExxonMobil, and Mukul M. Sharma,
University of Texas at Austin

OBJECTIVE OF THIS RESEARCH:
1. To compare the interfacial properties between
conventional surfactant and seven different
anionic Gemini surfactants; different length of
hydrophobic tail and linking spacer towards
reducing IFT and static adsorption and retention.
2. To find the best Gemini surfactant among 7
types.
3. Discuss the IFT, phase behavior (precipitation)
and adsorption behavior of Gemini surfactants
series.

PROBLEM OF NORMAL SURFACTANT FLOODING:
1. High concentration of surfactant (0.2 ~ 2% wt or
2000 ~ 20,000 ppm) to achieve CMC.
2. High adsorption on rock which loss the surfactant.
3. High retention on rock which loss the surfactant.
4. Less effective in high temperature (85~120oC) and
high salinity (up to 200,000 mg/L) and hard to
find surfactant at low salinity (below 5000 mg/L).
Therefore, it’s hard to find surfactants for
producing ultra low crude oil/water IFT at this
reservoir conditions.

CONVENTIONAL ANIONIC SURFACTANT:
1. Anionic surfactant are most widely
used in chemical EOR process because
low adsorption on sandstone rock whose
surface charge is negative.
2. Nonionic primarily serve as co-
surfactant to improve system phase
behavior.
3. Quite often, a mixture of anionic and
nonionic is used to increase the
tolerance to salinity.
4. Cationic surfactants can strongly
adsorb in sandstone rock, therefore they
used in the carbonate rock to change the
wettability from oil wet to water wet.
(Sheng, J. 2011).

RECENT ADVANCED SURFACTANT FLOODING FOR HARSH CONDITION
RESERVOIR WITH LARGE HYDROPHOBIC :
1. Dimeric / Gemini surfactants (Iglauer et al, 2010; Gao et al, 2012,
Wei, 2012; Zana, 2002; Bae et al, 1989).
2. Polymeric surfactants (Wang et al, 2010; Elraies et al, 2011; Zhang
et al, 2010; Zeron et al, 2012).
3. Oligometric surfactants.
4. Guerbet alkoxy sulfates.
5. Guerbet alkoxy carboxylates (Lu et al, 2012; Adkins et al, 2012).
6. Alkoxy carboxylates and/or sulfonates (Weerasooriya et al, 2012;
Berger et al, 2007, 2009).
To the best of our knowledge, these surfactants are not being utilized in
commercial applications till now; nevertheless, the price of surfactant is
still too high. Therefore, new surfactants types and techniques must be
developed for an economically viable EOR process. (SPE169051-MS).

GEMINI SURFACTANT:
1. Gemini surfactant consist of two
covalently linked “conventional”
surfactants by means of a spacer.
2. The hydrocarbon tail can vary in
length, the spacer group can be
flexible or rigid, hydrophilic or
hydrophobic, the polar group can
be anionic, cationic, nonionic or
zwitterionic.
3. This Gemini surfactants have
significant water solubility, form
micelles, substantially reduce the
surface tension, and exhibit more
interesting rheological properties
behavior.

GEMINI SURFACTANT EXPERIMENT METHODS:
1. Gemini surfactant solutions are prepared by weighing the surfactant
in distilled water and stirring with a magnetic stirrer at the desired
experimental temperature.
2. The oil phase used in IFT measurements was pure hydrocarbons
purchased from Sigma Aldrich.
3. Salt that used to make the brine (NaCl, CaCl2) were obtained from the
Fisher Chemical and used as received.
4. Then, blend the surfactants at reservoir temperature using equal
volumes of reservoir brine and crude oil.
5. Recorded the Krafft temperature and CMC for each Gemini
surfactants and changed for different temperature.
6. Measured the IFT of after increased the temperature.
7. Changed the alkyl length and recorded the IFT.
8. Changed the salinities of monovalent and divalent ions and recorded
the change of IFT, adsorption and phase behavior (precipitation).
9. Changed the spacer length and recorded the adsorption.
10. Recorded all data.

RESULT AND DISCUSSION (NORMAL VS. 7 GEMINI SURFACTANTS:
1. The solubility of ionic surfactants is commonly characterized by the Krafft
temperature, Tk which is the minimal temperature at which surfactants form
micelles.
2. Anionic Gemini surfactants synthesized in the current study have Tk lower
than 20oC (Gao 2012).
3. The low Tk of these surfactants can be explained by the concept of
hydrophilic/lipophilic balance (HLB) (Becher 1984).
4. Although bearing the same tail carbon chain and head group, the Gemini
surfactants show much higher HLB values and thus correspondingly better
aqueous solubility, compared with conventional counterparts.

THE KRAFFT POINT:
1. Below the Krafft point the solubility of the surfactants is too low for
micellization so solubility alone determines the surfactant monomer
concentration.
2. As temperature increase the solubility increases until at Tk the CMC is
reached. At this temperature a relatively large amount of surfactant can
be dispersed in micelles and solubility increases greatly.
3. Above the Krafft point maximum reduction in surface or IFT occurs at
the CMC because the CMC then determines the surfactants monomer
concentration.

HYDROPHILE–LIPOPHILE BALANCE (HLB)
1. The hydrophile–lipophile balance (HLB) has been used to characterize surfactants. This
number indicates relatively the tendency to solubilize in oil or water and thus the tendency
to form water-in-oil or oil-in-water emulsions. Low HLB numbers are assigned to
surfactants that tend to be more soluble in oil and to form water-in-oil emulsions. When the
formation salinity is low, a low HLB surfactant should be selected. Such a surfactant can
make middle-phase microemulsion at low salinity. When the formation salinity is high, a
high HLB surfactant should be selected. Such a surfactant is more hydrophilic and can make
middle-phase microemulsion at high salinity.
2. Surfactants HLB is determined by calculating values for the different regions of the
molecule, as described by Griffin (1949, 1954). Other methods have been suggested, notably
by Davies (1957). Griffin’s equation to calculate HLB for nonionic surfactants is
HLB = 20 MWh / MW
where MWh is the molecular mass of the hydrophilic portion of the molecule, and MW is the
molecular mass of the whole molecule, giving a result on an arbitrary scale of 0 to 20.
An HLB value of 0 corresponds to a completely hydrophobic molecule, and a value of 20
corresponds to a molecule made up completely of hydrophilic components. The HLB value
can be used to predict the following surfactant properties:
● A value from 0 to 3 indicates an antifoaming agent.
● A value from 4 to 6 indicates a W/O emulsifier.
● A value from 7 to 9 indicates a wetting agent.
● A value from 8 to 18 indicates an O/W emulsifier.
● A value from 13 to 15 is typical of detergents.
● A value of 10 to 18 indicates a solubilizer or hydrotrope.
(Sheng, J. 2011).

CRITICAL MICELLE CONCENTRATION:
1. Another important characteristic of a surfactant is critical micelle
concentration (CMC) which show the effectiveness of the
surfactant.
2. It is defined by minimum concentration of surfactant (mg/L) to
get the minimum IFT between oil and water (dynes/cm).
3. The standard IFT of waterflooding is from 10-30 dynes/cm and
the Gemini surfactant must be reduce to 0.001 dynes/cm or less.

CRITICAL MICELLE CONCENTRATION:
1. Upon reaching CMC, any further addition of surfactants will just
increase the number of micelles (in the ideal case), as shown in
Figure 7.1. In other words, before reaching the CMC, the surface
tension decreases sharply with the concentration of the
surfactant.
2. After reaching the CMC, the surface tension stays more or less
constant. (Sheng, J. 2011).

EFFECT OF TEMPERATURE ON IFT GEMINI SURFACTANTS:
1. The IFT of Gemini surfactants decreased from 1 to less than 0.001
dyne/cm when the temperature increased from 55oC to 85oC.
2. Obviously, even at an extremely low concentration level, Gemini
surfactants (at least for the 18-4-18 molecule), are still capable of
reducing the IFT to ultralow levels (less than 0.001 dyne/cm).
3. In all measurements that follow, a surfactant concentration of 0.02 wt%
(approximately 200 mg/L) will be used to make sure we stay safely
above CMC, and in the meantime still remain much lower than
concentration typically used in a conventional surfactants.

IMPACT OF ALKYL LENGTH ON IFT:
1. As the alkyl chain get longer, we see a gradual decrease in IFT.
2. Indeed, as the hydrophobes get larger, the HLB is adjusted in such a
way that the surfactant molecule become more lipophilic, and thus
have a higher tendency to move from the bulk aqueous phase onto
the oil/water interface.
3. Once there, they can orient themselves so that the large
hydrophobes point toward the oil phase to reduce the free energy of
the system.

IMPACT OF MONOVALENT SALT (NaCl) CONCENTRATION
TOWARD IFT:
1. Figure 8 show the positive impact of a higher NaCl concentration on
lowering the tension of an oil/water interface.
2. The solubility of Gemini surfactants in highly saline solutions should
be noted. As more NaCl is added, the IFT steadily goes down.

1. Divalent ions such as Ca2+ and Mg2+ are more efficient in driving
surfactant molecules onto the oil/water interface than monovalent ions.
2. Most conventional EOR surfactants do not work well at high
concentrations of divalent ions, often showing precipitation or phase
separation upon the addition of Ca2+ and Mg2+ to their aqueous
solutions.
3. First and most importantly, no solubility problems were encountered in
these test, even when the CaCl2 when as high as 4%.
4. The addition of divalent ions help further reduce the IFT, and ultralow
IFT observed.
IMPACT OF DIVALENT SALT (CaCl2) CONCENTRATION TOWARD IFT:

IMPACT OF SALINITY ON PRECIPITATION (PHASE BEHAVIOR):
1. Even a salinity as high as 20
wt%, no phase separation or
precipitation take place, showing
the high salinity (and/or
hardness) of this molecule.
2. No obvious transition in
microemulsion appearance
(volume and color) was observed
from low to high surfactant
concentrations because no
visually discernible middle phase
can be identified across the
board.

ADSORPTION COMPARISON
1. Maximal adsorption densities of the three surfactants follow the trend of 16-4-16 <
SHS < S13-C.
2. First of all, Gemini surfactants are much more hydrophilic than their conventional
counterparts. Therefore, they will have a higher tendency to go into the bulk aqueous
phase than conventional surfactants, which makes it more difficult for Gemini to get
adsorbed at the solid surface.
3. Second, the two sulfate head groups in one molecule make a Gemini effectively a
bifunctional ion.
4. Therefore, one Gemini molecule can potentially interact with more than two adsorption
sites on the solid surface, and thus saturate the adsorption sites more efficiently.
5. However, the different is only little compared with other two conventional surfactants.

EFFECT OF SPACER LENGTH ON THE ADSORPTION OF GEMINIS:
1. As can be seen on above figure, the molecule with a shorter space has a
smaller plateau adsorption density for basically the same reason
mentioned previously; stronger intermolecular interactions and reduced
solubility.
2. Longer spacer groups promote surfactant adsorption.

CONCLUSION:
1. These 7 molecules of anionic Gemini surfactants showed
excellent aqueous stability even in high salinity and hard brines.
2. The IFT of Gemini surfactants decreased from 1 to less than
0.001 dyne/cm when the temperature increased from 55oC to
85oC.
3. As the alkyl chain get longer, we see a gradual decrease in IFT.
4. As the salinity of monovalent ion increased, IFT decreased
(same effect with conventional surfactant).
5. As the salinity of divalent ion increase, IFT also decreased
(contrast effect with conventional surfactant).
6. Even with extremely high concentration of NaCl (up to 20 wt%)
and or CaCl2 (up to 5 wt%), no phase separation or precipitation
of any kind was observed for all the samples prepared.
7. Showed lower maximal adsorption densities than the
conventional single chain surfactants. However, the amount is
quite small (1~2 mg/g).

CONCLUSION (continued):
8. With increasing brine salinity, at a fixed temperature, the CMC
decreased.
9. Only used 0.02% (200 ppm) of Gemini Surfactant to achieve
CMC, compared with conventional surfactant (0.2 ~ 2% wt or
2000 ~ 20,000 ppm).
10. The molecular interaction between Gemini and conventional
surfactants provides mutual benefits that contribute to aquoues
stability and interfacial activity. This leads to a new possibility of
making use of Gemini surfactants as co-solvents that help
improve the performance of the surfactant mixture.
11. All the Gemini surfactant synthesized are very hydrophilic.
12. The HLB could be further adjusted through modifications to
the tail length and changes in the head group for better
performance.
13. Gemini surfactant shows a lower plateau adsorption density
than conventional EOR surfactants.
14. Lower adsorption can be achieved by decreasing the solution
salinity.

RECOMMENDATION:
1. Due to the potential of using this surfactant at low
concentration and in harsh reservoir conditions (high T
and salinity – commonly encountered in oil reservoirs
around the world), it’s compulsory to do the lab core
analysis as to measure the oil recovery before propose
to pilot field test.
2. Besides, the table 2 data also inaccurate for the Krafft
point comparison, due to Gemini surfactant used year
2001 data but the conventional surfactant used 1971
data. (Supposedly to do at the same time for better
apple to apple comparison).

OTHER REFERENCES:
Adkins, S., et al. 2010. A New Process for Manufacturing and Stabilizing High
Performance EOR Surfactants at Low Cost for High Temperature, High
Salinity Oil Reservoir. Paper SPE 129923 presented at the SPE Improved
Recovery Symposium, Tulsa, Oklahoma, USA, 24-28 April 2010.
Li, Y., et al. 2014. Mixtures of Anionic-Cationic Surfactants: A New Approach for
Enhanced Oil Recovery in Low Salinity, High Temperature Sandstone
Reservoir. Paper SPE 169051-MS presented at the SPE Improved Recovery
Symposium, Tulsa, Oklahoma, 12-16 April 2014.
Liu, S. 2007. Alkaline Surfactant Polymer Enhanced Oil Recovery Process, MS Thesis,
The University of Rice at Houston, Texas, January 2008.
Noll, L.A. 1991. The Effect of Temperature, Salinity, and Alcohol on the Critical
Micelle Concentration of Surfactants. Paper SPE 21032-MS was prepared for
presentation at the SPE International Symposium of Oilfield Chemistry held
in Anaheim, California, 20-22 February 1991.
Sheng, J. 2011. Modern Chemical Oil Recovery, USA: Gulf Professional Publishing.
THANK YOU

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