Biosci. Biotech. Res. Comm. 10(4): 704-709 (2017)
Wettability alteration in enhanced oil recovery process
using new amphoteric and cationic surfactants
Reza Qanbari Moqaddam Nouqabi
, Ghasem Zargar
*, Mohammad Ali Takassi
Siyamak Moradi
M.S. Student of Petroleum Exploration Engineering, Abadan Faculty of Petroleum Engineering,
Petroleum University of Technology, Northern Bowarde, Abadan, Iran
Department of Petroleum Exploration Engineering, Petroleum University of Technology, Northern
Bowarde, Abadan, Iran
The Department of Science, Petroleum University of Technology, Ahwaz, Iran
Department of Petroleum Exploration Engineering, Petroleum University of Technology, Northern
Bowarde, Abadan, Iran
Over time, production of hydrocarbons decreases due to sequential producing and nowadays using Enhanced oil
recovery (EOR) methods is a necessity. One of the methods in order to improve the oil recovery is altering the rock
wettability toward water-wet by using Surfactant  ooding. Surfactants have a variety of applications in the petro-
leum industry due to their remarkable ability to lower the oil-water interfacial tension and alter wettability. In this
study new cationic and amphoteric surfactants synthesis and investigation of wettability alteration in EOR process
is described. The goal of this work is to compare the wettability of a carbonate rocks from oil (mixed)-wet towards
water-wet. Changing the wettability to preferentially water-wet condition will reduce the residual oil saturation (Sor).
Wettability alteration is measured based on the contact angle method.
*Corresponding Author:
Received 1
Oct, 2017
Accepted after revision 30
Dec, 2017
BBRC Print ISSN: 0974-6455
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© A Society of Science and Nature Publication, 2017. All rights
Online Contents Available at:
DOI: 10.21786/bbrc/10.4/14
Reza Qanbari et al.
Oil recovery from a reservoir can be divided into three
steps which are primary recovery, secondary recovery
and tertiary recovery. Further discussion will be well
served by a brief review of the “primary”, “second-
ary” and “tertiary” terms. These terms are generally
understood and accepted (although a formal de nition
of these terms does not exist, either). They re ect and
describe the natural progression of oil production from
its inception to the point where economic production is
no longer feasible. Production depends on the natural
energy of the reservoir itself. The natural energy varies
from pressure decline and the accompanying evolution
of dissolved gas, to the expansion of gas cap, or the
in ux of water. The key element forces are “natural”.
When natural drive energy is depleted, or too small for
economic oil recovery, energy must be added to the res-
ervoir to permit additional oil recovery. That additional
energy is usually in the form of injected water or gas.
The process depends mainly on physical displacement
to recover additional oil. It can be said that it mimics
the natural process of water in ux or gas expansion.
The key element forces are not natural; rather they are
physical, as opposed to thermal, chemical, solvent, inter-
facial tension, etc. One could think of these as being a
physical augmentation of the natural drive mechanism,
(Stosur et al 2003 and Ge and Wang, 2015).
When secondary recovery is no longer economic,
supplemental energy of a different kind permits addi-
tional oil recovery. A critical distinction that should be
noted is that this energy (ies) is (are) in addition to, or in
lieu of the natural or physical displacement mechanisms
of the primary or secondary methods. Enhanced  uid
ow conditions within the reservoir are usually induced
by addition of heat, chemical interaction between the
injected  uid and the reservoir oil, mass transfer, and/or
changing of oil properties in such a way that the process
facilitates oil movement through the reservoir. Tertiary
recovery processes generally include thermal, chemical,
gas miscible and microbial. They are also often referred
to as enhanced oil recovery (EOR) processes Almost half
of the world’s discovered oil reserves are located in car-
bonate fractured formations, which are mostly oil-wet
. These oil reservoirs are good candidates for enhanced
oil recovery if the wettability of the matrixes is altered
more toward water-wetness. Sandstone reservoirs are
more complex than carbonate reservoirs. The wettability
of sandstone reservoirs may vary widely from strongly
water-wet to strongly oil-wet states. Neutral or interme-
diate wettability is also common, (El Mofty 2012, Ge and
Wang 2015 Mohammed and Babadagli 2015).
Buckley and Leverett (1942) published one of the
rst papers on the effect of wettability on oil recovery.
Since then, studies have continuously debated the opti-
mum wettability that provides maximum oil recovery.
Recently, Enhanced Oil Recovery methods based on
chemically-induced wettability alteration have gained
a great deal of attention. Yong Zhu et al. (2012) inves-
tigated the adsorption of cationic-nonionic mixed sur-
factant (HDPB/TX100) onto bentonite and showed the
cationic surfactant improved the adsorption of TX100
and total adsorbed amount signi cantly, indicating the
good synergistic effect between HDPB and TX100. The
co-adsorption of the cationic and nonionic surfactants
increased the ordering conformation of the adsorbed
surfactants on bentonite, but decreased the thermal sta-
bility of the organo bentonite system. The goal of this
study is to describe the wettability of reservoirs and
some surfactants, in addition to their measures and
method. The motivation behind this approach is to keep
the injection architecture similar to that of water ood.
Wettability is de ned as “the tendency of one  uid to
spread on or adhere to a solid surface in the presence of
other immiscible  uids.Types of wettability are divided
into 3 classes: (1) Strong Wettability, (2) Neutral Wetta-
bility and (3) Fractional Wettability which is described
below: Strong Wettability: this class is divided into 2
types as below: Water-Wet: When the rock is water-wet,
there is a tendency for water to occupy the small pores
and to contact the majority of the rock surface Anderson
(1986). Oil-Wet: Similarly, in an oil-wet system, the rock
is preferentially in contact with the oil; the location of the
two  uids is reversed from the water-wet case, and oil
will occupy the small pores and contact tie majority of the
rock surface. Neutral Wettability: When the rock has no
strong preference for either oil or water, the system is said
to be of neutral (or intermediate) wettability. Fractional
Wettability: Besides strong and neutral wettability, a third
type is fractional wettability, where different areas of the
core have different wetting preferences (Fall 2016).
Almost all minerals in a natural, clean state exhibit
water-wet behavior. Certain components, primarily
heavy asphaltene and the resin fractions of crude oil,
can alter the wettability of the original water-wet rock.
Components carrying a charged group, such as an acid or
a base, signi cantly affect wettability during the forma-
tion of the reservoir. Additional signi cant components
include oil and mineral composition, water solubility of
polar oil components, capillary pressure and thin  lm
forces. Mohammed and Babadagli (2012). Temperature,
salinity, pressure and initial water saturation can affect
the degree of wettability alteration as well.
Many different methods have been proposed for
measuring the wettability of a system. They include
Reza Qanbari et al.
quantitative methods such as contact angles, imbibition
and forced displacement (Amott), and USBM wettabil-
ity method and qualitative methods such as imbibition
rates, microscope examination,  otation, glass slide
method, relative permeability curves, permeability/satu-
ration relationships, capillary pressure curves, capillary
metric method, displacement capillary pressure, reservoir
logs, nuclear magnetic resonance, and dye adsorption.
Although no single accepted method exists, three quan-
titative methods generally are used: (1) contact-angle
measurement, (2) the Amott, and (3) the USBM method.
The contact angle measures the wettability of a speci c
surface, while the Amott and USBM methods measure
the average wettability of a core (Anderson 1986).
This is an imbibition-based method to measure the
wettability of a core. The principle is that the wetting
uid will spontaneously imbibe into a core and dis-
place the non-wetting  uid. The experiment begins
with a restored state core sample at irreducible water
saturation (Swirr) and high initial oil saturation. In this
method drainage and imbibition capillary pressures are
measured through centrifuge tests. The sample is satu-
rated initially with water. The water is then displaced
by oil to irreducible water saturation (Swi) using the
centrifuge. Afterward, the sample which contains ini-
tial oil saturation and irreducible water saturation (Swi)
is then centrifuged in water to residual oil saturation
(Sor). Qualitative methods for wettability measurement
are: imbibition rates, microscope examination,  ota-
tion, glass slide method, relative permeability curves,
permeability/saturation relationships, capillary pressure
curves, capillary metric method, displacement capillary
pressure, reservoir logs, nuclear magnetic resonance and
dye adsorption. In below explain some important quali-
tative methods for wettability measurement:
Wettability alteration
Changing the wetting state of materials is a growing
eld of research in many areas of engineering and sci-
ence. In the oil industry, the term wettability alteration
usually refers to the process of making the reservoir
rock more water-wet. This is of particular importance in
naturally hydrophobic carbonates, fractured formations,
and heavy-oil systems. This shift in wettability enhances
oil recovery in oil-wet and weakly water-wet reservoirs
and eventually increases the ultimate oil recovery.Wet-
tability alteration process in each reservoir is a unique
process and requires the understanding of the mecha-
nisms that caused a reservoir to be oil-wet.Wettability
alteration may increase oil recovery by gravity or capil-
lary imbibition, (Mohammed and Babadagli 2012).
Surfactants may be one of the best options to improve
recovery from geologically challenging reservoirs. Dur-
ing recent years, depressed oil prices have limited sur-
factant consideration. However, surfactant recovery can
be economically attractive for reservoirs where recov-
ery is dominated by gravity and imbibition processes.
Surfactant is an abbreviation for surface active agent,
which literally means active at a surface Holmberg
et al., (2002).
It is common practice to divide surfactants into the
categories anionics, cationics, non-ionics and zwitteri-
onics as following classi cation: Anionics are used in
greater volume than any other surfactant class. Impor-
tant facts about anionic surfactants: 1. They are by far
the largest surfactant class. 2. They are generally not
compatible with cationics (although there are impor-
tant exceptions). 3. They are generally sensitive to hard
water. Sensitivity decreases in the order carboxylate >
phosphate > sulfate ~ sulfonate. 4. Sulfates are rapidly
hydrolysed by acids in an autocatalytic process. The
other types are stable unless extreme conditions are used
Holmberg et al.,2002).
Nonionic surfactants come as a close second with
about 45% of the overall industrial production. They
do not ionize in aqueous solution, because their hydro-
philic group is of a non-dissociable type, such as alco-
hol, phenol, ether, ester, or amide. Important facts about
nonionic surfactants: 1. They are the second largest class
of surfactant. 2. They are normally compatible with all
other types of surfactants. 3. They are not sensitive to
hard water. 4. Contrary to ionic surfactants, their phys-
icochemical properties are not markedly affected by elec-
trolytes. 5. The physicochemical properties of ethoxylates
are very temperature dependent. Contrary to most organic
compounds they become less water soluble – more hydro-
phobic – at higher temperatures (Holmberg et al.,2014).
Cationic Surfactants are dissociated in water into an
amphiphilic cation and an anion, most often of the halo-
gen type. A very large proportion of this class corre-
sponds to nitrogen compounds such as fatty amine salts
and quaternary ammoniums.Important facts about cati-
onic surfactants: 1. They are the third largest surfactant
class. 2. They are generally not compatible with anion-
ics (although there are important exceptions). 3. Hydro-
lytically stable cationics show higher aquatic toxicity
than most other classes of surfactants. 4. They adsorb
strongly to most surfaces and their main uses are related
to in situ surface modi cation (Holmberg et al., 2014).
Zwitterionic surfactants contain two charged groups
of different sign. Whereas the positive charge is almost
invariably ammonium, the source of negative charge
may vary, although carboxylate is by far the most com-
mon. Zwitterionics are often referred to as amphoterics
.Important facts about zwitterionic surfactants: 1. They
are the smallest class of surfactant (partly due to high
price). 2. They are normally compatible with all other
types of surfactants. 3. They are not sensitive to hard
Reza Qanbari et al.
water. 4. They are generally stable in acids and bases.
The betaines, in particular, retain their surface activity at
high pH, which is unusual. 5. Most types show very low
eye and skin irritation. They are, therefore, well suited
for use in shampoos and other personal care products
Holmberg et al., 2014),
Two surfactants, one new amphoteric and one cationic
surfactant are considered in this study. Initial surfactant
is hexadecylaminobenzenesulfonic acid (HABSA) which
recognized amphoteric surfactant. HABSA formulation
is (C16H33C6H3NH2SO3H) that show, when it dissolves
in water, it contains two charged groups of different sign
at its head and a long alkyl tail. The second surfactant is
Cetrimonium bromide ((C16H33)N(CH3)3Br, cetyltrime-
thyl ammonium bromide, hexadecyl trimethyl ammo-
nium bromide, CTAB) which is one of the components
of the topical antiseptic cetrimide. The cetrimonium
cation is an effective antiseptic agent against bacteria
and fungi. It is a cationic surfactant. Its uses include
providing a buffer solution for the extraction of DNA. It
has been widely used in synthesis of gold nanoparticles
(e.g., spheres, rods, and bipyramids). It is also widely
used in hair conditioning products. Because of Property
soapy this is a good candidate for chemical oil recovery
in world (Ito et al 2016).
Experimental procedures
Synthesis of new surfactants: Two different surfactants
are considered in this study that synthesized in PUT lab
in Ahwaz: New amphoteric surfactant (hexadecylam-
inobenzenesulfonic acid (C16H33C6H3NH2SO3H),
HABSA) A cationic surfactant (hexadecyltrimethylam-
monium bromide ((C16H33)N(CH3)3Br), CTAB)
Synthesizing procedure of HABSA:
5 mL of concentrated hydrochloric acid and 54 mmol
of ortho-sulfanilic acid are added to 250 mL beaker (A)
with 125 mL water. It is stirred until a homogenous solu-
tion is obtained. 6.5 mL (69 mmol) of acetic anhydride is
added to this mixture. To another 250 mL beaker (B), 5.6
g (69 mmol) of sodium acetate is dissolved in 35 mL of
water. Then the content of beaker A is added to beaker
B and the mixture is vigorously stirred in an ice bath. A
white precipitate (compound 1) is obtained. It is collected
by  ltration and dried in vacuum oven at 80 ºC. Anhy-
drous aluminum chloride (0.13 g, 1.0 mmol) is weighed
into an aluminum weighing boat in the fume hood and
quickly transferred to a clean dry 100 mL round bottom
ask containing a magnetic stir bar. The  ask is stop-
pered and brought to the bench where it is  tted with
a Claisen adaptor, a dropping funnel, and a condenser
vented to a gas trap. 3.46 g (15 mmol) of the aforemen-
tioned white product (1) and 20 mL of acetonitrile are
added to the  ask. While rapidly stirring the mixture,
15 mmol hexadecyl bromide is added slowly drop wise
over a period of about 10 minutes. After the addition is
completed, the stirring is continued at re ux tempera-
ture for an additional 24 h. Then the reaction mixture is
cooled to room temperature. The resulting product (2) is
collected by  ltration and dried under reduced pressure
at 80 ºC. Into a 100 mL round-bottomed  ask equipped
with a condenser and a magnetic stirring bar, 7.6 mmol
of compound 2 and 17 mL of a 5.0 M hydrochloric acid
solution are added and re uxed. After 10 minutes, the
reaction mixture is cooled to room temperature. On com-
pletion of the reaction, the solution is neutralized with
25% w/w sodium hydroxide solution, and a precipitate
is formed slowly. (Yield = 80%, m.p. 283-284 ºC).
Synthesizing procedure of CTAB:
10 ml of hexadecyl bromide (C16H33Br) is placed in a
250 mL round-bottomed  ask, and 5 ml of tri Meth-
ylamine [(CH3)3N] and 100 ml of solvent acetonitrile
(CH3CN) are added to the  ask. A magnetic stirring rod
is placed in the  ask. The  ask continent is heated under
re ux and stirred using a magnetic stirrer for 24 hours.
The solution is cooled to room temperature. The product
is formed as a white precipitated. The product is col-
lected ished with small amount of acetonitrile then air
There are many ways in which CMC could be deter-
mined. The CMC is the narrow concentration range
over which amphiphilic or surfactant solutions show
an abrupt change in a physical property such as elec-
trical conductivity, surface tension, osmotic pressure,
density, light scattering or refractive index Hoolmberg
et al (2002). The conductance of a solution, can give
important quantitative information regarding the ionic
composition of a sample. Conductance is a measure of a
sample’s ability to pass a current and strongly depends
on the concentration, mobility, and charge of ions in
solution (Settle 2017).
The Jenway model 4510 Conductivity/temp meter
with dual display and TDS range is easy to use with a
exibility that will enable it to meet the broadest range
of applications. Set-up menu options include cell con-
stant, temperature coef cient and reference temperature.
With automatic range selection and endpoint detec-
tion, readings can be taken quickly and with minimum
intervention. For applications where greater accuracy is
required the 4510 has automatic conductivity standard
recognition which can be overridden by entry of user
Reza Qanbari et al.
speci c values. This setup includes following issues:
Auto ranging to give best resolution Simultane-
ous display of conductivity or TDS and temperature
Calibration to cell constant or standard solutions Auto
Standard recognition with manual override 32 loca-
tion memory Bi-directional RS232 link to printer or
PC Technical speci cation, (Fall 2016).
When conductivity meter is used to  nd the CMC,
conductivity of the solution increases linearly with total
surfactant concentration. However, the slope of the lines
has an in ection point that indicates the CMC.The pellets
and plug are cleaned by Toluene with Soxhlet extractor.
Two main reasons to clean core are: To remove all liq-
uids from the core so that porosity, permeability, and
uid saturations can be measured. To clean the core as a
rst step in restoring the wettability of cores are altered.
Distilled water is used as the aqueous phase for con-
tact angle,  ooding tests and solutions. One of the best
wettability measurement methods when pure  uids and
arti cial cores are used is the contact angle.
In the sessile drop method the  at surface of pellet is
suspended horizontally in the oil (kerosene) and placed a
drop of water on the surface of the pellet. Then the con-
tact angle between water drop, slice surface and oil is
measured. When is between 0° and 60° to 75° in such
a system, it is de ned as water-wet. When is between
105° to 120° and 180° the system is de ned as oil-wet.
In the range of a 75° to 105° contact angle, the system
is neutral-wet.
After preparing and cleaning the core sample, it is
saturated with distilled water by vacuumed pump. Then
the core is placed in the rubber sleeve in the core holder.
This sleeve is used as a connection to exert overbur-
den pressure on the rock. In these experiments the
overburden pressure is provided by water (2500 psi). To
reach Swi, injection of oil is continued until no water
is detected at the outlet. Volume of discharged water is
measured and the Swi is calculated by: S
= 1 – (Volume
of produced water/Pore volume)Now to reach residual
oil saturation Sor, distilled water is injected into the core
plug at constant  ow rate of 1 cc/min until no oil is
produced at the out let. Difference between injected oil
volume and produced oil divided to total pore volume
indicates residual oil saturation, Sor. The core sample is
ooded with two surfactants (at CMC). At this step, core
holder is connected to another transfer vessel and sur-
factant solution is injected into the core with a constant
rate. The oil produced would be measured to calculate
the oil recovery.
This study was conducted to compare wettability altera-
tion in EOR process, using new amphoteric and cationic
surfactants. New cationic and amphoteric surfactants
synthesis and investigation of wettability alteration in
EOR process is described. The goal of this work is to
compare the wettability of a carbonate rocks from oil
(mixed)-wet towards water-wet. Changing the wetta-
bility to preferentially water-wet condition will reduce
the residual oil saturation (Sor). Wettability alteration is
measured based on the contact angle method. Cationic
Surfactants are in general more expensive than anionic
ones, because of the high pressure hydrogenation reac-
tion to be carried out during their synthesis. As a conse-
quence, they are only used in two cases in which there is
no cheaper substitute.
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