Technological

Communication

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

and

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

ABSTRACT

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.

KEY WORDS: EOR, PETROLEUM, WETTABILITY, CTAB, HABSA

704

ARTICLE INFORMATION:

*Corresponding Author: ghasemzargar796@gmail.com

Received 1

Oct, 2017

Accepted after revision 30

Dec, 2017

BBRC Print ISSN: 0974-6455

Online ISSN: 2321-4007 CODEN: USA BBRCBA

Thomson Reuters ISI ESC and Crossref Indexed Journal

NAAS Journal Score 2017: 4.31 Cosmos IF: 4.006

reserved.

Online Contents Available at:

http//www.bbrc.in/

DOI: 10.21786/bbrc/10.4/14

Reza Qanbari et al.

INTRODUCTION

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.

MAIN SUBJECTS

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

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS WETTABILITY ALTERATION IN ENHANCED OIL RECOVERY PROCESS 705

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

706 WETTABILITY ALTERATION IN ENHANCED OIL RECOVERY PROCESS BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

Reza Qanbari et al.

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS WETTABILITY ALTERATION IN ENHANCED OIL RECOVERY PROCESS 707

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),

MATERIALS AND METHODS

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

dried.

RESULTS AND DISCUSSION

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.

708 WETTABILITY ALTERATION IN ENHANCED OIL RECOVERY PROCESS BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

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.

CONCLUSION

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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