Polymer coated on magnetic nanoparticles orienting in enhanced oil recovery application

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY --- NGO TRUNG KIEN POLYMER COATED ON MAGNETIC NANOPARTICLES ORIENTING IN ENHANCED OIL RECOVERY... Name of theme: Polymer coated on magnetic na

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY

-

NGO TRUNG KIEN

POLYMER COATED ON MAGNETIC NANOPARTICLES

ORIENTING IN ENHANCED OIL RECOVERY

THIS WORK WAS DONE AT HO CHI MINH CITY UNIVERSITY OF

TECHNOLOGY – VIETNAM NATIONAL UNIVERSITY

Scientific supervisor: Assoc Prof Dr Nguyen Phuong Tung Signature:

Scientific co-supervisor: Dr Dinh Xuan Loc Signature

Reviewer 1: Assoc Prof Dr Nguyen Thi Phuong Phong Signature

Reviewer 2: Dr Hoang Thi Kim Dung Signature

This master thesis was defended at Ho Chi Minh City University of Technology, Vietnam National University on January 5th, 2017

The member of Council for assessing master thesis includes:

1 Assoc Prof Dr Le Thi Hong Nhan

2 Assoc Prof Dr Nguyen Thi Phuong Phong

3 Dr Hoang Thi Kim Dung

4 Dr Tong Thanh Danh

HCM CITY UNVIERSITY OF TECHNOLOGY Independence – Freedom - Happiness

ASSIGNMENT OF MASTER THESIS

Learner’s full name: Ngo Trung Kien Learner’s code: 7141159

Date of birth: January 1st, 1991 Place of birth: Bac Lieu

Major : Chemical Engineering Code : 60.52.03.01

I Name of theme: Polymer coated on magnetic nanoparticles orienting in enhanced oil

recovery application

II Assignment and contents:

 Synthesis of copolymer AMPS-MMA coated on magnetic nanoparticles (PMNPs)

 Synthesis of nonylphenoxy carboxylated surfactant

 Characterization of obtained PMNPs’ properties

 Evaluation thermal and chemical stability of PMNPs for orienting in enhanced oil recovery

III Date of giving assignment : Januray 11th, 2016

IV Date of finishing assignment: December 2nd, 2016

V Supervisor: Assoc Prof Dr Nguyen Phuong Tung

Co-supervisor: Dr Dinh Xuan Loc

Ho Chi Minh City, January 11 th , 2016

Supervisor

(Full name and signature)

Dean of department

(Full name and signature)

Co-supervisor Dean of faculty

(Full name and signature) (Full name and signature)

ACKNOWLEDGEMENTS

Firstly, I would like to express my deepest sincere gratitude to supervisor Assoc Prof

Dr Nguyen Phuong Tung and co-supervisor Dr Dinh Xuan Loc for their support, thorough

guidance, encouragement, valuable discussions in theory and practical Without continuous support from supervisors I will not complete the master thesis as presented here

I also would like to thank all lectures, teachers, and researchers in Faculty of Chemical Engineering - Ho Chi Minh city University of Technology for helping and guiding

me throughout the studying in university and doing master thesis Thanks to the teachers and

my friends in the Materials for enhanced oil recovery and energy conversion Lab for helping

me to complete the thesis especially Dr Luong Thi Bich, Mr Pham Duy Khanh and other

members in the lab

Finally, I would like to express deepest gratitude to my father, my mother and my relative for helping about the finance, spirit These encouragements and supports help me so much to finish the thesis

Magnetic nanoparticles modified by oleic acid were coated co-polymer methyl methacrylate (MMA) and 2-acrylamido-1-propanesulfonic acid (AMPS) via mini-emulsion polymerization and this material was called PMNPs The iron source for synthesis of MNPs was prepared from red mud of Saigon Ground Water Company Limited with the mass

percentage 57% of Fe MNPs were synthesized by the combination of co-precipitation and

mini-emulsion under the presence of sodium dodecyl sulfate (SDS) as surfactant The physical and chemical characterization method such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscope (TEM) showed the PMNPs was synthesized

successfully, the average size of 12 nm for MNPs and 16 nm for PMNPs through TEM

images

At the same time, nonylphenoxy carboxylated surfactant (NPC) was also synthesized by

carboxymethylation method with the mass percentage 51% of NPC to prepare for surveying the thermal and chemical stability of mixture PMNPs-NPC The mass ratio of 200 ppm PMNPs and 800 ppm NPC represented the capacity to reduce the interfacial tension between brine and oil better than other ratios, and their combination was also be stable after 31 days in high temperature (120 o C) and high salinity environment that simulating White Tiger reservoir

condition The hydrophilic property (AMPS) and hydrophobic (MMA) of PMNPs help them

disperse well in brine and change the contact angle of oil drop and rock surface And the

result was even better when combination 200 ppm PMNPs with 800 ppm of NPC, they can

change the contact angle from 66 o to 144 o PMNPs also disperse well, be thermal and

chemical stable until the fourth using after treating with ethanol

ASSURANCE FOR MASTER THESIS

I assure that the data and researching results in this master thesis are true and they are not used to protect any degree or thesis Any help in this thesis was thanked and reference information such as method, data, figures, and pictures was cited clearly

Ho Chi Minh city, December 2nd, 2016

Learner

Ngo Trung Kien

CONTENTS

CONTENTS i

LIST OF FIGURES iv

LIST OF TABLES vi

LIST OF ABBREVIATIONS vii

Chapter 1: Introduction .1

Chapter 2: Literature Review .3

2.1 Enhanced oil recovery (EOR) 3

2.1.1 Introduction to Enhanced Oil Recovery 3

2.1.2 Mechanism of enhanced oil recovery 3

2.1.3 Enhanced oil recovery methods 6

2.2 Magnetic nanoparticles (MNPs) 7

2.2.1 Introduction 7

2.2.2 Synthesis of MNPs 7

2.2.3 Protection/Stabilization of MNPs 10

2.3 The physical chemistry properties of polymer coated nanoparticles orienting in EOR 11

2.3.1 The mobility control property 11

2.3.2 The surface wettability alteration property 14

2.3.3 Transport of PNPs in porous media 16

2.3.4 The researches about polymer coated NPs for EOR applications 17

Chapter 3: Experimental 19

3.1 Chemical and materials 19

3.2 Equipments, instrument, software 21

3.3 Synthesis of PMNPs 23

3.3.1 Preparing FeCl2 and FeCl3 from red mud 23

3.3.2 Synthesis of MNPs 25

3.3.3 Synthesis of PMNPs from OMNPs 27

3.4 Synthesis of Nonylphenoxy carboxylate surfactant 34

3.4.1 Synthesis procedure 34

3.4.2 Determination the yield of reactions and characterize the NPC surfactant 35

Contents

3.4.3 Investigating the effect of temperature on carboxymethylation reactions 36

3.5 Evaluation thermal and chemical stability of PMNPs 36

3.6 Evaluation the wettability alteration of PMNPs and mixture PMNPs-NPC surfactants 37

3.7 Evaluation the reusing capacity of PMNPs 38

Chapter 4: Results and Discussion 39

4.1 Characterization of MNPs and PMNPs 39

4.1.1 XRD patterns of MNPs from red mud and MNPs reference 39

4.1.2 VSM of MNPs and PMNPs 41

4.1.3 FT-IR of MNPs, OMNPs and PMNPs 42

4.1.4 TGA for OMNPs–MMA–co-AMPS 43

4.1.5 TEM images of MNPs and PMNPs 45

4.1.6 Result of optimization the reaction of copolymer coated on MNPs 46

4.2 Synthesis of Nonylphenoxy carboxylate (NPC) surfactant 51

4.2.1 Investigating the effect of temperature on carboxymethylation reactions 51

4.2.2 FT-IR spectroscopy of NPC surfactant 52

4.3 Evaluation thermostability of the mixtures PMNPs-NPC 52

4.4 Evaluation the wettability alteration of PMNPs and mixture PMNPs-NPC surfactants 58

4.5 Evaluation the reusing capacity of PMNPs 61

4.5.1 Observing the appearance the solution after being reusing 61

4.5.2 IFT and viscosity of MNPs and PMNPs after being reused 62

Chapter 5: Conclusions & Recommendations 63

5.1 Conclusions 63

5.2 Recommendations 64

LIST OF PUBLISHED PAPERS RELATED TO LEARNER 65 REFERENCES .a APPENDIX d

A.1 Pictures of the equipments and instruments .d A.2 Original images in this thesis g A.3 Microsoft Excel for calculating th optimization the copolymer coated MNPs reaction p A.4 Origin 8.0 for plotting graphs s A.5 Matlab 2012 for plotting 3D response surface of copolymer coated MNPs u

A.6 ChemBio Draw Ultra 12.0 for drawing chemical formulas .uA.7 Endnote X7 for citing the references vA.8 Google scholar for finding the references documents v

List of Figures

LIST OF FIGURES

Figure 2.1: Oil recovery categories Figure 2.2: Target for different crude oil systems 4

Figure 2.3: Effect of Nc on residual oil saturation 5

Figure 2.4: Enhanced oil recovery methods 6

Figure 2.5: Left: TEM images of magnetic and dielectric nanocrystals: Fe3O4 (9.1±0.8 nm; Fe2+:Fe3+, 1:2; 160oC), CoFe2O4 (11.5±0.6 nm; Co2+:Fe2+, 1:2, 180oC), BaTiO3 (16.8±1.7 nm; 180oC), TiO2 (4.3±0.2 nm; 180oC) Right: The liquid-solid-solution (LSS) phase-transfer synthetic strategy [19] 10

Figure 2.6: (a) Form as viscous fluid is a dispersion of air in water and each air droplet is surrounded by SNPs; (b) Cryo-SEM image of a foam with NPs closed packed; (c) schematic representation of the effect of concentration ratio of NP and surfactant [20] 12

Figure 2.7: CT-scan of the cross section of a core flooded with CO2 and (a) 2% NaBr brine and (b) 2% NaBr brine and 5% PEG-coated silica nanoparticles; pure brine and CO2 are illustrated with red and blue, respectively The scan is taken after 0.25 pore volume of CO2 injected and each slice is 1 cm apart longitudinally [21] 13

Figure 2.8: Schematic and SEM image of BrightWater polymeric NPs The particles expand at elevated temperatures, diverting flow to low permeability regions [22] 14

Figure 2.9: The inner and outer contact line due to ordering of NPs; (a) the oscillatory disjoining pressure due to ordering of the NPs near the wedge-like inner contact line; (b) visual and schematic pictures of inner and outer contact lines [23] 15

Figure 3.1: The compounds in red mud via analyzing EDS method 24

Figure 3.2: Process of synthesis of iron oxide nanoparticles (MNPs) 27

Figure 3.3: Synthesis of MNPs via oleate linker 28

Figure 3.4: Process of synthesis of OMNPs 29

Figure 3.5: Synthesis of PMNPs from OMNPs 30

Figure 3.6: The synthesis process of PMNPs from OMNPs 31

Figure 3.7: The illustration of synthesis of PMNPs from red mud 32

Figure 3.8: The procedure for synthesis of NPC surfactant 35

Figure 4.1: XRD pattern of MNPs 40

Figure 4.2: VSM of MNP and PMNPs 41

Figure 4.3: FT-IR spectrum of MNPs, oleic acid and OMNPs 42

Figure 4.4: FT-IR spectra of (a) OMNPs, (b) Copolymer MMA-AMPS, and (c) PMNPs 43

Figure 4.5: TGA patterns of copolymer MMA-AMPS 44

Figure 4.6: TGA patterns of PMNPs 44

Figure 4.7: TEM of MNPs 45

Figure 4.8: TEM image of PMNPs 46

Figure 4.9: Response surface of mass percentage of copolymer MMA-AMPS coated on MNPs

50

Figure 4.10: Yield of reactions at various temperatures 51

Figure 4.11: FT-IR spectroscopy of NPA, NPC and other substances in the reaction 52

Figure 4.12: (a) The color of MNPs solution (a) before applying super magnet and (b) after applying super magnet 53

Figure 4.13: Thermal stability of mixture PMNPs-NPC surfactants by time 56

Figure 4.14: FT-IR spectra of PMNPs before and after annealing experiment 57

Figure 4.15: The picture of oil drop in brine environment 58

Figure 4.16: The picture of oil drop in solution PMNPs 1000 ppm 59

Figure 4.17: The picture of oil drop in solution NPC surfactant 1000 ppm 59

Figure 4.18: The picture of oil drop in mixture PMNPs-NPC with mass ratio 200-800 in respective 60

Figure 4.19: The mechanism of PMNPs for wettability alternation of rock surface in reservoir 61 Figure A.1: Ultrasonic machine - Powersonic 603 Hwashin Technology d Figure A.2: Viscosity machine – Brookfield DV-III Ultra, USA d Figure A.3: Drying/Oven – Shellap USA e Figure A.4: Interfacial tensiometer machine – TEMCO Inc Texas, USA e Figure A.5: Contact angle measurement machine – OCA 15EC with software SCA 20 f Figure A.6: Transmission electronic microscope (TEM) - TEM JEM1010-JEOL g Figure A.7: XRD pattern of MNPs from red mud g Figure A.8: XRD pattern of MNPs from red mud h Figure A.9: VSM curve of MNPs .h Figure A.10: VSM curve of PMNPs .h Figure A.11: IR spectra of NPA i

Figure A.12: IR spectra of ClCH2COOH i Figure A.13: IR spectra of ClCH2COONa j Figure A.14: IR spectra of acetone j Figure A.15: IR spectra of NPC .k Figure A.16: TGA diagram of copolymer AMPS-MMA k

List of Figures

Figure A.17: TGA diagram of copolymer PMNPs lFigure A.18: TEM images of MNPs (10 images) nFigure A.19: Images of PMNPs (10 images) p

LIST OF TABLES

Table 2.1: Summary comparison of the synthetic methods 9

Table 3.1: Chemical and materials using for experiments 19

Table 3.2: The ingredient and properties of brine 21

Table 3.3: The properties of crude oil at White Tiger reservoir [29] 21

Table 3.4: Equipments, instruments, and software using for characterizing/researching the obtained materials 21

Table 3.5: The mass percentage of compounds in red mud 24

Table 3.6: The different conditions for polymerization 33

Table 3.7: The parameters of orthogonal planning level 2 33

Table 3.8: Value and variable range of affecting parameters 33

Table 3.9: Matrix for orthogonal planning level 2 for polymerization 34

Table 3.10: Appearance of mixtures PMNPs-NPC surfactant by the time 37

Table 3.11: Interfacial tensiometer (IFT) of mixtures PMNPs-NPC surfactant by the time 37

Table 4.1: Matrix for orthogonal planning level 2 for polymerization 47

Table 4.2: Interfacial tensiometer of mixtures PMNPs-NPC surfactant by the time 53

Table 4.3: Appearance of mixtures PMNPs-NPC surfactant by the time 54

Table 4.4: Appearance of the MNPs and PMNPs solutions after being reused 61

Table 4.5: IFT of MNPs and PMNPs after being used 62

Chapter 1: Abbreviations

LIST OF ABBREVIATIONS

Btu British thermal units

OOIP Original oil in place

EOR Enhanced oil recovery

PEG Polyethylene glycol

PVA Polyvinyl alcohol

CTAB Cetyltrimethylammonium bromide

TEM Transmission electron microscope

FE-SEM Field emission scanning electron microscope

TGA Thermogravimetric analysis

DSC Differential Scanning Calorimetry

TEMCO Company’s name for produce interfacial tension measuring machine

USA United State America

EDS Energy-dispersive X-ray spectroscope

SDS Sodium dodecyl sulfate

VSM Vibrating sample magnetometer

OMNPs Oleic-coated magnetic nanoparticles

FT-IR Fourier transfer infrared

AMPS 2-acrylamido-2-methypropane sulfonic acid

MMA Methyl methacrylate

Chapter 1: Introduction

Chapter 1

Introduction

The world energy consumption will grow by 56% between 2010 and 2040, from 524 quadrillion British thermal units (Btu) to 820 quadrillion Btu [1] Renewable resource cannot meet this growth so oil is still an important energy resource in the future Only 15-30% of the original oil in place (OOIP) is obtained by primary and secondary recovery methods because of the compressibility of fluids and initial pressure of the reservoir While in Vietnam, many major oil fields in Vietnam, such as White Tiger, Dragon, and Dawn, have passed the peak harvesting period and their production is rapidly declining It still remains large amounts of trapped oil in reservoirs; therefore, enhanced oil recovery (EOR) method should be carried out

Nanoparticles (NPs) have been studied for a variety of applications as polymer composites [2], drug delivery [3-8], solar cells [9-12], lipase immobilization [13], metal ion removing [14], imaging [6, 15, 16], and EOR [17] NPs show that they can stabilize foams and emulsions or change the wettability of rock The dispersibility of NPs can be improved by attaching polymers

to the nanoparticles surface, creating polymer-coated nanoparticles (PNPs) PNPs have interested properties as additives and interfacial active materials and more recently they have been studied for EOR because they can use as mobility control agents and for wettability alteration Magnetic nanoparticles (MNPs) inherits the outstanding properties of NPs; in addition, they can be easily recovered and reused because of magnetic property and crude oil absorbed on MNPs can isolated when applying the external magnetic field But the surface MNPs need to be modified for migration through porous media, dispersibility in brine and injectable capacity into a reservoir And polymer-coated nanoparticles (PNPs) were considered as an additives and interfacial active materials for EOR because of their properties in controlling mobility and alternating wettability between liquid surface and solid surface

Nowadays, pollution environment is an urgent and global problem To face with this problem, it needs to utilize the waste sources to produce new products A source of solid waste red mud with the main content of Fe from groundwater treating plants that may contribute to soil and groundwater pollution was used to provide the iron source for synthesis of MNPs in this thesis Besides, a surfactant also needs to be prepared for evaluation oil recovery capacity Nonylphenoxy polyethoxycarboxylate (NPC) with the structure of hydrophilic group (carboxylate) and hydrophobic tail group separated by ethoxylate (EO) groups helps to liberate the residual oil in enhanced oil recovery application through reducing the interfacial tension between oil and brine This thesis will evaluate the thermal and chemical stability of the mixture PMNPs and NPC in harshness environment that simulates the White Tiger reservoir

This work has been done with 2 related papers including (1) Facile procedure to synthesize

ankylphenoxy polyethoxycarboxylate surfactants and investigate the properties for enhanced oil recovery application published in Vietnam Journal Chemistry, and (2) Synthesis of polymer- coated magnetic nanoparticles from red mud waste for enhanced oil recovery in offshore reservoir published in Journal of Electronic Materials – Springer

Chapter 2: Literature review

Chapter 2

Literature Review

2.1 Enhanced oil recovery (EOR)

2.1.1 Introduction to Enhanced Oil Recovery

According to the method of production or the time at which hydrocarbons are obtained, there are three terms: primary oil recovery, secondary oil recovery, and tertiary (enhanced) oil recovery Primary oil recovery describes the production of hydrocarbons under the natural driving mechanisms present in the reservoir without supplementary help from injected fluids such as gas or water Secondary oil recovery refers to the additional recovery resulting from the conventional methods of water injection and immiscible gas injection Tertiary (enhanced) oil recovery is the additional recovery over and above what could be recovered by secondary recovery methods Various methods of enhanced oil recovery (EOR) are essentially designed to recover oil, commonly described as residual oil, left in the reservoir after both primary and secondary recovery methods have been exploited to their respective economic limits The

concept of the three recovery categories is illustrated in Figure 2.1

2.1.2 Mechanism of enhanced oil recovery

Improved oil recovery (IOR) is a general term that implies improving oil recovery by any means (operational strategies, such as infill drilling, horizontal wells, and improve vertical and areal sweep) Enhanced oil recovery (EOR) is more specific in concept and it can be considered

as a subset of IOR EOR implies the process of enhancing oil recovery by reducing oil saturation

below the residual oil saturation “S or” The target of EOR varies considerably by different types

of hydrocarbons Figure 2.2 shows the fluid saturations and the target of EOR for typical light

and heavy oil reservoirs and tar sand For light oil reservoir, EOR is usually applicable after secondary recovery operations with an EOR target of approximately 45% original oil in place

(OOIP) Heavy oils and tar sands respond poorly to primary and secondary recovery methods, and the bulk of the production from these types of reservoirs come from EOR methods

Figure 2.1: Oil recovery categories Figure 2.2: Target for different crude oil systems

The magnitude of the reduction and mobilization of residual oil saturation “S or” by an EOR process is controlled by two major factors, they are:

μ = viscosity of the displacing fluid

σ = interfacial tension (IFT) between the displacing fluid and the displaced fluid (oil)

v = Darcy velocityθ = the contact angle

 = porosity

k 0 = effective permeability of the displaced fluid

Δp/L = pressure gradient

Chapter 2: Literature review

Figure 2.3: Effect of N c on residual oil saturation Figure 2.3 is a schematic representation of the capillary number and the ratio of residual oil

saturation (after conduction of an EOR process to residual oil saturation before the EOR process) The illustration shows the reduction in the residual oil saturation with the increase in the capillary number It is clear that the capillary number can be increased by:

- Increasing the pressure gradient Δp/L

- Increasing the viscosity of the displacing fluid

- Increasing displacing fluid viscosity μ

- Decreasing the interfacial tension between the injection fluid and displaced fluid

It is easy to understand that the capillary number cannot be practically increased 1000 times

by the first two ways It is known that the interfacial tension between a surfactant solution and oil can be reduced from 20 to 30 to the order of 10-3 mN/m In other words, by adding surfactants, the capillary number can be practically increased by more than 1000 times Due to the low IFT, oil droplets can flow more easily through pore throats because of reduced capillary trapping The oil droplets move forward and merge with the oil down the stream to form an oil bank

Another important concept in understanding the displacing mechanism of an EOR process is the mobility ratio “M” The mobility ratio is defined as the ratio of the displacing fluid mobility

to that of the displaced fluid, or:

0 0

( / )( / )

 displacing  displacing displaced displaced

k M

A value of M > 1 is considered unfavorable because it indicates that the displacing fluid flows more readily than the displaced fluid (oil) This unfavorable condition can cause channeling and bypassing of residual oil Improvement in mobility ratio can be achieved by increasing the viscosity of the injection fluid, polymer flood

2.1.3 Enhanced oil recovery methods

All EOR methods that have been developed are designed to increase the capillary number In general, EOR technologies can be broadly grouped into the following four categories:

- Thermal

- Chemical

- Miscible

- Others

Each of the four categories contains an assortment of injection schemes and a different variety of

injection fluids, as summarized in Figure 2.4:

Figure 2.4: Enhanced oil recovery methods

Foam

Chapter 2: Literature review

2.2 Magnetic nanoparticles (MNPs)

2.2.1 Introduction

Magnetic nanoparticles (MNPs) are of great interest for researchers from a wide range of disciplines, including magnetic fluids, catalysis, biotechnology/biomedicine, magnetic resonance imaging, data storage, and environmental remediation Recently they are also being studied for enhanced oil recovery field [18] While a number of suitable methods have been developed for the synthesis of MNPs of various different compositions, successful application of such MNPs in the areas listed above is highly dependent on the stability of the particles under a range of different conditions In most of the envisaged applications, the particles perform best when the size of the NPs is below a critical value, which is dependent on the material but is typically around 10-20 nm However, an unavoidable problem associated with particles in this size range

is their intrinsic instability over longer periods of time Such small particles tend to form agglomerates to reduce the energy associated with the high surface area to volume ratio of the nanosized particles Moreover, naked metallic NPs are chemically highly active, and are easily oxidized in air, resulting generally in loss of magnetism and dispersibility For many applications

it is thus crucial to develop protection strategies to chemically stabilize the naked MNPs against degradation during or after the synthesis These strategies include grafting or coating with organic species, including surfactants or polymers, or coating with an inorganic layer, such as silica or carbon

2.2.2 Synthesis of MNPs

MNPs have been synthesized with a number of different compositions and phases, including iron oxide, such as Fe3O4 and γ-Fe2O3, pure metals such as Fe and Co, spinel-type ferromagnets such as MgFe2O4, MnFe2O4 and CoFe2O4 as well as alloys such as CoPt3 and FePt Several popular methods include co-precipitation, thermal decomposition and/or reduction, micelle synthesis, hydrothermal synthesis

Co-precipitation

Co-precipitation is a facile and convenient way to synthesize iron oxides (either Fe3O4 or

γ-Fe2O3) from aqueous Fe2+/Fe3+ salt solutions by the addition of a base under inert atmosphere at room temperature or at elevated temperature The size, shape, and composition of the MNPs very much depends on the type of salts used (e.g chlorides, sulfates, nitrates), the Fe2+/Fe3+ ratio, the reaction temperature, the pH value and ionic strength of the media

Recently, significant advances in preparing monodisperse MNPs, of different sizes, have been made by the use of organic additives as stabilization and/or reducing agents For example, MNPs with sizes of 4-10 nm can be stabilized in an aqueous solution of 1wt% polyvinyl alcohol (PVA) The effect of organic ions on the formation of metal oxides or oxyhydroxides can be rationalized by two competing mechanisms Chelation of the metal ions can prevent nucleation and lead to the formation of larger particles because the number of nuclei formed is small and the system is dominated by particle growth On the other hand, the adsorption of additives on the nuclei and the growing crystals may inhibit the growth of the particles, which favors the formation of small units

Thermal decomposition

Monodisperse magnetic nanocrystals with smaller size can essentially be synthesized through the thermal decomposition of organometallic compounds in high-boiling organic solvents containing stabilizing surfactants The organometallic precursors include metal acetylacetonates [M(acc)n], (M = Fe, Mn, Co, Ni, Cr; n = 2 or 3, aac = acetylacetonates), metal cupferronates [MxCupx] (M = metal ion; Cup = N-nitrosophenylhydroxylamine, C6H5N(NO)O-),

or carbonyl Fatty acids, oleic acid and hexadecylamine are often used as surfactants In principle, the ratios of the starting reagents including organometallic compounds, surfactant, and solvent are the decisive parameters for the control of the size and morphology of MNPs The reaction temperature, reaction time, as well as aging period may also be crucial for the precise control of size and morphology

Microemulsion

A microemulsion is a thermodynamically stable isotropic dispersion of two immiscible liquids, where the microdomain of either or both liquid is stabilized by an interfacial film of surfactant molecules In water-in-oil microemulsions, the aqueous phase is dispersed as microdroplets (typically 1-50 nm in diameter) surrounded by a monolayer of surfactant molecules in the continuous hydrocarbon phase The size of the reverse micelle is determined by the molar ratio of water to surfactant By mixing two identical water-in-oil microemulsions containing the desired reactants, the microdroplets will continuously collide, coalesce, and break again, and finally a precipitate forms in the micelles By the addition of solvent such as acetone

or ethanol to the microemulsions, the precipitate can be extracted by filtering or centrifuging the mixture In this sense, a microemulsion can be used as a nanoreactor for the formation of NPs

Chapter 2: Literature review

Using the microemulsion technique, metallic cobalt, cobalt/platinum alloys, and gold-coated cobalt/platinum NPs have been synthesized in reverse micelles of cetyltrimethylammonium bromide (CTAB), using 1-butanol as the co-surfactant and octane as the oil phase

Hydrothermal synthesis

Under hydrothermal conditions a broad range of nanostructured material can be formed Li

et al reported a generalized hydrothermal method for synthesizing a variety of different nanocrystals by a liquid-solid-solution reaction The system consists of metal linoleate (solid), an ethanol-linoleic acid liquid phase, and a water-ethanol solution at different reaction temperature

under hydrothermal conditions [19] As illustrated in Figure 2.5, this strategy is based on a

general phase transfer and separation mechanism occurring at the interfaces of the liquid, solid, and solution phases present during the synthesis As an example, Fe3O4 and CoFe2O4 NPs can be

prepared in very uniform sized of about 9 and 12 nm, respectively (Figure 2.5)

The advantages and disadvantages of the four above-mentioned synthetic methods are briefly

summarized in Table 2.1 In terms of simplicity of the synthesis, co-precipitation is the preferred

route In terms of size and morphology control of the NPs, thermal decomposition seems the best method developed to date As an alternative microemulsions can also be used to synthesize monodispersed NPs with various morphologies However, this method requires a large amount

of solvent Hydrothermal synthesis is a relatively little explored method for the synthesis of MNPs, although it allows the synthesis of high-quality NPs To date, MNPs prepared from co-precipitation and thermal decomposition are the best studied, they can be prepared on a large scale

Table 2.1: Summary comparison of the synthetic methods

Synthetic

method

Synthesis Reaction

temperature ( o C)

Reaction period

Solvent

Surface-capping agents

Size distribution

Shape control

Yield

Co-precipitation Very

simple, ambient conditions

20-90 Minutes Water Needed,

added during or after reaction

Relative narrow

Not good

High/ scalable

Thermal

decomposition

Complicate , inert atmosphere

100-320 Hours –

days

Organic compou

nd

Needed, added during reaction

Very narrow Very

good

High/ scalable

Microemulsion Complicate

, ambient conditions

20-50 Hours Organic

compou

nd

Needed, added during reaction

Relative narrow

Good Low

Hydrothermal

synthesis

Simple, high pressure

220 Hours ca

days

ethanol

Water-Needed, added during reaction

Very narrow Very

good

Medium

Figure 2.5: Left: TEM images of magnetic and dielectric nanocrystals: Fe 3 O 4 (9.1±0.8 nm;

Fe 2+ :Fe 3+ , 1:2; 160 o C), CoFe 2 O4 (11.5±0.6 nm; Co 2+ :Fe 2+ , 1:2, 180 o C), BaTiO 3 (16.8±1.7 nm; 180 o C), TiO 2 (4.3±0.2 nm; 180 o C) Right: The liquid-solid-solution (LSS) phase-

transfer synthetic strategy [19]

2.2.3 Protection/Stabilization of MNPs

Although there have been many significant developments in the synthesis of MNPs, maintaining the stability of these particles for a long time without agglomeration or precipitation

is an important issue All the protection strategies result in MNPs as a core-shell structure, that

is, the naked MNPs as a core is coated by a shell, isolating the core against the environment The applied coating strategies can roughly be divided into two major groups: coating with organic shells, including surfactant and polymers, or coating with inorganic components, including silica, carbon, precious metals (such as Ag, Au) or oxides which can be created by gentle oxidation of the outer shell of the NPs, or additionally deposited such as Y2O3 But in the scope of this thesis,

it is focused on coating with polymer

Surfactants or polymers are often employed to passivate the surface of the NPs during or after the synthesis to avoid agglomeration In general, electrostatic repulsion or steric repulsion can be

Chapter 2: Literature review

used to disperse NPs and keep them in a stable colloidal state Surfactants or polymers can be chemically anchored or physically adsorbed on MNPs to form a single or double layer, which creates repulsive (mainly as steric repulsion) forces to balance the magnetic and the van der Waals attractive forces acting on the NPs Thus by steric repulsion, the MNPs are stabilized in suspension Polymer containing functional group, such as carboxylic acid, phosphates, and sulfates can bind to the surface of magnetite Suitable polymers for coating include poly(pyrrole), poly(aniline), poly(alkylcyanoacrylates), poly(methylidende malonate), and polyesters, such as poly(lactic acid), poly(glycolic acid), poly(ε-caprolactone), and their copolymers

2.3 The physical chemistry properties of polymer coated nanoparticles orienting in EOR

2.3.1 The mobility control property

In EOR, mobility ratio is the mobility of the injected displacing fluid to that of the oil being displaced Good mobility control is obtained when the viscosity of the injected fluid is higher than the viscosity of the oil in the reservoir This can be attained through generation of foams and emulsions, which can form in the presence of surfactant or NPs Unlike surfactants, NPs have the advantage that they can irreversibly adsorb to a liquid-liquid or gas-liquid interface, forming very stable foams and emulsions Bare NPs may be too hydrophobic or hydrophilic for stabilizing an interface so PNPs can be tailored for a specific interface and application

Using surfactant-coated nanoparticles (SNPs) and PNPs for stabilizing foam and emulsion

SNPs are prepared by blending surfactants and NPs Surfactant can form a monolayer on the

NP surface, creating more hydrophobic particles Figure 2.6 shows a schematic representation of

surfactant adsorption onto a NPs and examples of foams and emulsions stabilized by SNPs This adsorption is confirmed through contact angle measurement, adsorption isotherms of surfactants

on NPs, zeta potential measurements and dispersion stability measurements as a function of concentration of surfactant and NPs

Figure 2.6: (a) Form as viscous fluid is a dispersion of air in water and each air droplet is surrounded by SNPs; (b) Cryo-SEM image of a foam with NPs closed packed; (c) schematic representation of the effect of concentration ratio of NP and surfactant [20]

The relative concentration of surfactant and NPs affect to the properties of SNPs, the rheology of foams and emulsions formed by SNPs Another role of the surfactant in this process

is to lower the interfacial tension and form an initial dispersion of air/water or oil/water in case

of foam or emulsion, respectively Once this dispersion is formed due to shear and a decreased amount of interfacial tension, the stability of foam/emulsion is augmented by adsorption of NPs

at the interface Similar to surfactant-coated nanoparticles, PNPs can be used to stabilize foams and emulsions because they can decrease the interfacial tension of oil and water and air, which can lead to more stable emulsion PNPs can reduce interfacial tension (IFT) from 25 to 1 mN/m

By comparison, surfactant additives can lead to much greater reductions in oil-water IFT, down

to 0.001 mN/m and below Therefore, the reduction in oil-water IFT is modest compared with suitably chosen surfactant additives In addition to surface energy, entropy is important to the interfacial properties of PNPs Polymers can exhibit conformational change that influence the thermodynamics of PNPs adsorption at the fluid-fluid interface

Chapter 2: Literature review

Surfactant and PNPs for mobility control

Foams and/or emulsion formation are not only relying on increasing the viscosity of the displacing fluid and the recovery of oil but also through CT scans, an increased pressure drop across the core, and effluent analysis

Figure 2.7 shows the CT-scan of different cross sections of a Boise sandstone core after

flooding with brine and CO2, both with and without PEG-coated silica NPs The difference in these two experiments is only the presence or absence of PNP and the same core has been scanned at the same injected pore volume of CO2 Large regions of the core are bypassed due to

viscous fingering (Figure 2.7a) when no PNP added, while the CT-scan results show greater sweep efficiency in the presence of PNP (Figure 2.7b),

Figure 2.7: CT-scan of the cross section of a core flooded with CO 2 and (a) 2% NaBr brine and (b) 2% NaBr brine and 5% PEG-coated silica nanoparticles; pure brine and CO 2 are illustrated with red and blue, respectively The scan is taken after 0.25 pore volume of CO 2

injected and each slice is 1 cm apart longitudinally [21]

One practical challenge in the application of foam and emulsions from PNPs is the energy needed for foam and emulsion formation There is a threshold shear rate needed for NPs to start generating foams and emulsions This threshold injection flow may be much greater than the practical injection rates in reservoirs Pregeneration of foams and emulsions outside the reservoir before injection increases the cost and difficult of injection into reservoir

A type of polymeric nanoparticles with commercial name BrightWater was the first successfully field-tested nanoparticles to increase the sweep efficiency in an actual oil reservoir (Salema field, Campos Basin, Brazil) [22] BrightWater is a polymeric nanoparticle that hydrolyzes at a specific temperature and expands to many times its original volume By blocking

the pores in the high-permeability regions of reservoir, the injected flow will be directed toward low-permeability zones of the reservoir, which may have been previously untouched

Figure 2.8: Schematic and SEM image of BrightWater polymeric NPs The particles expand at elevated temperatures, diverting flow to low permeability regions [22] Figure 2.8 illustrates the basic idea behind the application of these polymeric nanoparticles,

which can lead to significant increase in oil recovery Although BrightWater is not a PNP, its successful implementation provides guidelines for the design of PNPs and demonstrates that PNPs do have potential for use in EOR

2.3.2 The surface wettability alteration property

Oil can be extracted easily from water-wet rock than from oil-wet rock, and one approach to improve oil recovery is through changing the wettability of the reservoir rock from oil-wet towards water-wet A surface is called water-wet if the water contact angle is < 90o and oil-wet if the water contact angle is >90o

Mechanisms of surface wettability alteration by PNPs

Surface and interfacial energies determine whether a surface is water-wet or oil-wet A spreading coefficient S of water on a solid in contact with both oil and water can be defined in terms of the IFTs between each phase in following equation:

S = γO/S – γW/S - γO/W

Where γO/S, γW/S, and γO/W are the interfacial energies between oil/solid, water/solid, and oil/water Reducing the oil-water interfacial tension results in an increase in S and a more water-wet surface “Rollup” is a well-known mechanism for removal of oily soils from solid surfaces

by wettability alteration using surfactants

Chapter 2: Literature review

However, in a fluid containing nanoparticles or spherical surfactant micelles, phenomena are observed that may not be fully explained through the previously known mechanisms The underlying mechanism that can explain for this unusual interfacial behavior is related to the size

of NPs Adjacent to the wedge-shape inner contact line, the NPs can form ordered structures, as

shown in Figure 2.9

Figure 2.9: The inner and outer contact line due to ordering of NPs; (a) the oscillatory disjoining pressure due to ordering of the NPs near the wedge-like inner contact line; (b)

visual and schematic pictures of inner and outer contact lines [23]

Structural disjoining pressure is just one of the components affecting disjoining pressure Val der Waals, electrostatic, and solvation forces are other components that can affect the disjoining pressure Electrostatic can be very effective in increasing wettability alteration properties of NPs If the NP is coated by a polyelectrolyte, electrostatic repulsive forces can increase the disjoining pressure and may cause significant increase in spreading of the phase with dispersed NPs

NPs EOR processes through wettability alteration

A number of studies have reported the application of NPs in EOR through wettability alteration, but studies of the effect of PNPs on wettability is in the early stages Relative permeability curves of oil and water also change after contacting with NPs; that is, the relative permeability of oil and water increases and decreases, respectively Ju et al developed simulations to analyze wettability alterations caused by NPs They analyzed the effect of different physical and chemical properties of the NPs, such as polymer coating, contact angle, and size in terms of empirical coefficients [24, 25] They report that both permeability and porosity of the core decrease with injection of NPs, and the decrease in permeability is more

significant than porosity Based on their simulations, oil recovery can be improved through wettability alteration by up to 20% when a high concentration of nanoparticle is injected At the same time, increasing nanoparticles concentration leads to greater reductions in permeability Therefore, they suggest an optimum concentration of nanoparticle (2-3%) for injection into the core

2.3.3 Transport of PNPs in porous media

PNPs can improve oil recovery but they must also be able to propagate deep into the reservoir to assist oil displacement Three mechanisms primarily affect propagation of NPs in porous media: physical filtration, solution chemical stability, and adsorption on the rock/porous media surface

Physical filtration

Physical filtration occurs when the particles are larger than some of the pores in the porous media This may even occur for well-dispersed (nonaggregated) NPs in case of injection in low-permeability rocks, such as tight sandstones For nonaggregated NPs, the size, shape and aspect ratio of the particle are relevant parameters that can affect filtration The particle size-distribution

is also important since filtration may be initiated with the large particles In the case of PNPs, both NPs and polymeric coating can be polydisperse

Solution and chemical stability of PNPs

In the presence of high salinity and hardness (which is often the case in oil reservoir), poor chemical stability can lead to aggregation or precipitation of NPs because of van der Waals and hydrophobic attractions Polymeric coatings on NPs can potentially inhibit aggregation by providing electrostatic or steric repulsions [26] Some polyelectrolytes such as poly(acrylic acid), poly(vinyl pyrrodine), poly(styrene sulfonate), and bilayers of ionic surfactants have been used

to provide electrostatic repulsion between nanoparticles The challenge with these types of coatings is that they are usually highly pH-dependent Salinity and the presence of divalent ions can also affect the stability of PNPs NPs can also be coated with a combination of polymers to provide both providing steric inhibition and electrostatic repulsion to optimize the stabilization and adsorption [27]

Another factor to consider is that PNPs may behave differently and even have different sizes under static and dynamic conditions [28] Ersenkal et al investigated the size of poly(acrylic acid)-coated iron nanoparticles in static (in solution) and dynamic conditions (passed through a

Chapter 2: Literature review

porous medium) They found that the NP size appeared to depend on NP solution concentration

in dynamic tests but not static measurements This result highlights the complexity of the effects

of dynamic factors (such as flow rate, permeability, etc.) on the effective size of the NPs and questions the validity of static measurements to determine the chemical stability of NPs under dynamic conditions

Adsorption on the porous media

Even for NPs of appropriate size and shape and good stability in solution, adsorption onto solid surfaces may impede NP transport Low adsorption of the injected chemicals on rock also improves the economics of the oil recovery process Electrostatic repulsions and reduced hydrophobic-hydrophobic interactions between PNPs and the rock surface can reduce NP adsorption PNPs with a surface charge that matches that of the rock surface or that are less hydrophobic may exhibit reduced adsorption

2.3.4 The researches about polymer coated NPs for EOR applications

Caetano Rodrigues Miranda and et al researched about stability and mobility of functionalized (hydroxylated, PEG, and sulfonic acid) silica NPs for EOR application at high temperature and high salt concentration in 2012 The results showed that ions tends to modify the transport properties of the NPs itself to stabilize the interfacial energy in the nanoparticle-brine interface [29] The author Nguyen Phuong Tung and et al also published about composite silica-core/polymer-shell NPs blended with surfactant systems for evaluation the EOR capacity in this year The SiO2 nanoparticles were introduced to the polymer matrix through core-shell encapsulation-polymerization The results showed that the nanocomposites can reduce IFT and enhance the viscosity

In 2013, Hitesh G Bagaria et al studied about stabilization of iron oxide NPs in high sodium and calcium brine at high temperature with adsorbed sulfonated copolymers Steric stabilization

of iron oxide NPs coated with poly (2-methyl-2-acrylamidopropanesulfonate-co-acrylic acid) (1:1 mol:mol) provided colloidal stability in brine at room temperature and 90oC for up to 1 month [30]

In 2014, Rasha A.El-Ghazawy and et al reported about synthesis of polymer/magnetites nanocomposite via emulsion polymerization with magnetite NPs as core and poly (sodium methacrylate) as shell The synthesized nanocomposites exhibited the good thermal stability in EOR application

In 2015, Wan-Fen Pu and et al published about water soluble core-shell hyperbranches polymers for EOR Novel water soluble core-shell hyperbranched polymer (HBPAMs) was synthesized with nano-silica as core, hyperbranched polyamidoamide (PAMAM) as subshell and linear hydrophilic chains as outermost layer via free radical polymerization The rheological measurements, core flooding experiments showed that this structure core-shell polymer may use

in EOR applications [31]

The reports from 2012 to 2015 mainly focused on silica nanoparticles but magnetic nanoparticles coated polymer was still not studied more Therefore, this material will be synthesized and studied about capacity of using in enhanced oil recovery The combination will utilize the advantages both magnetic nanoparticles and polymer

Chapter 3: Experimental

Chapter 3

Experimental 3.1 Chemical and materials

Table 3.1: Chemical and materials using for experiments

Germany

9 Sodium dodecyl

10 Ammonium

14

USA Aldrich)

(Sigma-sulfonate

15 Methyl

USA Aldrich)

(Sigma-16 Ammonium

For synthesis and analysis of nonylphenoxy polyethoxy carboxylate (NPC) surfactant

(Sigma-7 Safranine O

Basic Red 2, Cotton Red, Gossypimine, Safranin T, Safranin Y

or A (Trade name)

Solid

USA Aldrich)

2 Crude oil, brine -

Liquid, the

properties as Table

3.4

White Tiger Oligocene oilfield

of Vietnam

Table 3.3: The properties of crude oil at White Tiger reservoir [32]

The properties The value

3.2 Equipments, instrument, software

Table 3.4: Equipments, instruments, and software using for characterizing/researching the

obtained materials

No Using for Equipment/Instrument Condition in thesis Equipment’s

origin

For synthesis, characterization and evaluation of MNPs, PMNPs

Technology

3 Measuring

5 Measuring pH pH Accument Research

Fisher Scientific - USA

Analyzing the solid

The temperature is from

30 to 800oC with a heating rate of

10oC/min, under dynamic flow of nitrogen using differential scanning calorimeter (DSC)

Labsys Evo - France

Disperse material in

3 Orgin 8.0 for plotting XRD patterns, FT-IR spectra USA

5 ChemBio Draw Ultra 12.0 for drawing chemical formulas USA

6 Google scholar for find the reference documents USA

3.3 Synthesis of PMNPs

3.3.1 Preparing FeCl 2 and FeCl 3 from red mud

Red mud source was taken from Saigon Ground Water Company Limited (SAGROWA CO LTD) The mass percentage of elements in red mud was analyzed according to Energy-dispersive

X-ray spectroscopy (EDS) method The result analysis was showed in Figure 3.1 and Table 3.5

Figure 3.1: The compounds in red mud via analyzing EDS method

Table 3.5: The mass percentage of compounds in red mud

Element The mass percentage (%)

Fe

Fe

Fe

Chapter 3: Experimental

Al2O3 + 6HCl → 2AlCl3 + 3H2O FeO + 2HCl → FeCl2 + H2O

Fe2O3 + 6HCl → 2FeCl3 + 3H2O

Al2(CO3)3 + HCl  AlCl3 + H2O + CO2CaCO3 + HCl  CaCl2 + H2O + CO2FeCO3 + HCl  FeCl2 + H2O + CO2

AlPO4 + HCl  AlCl3 + H3PO4

Ca3(PO4)2 + HCl  CaCl2 + H3PO4The insoluble compound (SiO2) was removed after reaction The obtained solution includes AlCl3, FeCl2, FeCl3, CaCl2

After that, mount of redundant NaOH was added into above solution to dissolve completely precipitate Al(OH)3 and obtained Fe(OH)2, Fe(OH)3 The oxygen was pumped into solution to obtained only Fe(OH)3 The reactions happen as follows:

AlCl3 + 3NaOH → Al(OH)3 + 3H2O Al(OH)3 + NaOH → NaAlO2 + 2H2O FeCl2 + 2NaOH → Fe(OH)2 + 2NaCl 4Fe(OH)2 + O2 + 2H2O 4Fe(OH)3

2FeCl3 + 6NaOH  2Fe(OH)3 + 6NaCl

A part of Fe(OH)3 was dissolve into N2H4 to obtained Fe(OH)2

4Fe(OH)3 + N2H4  4Fe(OH)2 + N2 + 4H2O FeCl2 and FeCl3 salts were obtained by adding HCl into Fe(OH)2 and Fe(OH)3

Fe(OH)2 + 2HCl  FeCl2 + 2H2O 2Fe(OH)3 + 6HCl  2FeCl3 + 3H2O

3.3.2 Synthesis of MNPs

MNPs were synthesized using the combined method of co-precipitation and mini-emulsion under the presence of SDS as surfactant 40 mL of FeCl2 0.625M and 40mL of FeCl3 1.25M

from preparing Section 3.3.1 were put in a 250 mL three-neck round-bottom flask, which was

equipped with a mechanical stirrer under inert gas (nitrogen) Meanwhile, 1 g of SDS was dissolved into 20 mL of deoxygenated distilled water, which was poured into three-neck round-bottom flask through a funnel The mixture was stirred vigorously with the speed of 900 rounds per minute (rpm) and heated gradually to 80 °C MNPs was also synthesized from FeCl2 and