A mechanistic study of wettability changes on calcite by molecules

Subscriber access provided by Gothenburg University Library

Interfaces: Adsorption, Reactions, Films, Forces, Measurement Techniques, Charge Transfer, Electrochemistry, Electrocatalysis, Energy Production and Storage

A mechanistic study of wettability changes on calcite by molecules containing a polar hydroxyl functional group and non-polar benzene rings Sooyeon Kim, Maria C. Marcano, and Udo Becker Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.8b03666 • Publication Date (Web): 25 Jan 2019 Downloaded from http://pubs.acs.org on January 28, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

1

A mechanistic study of wettability changes on calcite by molecules containing

2

a polar hydroxyl functional group and non-polar benzene rings

3

Sooyeon Kim, Maria C. Marcano, and Udo Becker*

4 5

Department of Earth and Environmental Sciences, University of Michigan, 3021 North University Building, 1100 North University Avenue, Ann Arbor, MI 48109-1005, USA

6

*Corresponding author Udo Becker. Tel.: +1 734 615-6894; email: [email protected]

7

Abstract

8

Oil extraction efficiency strongly depends on the wettability status (oil vs. water-wet) of reservoir

9

rocks during oil recovery. Aromatic compounds with polar functional groups in crude oil have a significant

10

influence on binding hydrophobic molecules to mineral surfaces. Most of these compounds are in the

11

asphaltene fraction of crude oil. This study focuses on the hydroxyl functional group, an identified

12

functional group in asphaltenes, to understand how the interactions between hydroxyl groups in asphaltenes

13

and mineral surfaces begin. Phenol and 1-naphthol are used as asphaltene surrogates to model the simplest

14

version of asphaltenes. Adsorption of oil molecules on the calcite {1014} surface is described using static

15

quantum-mechanical Density Functional Theory (DFT) calculations and classical Molecular Dynamics

16

(MD) simulations. DFT calculations indicate that adsorption of phenol and 1-naphthol occurs preferentially

17

between their hydroxyl group and calcite step edges. 1-naphthol adsorbs more strongly than phenol, with

18

different adsorption geometries due to the larger hydrophobic part of 1-naphthol. MD simulations show

19

that phenol can behave as an agent to separate oil from water phase, and to bind oil phase to the calcite

20

surface in water/oil mixture. In the presence of phenol, partial separation of water/oil with an incomplete

21

lining of phenol at the water/oil boundary is observed after 0.2 ns. After 1 ns, perfect separation of water/oil

22

with a complete lining of phenol at the water/oil boundary is observed, and the calcite surface become oil-

23

wet. Phenol molecules enclose decane molecules at the water/decane boundary preventing water from

24

repelling decane molecules from the calcite surface, and facilitate further accumulation of hydrocarbons

25

near the surface rendering the surface oil-wet. This study indicates phenol and 1-naphthol being good

1 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

26

proxies for polar components in oil, and they can be used in designing further experiment to test pH, salinity,

27

and temperature dependence to improve oil recovery.

28

Introduction

29

Oil production can be divided into three phases: primary, secondary, and tertiary. The primary oil

30

recovery refers to the natural rising of oil due to the pressure differences between the oil reservoir and the

31

wellbore or the use of lift systems such as rod pumps. Only around 10% of oil can be produced by these

32

primary methods. Water or gas injection can improve oil production, which is called secondary oil recovery.

33

Water or gas is injected into oil reservoirs to sweep oil to wellbores; then about 20 to 40 percent of the oil

34

can be produced using this recovery. Changing the properties of oil to make it more conducive to extraction

35

by injection of heat, gas, or chemicals is tertiary oil recovery, which is commonly known as enhanced oil

36

recovery (EOR). Oil production from the oil reservoir will be increased up to 70% by EOR.1

37

Lowering oil viscosity, surface tension, and capillary pressure are the main principles of EOR. Oil

38

flow is enhanced due to the reduced oil viscosity and surface tension, and this improves oil recovery.

39

Capillary forces play an important role in preventing micron-sized reservoir rock pores from releasing oil;

40

therefore, a lower capillary pressure also improves oil recovery. Wettability, which refers to a characteristic

41

of a solid surface showing a preference to be in contact with one fluid over another2, is one of the major

42

factors that control capillary pressure in pore spaces of rocks.3 Furthermore, secondary oil recovery by

43

waterflooding is directly related to the wettability of oil reservoir. Wettability also affects many crucial

44

parameters for evaluation of oil reservoirs, such as the relative permeability or the saturation profiles of the

45

oil reservoir.2, 4 Thus, understanding the wettability alteration of the reservoir rock surface is a key factor

46

for improving the efficiency of oil recovery.

47

While a mineral surface is often referred to as water-wet (hydrophilic) or oil-wet (lipophilic),

48

surface wettability is instead a continuum between an absolute preference for water (i.e., water-wet) and an

49

absolute preference for oil (i.e., oil-wet). Therefore, it is typically complicated to describe the actual wetting


Page 2 of 34

Page 3 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

50

scenarios in oil production because any reservoir will likely exhibit variable degrees or types of wettability.

51

Despite this complexity, a suitable model to predict the wettability alteration of mineral surfaces is needed

52

to increase our understanding of wettability change and ultimately to control the wettability for the purpose

53

of increasing the efficiency of oil recovery.

54

There are multiple factors that affect the wettability of mineral surfaces, including temperature,

55

pressure, pH, composition of crude oil, connate fluid compositions, and reservoir mineralogy.5 What makes

56

the oil molecules bind onto the rock surface are believed to be polar compounds, which are mostly found

57

in the asphaltene fraction of crude oil. Asphaltene is one of the four solubility classes obtained by the SARA

58

fractionation technique (i.e., Saturates, Aromatics, Resins, and Asphaltenes), which separates crude oil

59

based on solubility and polarity. Asphaltenes are the heaviest and the most polar among the four classes.

60

Although the chemical composition of asphaltenes is not well-defined, they generally consist of polycyclic

61

aromatic rings (usually 4 to 10) containing heteroatoms, such as S and N, and trace metal elements, with

62

peripheral alkane chains. The polar compounds in the asphaltene fraction are surface-active substances and

63

considered to be wettability modifiers in oil itself. Still, the mechanism of the wettability change of reservoir

64

rocks through these polar compounds is not fully understood due to the molecular complexity of crude oil.

65

Asphaltenes, as well as various polar compounds possibly existing in crude oil, have been used to

66

investigate the wettability alteration of mineral surfaces. Kumar et al.6 observed that surface wettability

67

change is controlled by asphaltene adsorption on mineral surfaces such as mica. In addition, they observed

68

similar adhesion forces for minerals aged with asphaltene fraction to that of the whole crude oil. Buckley7

69

has shown that the mechanisms of interaction between asphaltene and rock surfaces differ depending on

70

the presence of water. Ionic and colloidal interactions were suggested as the two main interaction

71

mechanisms that contribute to wetting alteration by asphaltene in a reservoir rock.

72

Polar compounds in crude oil contain various heteroatoms such as oxygen, nitrogen, and sulfur.8 O

73

atoms in asphaltenes mostly exist in compounds containing of carboxylic acid, hydroxyl, carbonyl groups,

74

or ethers.9 Previous studies have shown that carboxylic acids render the carbonate surfaces oil-wet.10-14 3 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

75

Hydroxyl groups also appear to be good wettability modifiers as shown in early studies when calcite

76

surfaces were exposed to short carbon chains of alcohols such as ethanol, propanol, and pentanol.15-19

77

Hydrogen bonding of ethanol to the calcite surface is stronger than that of water, so ethanol is firmly bonded

78

onto calcite {1014} terraces and forming an ordered and stable adsorption layer15-16, which can be disrupted

79

at steps17. Some previous works20-21 proved that diols (ethylene glycol and triethylene glycol) also work as

80

wettability modifiers decreasing water-wetting of calcite with a different orientation toward the calcite

81

surface compared to ethanol. Van Duin et al.22 calculated adsorption differences of polar and non-polar

82

compounds onto the calcite and quartz surfaces. They showed that phenol, as a polar compound, could

83

penetrate through thin water films and adsorb onto the mineral surfaces from a water-phenol mixture, and

84

even at low concentrations, phenol influences surface wettability.

85

In this study, we chose phenol and 1-naphthol as model surface-active substances to simulate the

86

binding of a polar hydroxyl functional groups to water-wet mineral surfaces and change them to an oil-wet

87

state by providing non-polar molecular terminations. Phenol and 1-naphthol carry both a hydroxyl

88

functional group and benzene rings, so they represent simplified asphaltenes which carry the core

89

characteristics of asphaltenes. The additional benzene ring of 1-naphthol is to determine the effect of

90

aromatic rings on the adsorption of asphaltenes by comparison with phenol adsorption reaction. A non-polar

91

component, decane, was chosen to model a general oil phase. We calculated oil molecule adsorption on the

92

calcite {1014} surface using both static quantum-mechanical Density Functional Theory (DFT)

93

calculations and Molecular Dynamics (MD) simulations using classical force-fields. The goal was to

94

understand the molecular mechanisms of the wettability changes on calcite surfaces by hydroxyl functional

95

group of polar components in crude oil. The calcite surface was selected because it is one of the most

96

abundant minerals in oil reservoirs and has stable and well-defined cleavage planes which are easy to model

97

and explore.

98

Using DFT computational method, adsorption energies and geometries of two asphaltene

99

surrogates, phenol and 1-naphthol, were investigated. Classical MD simulations were performed to 4 ACS Paragon Plus Environment

Page 4 of 34

Page 5 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

100

investigate the molecular sorption behaviors of phenol molecules on calcite surfaces in several different oil

101

(mimicked by decane)-water mixture scenarios. To determine how calcite surface wettability changes

102

between water-wet and oil-wet by phenol, simulation cells with and without phenol were calculated.

103

Throughout these calculations, we aim to determine whether phenol is a good wettability modifier of the

104

calcite surface (i.e., from water-wet to oil-wet) and how it changes surface wettability, which would further

105

our understanding of wettability-change mechanisms on calcite surfaces. Density profiles and radial

106

distribution functions (RDFs) were calculated to obtain the density changes of water and oil molecules on

107

the calcite surfaces to get molecular level information about dynamical and structural properties of the

108

adsorbates. A new set of force field parameters was developed using quantum-mechanical results to

109

describe decane-calcite interactions for classical MD simulations.

110

Methods

111

Quantum-mechanical calculations

112

The adsorption energies and optimized geometries of two different asphaltene surrogates (phenol,

113

1-naphthol) on the calcite {1014} surface were examined using DFT calculations implemented in the

114

software package DMol3 (local Density functional calculations on Molecules)23. The GGA-PBE exchange-

115

correlation potential24 was used, and core electrons were treated using effective core potentials. Double

116

Numerical plus d-functions (DND) were used as a basis set for atomic orbitals; d-functions were added to

117

improve the modeling of polarizability of atoms. The COnductor-like Screening MOdel (COSMO) was

118

used to approximate the effect of hydration by replacing the water solvent by a continuous dielectric fluid.25

119

The calcite {1014} surface was constructed by cleaving a bulk crystal to obtain a slab of three

120

molecular layers with a 20 Å thick vacuum layer, resulting in a supercell with dimensions of 25.70 Å ×

121

25.70 Å × 27.63 Å. All atoms in the top two molecular layers of the calcite substrate were allowed to relax,

122

and the bottom molecular layer was fixed in its bulk position during the adsorption reaction of the phenol

123

and 1-naphthol.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

124

Page 6 of 34

Adsorption energies (Ead) were calculated as,

125

Ead = Emolecule-calcite – Ecalcite – Emolecule

(1)

126

where Ead is the adsorption energy of a molecule (adsorbate) on the calcite surface, Emolecule-calcite is

127

the total energy of the calcite slab with the adsorbate, Ecalcite is the energy of the calcite slab, and Emolecule is

128

the energy of the adsorbate.

129

Charge density differences were also calculated using CASTEP26, which visualize how the

130

adsorption of a molecule affects the electron distribution relative to the isolated molecule and the

131

unperturbed calcite surface. The charge density differences were given by

132

∆ρ = ρmolecule-calcite – (ρcalcite + ρmolecule)

(2)

133

where ρmolecule-calcite is the electron density of the total system (an adsorbate and the calcite surface),

134

ρmolecule and ρcalcite are the unperturbed electron densities of the adsorbate and the calcite surface, respectively.

135

Potential model for classical MD and the simulation details

136

Classical MD simulations were used to examine the dynamic behavior of the polar-nonpolar

137

character and its effects on the calcite surface wettability change. The TIP3P27 force field was used to

138

represent water molecules as a three-point model. For all organic molecules that represent our model oil

139

and asphaltene surrogate substances, the OPLS-AA (Optimized Potentials for Liquid Simulations-All

140

Atoms) force field28 was used. The force field for calcite is adopted from the potential by Pavese et al29.

141

Although this potential was fitted to the bulk properties of calcite, it is generally possible to use bulk fitted

142

potential sets to surface calculations in case of ionic materials.30 According to de Leeuw and Parker31, the

143

surface energy of {1014} face calculated using the potential set by Pavese et al. is 0.6 J/m2 in vacuum and

144

0.3 J/m2 when hydrated. To increase computational efficiency, polarization shells of the carbonate oxygen

145

were removed from the potential by Pavese et al., such that the O atoms have a charge of –1.045 e. After

146

removing polarization shells of the O atoms, the Buckingham potential parameters of both Ca-O and O-O


Page 7 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

147

interactions were modified to fit the lattice parameters of calcite to the experimental values32 (Table S1 and

148

Table S2). The surface energy of the {1014} face by this modified potential set is 0.56 J/m2.

149

While TIP3P, OPLS-AA, and the modified Pavese potential set are good representations of water,

150

organic molecules, and calcite, respectively, it is particularly important to have proper interatomic

151

potentials between mineral, water, and organic molecules. Reliable potential estimates are crucial in order

152

to properly describe immiscibility (e.g., of the water and oil phase) and competition of adsorption between

153

water and organic molecules on the calcite surface. Between water and organic molecules, the geometric

154

mixing rule was used to calculate interatomic forces. However, due to the differences of the bond character

155

(the organic molecules are described with a covalent model, while the calcite structure is described using

156

an ionic model), the method proposed by Freeman et al.33 was used to calculate interactions of calcite-water

157

and calcite-organics (Table S1). This method is generally in good agreement for polar organic molecules.

158

However, the interaction of calcite and non-polar molecules needs some modification to supplement Ca-

159

organic interactions. Thus, decane-calcite interatomic potentials were derived by reproducing our DFT

160

results (in Section 2.3).

161

The calcite and water-oil mixture model were prepared using Materials Studio 7.0 (Accelrys)34.

162

The calcite slab was cleaved along the {1014} face resulting in a 40.5 Å × 39.9 Å × 22.8 Å slab with a

163

60 Å thick vacuum layer in between the calcite slabs. A calcite slab of eight molecular layers was first

164

energy minimized and then relaxed using an NPT ensemble at 300 K and 1 atm. Then, the position of the

165

calcite slab was fixed in its relaxed geometry during subsequent MD calculations. A water-decane mixture

166

solvent (1:1 volume ratio) was added into the initial vacuum layer with an appropriate number of molecules

167

to obtain the density of the respective solvent at ambient conditions. In order to investigate the role of

168

hydroxyl functional group on the wettability alteration of the calcite surface, phenol molecules were added

169

into the solvent layer. The resulting solution had a 1:1 molecular number ratio of decane and phenol in its

170

oil phase.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

171

Classical molecular-dynamics simulations were performed using the LAMMPS package35 for (i)

172

the water-decane random mixture and (ii) the water-decane-phenol random mixture, either on mixed-wet

173

or oil-wet calcite surfaces for both cases. For mixed-wet surfaces, a random mixture of oil/water was

174

adsorbed on calcite surfaces, showing more oil-wet conditions where phenol or decane is adsorbed and

175

more water-wet ones where no phenol is adsorbed. In contrast, only oil molecules (includes both decane

176

and phenol) were adsorbed for oil-wet calcite surfaces at the beginning. All calculations were carried out

177

at 300 K using a Nosé-Hoover thermostat in the NVT ensemble. The “sandwiching” a layer of the liquid

178

mixture between the two relaxed calcite surface is more of a computational necessity rather than the intent

179

to model oil behavior in nano-pore spaces. Since the actual pores from which oil can be extracted are

180

typically more than a few nm wide, ambient conditions reflect more natural conditions, unless one would

181

want to model wettability under different pressure conditions which is beyond the scope of this study. A

182

cutoff of 10.1 Å was applied for all short-range potentials, and, due to the periodicity of the cell, Ewald

183

summation was used for Coulomb interactions. The total simulation time was 1 ns with a time step of 1 fs

184

(e.g., one million time steps), and the results were visualized using VMD (Visual Molecular Dynamics)36.

185

Derivation of calcite-decane interatomic potentials for classical MD

186

The potential parameters to describe calcite-decane interactions were calculated by fitting the

187

energy curve using LAMMPS to the result of DFT calculations. A calcite slab made of four molecular

188

layers was used for this calculation. The general method by Freeman et al.33 was used to estimate the

189

mineral-organic interatomic potential. To adjust the Ca(calcite)-C(decane) interactions, Buckingham

190

potentials plus Coulomb terms were added to the potential initially calculated by the Freeman et al. method.

191

Using this potential (Table S3), one decane molecule was put onto the calcite surface, and energy

192

minimization was performed. After energy minimization, adsorption energies were calculated at different

193

distances from the calcite surface. The adsorption energies were calculated using Equation (1).

194

All geometries at various distances from the calcite surface were applied for DFT energy

195

calculations in order to calibrate the potentials used for classical-mechanics force fields (as used with 8 ACS Paragon Plus Environment

Page 8 of 34

Page 9 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

196

LAMMPS). Single point energy calculations were performed for each distance using the GGA-PBE

197

exchange-correlation potential and the effective core potential for core electrons treatment. The resulting

198

energy curves of DFT and classical-mechanics force fields (FF) show some differences between the two

199

energy-well minima, but the Ca-C1 distance difference is only 0.11 Å (Figure S1). Dispersion correction

200

can, in general, be used to correct van der Waals interactions, which can improve the accuracy of adsorption

201

energy calculations of organic molecules. We have compared our energy versus distance curves against

202

conventional DFT, as described above, DFT-D using TS (Tkatchenko-Scheffler) scheme37, and finally the

203

Grimme approach38. Using those data, our energy vs. distance curve fall within the range of those

204

corrections schemes. The potential parameters derived here were used throughout this study to describe

205

calcite-decane interactions.

206 207 208 209

Results and Discussion Quantum-mechanical calculations to determine the adsorption energies and optimized structures of organic-mineral interactions

210

The adsorption energies of two asphaltene surrogates, phenol and 1-naphthol, were calculated on

211

the calcite {1014} surface, and their optimized geometries were analyzed. Since the pKa values of phenol

212

and 1-naphthol are 9.95 and 9.34, respectively, protonated forms of these molecules are expected in most

213

environments. Thus, throughout this study, the protonated form of phenol and 1-naphthol are used. Table 1

214

shows the adsorption energies of phenol and 1-naphthol in vacuum, water solvent, and n-decane solvent.

215

More negative values of adsorption energies indicate more favorable adsorption. As shown in Table 1(a),

216

for the calcite surface terrace sites, the adsorption energy of 1-naphthol (-1.72 eV (~ -66.9 kBT [J] with

217

T=298 K)) is stronger than that of phenol (-1.30 eV (~ -50.6 kBT [J] with T=298 K)) in vacuum. This trend

218

is consistent with the results in water and decane.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 34

219

Table 1. Adsorption energies (in eV per molecule) of phenol and 1-naphthol to the calcite {1014} surface in vacuum, water, and decane: on flat terrace, and step edges. surface site (a) Terrace (b) Obtuse step (c) Acute step

substances phenol 1-naphthol phenol 1-naphthol phenol 1-naphthol

Ead (in vacuum) [eV] -1.30 -1.72 -1.40 -1.70 -1.62 -1.91

Ead (in water) [eV] -0.79 -1.04 -0.65 -0.82 -0.89 -0.93

Ead (in decane) [eV] -1.10 -1.46 -1.12 -1.41 -1.32 -1.53

Figure 1. Optimized geometries of two asphaltene surrogate substances with a hydroxyl functional group on the flat terrace of calcite {1014} surface. Two adsorbates are represented in ball-and-stick model, and the calcite slab are displayed using bond lines for clarity. (Ca-green, O-red, C- grey, H-white)

220 221

For both phenol and 1-naphthol, the distances from the calcite surface to their hydroxyl groups are

222

quite close (Figure 1, Ccalcite-Ohydroxyl is 2.6 Å for phenol, 2.7 Å for 1-naphthol). Hydroxyl groups are 10 ACS Paragon Plus Environment

Page 11 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

223

positioned like an anchor while the benzene ring part of the molecules floats away from the surface to be

224

available to bond with other oil components. The phenol molecule has a tilted geometry on the calcite

225

surface with an angle of 35° interacting with the calcite surface mainly through its hydroxyl functional

226

group (Figure 1(a)). 1-naphthol lies at a lower angle (~20°) with respect to the surface, thus increasing the

227

area of calcite covered per adsorbed molecule (Figure 1(b)). As the size of the molecule increases, more

228

van der Waals interactions occur. Since the side group of 1-naphthol is twice the size of that of phenol, with

229

two benzene rings rather than one, 1-naphthol experiences more van der Waals interactions with the calcite

230

surface resulting in a flatter geometry. This is reflected by the stronger adsorption of 1-naphthol to the

231

calcite surface compared to phenol. Similar adsorption geometries were observed by Torres et al.39 for the

232

adsorption of a prototypical asphaltene with four aromatic rings on the α-quartz surface using DFT

233

calculations. The model asphaltene molecule showed preferred adsorption in a parallel position to the

234

calcite surface due to its strong interaction with the α-quartz surface by London dispersion forces associated

235

with its four aromatic rings.

236

In addition, hydroxyl functional groups form hydrogen bonds with the carbonates of the calcite

237

surface. For example, ethanol more strongly adsorbs to the calcite surface than water via Ca-Ohydroxyl and

238

OHhydroxyl-Ocarbonate interactions15-16; thus, ethanol could replace water molecules at the calcite surface in

239

water/ethanol mixture solution.17 Our calculated distances between H of the hydroxyl group and adjacent

240

O of calcite carbonate are 1.7 Å and 1.6 Å for phenol and 1-naphthol, respectively, which are small enough

241

to be considered as H bonds.

242

Since hydrogen bonding has some non-negligible covalent character, it confers some charge-

243

transfer from an electron donor to an electron acceptor. Thus, hydrogen bonding causes some atomic charge

244

differences for both electron donor and acceptor.40-41 From the atomic charge analysis of phenol and

245

1-naphthol by Mulliken population analysis42, there are charge differences for both hydroxyl O and H when

246

we compare the charge values of the two species before and after adsorption reactions. This change in

247

charge for hydroxyl H (+0.1 e for both phenol and 1-naphthol) further confirms the existence of hydrogen 11 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 34

248

bonding with the calcite surface. Since both O and H of the hydroxyl group make strong bonds with calcite

249

through Ca-Ohydroxyl electrostatic interaction and OHhydroxyl-Ocarbonate hydrogen bonding, phenol and

250

1-naphthol can strongly bond onto the calcite surface.

251

Charge density differences were examined for the optimized adsorption geometries of both phenol

252

and 1-naphthol on the calcite {1014} surface. In Figure 2, the electron density increased (red surface) for

253

hydroxyl O and decreased (blue surface) for calcite Ca. Likewise, the electron density increased for

254

carbonate O, while it decreased for hydroxyl H. Therefore, Ca-Ohydroxyl and Hhydroxyl-Ocarbonate are the major

255

contributors to the adsorption of the both phenol and 1-naphthol onto the calcite surface. Previous work43

256

reported similar charge density differences for water molecules on the calcite surface, showing strong bonds

257

for Ca-Owater and Ocarbonate-Hwater.

(a)

(b)

Z

Z Y

X

X Y

Figure 2. Charge density differences for (a) phenol, and (b) 1-naphthol. The red and blue colors indicate increase and depletion of the charge density, respectively. (Ca-green, O-red, C- grey, H-white)

258 259

Moreover, the aromatic rings of 1-naphthol have strong interactions with the calcite surface as

260

shown in Figure 2(b). This confirms the stronger interactions of 1-naphthol with the calcite surface, which

261

were already suggested by the flatter placement of the 1-naphthol benzene rings compared to that of phenol.

262

The charge density differences for a model asphaltene calculation by Alvim et al.44 also showed increased


Page 13 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

263

and decreased electron densities mainly at the aromatic rings. Their asphaltene model had eleven aromatic

264

rings and charge density changes were observed mostly between the aromatic rings and the calcite surface.

265

The influence of the calcite surface geometry on the adsorption of asphaltene surrogates were also

266

investigated. Adsorption of phenol and 1-naphthol to calcite step edges were energetically more favorable

267

than to flat terraces (Table 1). Calcite step edges were constructed by deleting the middle two rows of the

268

top molecular layer along [481] direction from the calcite model. Two layers from the top of the calcite

269

structure including the step features were free to relax and the bottom layer was fixed at its bulk state during

270

the calculation. When phenol was adsorbed to the calcite acute step edge (with an angle of 78° at its step

271

edge) in vacuum, the adsorption energy was 0.32 eV more negative (stronger) than the adsorption to the

272

terrace surface. 1-naphthol also showed a 0.19 eV more negative adsorption energy to the calcite acute step

273

edge than to the calcite flat terrace in vacuum. Comparing the two different step edges of the calcite surface,

274

the adsorption energy of phenol to the acute step edge is 0.22 eV more favorable than the one to the obtuse

275

step edge. 1-naphthol also shows 0.21 eV of favorable adsorption reaction to the acute step edge than the

276

obtuse one.

277

The optimized adsorption geometries of both species at the calcite acute step edges are similar. In

278

both cases, hydroxyl O is located near the Ca2+ at the step edges, and hydroxyl H forms a hydrogen bond

279

with carbonate O at the step edges as shown in Figure 3. Adsorption to the acute step edge is more favorable

280

than to the obtuse step edge due to the shorter distance (less than 3.0 Å) between the two adjacent Ca2+

281

atoms: one is at the step edge and the other one is in the 2nd layer of the calcite slab right underneath the

282

hydroxyl O (shown in Figure 3 with arrows). Van der Waals interactions between the calcite surface and

283

the benzene rings of both species also stabilize adsorbed structures of these molecules. Likewise, the

284

adsorption to the flat terrace, 1-naphthol lies flatter than phenol due to the stronger van der Waals

285

interactions. Since the contribution of Ca-Ohydroxyl electrostatic interaction is significant for the adsorption

286

of both substances, acute step edges with two adjacent Ca2+ result in stronger interactions compared to

287

obtuse step edges where there is only one Ca2+. 13 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

288

Considering the solvent effect for both surface terrace and step edge sites, adsorption reactions in

289

hydrophobic decane solvent were much more favorable for both phenol and 1-naphthol compared to the

290

adsorption reactions in hydrophilic water solvent (Table 1). Similar to the vacuum case, phenol and

291

naphthol adsorption to acute step edges were favored over obtuse step edges in water and decane solvents.

292

For all cases, the optimized geometries show that both phenol and 1-naphthol molecules interact with the

293

calcite slab mainly through their hydroxyl functional groups, leaving the hydrophobic parts toward solution

294

to interact with surrounding hydrophobic oil molecules.

295

Figure 3. Optimized geometries of phenol and 1-naphthol simulating the role of asphaltenes for subsequent bonding of oil to calcite {1014} surface with step edges along the [481] direction. (a) Phenol and (b) 1-naphthol at the acute step edge of the calcite surface. Two adsorbates and the first molecular layer of the calcite slab are represented by balland-stick model, and the second and the third layers of the calcite slab are displayed using bond lines for clarity. (Cagreen, O-red, C- grey, H-white)


Page 14 of 34

Page 15 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

296 297

Langmuir

Classical-mechanics molecular-dynamics simulations to study dynamical and structural properties of the organic-mineral interactions

298

Water-decane mixture

299

Water and decane were randomly mixed and inserted into the gap between the calcite slabs of {101

300

4} face with 1:1 volume ratio (Simulation 1). This was done to determine if immiscibility can be observed

301

at the time and length scale of MD calculations. In addition, we wanted to observe whether there is a

302

preference for water (“water wet”) or decane (“oil wet”) to adsorb to the calcite surface. As shown in Figure

303

4(A), most of the decane molecules had separated from irregular regions of water after 0.1 ns. After 0.3 ns,

304

approximately regular water layers had occupied the upper (calcite surface above the liquid phase due to

305

the periodic boundary conditions) and lower (calcite surface under the liquid phase) surface of the calcite

306

slab, and a decane layer became isolated as in Figure 4(A)-(iii). After separation between water and decane,

307

no significant change of the overall shape of the liquid fractions was observed. Thus, the calcite surface

308

became water-wet at 0.5 ns. Although both water and decane had a chance to adsorb onto the calcite surface,

309

the calcite surface preferred water rather than decane because of much stronger interactions between calcite

310

and water O atoms.

311

The same calculation as in Figure 4(A), but with an initial “oil (decane)-wet” calcite surface was

312

performed (Simulation 2) to test whether initially adsorbed hydrophobic decane molecules can stay

313

adsorbed on the calcite surface when they compete with water molecules. At the beginning of this

314

simulation, each side of surfaces is fully covered by one molecular layer of decane (~26 molecules each,

315

shown in black arrows in Figure 4(B)-(i)). The thickness of decane layer would affect the behavior of decane

316

and water on the calcite surface. Further testing could be performed using thicker decane layers, but for this

317

study, we used one monolayer of decane. After 0.2 ns, some of the water molecules have passed through

318

the decane layer and adsorbed onto the calcite surface, while the water/decane mixture became separated.

319

The decane layer initially adsorbed to the upper surface expands as the decane molecules agglomerate, but

320

still some water molecules are adsorbed onto the upper calcite surface. Gradually, more water molecules 15 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

321

break through the decane layer on the upper surface and get adsorbed onto the calcite. After 0.6 ns, about

322

two thirds of the upper calcite surface was covered by water molecules, with a completely water-wetted

323

calcite surface at the lower calcite surface. After 1 ns, the fluid is divided in three discrete layers as in

324

Simulation 1 (water-decane-water), and both sides of the calcite slab become water-wet surfaces. However,

325

the two simulation cells of water/decane mixture without any surface-active molecules are an incomplete

326

oil model, because most carbonate reservoirs are oil-wet.


Page 16 of 34

Page 17 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Figure 4. (A) Simulation 1 snapshots of water and decane mixture on the calcite {1014} surface. (i) At time 0 ns, decane and water were thoroughly mixed. (ii) After 0.1 ns, water and decane were separated in most areas with some smaller mixed regions remaining. (iii) After 0.5 ns, the whole liquid splits up into three parts; water-decane-water. (B) Simulation 2 snapshots of water and decane mixture on the oil-wet calcite {1014} surface. (i) At time 0 ns, the simulation starts with a monolayer of decane covering the calcite surface and a random mixture solution of water and decane filling the gap; (ii) after 0.2 ns, water covers a large portion of the calcite surface and significant immiscibility has taken place. (iii) After 1 ns, complete water wetting of calcite and complete separation of the fluids has taken place. The two black arrows indicate the oil-wet surface layers at both sides of the calcite surface. Teal represents water molecules, red molecules are decane, and grey molecules are calcite.

327


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

328 329

Water-decane-phenol mixture with pre-adsorbed phenol molecules on the calcite surface

330

Calculations with phenol as an asphaltene surrogate with a hydroxyl functional group were

331

performed on the calcite surface. The phenol in this calculation is to mimic the polar-nonpolar character of

332

asphaltenes in crude oil. Since DFT calculations already compared the effect of additional benzene ring in

333

1-naphthol, only phenol was added for MD simulations. The goal is to investigate the dynamic behavior of

334

the polar-nonpolar character and its effects on the calcite surface wettability change. The research questions

335

to be answered here include: Does phenol function as a bridge between the calcite surface and the oil-

336

mimicking decane? Can phenol link non-polar decane droplets and polar water ones? Based on this, two

337

simulations were performed, water-decane-phenol mixtures with pre-adsorbed phenol on the (i) basic

338

calcite surface (mixed-wet surface; Simulation 3), and (ii) oil-wet (with both phenol and decane) calcite

339

surface (Simulation 4).

340

Simulation 3 (Figure 5(A)) started with 10/12 (upper/lower) phenol molecules pre-adsorbed on the

341

calcite surface. The number of pre-adsorbed phenol molecules was carefully tested and chosen to effectively

342

show the effect of phenol on wettability changes. The pre-adsorbed phenol molecules slowly drifted along

343

the surface, but they preferred to stay on the calcite surface. These phenol molecules attracted more phenol

344

molecules to the surface. The decane and phenol molecules away from the surfaces clustered and got

345

separated from the water phase. The liquid part eventually separated into two phases, an oil one (including

346

both phenol and decane) and a water one. The oil phase extended from the upper calcite layer to the lower

347

calcite layer until ~ 0.9 ns, and then it separated from the lower calcite surface. The number of surface

348

adsorbed phenol as a function of time was measured and shown in Figure S2, and there were 21/10

349

(upper/lower) phenol molecules adsorbed on the calcite surface after 1 ns. At this point, about 75% of the

350

initially pre-adsorbed phenol molecules were still attached to the lower calcite surface. Near the upper

351

calcite surface, ~ 60% of the calcite surface was covered with the oil phase and the remainder of the surface

352

was water-wet at 1 ns. From the comparison between the two surfaces with 10 vs. 12 pre-adsorbed phenol, 18 ACS Paragon Plus Environment

Page 18 of 34

Page 19 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

353

phenol and decane distribution (whether they are distributed close each other or away from each other) in

354

the solution is a more relevant condition that determines the wettability changes than the number of pre-

355

adsorbed phenol, at this coverage. Most of the phenol molecules that were not adsorbed on the calcite

356

surfaces were located at the water-decane boundary.

357

In Simulation 4, the same number of phenol molecules were pre-adsorbed at the beginning (10/12

358

at upper/lower calcite surface), but this time the calcite surfaces were “oil-wet” (Figure 5(B)). At the start

359

of the simulation, there were twelve molecules of phenol with 20 decane molecules and no water molecules

360

in the first adsorbed layer (shown in black arrows) on the lower calcite surface and ten phenol molecules

361

with 21 decane molecules and no water in the upper calcite surface first adsorbed layer. After 0.1 ns, decane

362

molecules show aggregation, and the pre-adsorbed phenol molecules held onto the calcite surface and

363

attracted more decane and phenol molecules toward the surface. After 0.2 ns, decane molecules

364

agglomerated into two groups and separated from water with phenols at the interfaces. Unlike Simulation 2,

365

the anchored phenols on the calcite surfaces cause the oil-phase layers (black arrows) to remain attached to

366

the surfaces in Simulation 4. After 1 ns, the number of phenol molecules adsorbed on the calcite surface

367

increased from 10/12 (upper/lower) to 21/24 (upper/lower) (Figure S2).


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 5. (A) Simulation 3 snapshots of water, decane, and phenol mixture on the calcite {1014} surface with 10/12 (upper/lower) molecules of pre-adsorbed phenol molecules on the calcite surface, (i) at time 0 ns, (ii) after 0.5 ns, and (iii) after 1 ns. (B) Simulation 4 snapshots of a water-decane-phenol mixture on an oil-wet calcite {1014} surface with 10/12 (upper/lower) molecules of pre-adsorbed phenols on each side of the calcite surface; (i) at time 0 ns, (ii) after 0.2 ns, and (iii) after 1 ns. The two black arrows indicate the oil-wet surface layers on both sides of the calcite surface consisting of phenol and decane. Teal represents water molecules, red molecules are decane, light green molecules are phenol, and grey molecules are calcite.

368 369

Analysis of molecular distributions

370

Radial distribution functions (RDFs, g(r)) yield the number density of particles at a given distance

371

interval from a reference atom relative to the average number density of those particles. Therefore, 20 ACS Paragon Plus Environment

Page 20 of 34

Page 21 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

372

calculating RDFs for pairs of atoms shows how the density of a particle varies as a function of distance

373

from a reference atom. To investigate differences between water-calcite and phenol-calcite interactions,

374

RDFs were calculated for both cases. The procedure consists in creating a histogram of distances between

375

all the particle pairs and normalizing that histogram with respect to the volume of each spherical shell. As

376

the distance increases toward infinity, g(r) functions converge to one, which means that the number density

377

of the atoms around the reference atom is homogeneous and equal to the average number density. The first

378

peak of the RDFs corresponds to the average distance between the two atoms in a pair.

379

The RDFs of water (Figure S3(a)) calculated from the final result of Simulation 1 show the average

380

distance between water and the calcite surface because the calcite surface became completely water-wet at

381

the end of the simulation. Cacalcite-Owater shows its first peak at 2.5 Å, and Ocalcite-Hwater has its first peak at

382

1.9 Å, which agrees well with previous studies15-16. For phenol adsorption onto the calcite surface, RDF of

383

Ca-Ophenol has its first peak at 2.6 Å, and Ocalcite-Hphenol (hydroxyl group) has its first peak at 1.7 Å (Figure S3(c)).

384

These distances are almost the same as the ones in our DFT calculations, meaning that our interatomic

385

potentials between phenol and calcite are consistent with our quantum-mechanical calculations.

386

According to the RDF analyses, the average distance of Cacalcite-Owater is shorter than Cacalcite-Ophenol

387

distance. However, the adsorption energy calculation using the force fields showed a 0.08 eV more

388

favorable adsorption of phenol than that of water on the calcite {1014} surface. This explains why 75% of

389

the pre-adsorbed phenol molecules in Simulation 3 remained on the calcite surface after 1 ns, while decane

390

molecules were driven away from the surface by water molecules. Putting together the Ca-O distances and

391

the adsorption energy values of water and phenol adsorption reactions, we can infer that phenol has

392

attractive interactions with calcite not only through its hydroxyl functional group but also through its

393

benzene ring.

394

However, the interaction between calcite and the benzene ring of phenol is considered to be

395

somewhat weaker than the Ca-Ophenol interaction. This is obviously observed when we compare the

396

optimized geometries of phenol at high vs. low coverage. The energy optimized geometry of one phenol 21 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

397

molecule on the calcite surface using our force field was almost the same as our DFT calculation result

398

(2.6 Å of Ca-Ophenol distance and ~35° angle relative to the calcite surface). However, when the surface

399

coverage increases, as shown in Figures 5 simulation images, phenol interacts with the calcite surface

400

mainly through its hydroxyl group and shows a more upright position with respect to the surface.

401

Interactions between the benzene rings of neighboring phenol molecules could also play a role to their

402

upright position at high coverage. Similar results were observed in calculations for benzoate, which has one

403

benzene ring with a carboxyl functional group, adsorption onto the calcite surface by Chun et al45. With a

404

high coverage of benzoate, benzoate molecules stood perpendicular to the surface. In contrast, at low

405

coverage, half of the benzoate molecules lay at a low angle due to the interactions between the phenyl group

406

of benzoate and the calcite surface. At high surface coverage, adsorbates predominantly interact with

407

mineral surfaces through their functional groups, while at low surface coverage, the hydrophobic

408

hydrocarbons can play a more relevant role.

409

Comparison between the density profiles of Simulation 2 and that of Simulation 4 graphically

410

demonstrates the effect of phenol on the wettability change of the calcite surface. Simulation 2 contains

411

only decane in its oil phase, and simulation 4 contains both decane and phenol in its oil phase. The initial

412

density profiles of the two cases are almost the same (dotted lines in Figure 6). In both scenarios, only the

413

oil phase (black lines) without any water is located near the calcite surfaces, and water molecules were

414

initially distributed in between the two surface-adsorbed oil layers with a density of ~0.53 g/cm3 (as the

415

liquid phase is half water and half oil).

416

After 1 ns, the calcite surfaces conditioned with only decane (Figure 6(a)) were covered by water

417

molecules (red solid line), and oil molecules (black solid line) concentrated in the middle between the two

418

calcite slabs. In contrast, the calcite surfaces conditioned with both decane and phenol (Figure 6(b)) show

419

two aggregates of oil phases near the calcite surfaces. Water molecules were mostly located in between the

420

two oil phases, although there were still some water molecules near the calcite surfaces. As observed in the

421

snapshots of each simulation, phenol molecules were strongly bonded to the calcite surface through its 22 ACS Paragon Plus Environment

Page 22 of 34

Page 23 of 34

422

hydroxyl functional group and attracted oil-mimicking decane molecules toward the calcite surfaces. Since

423

there was no polar components in the oil phase of the Figure 6(a), decane molecules were driven away from

424

the calcite surface by water molecules and eventually, water molecules covered the whole calcite surfaces.

2.0

2.0 0s

1 ns

0s

oil (decane) water

1.5

Density (g/cm3)

Density (g/cm3)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

1.0

0.5

0.0

0

20

40

Distance from the calcite surface (Å)

oil (decane+phenol) water

1.5

1.0

0.5

0.0

60

1 ns

0

20

40

60


Figure 6. Mass density profiles of water-oil random mixtures on the oil-wet calcite surface with (a) only decane (Simulation 2) and (b) both phenol and decane (Simulation 4) in their oil phase. The distance from the calcite surface shows the perpendicular distance from the calcite {1014} surface. At both distances of 0 Å and 60 Å, the liquid phase is in contact with calcite surfaces due to the periodic boundary conditions. Red lines represent the water density profiles and black lines represent the oil phase (includes both phenol and decane) density profiles. Dashed lines show the density profiles at time 0 s, and solid lines show the density profiles at 1 ns. Data were collected with a bin width of 1 Å.

425

In order to compare the interactions of a decane molecule with a monolayer of water vs. a

426

monolayer of phenol, the adsorption strength of the decane molecule on each monolayer was calculated.

427

First, a monolayer of phenol or water previously adsorbed to a calcite slab was relaxed to its lowest energy

428

level. Then, the optimized positions of a decane molecule on both monolayers were calculated (Figure 7(a)

429

and (b)). Finally, with fixed geometries of phenol or water monolayer, the adsorption energies of a decane

430

molecule were calculated at several different distances between the decane molecule and the calcite surface

431

using the equation (1) (Figure 7(c)). Results show that decane is more strongly bonded onto the

432

phenol-wetted calcite surface than onto the water-wetted surface (by 0.3 eV). Considering the enthalpy of

433

vaporization for decane molecules (51.5 kJ/mol or 0.53 eV)46, the interaction with other decane molecules

434

is stronger than the interaction with a water monolayer (0.25 eV) and is comparable to the adsorption energy 23 ACS Paragon Plus Environment

Langmuir

435

to a phenol monolayer (0.54 eV). Thus, decane would prefer to stick to itself rather than adsorb onto water

436

layer, while decane self-aggregation and adsorption onto the phenol layer would compete with each other.

437

This explains why the oil phase accumulates on the calcite surfaces only when phenol molecules were pre-

438

adsorbed on the surfaces.

(a)

decane

(c) phenol

(b) water

Adsorption energy (eV)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 34

Water layer Phenol layer

0.5

0.0

-0.5 0

2

4

6

Distance (Å)

Figure 7. Adsorption energy calculations of a decane molecule on either a phenol layer or a water layer adsorbed on a calcite surface. Optimized geometry of a decane molecule adsorbed on (a) a phenol-wetted calcite surface, and (b) a water-wetted calcite surface (Ca-green, O-red, C- grey, H-pink). (c) Adsorption energy curves as a function of the distance from the calcite surface to the decane carbon, where the distance 0 Å is set to be the optimized height for each case; 7.6 Å for phenol and 5.2 Å for water.

439

Although there are polar components like phenol in the oil phase, the non-polar oil components

440

will not easily stick onto calcite surfaces unless the surfaces are already oil-wet. In the density profiles from

441

results of Simulation 3 and Simulation 4 (Figure 8), both simulations had the same number of surface-

442

adsorbed phenol molecules at the beginning. However, only the simulation that started with an oil-wet

443

surface (Simulation 4) showed adsorbed decane molecules at its lower calcite surface at time 1 ns (Figure

444

8(a), black lines). In the density profiles from the final result of Simulation 4 (solid lines), decane molecules

445

are attracted to the calcite surface adsorption layers (shaded areas) where there is a high concentration of

446

phenol with consequently a lower water density. In contrast, the density profiles obtained from the final

447

result of Simulation 3 (dotted lines) show no decane in the lower surface adsorption layer and few decane


Page 25 of 34

448

in the upper surface adsorption layer. The water density is ~1 g/cm3 near the lower calcite surface for

449

Simulation 3, which means that the surface is almost exclusively covered by water molecules at t = 1 ns.

450

When phenol molecules were adsorbed onto the calcite surface sporadically, this did not necessarily induce

451

oil accumulation on the surface. However, forming even one monolayer of oil film, which contains phenol

452

molecules, facilitates further accumulation of hydrocarbons close to the surface.

(a)

(b) 1.2

1.2

decane water phenol non oil-wet surface oil-wet surface

1.0

Density (g/cm3)

Density (g/cm3)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

0.8 0.6 0.4

1.0

decane water phenol non oil-wet surface oil-wet surface

0.8 0.6 0.4 0.2

0.2

0.0

0.0 0

5

10

15

40

20

45

50

55

60



Figure 8. Mass density profiles of water-phenol-decane random mixture on the mixed-wet calcite surface (dotted lines, open symbols, Simulation 3) and oil-wet calcite surface (solid lines, closed symbols, Simulation 4) at time 1 ns. Mixed-wet and oil-wet surfaces describe the initial surface configurations at time t=0 s. The distance from the calcite surface shows the perpendicular distance from the calcite {1014} surface. At both distances of 0 Å and 60 Å, the liquid is in contact with the calcite surfaces due to the periodic boundary conditions. (a) Density profiles near the lower calcite surface with a distance range from 0 Å to 20 Å, and (b) density profiles near the upper calcite surface with a distance range from 40 Å to 60 Å. Shaded areas indicate the surface adsorption layers. Black lines – decane, blue lines –water, red lines – phenol.

453

Our calculations show that decane molecules hardly stay on the calcite surface when they compete

454

with water molecules. However, when they co-exist with polar components of oil like phenol, which bind

455

strongly on the calcite surface through their polar functional groups, decane molecules can stay on the

456

calcite surface linked by phenol molecules. At the interface of water-decane, phenol molecules enclose

457

clusters of decane molecules (mimicking “oil droplets”) and prevent water from pushing away decane

458

molecules from the surface. Phenol also attract other phenol and decane molecules toward the calcite

459

surface which results in a bigger aggregation of oil molecules.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

460

To investigate the influence of temperature on the behavior of oil molecules on calcite surfaces,

461

additional simulations were performed at 390 K (Simulation 5), which is a plausible temperature range in

462

an oil reservoir. Simulation 5 (Figure S4) started with the same configuration as in Simulation 4 (Figure

463

5(B)). At this high temperature, water penetrated faster into the oil-wetted layer to reach the calcite surface

464

compared to the results at 300 K. Even at 0.1 ns, some water molecules adsorbed onto the upper calcite

465

surface, starting to make the upper calcite surface mixed-wet. Density profiles of the final configuration (at

466

t=1 ns) are shown in Figure S5. More water molecules gathered near the upper calcite surface compared to

467

the 300 K result. But the overall density profile shape is similar; oil molecules agglomerate into two groups

468

near the calcite surface, and water phase mostly centered in between the two oil phases. In this higher

469

temperature condition, phenol defines and decorates the phase boundary between decane and water less

470

well than at 300 K.

471

Temperature dependence of wettability changes depends on the reservoir conditions. In the case of

472

low salinity water (LSW), wettability change to water-wet state was more activated at high temperature in

473

several studies. Zhang et al.47 have proven that lowering salinity but increasing sulfate concentration

474

significantly improves oil release at higher temperature when comparing the oil recovery of the core

475

samples at 70 °C and 120 °C. Heidari et al.48 showed obtaining the intermediate wetting condition from

476

aged core samples took less time at higher temperature. In combination of high temperature with

477

appropriate salinity condition, we could increase the extent of water wetting in the oil reservoir.

478

At higher temperature, dissolution of calcite could takes place. Calcite dissolution is also one of

479

the possible mechanisms that releases oil from the reservoir pore spaces, which increases oil recovery.49-50

480

However, due to the limitation of simulation time scale and the size of the system, modeling the calcite

481

dissolution contribution in our system is left for further study. Other conditions such as lower pH, different

482

water compositions, and even salinity changes can also cause calcite dissolution.

483

During oil migration in a reservoir, the water film on the water-wet calcite surface can be

484

destabilized by the high disjoining pressure51-53. At this point, crude oil can break through the water film 26 ACS Paragon Plus Environment

Page 26 of 34

Page 27 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

485

and reach calcite surfaces. After the water-film breakage, if the oil phase covers the calcite surface and

486

forms a locally oil-wet surface (similarly in our Simulation 4), the surface-active molecules in oil will

487

aggregate and stay on the calcite surface changing the mineral surface wettability to oil-wet. In addition,

488

π-π stacking interactions between asphaltenes facilitate the formation of asphaltene nanoaggregates44. Thus,

489

when polar components of crude oil such as asphaltenes break through the water film and adsorb onto the

490

calcite surface through their polar functional groups, such as hydroxyl, they will form aggregates and

491

clusters that can stick onto the calcite surface making the calcite surface oil-wet.

492

Conclusions

493

The effect of phenol and 1-naphthol on the wettability alteration of the calcite surface were studied

494

using DFT and classical MD calculations. DFT results show that the adsorption of phenol and 1-naphthol

495

occur preferentially between their hydroxyl group and step edges of the calcite surface. However, their

496

adsorption geometries were different due to the larger van der Waals interactions associated with the

497

additional benzene ring in 1-naphthol. In the classical MD simulations, separation of oil and water was

498

clearly observed. Non-polar oil components (decane) were separated from the water phase, while phenol

499

locates at the oil/water interface. When oil contains only non-polar oil components, the oil phase is repelled

500

from the calcite surface by water molecules. In contrast, the oil phase can reside on the calcite surface when

501

it contains phenol. The results show that phenol is an appropriate representative of asphaltenes in crude oil

502

with a hydroxyl functional group, and this hydroxyl group has a relevant role in adsorption processes of oil

503

onto mineral surfaces that will result in surface wettability changes. However, although the oil phase is a

504

mixture of polar and non-polar components, non-polar components were found to reside on the calcite

505

surface only when the simulations began with an oil-wet calcite surface. Initially mixed-wet calcite surface

506

resulted in one side of the surface water-wet while the other side showing mixed-wet after 1 ns of simulation.

507

Having model substances that mimic the role of wettability modifiers in oil helps designing

508

experiments and computational approaches to better understand and control how oil ad- and desorbs from

509

specific mineral surfaces. This study elucidates to what degree phenol and 1-naphthol can be used as such 27 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

510

model substances. Overall, we find that phenol and 1-naphthol have a similar adsorption behavior to

511

compounds, mainly in the asphaltene fraction of oil, that are responsible for creating the link between the

512

non-polar fraction of the oil and the typically polar mineral surfaces. One difference though is the greater

513

size of molecules in asphaltene which also causes some differences in the physicochemical adsorption

514

properties, e.g., obscuring small surface steps by asphaltene rather than pronouncing them. However, there

515

is good enough of an agreement to experimentally and computationally test the influence of, e.g., pH on

516

the wettability changes caused by phenol/1-naphthol. Since the pH of ocean water, the pKa of phenol, and

517

the point of zero charge (pzc) of calcite are all in the slightly basic range, small changes in pH can have a

518

significant influence on the strength of interaction between these. Given that phenol and 1-naphthol are

519

good proxies for wettability modifiers, they can also be used in future experimental and computational

520

studies to test the influence of temperature (to some degrees done in this study), pressure, salinity, and

521

competition with other surfactants that may be used in future enhance oil recovery procedures.

522

Acknowledgments

523

This work was supported by ACS-PRF grant #ACS PRF 55659-ND5. The authors are grateful for the

524

support from the American Chemical Society Petroleum Research Fund.

525

Supporting Information

526

The Supporting Information is available free of charge on the ACS Publications website.

527

Interatomic potential sets parameters (Table S1, Table S3); calculated calcite lattice parameters using our

528

potential sets (Table S2); energy curve for validity of our potential sets (Figure S1); number of surface

529

adsorbed phenol (Figure S2); RDF graphs (Figure S3); high temperature simulation (Figure S4) and its

530

density profile (Figure S5).

531


Page 28 of 34

Page 29 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

532

References

533

(1) Donaldson, E. C.; Chilingarian, G. V.; Yen, T. F., Enhanced oil recovery. Dev. Pet. Sci. 1989, 17 (Part

534

B).

535

(2) Abdallah, W.; Buckley, J. S.; Carnegie, A.; Herold, J. E. B.; Fordham, E.; Graue, A.; Signer, T. H. N.

536

S. C.; Hussain, H.; Montaron, B.; Ziauddin, M., Fundamentals of wettability. Oilfield Rev. 2007, 19,

537

44-63.

538 539 540 541 542 543 544 545 546 547 548 549 550 551 552

(3) Falode, O.; Manuel, E., Wettability effects on capillary pressure, relative permeability, and irredcucible saturation using porous plate. J. Pet. Eng. 2014, 2014 (465418). (4) Anderson, W. G., Wettability literature survey. Part 5: The effects of wettability on relative permeability. J. Pet. Technol. 1987, 39 (11), 1453-1468. (5) Anderson, W. G., Wettability literature survey. Part 1: Rock-oil-brine interactions and the effects of core handling on wettability. J. Pet. Technol. 1986, 38 (11), 1125-1144. (6) Kumar, K.; Dao, E. K.; Mohanty, K. K., Atomic force microscopy study of wettability alteration by surfactants. Soc. Pet. Eng. J. 2008, 13 (2), 137-145. (7) Buckley, J. S., Wetting alteration of solid surfaces by crude oils and their asphaltenes. Rev. Inst. Fr. Pet. 1998, 53 (3), 303-312. (8) Denekas, M. O.; Mattax, C. C.; Davis, G. T., Effects of crude oil components on rock wettability. Soc. Pet. Eng. J. 1959, 216, 330-333. (9) Yen, T. F.; Chilingarian, G. V., Asphaltenes and asphalts, 2. 1st ed.; Elsevier Science: Amsterdam ; New York, 2000. (10) Ghatee, M. H.; Koleini, M. M.; Ayatollahi, S., Molecular dynamics simulation investigation of

553

hexanoic acid adsorption onto calcite (1014) surface. Fluid Phase Equilib. 2015, 387, 24-31.

554

(11) Sedghi, M.; Piri, M.; Goual, L., Atomistic molecular dynamics simulations of crude oil/brine

555

displacement in calcite mesopores. Langmuir 2016, 32 (14), 3375-3384.


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

556 557

(12) Legens, C.; Palermo, T.; Toulhoat, H.; Fafet, A.; Koutsoukos, P., Carbonate rock wettability changes induced by organic compound adsorption. J. Pet. Sci. Eng. 1998, 20 (3-4), 277-282.

558

(13) Karoussi, O.; Skovbjerg, L. L.; Hassenkam, T.; Stipp, S. L. S.; Hamouda, A. A., AFM study of

559

calcite surface exposed to stearic and heptanoic acids. Colloid Surf., A 2008, 325 (3), 107-114.

560 561 562 563

(14) Standnes, D. C.; Austad, T., Wettability alteration in chalk 1. Preparation of core material and oil properties. J. Pet. Sci. Eng. 2000, 28 (3), 111-121. (15) Cooke, D. J.; Gray, R. J.; Sand, K. K.; Stipp, S. L.; Elliott, J. A., Interaction of ethanol and water with the {1014} surface of calcite. Langmuir 2010, 26 (18), 14520-14529.

564

(16) Sand, K. K.; Yang, M.; Makovicky, E.; Cooke, D. J.; Hassenkam, T.; Bechgaard, K.; Stipp, S. L. S.,

565

Binding of ethanol on calcite: The role of the oh bond and its relevance to biomineralization. Langmuir

566

2010, 26 (19), 15239-15247.

567

(17) Keller, K. S.; Olsson, M. H. M.; Yang, M.; Stipp, S. L. S., Adsorption of ethanol and water on

568

calcite: Dependence on surface geometry and effect on surface behavior. Langmuir 2015, 31 (13),

569

3847-3853.

570 571 572

(18) Bovet, N.; Yang, M.; Javadi, M. S.; Stipp, S. L. S., Interaction of alcohols with the calcite surface. Phys. Chem. Chem. Phys. 2015, 17 (5), 3490-3496. (19) Hakim, S. S.; Olsson, M. H. M.; Sørensen, H. O.; Bovet, N.; Bohr, J.; Feidenhans'l, R.; Stipp, S. L.

573

S., Interactions of the calcite {10.4} surface with organic compounds: Structure and behaviour at

574

mineral - organic interfaces. Sci. Rep. 2017, 7.

575

(20) Olsen, R.; Leirvik, K. N.; Kvamme, B.; Kuznetsova, T., Adsorption properties of triethylene glycol

576

on a hydrated {1014} calcite surface and its effect on adsorbed water. Langmuir 2015, 31 (31), 8606-

577

8617.

578 579 580 581

(21) Tomson, M. B.; Kan, A. T.; Fu, G.; Al-Thubaiti, M.; Shen, D.; Shipley, H. J., Scale formation and prevention in the presence of hydrate inhibitors. Soc. Pet. Eng. J. 2006, 11 (02), 248-258. (22) van Duin, A. C.; Larter, S. R., A computational chemical study of penetration and displacement of water films near mineral surfaces. Geochem. Trans. 2001, 2 (1), 35. 30 ACS Paragon Plus Environment

Page 30 of 34

Page 31 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

582 583 584 585 586

Langmuir

(23) Delley, B., DMol, a standard tool for density functional calculations: Review and advances. Theor. Comput. Chem. 1995, 2, 221-254. (24) Perdew, J. P.; Burke, K.; Wang, Y., Generalized gradient approximation for the exchange-correlation hole of a many-electron system. Phys Rev B Condens Matter 1996, 54 (23), 16533-16539. (25) Klamt, A.; Schuurmann, G., COSMO: a new approach to dielectric screening in solvents with

587

explicit expressions for the screening energy and its gradient. J. Chem. Soc., Perkin Trans. 2 1993, (5),

588

799-805.

589

(26) Segall, M. D.; Lindan, P. J. D.; Probert, M. J.; Pickard, C. J.; Hasnip, P. J.; Clark, S. J.; Payne, M. C.,

590

First-principles simulation: ideas, illustrations and the CASTEP code. J. Phys.: Condens. Matter 2002,

591

14 (11), 2717-2744.

592 593 594

(27) Price, D. J.; Brooks III, C. L., A modified TIP3P water potential for simulation with Ewald summation. J. Chem. Phys. 2004, 121 (20), 10096-10103. (28) Jorgensen, W. L.; Maxwell, D. S.; TiradoRives, J., Development and testing of the OPLS All-Atom

595

force field on conformational energetics and properties of organic liquids. J. Am. Chem. Soc. 1996, 118

596

(45), 11225-11236.

597 598 599 600

(29) Pavese, A.; Catti, M.; Parker, S. C.; Wall, A., Modelling of the thermal dependence of structural and elastic properties of calcite, CaCO3. Phys. Chem. Miner. 1996, 23 (2), 89-93. (30) de Leeuw, N. H.; Parker, S. C.; Harding, J. H., Molecular dynamics simulation of crystal dissolution from calcite. Phys. Rev. B 1999, 60 (19), 13792-13799.

601

(31) deLeeuw, N. H.; Parker, S. C., Atomistic simulation of the effect of molecular adsorption of water on

602

the surface structure and energies of calcite surfaces. J. Chem. Soc. Faraday T 1997, 93 (3), 467-475.

603

(32) Graf, D. L., Crystallographic tables for the rhombohedral carbonates. Am. Mineral. 1961, 46, 1283-

604 605 606 607

1316. (33) Freeman, C. L.; Harding, J. H.; Cooke, D. J.; Elliott, J. A.; Lardge, J. S.; Duffy, D. M., New forcefields for modeling biomineralization processes. J. Phys. Chem. C 2007, 111 (32), 11943-11951. (34) Dassault Systèmes BIOVIA, Materials Studion 7.0. San Diego: Dassault Systèmes 2018. 31 ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

608 609 610 611 612 613 614 615 616

(35) Plimpton, S., Fast parallel algorithms for short-range molecular dynamics. J. Compt. Phys. 1995, 117, 1-19. (36) Humphrey, W.; Dalke, A.; Schulten, K., VMD - Visual Molecular Dynamics. J. Mol. Graphics 1996, 14, 33-38. (37) Tkatchenko, A.; Scheffler, M., Accurate molecular van der waals interactions from ground-state electron density and free-atom reference data. Phys. Rev. Lett. 2009, 102 (7). (38) Grimme, S., Semiempirical GGA-type density functional constructed with a long-range dispersion correction. J. Comput. Chem. 2006, 27 (15), 1787-1799. (39) Torres, A.; Suarez, J. A.; Remesal, E. R.; Marquez, A. M.; Sanz, J. F.; Canibano, C. R., Adsorption

617

of prototypical asphaltenes on silica: First-principles DFT simulations including dispersion corrections.

618

J. Phys. Chem. B 2018, 122 (2), 618-624.

619 620 621

(40) Ronca, E.; Belpassi, L.; Tarantelli, F., A quantitative view of charge transfer in the hydrogen bond: the water dimer case. ChemPhysChem 2014, 15 (13), 2682-2687. (41) Ratajczak, H.; Orville-Thomas, W. J., Charge-transfer properties of hydrogen-bonds. 3. Charge-

622

transfer theory and relation between energy and enhancement of dipole-moment of hydrogen-bonded

623

complexes. J. Chem. Phys. 1973, 58 (3), 911-919.

624 625 626 627 628

(42) Mulliken, R. S., Electronic population analysis on LCAO-MO molecular wave functions. 1. J. Chem. Phys. 1955, 23 (10), 1833-1840. (43) Lu, J. Y.; Ge, Q.; Li, H.; Raza, A.; Zhang, T., Direct prediction of calcite surface wettability with first-principles quantum simulation. J. Phys. Chem. Lett. 2017, 8 (21), 5309-5316. (44) Alvim, R. S.; Lima, F. C. D. A.; Sanchez, V. M.; Headen, T. F.; Boek, E. S.; Miranda, C. R.,

629

Adsorption of asphaltenes on the calcite (10.4) surface by first-principles calculations. Rsc Adv. 2016, 6

630

(97), 95328-95336.

631 632

(45) Chun, B. J.; Lee, S. G.; Choi, J. I.; Jang, S. S., Adsorption of carboxylate on calcium carbonate (101 4) surface: Molecular simulation approach. Colloid Surf., A 2015, 474, 9-17.


Page 32 of 34

Page 33 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

633

Langmuir

(46) Viton, C.; Chavret, M.; Jose, J., Enthalpies of vaporization of normal alkanes from nonane to

634

pentadecane at temperatures from 298 to 359 K. ELDATA: Int. Electron. J. Phys.-Chem. Data 1996, 2

635

(3), 103.

636

(47) Zhang, Y.; Sarma, H., Improving waterflood recovery efficiency in carbonate reservoirs through

637

salinity variations and ionic exchanges: A promising low-cost "smart-waterflood" approach. Soc. Pet.

638

Eng. 2012.

639

(48) Heidari, M. A.; Habibi, A.; Ayatollahi, S.; Masihi, M.; Ashoorian, S., Effect of time and temperature

640

on crude oil aging to do a right surfactant flooding with a new approach. Proceedings of the Offshore

641

Technology Conference-Asia; Kuala Lumpur, Malaysia 2014.

642 643 644 645 646 647 648 649 650

(49) Morrow, N.; Buckley, J. S., Improved oil recovery by low-salinity waterflooding. J. Pet. Technol. 2011, 63 (5), 106-112. (50) Zahid, A.; Stenby, E. H.; Shapiro, A. A., Smart waterflooding (high sal/low sal) in carbonate reservoirs. J. Pet. Eng. 2012. (51) Jackson, M. D.; Al-Mahrouqi, D.; Vinogradov, J., Zeta potential in oil-water-carbonate systems and its impact on oil recovery during controlled salinity water-flooding. Sci. Rep. 2016, 6. (52) Sohal, M. A.; Thyne, G.; Søgaard, E. G., Review of recovery mechanisms of ionically modified waterflood in carbonate reservoirs. Energy Fuels 2016, 30 (3), 1904-1914. (53) Hirasaki, G. J., Wettability: Fundamentals and surface forces. SPE Form. Eval. 1991, 6, 217-226.

651


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

652

For Table of Contents Only

653

654 655 656


Page 34 of 34

A mechanistic study of wettability changes on calcite by molecules

Recommend Documents