A Novel Nanofluid Based on Fluorescent Carbon Nanoparticles for

Subscriber access provided by Eastern Michigan University | Bruce T. Halle Library

Article

A novel nanofluid based on fluorescent carbon nanoparticles for enhanced oil recovery Yuyang Li, Caili Dai, Hongda Zhou, Xinke Wang, Wenjiao Lv, Yining Wu, and Mingwei Zhao Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b03617 • Publication Date (Web): 16 Oct 2017 Downloaded from http://pubs.acs.org on October 17, 2017

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 free 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 accessible to all readers and 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.

Industrial & Engineering Chemistry Research 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 22

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

Industrial & Engineering Chemistry Research

1

A novel nanofluid based on fluorescent carbon

2

nanoparticles for enhanced oil recovery

3

Yuyang Li, Caili Dai,* Hongda Zhou, Xinke Wang, Wenjiao Lv, Yining Wu and Mingwei Zhao*

4

School of Petroleum Engineering, State Key Laboratory of Heavy Oil, China University of

5

Petroleum (East China), Qingdao, Shandong 266580, China

6

Email: [email protected] (Caili Dai), [email protected] (Mingwei Zhao)

7

Tel: (86) 532-86981183, Fax: (86) 532-86981161

8

1 ACS Paragon Plus Environment


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

9

ABSTRACT: A novel nanofluid based on fluorescent carbon nanoparticles for enhanced oil

10

recovery (EOR) was developed. Fluorescent carbon nanoparticles prepared by a simple and rapid

11

method were used as a chemical agent for EOR and fluorescence imaging. Transmission electron

12

microscope (TEM) and Fourier transform infrared spectrometer (FTIR) were employed to

13

observe the shape, size and surface components of the fluorescent carbon nanoparticles. The

14

fluorescent carbon nanoparticles could be instantly dispersed in water without any auxiliary

15

equipment. The nanofluid showed excellent anti-temperature, anti-salinity, oil displacement and

16

wettability alteration properties. The nanofluid (0.1 wt%) could reduce the oil-water interfacial

17

tension to 13.4 mN/m. The oil recovery of a core immersed in nanofluid was significantly

18

improved. The core intersection was observed by a fluorescence microscope. The fluorescence

19

image demonstrated that the fluorescent carbon nanoparticles had seeped into the core. The

20

fluorescent carbon nanoparticle-based nanofluid provides a promising and efficient chemical

21

agent for EOR.

22

KEYWORDS: Fluorescent carbon nanoparticles; Nanofluid; Wettability alteration; Structural

23

disjoining pressure; Fluorescence image; Enhanced oil recovery

24


Page 2 of 22

Page 3 of 22

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


25

1. Introduction

26

The world is facing serious challenges to meet our energy needs because the available

27

conventional energy is becoming increasingly difficult to extract. As tight reservoirs and ultra-

28

low permeable reservoirs are constantly being discovered, the crude oil reserves in tight

29

reservoirs and ultra-low permeable reservoirs are taking up an ever-greater proportion in the

30

global crude oil reserves.1-5 However, tight reservoirs and ultra-low permeable reservoirs, have

31

low porosity and low permeability. The pore-throat size of an ultra-low permeable reservoir is

32

mainly distributed on the sub-micron and micrometre scale. Primary and secondary oil

33

recoveries in ultra-low permeable reservoirs are low. It is thus a great challenge to enhance the

34

oil recovery in an ultra-low permeable reservoir.

35

Due to the nanoscale and large surface/volume ratio, nanoparticles have a high surface energy,

36

which results in their adsorption on a solid surface or at a water/oil interface. The surface

37

wettability or interfacial tension is affected because the surface or interface energy of the system

38

is changed by nanoparticles.6-9 In the field of oilfield development, using nanomaterials as a new

39

cost-effective material for high-temperature, high-salinity, and low permeable reservoirs has

40

attracted increasing attention due to their promising applications in enhanced oil recovery

41

(EOR).10-15 Some nanoparticles, such as silicon dioxide, titanium oxide and aluminium oxide,

42

have been reported to have potential applications in EOR.16-19

43

However, nanoparticles aggregate easily and are unstable in harsh environments. To disperse

44

nanoparticles in water, surfactants have generally been used as a dispersing agent.20 There is

45

competitive adsorption between the surfactant and nanoparticles at a liquid-liquid or solid-liquid

46

interface.21 The potential mechanisms of using nanofluids (suspensions of nanometre-sized

47

particles) for EOR cannot clearly confirm whether surfactants or nanoparticles are working in the



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

48

enhanced oil recovery process. In addition, an important issue is whether the nanofluid can seep

49

into the ultra-low permeable core. Hence, it is necessary to prepare a stable self-dispersing

50

nanoparticle for EOR and to develop an easy-to-use method that can prove that nanofluids can

51

seep into the pores of ultra-low permeable core.

52

Wasan et al. investigated oil displacement from a solid surface using a nanofluid. Based on

53

their experiment results and theoretical calculations, they proposed the novel concept of a

54

nanoparticle structural wedge film in the confines of a solid-oil-aqueous phase contact region.

55

The structural disjoining pressure in the wedge film is enhanced by the nanoparticles’ structural

56

wedge film. As nanoparticles come closer to the tip of the wedge film, the structural disjoining

57

pressure increases. With the increase in the structural disjoining pressure, the oil/aqueous

58

interface moves onward, and the nanofluid spreads over the solid surface, causing the oil to

59

detach from the solid surface.7, 22-26

60

In this work, we present a novel nanofluid based on fluorescent carbon nanoparticles for EOR

61

of ultra-low permeable core. The fluorescent carbon nanoparticles can be instantly dispersed in

62

water without any auxiliary equipment. Based on its features of excellent anti-temperature and

63

anti-salinity properties, a stable nanofluid for EOR of an ultra-low permeable core was prepared.

64

This nanofluid exhibited an excellent capability to make oil displace from a solid surface and

65

changed the surface wettability from oil-wet to water-wet. A larger oil recovery was achieved by

66

using the nanofluid as a highly efficient chemical agent for EOR. To prove that the fluorescent

67

carbon nanoparticles can seep into an ultra-low permeable core, fluorescence imaging was used

68

to observe the core intersection. The proposed nanofluid can be used as an effective chemical

69

agent for EOR in ultra-low permeable reservoirs. This strategy shows potential application value

70

for tracing and locating nanoparticles in an ultra-low permeable core.


Page 4 of 22

Page 5 of 22

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


71

2. Experimental section

72

2.1. Materials and apparatus

73

Glacial acetic acid (CH3COOH), diphosphorus pentoxide (P2O5) and sodium hydroxide (NaOH)

74

were purchased from Xilong Chemical Co., Ltd. China. Crude oil was obtained from Xinjiang

75

Oilfield. The oil phase used in this study was a mixture of dehydrated crude oil and kerosene

76

with a volume ratio of 1:19. The density and dynamic viscosity of oil were 0.801 g/cm3 and 1

77

mPa·s at 25 °C, respectively. NaCl solution (3 wt%) was used as reservoir brine with a density of

78

1.021 g/cm3 and a dynamic viscosity of 0.91 mPa·s at 25 °C. Ultra-low permeable sandstone

79

cores (length 2.5 cm and diameter 2.5 cm) with a gas permeability of 0.6 mD and a porosity of

80

14% were purchased from Haian Oil Scientific Research Apparatus Company.

81

Transmission electron microscope (TEM) images were obtained using a FEI-Tecnai-G20

82

microscope (USA). Infrared spectroscopy was conducted using a Fourier transform infrared

83

spectrometer (FTIR, NEXUS, Thermo Nicolet, USA). Zeta potential and dynamic light

84

scattering (DLS) measurements were carried out using a laser particle size analyser (Zetasizer

85

Nano ZSP, Malvern, England). Interfacial tension was measured by a spinning drop interfacial

86

tensiometer (TX500C, Kono, USA). The contact angle measurement was carried out using a

87

contact angle measuring system (Tracker, Teclis, France). The transmittance of the nanofluid

88

was measured by a UV-vis spectrophotometer (UV-5, Mettler Toledo, USA). Microscopic

89

fluorescence imaging was observed by a self-constructed fluorescence microscope which was

90

composed of a microscope (XSP-35TV, CIWA, China) and a spot UV lamp (UV-L03, Tank,

91

China). The pore size distribution of the ultra-low permeable core was measured by a mercury

92

intrusion porosimeter (AutoPore IV 9500, Micromeritics, USA).

93

2.2. Preparation of fluorescent carbon nanoparticles



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

94

Fluorescent carbon nanoparticles were synthesized in large quantity according to Wang’s

95

reported method.27 Fluorescent carbon nanoparticles fabrication process is shown in Figure 1.

96

Approximately 25 g of P2O5 was placed into a 500 mL beaker. Glacial acetic acid (10 mL) and

97

water (0.4 mL) were added to P2O5. A large amount of heat was released, and the temperature

98

increased rapidly during the reaction. Glacial acetic acid was carbonized under high temperature

99

and carbon nanoparticles were formed. After cooling down to room temperature, 300 mL of

100

water was added to the reaction mixture, and the dark brown solid was separated from the

101

mixture by centrifugation. The dark brown solid was washed with water three times. After

102

purification, the obtained dark brown solid was dried at 110 °C for 48 hours. Finally, 5.2 g of

103

fluorescent carbon nanoparticles was obtained.

104

105 106

Figure 1 Schematic illustration of the fluorescent carbon nanoparticles fabrication process.

107 108

2.3. Preparation of nanofluid


Page 6 of 22

Page 7 of 22

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


109

Approximately 1.0 g of fluorescent carbon nanoparticles was added to 1.0 L of brine. When the

110

pH of the mixture was adjusted to 8 by 1 mol/L NaOH solution, a dark brown nanofluid was

111

instantly obtained, appearing similar to instant coffee, without any auxiliary equipment. The

112

preparation process of fluorescent carbon nanoparticles aqueous solution was shown in Figure

113

1S.

114

2.4. Spontaneous imbibition tests

115

Cores were dried at 120 °C for 48 hours. After cooling down to room temperature, the weight of

116

the dry cores was measured by an electronic analytical balance. Then, these cores were

117

vacuumed to remove the gas in the cores. After 5 hours, these cores were saturated with oil under

118

a pressure of 15 MPa for 48 hours. Cores that had been saturated with oil were removed from the

119

oil. To avoid the effect of oil expansion at a high temperature, the cores were immersed in oil at

120

60 °C for 24 hours. Then, the cores were removed from the oil, and their weight was measured

121

quickly. In different imbibition devices, these cores were immersed in brine or different

122

concentrations of nanofluids. These imbibition devices were placed in a constant temperature

123

bath at 60 °C. The volumes of oil discharged from these cores with time were recorded.

124

3. Results and discussion

125

3.1. Characterization of fluorescent carbon nanoparticles

126

The structure and morphology of fluorescent carbon nanoparticles were observed through TEM

127

(Figure 2). The fluorescent carbon nanoparticles were generally of spherical shape, and their size

128

was approximately 10 nm, which would be beneficial to flowing in a low permeable porous

129

medium.



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

130 131

Figure 2 TEM image of fluorescent carbon nanoparticles.

132 133

Surface chemistry is key to the properties of fluorescent carbon nanoparticles. The fluorescent

134

carbon nanoparticles were analysed by FT-IR (Figure 3). Peaks at 2921 cm-1 and 2970 cm-1 were

135

ascribed to the group of -C-H. A peak at 1616 cm-1 was presented due to the conjugated C=C

136

stretching vibration. An absorption peak at 3426 cm-1 was ascribed to the group of -OH. An

137

absorption peak at 1660 cm-1 was due to the C=O group conjugated with condensed aromatic

138

carbons. The peaks at 3426 cm-1 and 1660 cm-1 indicated that the fluorescent carbon

139

nanoparticles had a large content of carboxylic groups, which gave excellent water dispersibility

140

properties to the fluorescent carbon nanoparticles.

141 142

Figure 3 FT-IR of fluorescent carbon nanoparticles.


Page 8 of 22

Page 9 of 22

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


143

3.2. Dispersion of fluorescent carbon nanoparticles

144

The fluorescent carbon nanoparticles aqueous solution (0.005 wt%) was light yellow and

145

transparent in daylight (Figure 4a), but it changed to bright green under UV excitation (365 nm)

146

(Figure 4b). DLS was employed to characterize the size distribution of fluorescent carbon

147

nanoparticles in water. As shown in Figure 4, the distribution of particle size was narrow,

148

between 10 and 30 nm. The Zeta potential of fluorescent carbon nanoparticles in water was -35

149

mV, which improved the electrostatic repulsion among fluorescent carbon nanoparticles. The

150

results indicated that the obtained fluorescent carbon nanoparticles were well dispersed in water.

151

152 153

Figure 4 Fluorescent carbon nanoparticles in water (0.005 wt%) (left) under daylight (a) and UV light (365 nm,

154

b). Size distribution of fluorescent carbon nanoparticles in water (right).

155 156

3.3. Performance of nanofluid

157

Low oil-water interfacial tension is conducive to enhance oil recovery. The oil-water interfacial

158

tensions of nanofluids with different concentrations were measured (Table 1). The oil-water

159

interfacial tension decreased with an increasing concentration of nanofluid. The nanofluid (0.1

160

wt%) could reduce the oil-water interfacial tension to 13.4 mN/m.

161



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

162

Page 10 of 22

Table 1 Oil-water interfacial tension of different concentrations of nanofluid at 60 °C. Concentration of nanofluid (w/w)

0.1 wt%

0.05 wt%

0.01 wt%

0.005 wt%

0.001 wt%

0

Oil-water interfacial tension (mN/m)

13.4

16.4

21.2

22.6

22.9

26.2

163 164

Figure 5 shows the dynamic contact angle of oil on the oil-wet surface in different

165

concentrations of nanofluid (0.1 wt%, 0.05 wt%, 0.01 wt%, 0.005 wt%, 0.001 wt%) and brine.

166

To obtain an oil-wet surface, glass slides as a model of sandstone surface were immersed in

167

paraffin at 80 °C for 72 hours. The oil droplet was captured on the oil-wet surface of the glass

168

slide immersed in brine. The dynamic contact angles of oil on the oil-wet surface in different

169

liquid phases were measured by contact angle measurement. Different concentrations of

170

nanofluid were obtained by adding nanofluid at a high concentration into the brine. In the initial

171

stage, the contact angle of oil on the surface in the nanofluid increased rapidly, and oil was

172

displaced from the surface gradually. With a decrease in the nanofluid concentration, the change

173

rate of the contact angle decreased. After the rapid change, the contact angle increased gently. In

174

the end, the contact angle almost did not change, and the change of the contact angle increased

175

with an increasing concentration of nanofluid. The contact angle of oil on the oil-wet surface

176

changed from 36° to 120° at the highest concentration of nanofluid and changed merely from 36°

177

to 38° at the lowest concentration of nanofluid. Compare with the nanofluid, the contact angle of

178

oil on the oil-wet surface in brine barely changed. According to the results, the fluorescent

179

carbon nanoparticles exhibited an excellent capability that made oil displace from an oil-wet

180

surface.


Page 11 of 22

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


181 182

Figure 5 Dynamic contact angles of oil on the oil-wet surface in different concentrations of nanofluid (a-0.1

183

wt%, b-0.05 wt%, c-0.01 wt%, d-0.005 wt%, e-0.001 wt%) and brine (f).

184 185

Wettability alteration is an extremely important influence factor for EOR.28-30 The capillary

186

driving force for the spontaneous imbibition process is strong in a water-wet core. Wettability

187

alteration can enhance the spontaneous imbibition of water into the core. The ability of

188

wettability alteration was estimated by measuring the contact angle of oil/water/solid. Oil-wet

189

glass slides were immersed in different liquid phases at 60 °C for 24 hours. The surface of the

190

glass slide was oil-wet due to the adsorption of paraffin on the surface (Figure 6a). After the

191

surface of the glass slide was treated with the 0.1 wt% nanofluid, the wettability of the glass slide

192

was altered to a water-wet state (Figure 6b). The good wettability alteration of fluorescent carbon

193

nanoparticles gave the essential foundation for the future application in spontaneous imbibition.

194

195 196

Figure 6 Oil droplets on oil-wet glass slides treated by brine (a) and nanofluid (b).



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 22

197

Due to the high temperature of reservoir, temperature resistance is an important indicator for

198

an oil recovery chemical agent. As temperature increases, the movement of nanoparticles

199

becomes increasingly severe, which can cause the agglomeration of nanoparticles. A high

200

temperature may produce a negative effect on the stability of nanofluid. To evaluate the stability

201

of the nanofluid, it was stored under different temperatures for 1 day, and the transmittance of

202

the nanofluid at different temperatures was measured by a UV-vis spectrophotometer. As shown

203

in Figure 7, the transmittance of the nanofluid exhibited basically no change with an increasing

204

temperature. To further explore the stability of the nanofluid at high temperature, it was stored at

205

90 °C. After 30 days, the transmittance of nanofluid basically had no change. According to the

206

results, the nanofluid had good temperature resistance.

207

208 209

Figure 7 Effect of temperature on the stability of nanofluid. Error bar=RSD (n=5)

210 211

Salt tolerance is an important indicator for an oil recovery chemical agent. The surface charge

212

density of nanoparticles can be affected by cations and anions. As the surface charge density

213

changes, the interactions among nanoparticles may be changed, which can cause the

214

agglomeration of nanoparticles. To evaluate the salt tolerance of the nanofluid, different amounts

215

of NaCl were added to the nanofluid, and its transmittance with different concentrations of NaCl 12 ACS Paragon Plus Environment

Page 13 of 22

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


216

was measured by a UV-vis spectrophotometer. As shown in Figure 8, the transmittance of the

217

nanofluid exhibited basically no change with an increase in the NaCl concentration. The results

218

showed that salinity did not have much impact on the stability of the nanofluid.

219

220 221

Figure 8 Effect of salinity on the stability of nanofluid. Error bar=RSD (n=5)

222 223

3.4. Spontaneous imbibition tests

224

In different imbibition devices, cores were immersed in different liquid phases. These imbibition

225

devices were placed in a constant temperature bath at 60 °C for verifying the EOR ability of the

226

nanofluids. The imbibition device was shown in Figure 2S. The volumes of oil discharged from

227

these cores with time were recorded. The results of spontaneous imbibition tests using different

228

concentrations of nanofluids and brine are shown in Figure 9. For the first 80 hours, the oil

229

recovery of the core immersed in nanofluid increased with an increasing nanofluid concentration.

230

After 80 hours, the oil recovery of 0.1 wt% nanofluid was below that of 0.05 wt% nanofluid, and

231

the oil recovery of 0.05 wt% nanofluid (39.1%) was slightly higher than that of 0.1 wt%

232

nanofluid (38.3%) in the end. The reason for this may be that some pores in the ultra-low

233

permeable core were partially blocked by a high concentration of fluorescent carbon



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 14 of 22

234

nanoparticles. Starting from a 0.05 wt% nanofluid, the oil recovery of nanofluid decreased with a

235

decrease in the nanofluid concentration. The oil recovery of the core immersed in nanofluid was

236

significantly higher than that of core immersed in brine. After the spontaneous imbibition tests,

237

38.3%, 39.1%, 37.3%, 34.4%, 24.4% and 16.8% of oil were extracted in cores immersed in

238

different concentrations of nanofluid, 0.1 wt%, 0.05 wt%, 0.01 wt%, 0.005 wt% and 0.001 wt%,

239

and brine, respectively. The results from our work showed that the obtained nanofluid had a

240

great potential for EOR.

241

242 243

Figure 9 Oil recovery with time in spontaneous imbibition tests.

244 245

3.5. Fluorescence imaging in porous media

246

The pore size distribution of an ultra-low permeable core is shown in Figure 3S. The pore sizes

247

were mainly distributed in the range of 0.4 µm to 3 µm. The fluorescent carbon nanoparticles

248

with a size of 10 nm should be able to seep into the ultra-low permeable core. To prove that

249

fluorescent carbon nanoparticles can seep into the ultra-low permeable core, cores were cut, and

250

the core intersection was observed by a self-constructed fluorescence microscope. As shown in

251

the bright field and fluorescence images of the core intersection (Figure 10), the pore wall 14 ACS Paragon Plus Environment

Page 15 of 22

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


252

showed light green or yellow photoluminescence when fluorescent carbon nanoparticles were

253

excited at 365 nm. The fluorescence image demonstrated that fluorescent carbon nanoparticles

254

had seeped into the ultra-low permeable core in the process of spontaneous imbibition.

255

256 257

Figure 10 Bright field image (left) and fluorescence image (right) of core intersection (excited at 365 nm,

258

scale bar = 10 µm)

259 260

3.6. Mechanism of fluorescent carbon nanoparticles for EOR

261

Comparing with surfactant, the nanofluid did not reduce the oil-water interfacial tension to 10-2

262

mN/m or lower. The effect of this nanofluid on the oil-water interfacial tension is not a major

263

factor for EOR. The result of the spontaneous imbibition tests was consistent with the oil

264

displacement from a solid surface and wettability alteration. According to the formula of

265

capillarity (Pc=2σcosθ/r), capillary force increases with a decrease in pore diameter. In the

266

process of spontaneous imbibition, nanofluid seeped into the ultra-low permeable core through

267

small pores, and oil was expelled from the core through large pores. According to the above

268

experiment of oil displacement from oil-wet solid surface by nanofluid, the results were in

269

accordance with the structural disjoining pressure mechanism reported by Darsh Wasan.7, 22-26

270

The fluorescent carbon nanoparticles in the oil/nanofluid/solid three-phase contact region tended



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 16 of 22

271

to form a wedge film. Due to Brownian motion and electrostatic repulsion among nanoparticles,

272

a structural disjoining pressure, which was conducive for displacing oil from the solid surface,

273

formed in the wedge film. Oil was displaced from the pore channel surface, and the wettability of

274

the pore channel surface changed from oil-wet to water-wet. The spontaneous imbibition process

275

is the most efficient in a water-wet core where the capillary driving force is strong. The recovery

276

efficiency can be improved by the nanofluid, which alters the wettability of the reservoir rock to

277

a water-wet state. The spontaneous imbibition mechanism of nanofluid includes three main

278

aspects: capillary force, structural disjoining pressure, and wettability alteration. The

279

spontaneous imbibition mechanism of nanofluid is shown in Figure 11.

280

281 282

Figure 11 Spontaneous imbibition mechanism of nanofluid.

283 284

4. Conclusions

285

In this work, we have developed a novel nanofluid based on fluorescent carbon nanoparticles

286

for the EOR of an ultra-low permeable core. The highlights of the developed nanofluid are as

287

follows: (1) fluorescent carbon nanoparticles can be instantly dispersed in water without any

288

auxiliary equipment; (2) the nanofluid showed excellent anti-temperature, anti-salinity, oil

289

displacement and wettability alteration properties; and (3) carbon nanoparticles with a good 16 ACS Paragon Plus Environment

Page 17 of 22

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


290

fluorescence property were used to prove the existence of fluorescent carbon nanoparticles in the

291

pores of an ultra-low permeable core using fluorescence imaging technology. In an operating

292

site, the nanofluid based on fluorescent carbon nanoparticles could be obtained easily because

293

fluorescent carbon nanoparticles can be instantly dispersed in water without any auxiliary

294

equipment. The proposed nanofluid showed excellent performance for EOR of ultra-low

295

permeable core. The fluorescence image demonstrated that the fluorescent carbon nanoparticles

296

had seeped into the ultra-low permeable core in the process of spontaneous imbibition. The

297

spontaneous imbibition mechanism of nanofluid includes three main aspects: capillary force,

298

structural disjoining pressure, and wettability alteration. Thus, the fluorescent carbon

299

nanoparticle-based nanofluid provides a promising and efficient chemical agent for EOR of an

300

ultra-low permeable reservoir.

301

Supporting Information

302

Photographs in the preparation process of fluorescent carbon nanoparticles aqueous solution,

303

photograph of imbibition device, and pore size distribution of the core.

304

Author Contributions

305

The manuscript was written through contributions of all authors. All authors have given approval

306

to the final version of the manuscript. The authors declare no competing financial interest.

307

ACKNOWLEDGMENT

308

This work was financially supported by the National Key Basic Research Program (No.

309

2015CB250904), the National Science Fund (U1663206, 51425406), the Chang Jiang Scholars

310

Program (T2014152), Climb Taishan Scholar Program in Shandong Province (tspd20161004),

311

and the Fundamental Research Funds for the Central Universities (15CX06028A).



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

312

REFERENCES

313

(1) Yu, W.; Lashgari, H. R.; Wu, K.; Sepehrnoori, K. CO2 injection for enhanced oil recovery in

314 315

Bakken tight oil reservoirs. Fuel 2015, 159, 354-363. (2) Luo, P.; Luo, W. G.; Li, S. Effectiveness of miscible and immiscible gas flooding in

316

recovering tight oil from Bakken reservoirs in Saskatchewan, Canada. Fuel 2017, 208, 626-

317

636.

318 319 320

(3) Kathel, P.; Mohanty, K. K. Wettability alteration in a tight oil reservoir. Energ. Fuel. 2013, 27, 6460-6468. (4) Yang, P.; Guo, H.; Yang, D. Y. Determination of residual oil distribution during

321

waterflooding in tight oil formations with nmr relaxometry measurements. Energ. Fuel.

322

2013, 27, 5750-5756.

323 324 325 326

(5) Guo, C. H.; Xu, J. C.; Wei, M. Z.; Jiang, R. Z. Experimental study and numerical simulation of hydraulic fracturing tight sandstone reservoirs. Fuel 2015, 159, 334-344. (6) Crossley, S.; Faria, J.; Shen, M.; Resasco, D. E. Solid nanoparticles that catalyze biofuel upgrade reactions at the water/oil interface. Science 2010, 327, 68-72.

327

(7) Wasan, D. T.; Nikolov, A. D. Spreading of nanofluids on solids. Nature 2003, 423, 156-159.

328

(8) Huang, J. P.; Yang, H. Q. A pH-switched Pickering emulsion catalytic system: high reaction

329

efficiency and facile catalyst recycling. Chem. Commun. 2015, 51, 7333-7336.

330

(9) Xu, K.; Zhu, P. X.; Huh, C.; Balhoff, M. T. Microfluidic investigation of nanoparticles’ role

331

in mobilizing trapped oil droplets in porous media. Langmuir 2015, 31, 13673-13679.

332

(10) Hashemi, R.; Nassar, N. N.; Almao, P. P. Nanoparticle technology for heavy oil in-situ

333

upgrading and recovery enhancement: opportunities and challenges. Appl. Energ. 2014,

334

133, 374-387.


Page 18 of 22

Page 19 of 22

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

335


(11) Huang, T. P.; Clark, D. E. Enhancing oil recovery with specialized nanoparticles by

336

controlling formation-fines migration at their sources in water flooding reservoirs. SPE J.

337

2015, 20, 743-746.

338

(12) Sharma, T.; Iglauer, S.; SangwaiSan, J. S. Silica Nanofluids in an oilfield polymer

339

polyacrylamide: interfacial properties, wettability alteration and applications for chemical

340

enhanced oil recovery. Ind. Eng. Chem. Res. 2016, 55, 12387-12397.

341

(13) Sajad, K.; Mostafa, M. Z.; Saeed, K.; Alimorad, R.; Jamshid, M. Newly prepared nano

342

gamma alumina and its application in enhanced oil recovery: an approach to low-salinity

343

waterflooding. Energ. Fuel. 2016, 30, 3791-3797.

344

(14) Luo, D.; Wang, F.; Zhu, J. Y.; Cao, F.; Liu, Y.; Li, X. G.; Willson, R. C.; Yang, Z. Z.; Chu, C.

345

W.; Ren, Z. F. Nanofluid of graphene-based amphiphilic Janus nanosheets for tertiary or

346

enhanced oil recovery: High performance at low concentration. PNAS, 2016, 113, 7711-7716.

347

(15) Meiriane, C. F. S. L.; Sthefany, Z. A.; Helio, R.; Antonio, L. S. J.; Marcelo, M. V.; Luciana,

348

M. S.; Roberto, M. P.; Glaura, G. S.; Vinicius, C. Aqueous suspensions of carbon black with

349

ethylenediamine and polyacrylamide-modified surfaces: Applications for chemically

350

enhanced oil recovery. Carbon 2016, 109, 290-299.

351

(16) Zheng, C.; Cheng, Y. M.; Wei, Q. B.; Li, X. H.; Zhang, Z. J. Suspension of surface-modified

352

nano-SiO2 in partially hydrolyzed aqueous solution of polyacrylamide for enhanced oil

353

recovery. Colloid. Surface A 2017, 524, 169-177.

354 355 356 357

(17) Zargartalebi, M.; Kharrat, R.; Barati, N. Enhancement of surfactant flooding performance by the use of silica nanoparticles. Fuel 2015, 143, 21-27. (18) Cheraghian,G.; Kiani, S.; Nassar, N. N.; Alexander, S.; Barron, A. R. Silica nanoparticle enhancement in the efficiency of surfactant flooding of heavy oil in a glass micromodel. Ind.



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

358 359

Page 20 of 22

Eng. Chem. Res. 2017, 56, 8528-8534. (19) Bayat, A. E.; Junin, R.; Samsuri, A; Piroozian, A; Hokmabadi, M. Impact of metal oxide

360

nanoparticles on enhanced oil recovery from limestone media at several temperatures. Energ.

361

Fuel. 2014, 28, 6255-6266.

362

(20) Ma, X. K.; Lee, N. H.; Oha, H. J.; Kim, J. W.; Rhee, C. K.; Park, K. S.; Kim, S. J. Surface

363

modification and characterization of highly dispersed silica nanoparticles by a cationic

364

surfactant. Colloid. Surface A 2010, 358, 172-176.

365

(21) Jiang, L.; Li, S. Y.; Yu, W. Y.; Wang, J. Q.; Sun, Q.; Li, Z. M. Interfacial study on the

366

interaction between hydrophobic nanoparticles and ionic surfactants. Colloid. Surface A

367

2016, 488, 20-27.

368 369 370 371 372

(22) Kondiparty, K.; Nikolov, A. D.; Wasan, D.; Liu, K. L. Dynamic spreading of nanofluids on solids. part I: experimental. Langmuir 2012, 28, 14618-14623. (23) Liu, K. L.; Kondiparty, K.; Nikolov, A. D.; Wasan, D. Dynamic spreading of nanofluids on solids part II: modeling. Langmuir 2012, 28, 16274-16284. (24) Kondiparty, K.; Nikolov, A.; Wu, S.; Wasan, D. Wetting and spreading of nanofluids on solid

373

surfaces driven by the structural disjoining pressure: statics analysis and experiments.

374

Langmuir 2011, 27, 3324-3335.

375

(25) Zhang, H.; Nikolov, A.; Wasan, D. Enhanced oil recovery (EOR) using nanoparticle

376

dispersions: underlying mechanism and imbibition experiments. Energ. Fuel. 2014, 28,

377

3002-3009.

378

(26) Zhang, H.; Ramakrishnan, T. S.; Nikolov, A.; Wasan, D. Enhanced oil recovery driven by

379

nanofilm structural disjoining pressure: flooding experiments and microvisualization. Energ.

380

Fuel. 2016, 30, 2771-2779.


Page 21 of 22

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


381

(27) Fang, Y. X.; Guo, S. J.; Li, D.; Zhu, C. Z.; Ren, W.; Dong, S. J.; Wang, E. K. Easy synthesis

382

and imaging applications of cross-linked green fluorescent hollow carbon nanoparticles.

383

ACS Nano 2012, 6, 400-409.

384

(28) El-hoshoudy, A. N.; Desouky, S. E. M.; Betiha, M. A.; Alsabagh, A. M. Use of 1-vinyl

385

imidazole based surfmers for preparation of polyacrylamide-SiO2 nanocomposite through

386

aza-Michael addition copolymerization reaction for rock wettability alteration. Fuel 2016,

387

170, 161-175.

388

(29) Hendraningrat, L.; Torsæter, O. Effects of the initial rock wettability on silica-based

389

nanofluid-enhanced oil recovery processes at reservoir temperatures. Energ. Fuel. 2014, 28,

390

6228-6241.

391

(30) Mahshid, E.; Mahshad, A.; Alimorad, R.; Ali, R.; Sara, K. Carbonate and sandstone

392

reservoirs wettability improvement without using surfactants for Chemical Enhanced Oil

393

Recovery (C-EOR). Fuel 2015, 153, 408-415.

394



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

395

Table of Contents and Abstract Graphics

396


Page 22 of 22

A Novel Nanofluid Based on Fluorescent Carbon Nanoparticles for

Recommend Documents