Synthesis and evaluation of a novel hydrophobically associating polymer based on acrylamide for enhanced oil recovery

Article abstract of DOI:10.1515/chempap-2015-0185

A novel polymerizable hydrophobic monomer 1-(4-dodecyloxy-phenyl)-propenone (DPP) was synthesized by esterification, Frise rearrangement and Williamson etherification; then, the obtained DPP was copolymerized with 2-(acrylamido)-dodecanesulfonic acid (AMC₁₂S) and acrylamide (AM) initiated by a redox initiation system in an aqueous medium to enhance oil recovery (EOR). AM/AMC₁₂S/DPP (PADP) was characterized by FT-IR, ¹H NMR spectroscopy, environmental scanning electron microscopy (ESEM), DSC-TG, fluorescent probe, core flood test, etc. Results of ESEM and fluorescent probe indicate that hydrophobic microdomains and associating threedimensional networks were formed in the aqueous solution of PADP. Results of DSC-TG demonstrated that long carbon chains, aromatic groups and sulfonic groups were incorporated into the PADP polymer, which can lead to a significant increase of the rigidity of molecular chains. Performance evaluation of experiments showed superior properties in regard to temperature-tolerance, shear-tolerance and salt-tolerance. In the Sandpack Flooding Test, PADP brine solution showed a significant increase in EOR at 65°C because of its high thickening capability. All these features indicate that PADP has a potential application in EOR at harsh conditions.

Full text of DOI:10.1515/chempap-2015-0185

Chemical Papers 69 (12) 1598–1607 (2015)
DOI: 10.1515/chempap-2015-0185
ORIGINAL PAPER
Synthesis and evaluation of a novel hydrophobically associating
polymer based on acrylamide for enhanced oil recovery
a,b
a
c
d
a
Jin-Sheng Sun, Wei-Chao Du*, Xiao-Lin Pu, Zhuan-Zheng Zou, Bo-Bo Zhu
aSchool of Chemistry and Chemical Engineering, Southwest Petroleum University, Xindu Avenue 8, Chengdu 610500, China
bResearch Institute of Drilling Engineering, CNPC, Beiwu Country 23, Beijing 100600, China
cState Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University,
Xindu Avenue 8, Chengdu 610500, China
dLangfang Great Petro-Technologies, Venture Avenue 600, Langfang 065001, China
Received 20 March 2015; Revised 16 June 2015; Accepted 16 June 2015
A novel polymerizable hydrophobic monomer 1-(4-dodecyloxy-phenyl)-propenone (DPP) was syn-
thesized by esterification, Frise rearrangement and Williamson etherification; then, the obtained
DPP was copolymerized with 2-(acrylamido)-dodecanesulfonic acid (AMC12S) and acrylamide
(
AM) initiated by a redox initiation system in an aqueous medium to enhance oil recovery (EOR).
1
AM/AMC12S/DPP (PADP) was characterized by FT-IR, H NMR spectroscopy, environmental
scanning electron microscopy (ESEM), DSC-TG, fluorescent probe, core flood test, etc. Results
of ESEM and fluorescent probe indicate that hydrophobic microdomains and associating three-
dimensional networks were formed in the aqueous solution of PADP. Results of DSC-TG demon-
strated that long carbon chains, aromatic groups and sulfonic groups were incorporated into the
PADP polymer, which can lead to a significant increase of the rigidity of molecular chains. Per-
formance evaluation of experiments showed superior properties in regard to temperature-tolerance,
shear-tolerance and salt-tolerance. In the Sandpack Flooding Test, PADP brine solution showed
◦
a significant increase in EOR at 65 C because of its high thickening capability. All these features
indicate that PADP has a potential application in EOR at harsh conditions.
ꢀ
c 2015 Institute of Chemistry, Slovak Academy of Sciences
Keywords: 1-(4-dodecyloxy-phenyl)-propenone, associating, acrylamide, enhanced oil recovery,
hydrophobically associating polymer
Introduction
salinity or high-temperature oil reservoirs (Thomas,
008; Zhou et al., 2011; Zou et al., 2013). Conse-
2
Polymer flooding is one of the most efficient ways
to enhance oil recovery (EOR), and partially hy-
drolyzed polyacrylamide (HPAM) is the most fre-
quently used compound in EOR (Samanta et al., 2010;
Veerabhadrappa et al., 2013). In the process of chem-
ical flooding, HPAM showed a series of useful abili-
ties including viscoelasticity, thickening and rheolog-
ical capability. However, the poor salt tolerance, low
shear resistance and poor temperature resistance limit
the application of traditional polyacrylamide in high-
quently, in order to exploit this kind of harsh reser-
voirs, a novel water-soluble acrylamide polymer sys-
tem with high temperature, salt and shear resistance
becomes the focus of world-wide oil industry scien-
tists. In recent decades, many researches (Hourdet et
al., 2013; Roy et al., 2014) have suggested that hy-
drophobically associating acrylamide copolymers con-
sisting of hydrophobic side groups are a novel class
of water-soluble polymers offering a more satisfying
polymer with higher thickening capability, and better
*Corresponding author, e-mail: duweichao0303@foxmail.com
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1599
Fig. 1. Preparation of 1-(4-dodecyloxy-phenyl)-propenone (III).
salt, shear and temperature resistance. By introduc-
ing a very low amount of hydrophobic groups to poly-
acrylamide, the copolymer chain assemble together
to generate a transitory three-dimensional network
at certain polymer concentration through strong in-
termolecular hydrophobic interactions, thus providing
particular transient rheological properties (Siano et
al., 1989). A considerable number of publications has
been reported regarding the hydrophobically water-
soluble polymers with potential applications, includ-
ing those associated with agriculture (Koromilas et al.,
monomers and the water-soluble hydrophobically as-
sociating polymer were characterized by FT-IR and
H NMR spectroscopy, PADP was also characterized
by ESEM, a fluorescent probe, DSC-TG and the sand-
pack flooding test (SFT).
1
Experimental
Dimethylformamide (dried over calcium hydride
for 1 day and then distilled under reduced pres-
sure prior to use), 1-dodecene (95 mass %), acry-
lamide, acrylic acid, SOCl2, AlCl3, CS2, (NH4)2S2O8,
KOH, NaOH, NaHSO3, 1-bromododecane, acryloni-
trile, acetic anhydride, ethyl alcohol (absolute) and
phenol, were all of analytical reagent grade and
purchased from Kelon Chemical Reagent Factory
(Chengdu, China).
2
014), water treatment (Volpert et al., 1998), cosmet-
ics (Jiménez-Regalado et al., 2000) and oil industry
(Wu et al., 2006; Bera et al., 2014a).
Surface-active monomer (surfmer), which contains
a hydrophobic-tail or a head group and polymeric
vinyl double bonds, has been widely used in biolog-
ical simulations, cereals and water-soluble hydropho-
bically associating polymers. However, the ester and
amide monomers can be hydrolyzed under alkali con-
ditions limiting their utilization (Stähler et al., 1998;
Zhu et al., 2006; Friedrich et al., 2011). Thus, research
on molecules containing a phenyl monomer may be
worthy as hydrolyzation of phenyl in alkali and acidic
solutions was not observed. The group is a hydration
group with a large steric hindrance and its particular
structure makes it insensitive to high temperatures
Preparation of 1-(4-dodecyloxy-phenyl)-
propenone (DPP)
DPP was prepared from phenol, thionyl chloride,
acrylic acid, aluminum trichloride, carbon disulfide,
bromododecane and dimethylformamide by the pro-
cedure described below (see Fig. 1). I and II were
prepared based on the reported method (Ma et al.,
2014). III was prepared as follows: in a dry flask
fitted with a reflux condenser and a sealed stirrer
unit, 29.6 g (0.2 mol) of the product of the pre-
vious step, 49.8 g (0.2 mol) of bromododecane and
100 mL of dimethylformamide (DMF) were placed
under argon atmosphere at room temperature. Then,
(Eastoe et al., 2001). Consequently, hydrophobically
associating polymers containing a sulfonic group have
superior salt and temperature resistance properties
(Nishida et al., 2010; Morales & Rivas, 2015).
In the present work, hydrophobic monomer
◦
1
-(4-dodecyloxy-phenyl)- propenone (DPP) and po-
lar monomer 2-(acrylamido)-dodecanesulfonic acid
AMC12S) were synthesized. Then, they were copoly-
the mixture was stirred at 150 C for 10 h. The re-
action mixture was gradually warmed to room tem-
perature and stirred for additional 2 h. The solvent
was removed on a rotary evaporator, and the mixture
was washed thoroughly with water and extracted with
ether. The organic layer was collected and dried using
MgSO4 overnight, filtered and the solvent was evapo-
rated. DPP (56 %), isolated in form of white crystals,
(
merized with AM to synthesize a hydrophobically
associating polymer (PADP) by introducing phenyl
ether hydrophobic groups, long chain and sulfonic
groups to AM. Where AM acts as the backbone,
DPP as a functional monomer for the preparation
of a hydrophobically associating copolymer, AMC12S
as a hydration monomer to ensure the formation of
a water-soluble hydrophobically associating polymer
with salt, shear and temperature resistance. The two
1
did not require further purification. DPP: H NMR
(400 MHz, CDCl3), δ: 1.48–1.52 (m, 3H, CH3), 1.58
(s, 20 H, CH2(CH2)10CH3), 1.69 (s, 2H, PhOCH2),
5.71 (s, 1H, H—CH—), 5.59 (s, 1H, H—CH—), 5.9 (s,
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600
J. S. Sun et al./Chemical Papers 69 (12) 1598–1607 (2015)
Fig. 2. Preparation of 2-(acrylamido)-dodecanesulfonic acid (AMC12S).
Fig. 3. Preparation of the AM/AMC12S/DPP copolymer (PADP).
1
(
H CH2—CH), 5.95–6.22 (m, 4H, aromatic ring). IR
KBr), ν˜ /cm : 1045, 1202, 1467, 1597, 1679, 2851,
Preparation of PADP
−
1
2
927.
The PADP terpolymer was synthesized by redox
free radical copolymerization (see Fig. 3). Appropri-
ate amounts of DPP (0.240 g) and AMC12S (0.638 g)
were dissolved in deionized water (19.665 g). pH was
adjusted to the indicated value of 7–8.5 using a 30
mass % NaOH solution. The mixture was stirred for
about 10–15 min, AM was added to the flask under
stirring at constant temperature and nitrogen atmo-
sphere for approximately 30–35 min. Then, the initia-
tor, K2S2O8/NaHSO3 (1.1–1.4 : 1, eq.), aqueous solu-
tions with the initiator concentration of 0.2 mass %
relative to the total monomer amount were added.
Preparation of 2-(acrylamido)-
dodecanesulfonic acid (AMC S)
AMC12S was prepared by the following procedure
(see Fig. 2) (Gao et al., 2007a): acrylonitrile (2 g), 1-
dodecene (4 g) and acetic anhydride (1 g) were added
to a 100 mL three-necked flask fitted with a reflux
condenser and a constant funnel. When the temper-
◦
ature of the flask decreased to –5 C, sulfur trioxide
(
4 g, 20 %) was slowly added into the flask using the
◦
constant funnel. During the dropwise addition, the
temperature could not exceed 0 C. After the drop-
wise addition was completed, stirring was continued
for 30 min at low temperature. Then, the mixture
was stirred at 25 C for 24 h. The resulting product
Polymerization was carried out at 45 C for approx.
◦
4.5–6 h under stirring. The resulting products were
obtained by repeated washing with ethanol to remove
monomers and the initiator. PADP was further dried
◦
◦
in a vacuum oven at 40 C for 24 h.
was isolated by filtration, washed with a large amount
of acetone and white powder samples of AMC12S
were obtained. AMC12S: H NMR (400 MHz, CDCl3),
Characterization
1
δ: 0.735–0.767 (m, 3H, CH3CH2(CH2))7CH2CH),
1H NMR spectra were measured on a Bruker AV-
400 nuclear magnetic resonance spectrometer with
chemical shift values in ppm downfield from TMS
using CDCl3 as solvents. FT-IR spectra of products
were acquired via a WQF-520 Fourier transform in-
frared spectrometer in the optical range of 4500–
1
1
.236 (s, 2H, CH3CH2(CH2))7CH2CH), 1.155 (s,
4H, CH3CH2(CH2))7CH2CH), 1.511–1.545 (m, 2H,
CH3CH2(CH2))7CH2CH), 3.026–3.125 (m, 1H, CH3
CH2(CH2))7CH2CH), 2.99 (d, 2H, CHCH2SO3H),
2
.95 (m, 1H, CHCH2SO3H), 6.249–6.291 (m, 1H,
−
1
CHNH(O)CHCH2), 6.147 (d, 1H, J = 16.4Hz,
CHNH(O)CHCH2), 5.721 (d, 2H, J = 9.6 Hz,
400 cm . DSC-TG was carried out on a STA-409 Si-
multaneous DSC-TG instrument under nitrogen flow
−
1
−1
◦
−1
.
CHNH(O)CHCH2). IR (KBr), ν˜ /cm : 721, 1103,
620, 1654, 3085, 3286.
(100 mL min ) with the heating rate of 10 C min
Environmental scanning electron microscopy (ESEM)
1
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1601
analysis of PADP solutions was obtained with a FEI
Apparent viscosity measurement
Quanta 450 (FEI, USA), in the magnifying multiple
ranges from 3× to 30000×, the copolymer was dis-
solved in degassed and distilled water forming a solu-
Apparent viscosity studies were conducted on a
6
rotational viscometer (NDJ-79/7, the range of 1–10
−
1
◦
tion (mass % ≈ 5 g L ). The images were obtained
mPa, Shanghai Changji Geological, China) at 25 C.
at 120–500 Pa and the acceleration of 20 kV.
In the process, polymer samples were weighed accu-
rately, swelled in distilled water and left at a constant
temperature for 24 h to make sure the polymers can
dissolve entirely.
Intrinsic viscosity measurement
Intrinsic viscosity (η) of PADP was determined by
an Ubbelohde viscometer at the constant temperature
Fluorescence spectroscopy
◦
of (30.0 ± 0.1) C in a 1.0 M NaCl aqueous solution,
and the relative and specific viscosities of copolymer
solutions at different concentrations were measured.
Viscosity average molecular mass of PADP was ob-
tained from the intrinsic viscosity value by employing
the Mark–Houwink equation together with the dilu-
tion extrapolation method (Zou et al., 2014).
The appropriate amount of pyrene (10.112 mg) was
added into a 50 mL volumetric flask and diluted to the
−
3
mark to 10 M with methanol. A certain amount of
polymer and 250 L of pyrene stock solutions were
added to a 50 mL volumetric flask, the mixture was
diluted to different concentrations with deionized wa-
Fig. 4. IR spectrum of DDP, AMC12S, PADP (a), scheme of PADP (b) and 1H NMR spectra of PADP (c).
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J. S. Sun et al./Chemical Papers 69 (12) 1598–1607 (2015)
Fig. 5. ESEM images of copolymers: PADP, 1000×, scale bar 100 m (a), PADP, 2000×, scale bar 50 m (b); PADP, 5000×, scale
−
1
bar 20 m (c); PADP, 10000×, scale bar 10 m (d) (polymer concentration = 5 g L ).
ter. The pyrene solution was stirred for 48 h before
the fluorescence measurements were made. Fluores-
cence spectroscopy measurements were conducted on
stretching vibration) in its IR spectra. Pure AMC12S
−
1
exhibited a very strong absorption at 3286 cm
,
−
1
−1
1597 cm , 1100 cm , which reflect the N—H, C—C
and SO3H stretching vibrations, respectively. PADP
has both functional groups of DPP and AMC12S, and
the C—C was not detected in the IR spectrum. The
◦
an F-4500 spectrofluorimeter at 25 C, using 5 nm
bandpass settings for emission and excitation, respec-
tively. The excitation wavelength was 335 nm, and the
scanning range was 350–550 nm. Pyrene was used as
the fluorescent probe (Gao et al., 2007b).
IR spectrum showed that the polymer was successfully
synthesized.
1H NMR of PADP is shown in Fig. 4. The chem-
ical shift at 1.04 ppm was assigned to the long chain
methyl protons (j). The chemical shift at 1.52 ppm
was ascribed to the methylene (a, i) protons of
Results and discussion
Characterizations
—
CH2CH3. The protons of —CH—C(O) (b, d) ap-
Purified DPP, AMC12S and PADP were pre-
pared in KBr pellets and characterized on a Fourier
transform infrared spectrometer. Structures of the
functional monomer and copolymer were confirmed
by IR spectra as illustrated in Fig. 4. Functional
monomer DPP was confirmed by strong absorp-
peared at 1.63 ppm and 1.64 ppm. The chemical shift
at 3.38 ppm was assigned to the —CH protons of
—CH—NH (l). The protons of —CH2—SO3H (m) ap-
peared at 3.49 ppm and those of Ar—O—CH2 (h) ap-
peared at 3.54 ppm. The chemical shift at 5.70 ppm
was assigned to the NH (e) protons of —CONH2. The
protons of Ar (f) appeared at 6.88–6.90 (J = 8 MHz)
and the chemical shift at 7.61–7.69 (J = 38 MHz) was
assigned to the protons of Ar (g).
−
1
tions at 2927 cm
(Ar—H stretching vibration),
−
1
−1
1
679 cm
(C—O stretching vibration), 1597 cm
−
1
(
C—C stretching vibration), 1200 cm
(C—O—C
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1603
Fig. 7. Intrinsic viscosity of PADP.
Fig. 6. DSC and TG of PADP.
ESEM images provided in Fig. 5 reveal that an ob-
vious gel-network microstructure of PADP was formed
and is clearly visible. The microscopic nets indicated
that intramolecular and intermolecular interactions
are accrued during the copolymerization process (Pat-
terson et al., 2013; Zhu et al., 2014). Hydrophobic in-
teractions between copolymers due to the hydrophobic
bonds of DPP, sulfonamide structures of AMC12S and
amide groups of AM were also observed.
both determined from the apparent viscosity of PADP.
The η was obtained by extrapolation of the plot of re-
duced specific viscosity (ηsp/c) vs. concentration to
−
1
the concentration of 0 g L . To obtain the viscos-
ity molecular mass, the following equations have to be
α
η
applied: η = KM , where η is the intrinsic viscosity
−
−
1
in mg L ; Mη is the viscosity-average molecular mass
1
in g mol and K and α are constants related to the
copolymer.
DSC-TG (Casarano et al., 2009) was used to in-
vestigate the thermal stability of copolymers and the
thermal gravimetric curve is presented in Fig. 6.
The diagram in Fig. 6 suggests that the process
of weight loss can be divided into four main steps.
In this paper, the equation used is: (Zou et al.,
2013). The result is shown in Fig. 7, where the intrinsic
−
1
viscosity was 1147 mL g and the viscosity molecular
6
−1
.
mass was 5.26 × 10 g mol
◦
To begin with, in the range of 25–128 C, the weight
decreased by about 14.34 mass % because of the evap-
oration of intermolecular and intramolecular moisture
combined with oxygen. In the second step, in the
Effect of temperature, shear rate and salt on
apparent viscosity
◦
range of 128–250 C, with a mass loss of 8.25 % can
Influence of shear rate, temperature, and salt on
the apparent viscosity of PADP was studied and the
results were shown in Fig. 8. Since high viscosity im-
proves the sweep efficiency during the enhanced oil re-
covery, the polymers should have excellent anti-shear
abilities (Pu et al., 2015). The shear resistance of
be divided into two parts: i) a gentle decrease from
◦ ◦
1
28 C to 210 C corresponding to the evaporated water
combined with the sulfonamide structure and amide
groups through hydrogen bonds; ii) a rapid decrease
◦
in the 210–250 C temperature range which can be as-
− −1
1
cribe to the decomposition of amide groups. The third
PADP (3000 mg L ) and HPAM (3000 mg L ) was
◦
−1 ◦
at 30 C. Fig. 8a
step occurred between 250–420 C, where the C—C
measured at a shear of 0–500 s
backbone and the side chains began to fracture re-
sulting in a PADP decomposite and with the signif-
icant loss of 35.65 mass %. The main structure was
destroyed mostly in the fourth stage at temperatures
presents the apparent viscosity versus shear rate for
PADP and HPAM. Viscosity of HPAM decreased
with the increase of the shear rate; however, vis-
cosity of PADP increased with the increasing shear
◦
−1
above 420 C.
rate, and it reached a maximum at 0.05 s , when it
started to decrease. Following from the balance be-
tween the disassociation and intermolecular associa-
tion, viscosity of PADP varied slightly, which showed
a pseudoplastic behavior. Shear thickening behavior
at low shear rates was attributed to the expansion
of the polymer chains and the shear thinning be-
havior at high shear rates was due to the disrup-
tion of the hydrophobic domains. Therefore, when a
PADP solution flowed through the pores of the shale
Intrinsic viscosity measurements of PDAP
Intrinsic viscosity of PADP at five different con-
−
1
−1
−1
centrations (250 g L , 330 g L , 500 g L ,
6
− −1
1
70 g L , 1 mg L ) was measured using a Ubbelo-
hde viscometer. The solvent efflux time was over 100 s
reproducible to 0.2 s. At each concentration, reduced
viscosity (ηsp/c) and inherent viscosity (ln(ηr/c)) were
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604
J. S. Sun et al./Chemical Papers 69 (12) 1598–1607 (2015)
◦
−1
−1
Fig. 8. Effect of shear rate on apparent viscosity (30 C, 3000 mg L ) (a); effect of temperature on apparent viscosity (15.8 s ,
− −1 ◦ −1
1
3
000 mg L ) (b); effect of NaCl on apparent viscosity (15.8 s , 30 C, 3000 mg L ) (c); effect of CaCl2 and MgCl2 on
apparent viscosity (15.8 s , 30 C, 3000 mg L ) (d).
−
1
◦
−1
at low shear rates, copolymer chains associated with
each other via molecular interactions of hydropho-
bic groups to enhance oil recovery (Zhong et al.,
shown in Figs. 8c and 8d, apparent viscosities of PADP
and HPAM displayed similar phenomena. With the in-
creasing NaCl, CaCl2 and MgCl2 concentration, the
hydrophobic microstructures became firm and con-
densed forming large aggregates, and the phase sepa-
ration generated and the apparent viscosity decreased
finally. However, the PADP solutions showed a bet-
ter anti-salt ability than HPAM due to their higher
apparent viscosity under the same conditions, which
is well explained by the sturdy network structure of
PADP.
2
009).
Fig. 8b shows the impact of temperature on the ap-
−
1
parent viscosity of PADP (3000 mg L ) and HPAM
−
1
−1
(3000 mg L ) at 15.8 s . Viscosity of HPAM de-
creased with the temperature increased; however, vis-
◦
◦
cosity of PADP initially increased from 25 C to 35 C,
and then it decreased. The hydrophobic association
behavior is an endothermic process of entropy in-
crease in a certain temperature range. Thus, under
low-temperature conditions, intermolecular associa-
Hydrophobic microdomains of PADP
tions can benefit from a temperature increase. Over
◦
3
5 C, apparent viscosity decreased when the temper-
A change of PADP viscosity reflected in its hy-
drophobic association properties, which can be illus-
trated by the fluorescence probe at molecular level
(Deng et al., 2014). As shown in Fig. 9a, five peaks
(around 368 nm, 379 nm, 390 nm, 411 nm and 436 nm)
were found in the pyrene emission spectrum; the in-
tensity ratio of the first peak to the third (I1/I3) is
ature increased due to the movement of molecular
chains and the destruction of the hydration sphere of
hydrophobic groups (Zhong et al., 2009).
The influence of salts (NaCl, CaCl2 and MgCl2)
on the apparent viscosity of PADP (3000 mg L
−
1
)
−
1
◦
and HPAM (3000 mg L ) was studied at 30 C. As
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Fig. 9. Fluorescence spectra of pyrene in PADP aqueous solution (a); I1/I3 ratio vs. PADP concentrations (b).
Fig. 10. Estimated oil recovery (EOR) (a) and water cut (WC) (b) vs. cumulative injection volume (CIV) capability of polymer
◦
solution at 65 C.
sensitive to the polarity of the solution, the stronger
the polarity the higher the value of (I1/I3); therefore,
this property of pyrene fluorescence emission spectrum
was called “polarity staff”.
occurred at low concentrations. In addition, the elec-
trostatic repulsion between the sulfonamide groups
of the polymer chain results in extended state. (2)
Values of I1/I3 diminished abruptly at Cp = 0.2 g
−
1
Fig. 9b shows the relationship between I1/I3 and
Cp, with the following conclusions: (1) with the in-
creasing Cp, the value of I1/I3 decreased continu-
dL
indicating the presence of a large number of
hydrophobic microdomains in the water solution. (3)
−
1
After the concentration (Cp = 0.2 g dL ), the type
of the association changed from intramolecular to in-
termolecular. In this case, the hydrophobic groups of
polymer molecules associated with each other gen-
erated supramolecular aggregates and formed a hy-
drophobic microarea. (4) With the increasing polymer
concentration, the number of hydrophobic domains
increased gradually. As the polarity of the pyrene
probe microenvironment continued to decrease, the
−
1
ously. At low concentrations (Cp < 0.2 g dL ), the
value of I1/I3 was close to the value of water (1.8),
and only little changes with the increasing polymer
concentration were observed. This information indi-
cates that the pyrene probe was in a high polarity
environment, where the distance between two macro-
molecules was large and only little chances in the
hydrophobic groups forming hydrophobic associations
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606
J. S. Sun et al./Chemical Papers 69 (12) 1598–1607 (2015)
Table 1. Results of sandpack flooding tests of copolymer flooding: injection pressure of the water saturation process (Pw), perme-
ability (Q), void volume (Vv), porosity(ϕ), oil saturation (So) and enhanced oil recovery (EOR)
Pw
Q
Vv
ϕ
So
EOR
Entry
Polymer solution
HPAM
−
2
MPa
K
m
mL
%
1-1
2-2
3-3
0.0025
0.0024
0.0023
1.7356
1.8223
1.7769
47
52
49
32.12
35.33
33.56
8992
89.86
89.79
6.23
11.26
15.67
−
−
1
PADP (0.5 g L
PADP (1.5 g L
)
)
1
non-polar molecules of pyrene entered the hydropho-
bic microarea.
in an aqueous medium. Results of DSC-TG indicate
that the hydrophobic long carbon chains of DPP and
the —SO3 of AMC12S enhance the thermal stabil-
−
Core flooding test
ity of copolymers. Results of systematical investiga-
tions showed that PADP possesses a series of superior
properties regarding salt, temperature and shear re-
sistance when compared with HPAM. ESEM images
and the fluorescence probe revealed that an obvious
gel-network microstructure of PADP is formed dur-
ing the copolymerization process. In addition, the core
flooding tests indicate that PADP has a potential ap-
plication in enhance oil recovery(EOR) and can be
used in some harsh reservoirs.
The core flooding tests (Samanta et al., 2011; Bera
et al., 2013; Bera et al., 2014b) were employed to inves-
tigate the enhanced oil recovery ability of the copoly-
−
1
−1
mer (500 mg L , η = 56 mPa s; 1500 mg L , η =
−
1
7
2 mPa s) and HPAM (500 mg L , η = 43 mPa s)
solutions.
In this work, the one-dimensional sand packed
model was 500 mm long with the diameter of 25 mm;
η of the simulated crude oil was 45.6 mPa s at 65 C;
ISCO 260D syringe pump with the maximum injec-
tion pressure of 50 MPa, accuracy of 0.1 %. The total
◦
Acknowledgements. The authors would like to thank the
Open Fund (PLN1424) of the State Key Laboratory of Oil and
Gas Reservoir Geology and Exploitation (Southwest Petroleum
University), National 973 Project (contract grant number:
2013CB228003) and the Natural Science Foundation of China
−
1
+
amount of dissolved solids was 5210 g L , ρ(Na )
− −1
1
2+
2+
=
1770 mg L , ρ(Ca ) = 102 mg L , ρ(Mg ) =
− − −1
1
2−
3
(No. 51304169) for financial support.
1
7 mg L , ρ(Cl ) = 2270 mg L , ρ(CO ) = 71 mg
−
1
−
−1
2−
−1
L
, ρ(HCO ) = 749 mg L , ρ(SO4 ) = 231 mg L .
3
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