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Received: 6 October 2021
|
Revised: 27 January 2022
|
Accepted: 22 February 2022
DOI: 10.1002/ese3.1116
ORIGINAL ARTICLE
Study on the application potential of lipopeptide
fermentation broth in oil recovery
Huidong Wang
1,2,3
|Jianlong Xiu
2,3
|Lixin Huang
2,3
|Li Yu
2,3
|Bo Wu
1,2,3
1
School of Chemical Sciences, University
of Chinese Academy of Sciences, Beijing,
China
2
Institute of Porous Flow and Fluid
Mechanics, Chinese Academy of
Sciences, Langfang, Hebei, China
3
State Key Laboratory of Enhanced Oil
Recovery, PetroChina Research Institute
of Petroleum Exploration &
Development, Beijing, China
Correspondence
Jianlong Xiu, Institute of Porous Flow
and Fluid Mechanics, Chinese Academy
of Sciences, Langfang, Hebei 065007,
China.
Email: xiujianlong69@petrochina.com.cn
Funding information
National Key reserch and development
Program, Grant/Award Number:
2018YFA0902104
Abstract
Microbial flooding is a new enhanced‐oil‐recovery technology for the
petroleum industry. In this study, a strain of Bacillus subtilis named SL‐2
was isolated from oil‐well‐produced fluid. B. subtilis produces the lipopeptide
surfactin. The fermentation broth of B. subtilis contains lipopeptide
biosurfactants (1.2 g/L) with good surface and interfacial activities. Adding
7% of this fermentation broth to water reduces its surface tension from 72 to
33.9 mN/m and the interfacial tension between hexadecane and water from 40
to 1 mN/m. Environmental adaptability analysis revealed that the lipopeptide
biosurfactants can tolerate a salinity of 50 g/L NaCl and a temperature of
120°C, and that they have a strong emulsifying effect on the oil phase as well
as good emulsification stability owing to their high interfacial shear viscosity.
Water contact angle measurements showed that this fermentation broth
changes the wettability properties of rock surfaces from hydrophobic to
hydrophilic. A new bio‐oil‐displacement system was developed by combining
the lipopeptide fermentation broth with xanthan gum, a biopolymer with
viscosifying properties. The new bio‐oil‐displacement system has the dual
functions of improving oil‐displacement efficiency and expanding sweep
volume. The results of laboratory simulation experiments revealed that the oil
recovery for a bio‐composite system containing 7% lipopeptide fermentation
broth is 18.7% higher than that for water flooding. Therefore, the system has
good field application potential. Direct preparation of the oil‐displacement
system using the lipopeptide fermentation liquid can reduce the purification
cost of the biosurfactant lipopeptide, which is economically conducive to the
application of this bio‐oil‐displacement technology.
KEYWORDS
biosurfactant, EOR, fermentation broth, lipopeptide surfactin, oil displacement efficiency
Energy Sci Eng. 2022;10:2065–2075. wileyonlinelibrary.com/journal/ese3
|
2065
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© 2022 The Authors. Energy Science & Engineering published by Society of Chemical Industry and John Wiley & Sons Ltd.
1|INTRODUCTION
Conventional primary and secondary oil recovery tech-
nologies only obtain ~40% of the geological reserves of
crude oil, so ~60% of the crude oil remains.
1,2
Therefore,
tertiary oil recovery, also termed enhanced oil recovery
(EOR), must be used to exploit the residual oil in a
reservoir after primary and secondary recovery. Accord-
ingly, EOR technology has been paid increasing attention
in recent years. Common EOR methods include thermal
flooding, chemical flooding, miscible flooding, and
microbial‐EOR (MEOR),
3
which is a method for improv-
ing oil recovery that involves injecting microorganisms or
microbial products into the well.
4
Here, the biosurfactant
product can reduce surface tension
5
and oil–water
interfacial tension,
6
change the wettability of the rock
surface, and promote emulsification of crude oil and
water,
7
so as to improve oil recovery. Compared with
chemically synthesized surfactants, biosurfactants have
the advantages of low toxicity, good biodegradation,
8
good environmental compatibility, renewable raw mate-
rials, and good emulsifying performance.
9
It is thus a
typical green environmental protection technology.
10
At
present, biosurfactants that can be used in MEOR
include rhamnolipid, locust glucolipid, lipopeptides,
and other small molecules. There are also high‐
molecular‐weight biosurfactants composed of a mixture
of heteropolysaccharides, lipopolysaccharides, lipopro-
teins, and proteins.
11
In terms of cost, She et al.
12
have demonstrated that
MEOR has a much lower total cost than other EOR
techniques in field studies. In a previous study, Li et al.
13
purified the lipopeptide from a Bacillus fermentation
broth, and the purified lipopeptide had a lower critical
micelle concentration (CMC) value and good stability
under extreme temperature, salinity, and other condi-
tions. Liu et al.
14
improved oil displacement efficiency by
increasing the content of C15‐surfactin in a fermentation
broth. Field trials have also been performed, with
Rebecca et al.
15
achieving 11%‐EOR in a field in the
Phoenix area in the 1990s. Liu et al.
16
carried out
research on endogenous microbial oil flooding technol-
ogy and performed experiments simulating the deep‐
burial, high‐temperature, and high‐salt conditions in the
Xin Block of Sheng Li oilfield in China. The results
showed that the displacement efficiency can be improved
by 8.5%, the oil production was increased from 1.0 to
1.8 t/day, and the water content decreased by 14%. This
oil displacement effect is remarkable. Kong et al. has
studied ways of flooding oil with endogenous micro-
organisms by injecting them with nutrients and air. The
air injection volume used in microbial oil recovery is
1:8–1:10 liquid/gas ratio.
17
Although there are many reports on the character-
istics of lipopeptides and their application potential in
MEOR, the acquisition cost of pure biosurfactants is
relatively high and the technology is complex. Consider-
ing a large amount of oil produced, it is unrealistic to
apply biosurfactants on site. Furthermore, in endogenous
microbial flooding, which is a mainstream microbial oil
flooding technology, the air injection volume is very
high.
17
Due to difficulties in terms of gas injection and
low utilization rate, the growth of aerobic bacteria is
slow, the oil displacement efficiency is low, and the risk
of gas injection is high, so there are certain potential
safety hazards. To further reduce costs and increase
security, oil displacement efficiency and stability can be
greatly improved by using a surface fermentation process
to make a single strain grow and ferment in an above‐
ground fermentation device. This is then injected into the
well with xanthan gum.
With this in mind, the oil displacement potential of
the SL‐2 strain fermentation broth was evaluated. The
composition of the fermentation broth as well as its
surface tension, interfacial tension, emulsification per-
formance, stability, and oil displacement efficiency of the
fermentation broth at different dilutions were evaluated.
The fermentation liquid shows good oil recovery
performance, and the EOR value of 18.7% is higher than
that reported in the present study, demonstrating its
suitability for field application. At the same time, since
emulsification is one of the core mechanisms of
MEOR,
10,18
we discuss the mechanism of emulsification
stability of the biosurfactant.
2|EXPERIMENTAL METHODS
2.1 |Preparation of fermentation broth
To obtain high‐concentration lipopeptide fermentation
broth, the following procedures were carried out:
The tested SL‐2 strain was stored in the strain bank
of the Microbial Percolation Laboratory, Institute of Porous
Flow and Fluid Mechanics, Chinese Academy of Sciences.
The strain activation medium was Luria‐Bertani (LB)
medium,
19
its nutrient proportions (mass percentages)
were as follows: NaCl 1%, peptone 1%, yeast powder
0.5% (all chemicals were of analytical grade). Culture
conditions: temperature, 37°C; rotation speed, 180 r/min;
liquid volume, 100/250 ml; incubation time, 12 h.
The fermentation medium was as follows: sucrose
50 g/L, NaNO
3
3.4 g/L, NH
4
Cl 1.1 g/L, KH
2
PO
4
2.5 g/L,
Na
2
HPO
4
·12H
2
O30g/L,MgSO
4
·7H
2
O0.8g/L(all
chemicals were of analytical grade). The pH of the
system was 7.5. First, 7.5 ml of the seed liquid prepared
2066
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WANG ET AL.
in the above process is put into a 250‐ml flask
containing 150 ml fermentation medium (i.e., an
inoculation dose of 5%, v/v). The flask oscillated
at 180 r/min and 37℃for 72 h.
2.2 |Analysis of fermentation broth
components
After fermentation, 1.2 ml methanol was added to
300 µm cell‐free supernatant, which was then shaken
for 1 min and centrifuged at 4°C 10,000 r/min for 10 min.
The supernatant was taken as the sample for testing and
analysis. The lipopeptide detection instrument was an
SR‐3000 Solvent Rack fitted with an Amethyst C18‐P
column (5 μm, 4.6 × 150 mm). Liquid phase injection
conditions were as follows: the mobile phase was 90%
chromatography‐grade methanol and 10% formic acid
solution (formic acid content 0.05%). The injection
volume was 20 µl, the flow rate was 0.7 ml/min, and
the column temperature was 35°C. A UV detector was
used, and the wavelength was set at 214 nm.
After analysis, high performance liquid chromatogra-
phy (HPLC) traces of a lipopeptide standard mix (Sigma)
and fermentation samples were compared to determine
the quality of the product, and the product composition
was quantified using the peak areas.
2.3 |Detection of fermentation broth
interface properties
2.3.1 |Surface tension
Distilled water was used to gradient dilute the fermenta-
tion broth, and the volume percentages of broth in the
systems were 1%, 3%, 5%, 7%, 10%, 20%, 30%, and 50%.
With increasing dilution, the surface tension decreases,
and there is a sudden change in the surface tension at a
certain point. The surface tension was measured with a
surface tensiometer (FTA1000 Drop Shape Instrument)
at 25°C, and the inflection point was found. This is the
critical concentration against oil displacement potential,
which is defined as critical micellar dilution (CMD).
20
2.3.2 |Oil/water interface tension
To study the interfacial activity of the fermentation
broth, the oil/water interface tension between the
fermentation broth and crude oil, hexadecane, or
simulated oil (crude oil/kerosene [1:9, v/v]) was mea-
sured using a Texas‐500c rotating drop interfacial tension
analyzer. The sample tube is filled with the system to be
tested. It is then sealed and attached to the rotating drop
interfacial tension meter so that the sample tube is
parallel to the rotating axis and concentric with the
rotating axis. The liquid is spun at an angular velocity of
5050 s
−1
and, under the action of centrifugal force,
gravity, and interfacial tension, the simulated oil forms
long spherical or cylindrical droplets in the system, the
shape of which is determined by the rotational speed and
interfacial tension. By measuring the length and width of
the droplets, the density difference between the two
phases, and the rotation speed, the interfacial tension
between the water and the simulated oil can be
calculated.
2.4 |Temperature and salt resistance
To study the temperature and salt resistance of the
lipopeptide, 100 ml of fermentation broth was incubated
in the temperature range 25–120°C for 1–2 days. The
surface tension after cooling to room temperature was
measured on Days 1 and 2.
To study the influence of salt concentration on the
product, the NaCl concentration of the fermentation
broth was set to 0.5, 1, 3, 5, 7, 10, 15, 20, 30, 40, 50, 70,
100, or 120 g/L. After preparation, the broth was
incubated at 37°C for 2 days, and then the surface
tension was measured at room temperature.
2.5 |Wettability
To evaluate the potential effect of the biosurfactant on
the wettability of the rock surfaces in a reservoir, an
artificial rock core was cut into thin slices, soaked in
crude oil, and then dried. Fermentation broth, 7%
fermentation broth, or water (blank control) were
dropped on the rock surface, and an FTA1000 Drop
Shape Instrument was used to measure the contact angle.
2.6 |Emulsification of crude oil
To determine the emulsification index, 10 ml of the
fermentation broth was added to 10 ml of simulated oil
(or hexadecane). The mixture was then vortexed at high
speed for 2 min and allowed to stand at 25°C for 24 h.
EI
24
is defined as the emulsion layer height as a
percentage of the total liquid column height after
24 h.
21
The emulsification mechanism of the fermenta-
tion liquor was also investigated. First, a rheometer
(GXZJ‐B013035) was used to measure the interfacial
WANG ET AL.
|
2067
shear viscosity (rotor type−2D), which reflects the
interfacial film strength. A zeta potentiometer was used
to determine the zeta‐potentials of different oil
emulsions.
2.7 |Simulation of biosurfactant
flooding
Artificial core tests were performed using the conditions
shown in Table 1(an artificial core was used to conduct the
flooding experiments). The artificial core flooding
experiment is schematized in Figure 1.First,thegas
permeability was measured, then the dehydrated crude oil
is used to saturate the oil. The pores of the core were filled
with oil and aged for 7 days. After aging, primary water
flooding was carried out. The injection water used in this
displacement experiment was separated water from the oil‐
well‐produced fluid. When the water cut reached 98%, 7%
fermentation broth + 0.1% biological xanthan gum (to
improve the swept volume of the lipopeptide) was
injected. A peristaltic pump was used to inject a 1 pore
volume (PV) injection system into the core at a constant flow
rate of 0.1 ml/min. After the injection volume reached 1 PV,
subsequent water flooding was carried out until the water
content of the produced fluid exceeded 98%, at which point
the displacement was stopped and the displacement
efficiency was calculated.
23
Toexcludetheinfluenceof
xanthan gum on the experiment, its physical effect was
evaluated separately, and the core data used are shown in
the second column of Table 1. To match the reservoir
conditions of the oilfield studied, a production temperature
of 55°C was adopted.
Oil displacement efficiency (%) = ([oil displacement
after injection system + oil displacement by subsequent
water flooding]/total oil displacement) × 100
3|RESULTS AND DISCUSSION
3.1 |Fermentation broth component
analysis
Qualitative analysis can be performed by comparing
fermentation broth samples with a standard lipopeptide
mix using HPLC. As shown in Figure 2, the peak
emergence times for the two samples are similar, and the
number of peaks is the same, which indicates that the
product contains lipopeptide biosurfactants. A lipopep-
tide contains a hydrophilic peptide chain and an
oleophilic β‐hydroxy fatty acid group, so it is an
amphiphilic compound.
13
Therefore, lipopeptides can
reduce the surface tension of water and its interfacial
tension with oil, change the wettability of a rock surface,
and promote the formation of water/crude oil emulsions.
Accordingly, crude oil that is difficult to recover can be
stripped from rock fractures and sand gaps and be
recovered with water using lipopeptides. The four
highest peaks correspond to four lipopeptide products
with different structures. These are C13‐surfactin, C14‐1‐
surfactin, C14‐2‐surfactin, and C15‐surfactin. Liu et al.'s
study
13
showed that the higher the proportion of C‐15‐
surfactin, the higher the oil displacement efficiency and
oil washing efficiency of a surfactin mixture. As can be
seen from Figure 2, the fermentation broth in this study
has C‐15‐surfactin as its most abundant component, so it
TABLE 1 Core parameters
Permeability
(mD)
Length
(cm) Diameter (cm)
Saturated
water (ml)
Saturated
oil (ml)
200 8 2.5 7.4 6.2
230 8 2.5 6.4 5.4
Permeability
(mD)
Length
(cm) Diameter (cm)
Saturated
water (ml)
Saturated
oil (ml)
200 8 2.5 7.4 6.2
230 8 2.5 6.4 5.4
FIGURE 1 Schematic of artificial core flooding test
apparatus
22
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|
WANG ET AL.
could be reasonably expected to exhibit excellent
performance in oil displacement.
The lipopeptides can be quantified by measuring their
peak areas, and the final lipopeptide yield of the process
is 1.2 g/L. In addition to lipopeptides, the main compo-
nents of the fermentation broth are small‐molecular‐
weight compounds such as acetic and lactic acid. They
are environmentally friendly biodegradable compounds
that do not cause pollution to the environment when
used for oil displacement and are safer than other
chemical oil displacement agents. Furthermore, acetic
and lactic acid can dissolve limestone and calcareous
cement, so as to increase the permeability and porosity of
rock and thus improve crude oil displacement by water.
3.2 |Properties of the biosurfactant
3.2.1 |Surface tension
As shown in Figure 3, surface tension changes rapidly
when the fermentation broth is diluted to 7%. Thus, this
FIGURE 2 HPLC analysis results for the
fermentation broth
FIGURE 3 Surface tension changes with
fermentation liquid concentration
WANG ET AL.
|
2069
concentration is a critical point for oil displacement. The
surface tension at the inflection point is 33.9 mN/m and
the CMD is 7%. These results show that the fermentation
broth reduces surface tension efficiently at a low
concentration. Low surface tension helps surfactant
products migrate well in a reservoir, which leads to a
change in the physical properties of the strata, oil, and
water in the reservoir, and achieves efficient oil
displacement.
24
3.2.2 |Interfacial tension
According to the results of surface tension analysis, the
minimum effective concentration of the fermentation
broth is 7%. Therefore, interfacial water/oil tensions were
determined for systems at this concentration. As seen in
Figure 4, the interfacial tension for each oil phase is
decreased to ~1 mN/m by the prepared system, and that
for hexadecane, the standard material, is decreased to
<1 mN/m, so the biosurfactant meets the requirements
of EOR.
11
Furthermore, it can be seen in Figure 4that
the interfacial tension between the two phases decreases
in the order crude oil > hexadecane > simulated oil.
Therefore, with a decrease in light‐component content,
the interfacial tension decreases, so the effect of the
system on light components is better.
Crude oil contains aromatic compounds, the interac-
tions between which are predominantly π–πinteractions,
which are stronger than the van der Waals forces
between alkane molecules. Thus, surfactant molecules
cannot disrupt the interactions between aromatic com-
pounds, so they do not concentrate at oil–water inter-
faces. The lower the interfacial tension effect is, the
worse the effect of the crude oil is. Hexadecane and the
simulated oil (mainly C10–16 alkanes) are alkanes. The
higher their molecular weight, the higher the van der
Waals force between them, and the less likely a
surfactant will enrich at the oil–water interface. There-
fore, the surfactant decreases the interfacial tension of
light components more effectively.
25
3.2.3 |Stability
The surface tension (γ
S
) of the original solution was
25.58 mN/m. It was treated at different temperatures for
1 to 2 days. The sample was then cooled to room
temperature and analyzed with a surface tensiometer
(FTA1000 Drop Shape Instrument) at 25°C to determine
the change in γ
S
value. The results in Table 2show that
the surface tension of the fermentation broth changes
little when treated at 25–120°C for 2 days. The surfactant
withstands heating at 120°C and exhibits wide adaptabil-
ity to formation temperature.
The salt tolerance of the surfactant was measured,
and the results are shown in Figure 5. The products in
the fermentation broth exhibit good tolerance to salt.
When the concentration of NaCl reaches 50 g/L, the
surface tension is still decreased to 43 mN/m. Therefore,
FIGURE 4 Changes in interfacial tension
between oils and water with time
2070
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WANG ET AL.
the tolerance of the fermentation broth to NaCl is very
good. Because Glu1 and Asp5 in the surfactin structure
contain COO
−
, it can form salt bridge with the Na
+
counterion to achieve a stable structure and maintain
activity, so it has good tolerance to NaCl.
26
Owing to the complex formation conditions, tempera-
ture, salinity, and other conditions fluctuate widely.
Therefore, good temperature and salt tolerance are
important for normal system functionality.
27
The lipopeptide
in the fermentation broth can withstand the high tempera-
ture of 120°C, and it can be used at different temperatures.
The salt‐tolerance test results show that the lipopeptide has a
high tolerance to NaCl. When the concentration reaches
50 g/L, it still exhibits good surface activity.
3.2.4 |Wettability evaluation
A contact angle of 0° represents total hydrophilicity,
while an angle of 180° represents total hydrophobicity.
28
As shown in Figure 6, the contact angle between the rock
surface and water is reduced from 105.01° to 27.65° by
the fermentation broth and to 39.24° with the 7%
fermentation broth. Thus, it reverses the properties of
the rock surface from hydrophobic to hydrophilic.
Wettability increase is an important mechanism of
microbial oil displacement.
28,29
The change in wettability
is mainly due to the amphiphilic structure of the
biosurfactant easily adsorbing onto reservoir rock, which
makes the oil‐wet surface of the reservoir rock become
water‐wet and is conducive to spalling of the oil film on
the rock surface.
30
3.3 |3.3 Bio‐surfactant flooding results
3.3.1 |Emulsifying ability
It can be seen from Figure 7that the biological surfactant is
more effective than petroleum sulfonate (provided by Daqing
TABLE 2 Variation in surface tension with temperature on
Days 1 and 2
Surface tension (mN/m)
t(℃) 1 day 2 days
25 25.58 25.81
40 25.54 25.79
60 25.64 26.01
80 25.88 25.92
100 25.69 25.84
120 25.66 25.99
Surface tension (mN/m)
t(℃) 1 day 2 days
25 25.58 25.81
40 25.54 25.79
60 25.64 26.01
80 25.88 25.92
100 25.69 25.84
120 25.66 25.99
FIGURE 5 Variation of surface tension
with salt concentration
WANG ET AL.
|
2071
Huali Energy Biotechnology Co. Ltd. The effective concen-
tration is 40%, the amount used in the experiment was 0.3 wt
%), a chemical surfactant commonly used in oil recovery.
Furthermore, the fermentation broth has a good emulsifying
effect on hexadecane and simulated oil, and the emulsifying
effect for simulated oil is stronger than that for hexadecane.
The fermentation broth also has a better emulsification effect
on hydrocarbons with higher light‐component contents,
which is consistent with the results of the interfacial tension
measurements. Compared with the chemical surfactant, the
biosurfactant has a better emulsifying effect.
Crude oil emulsification is one of the core mecha-
nisms of microbial oil displacement.
31
Good emulsifica-
tion ability improves the emulsification and dispersal of
crude oil, making it more easily carried by water, so as to
improve oil displacement efficiency.
32
Zeta‐potential and the strength of the interface film
are two important factors affecting emulsification. The
larger the absolute zeta‐potential value, the larger
the electrostatic repulsion between the droplets in the
emulsion, and the less likely it is to sink, so the emulsion
is more stable.
33
The higher the interfacial shear viscosity
and the stronger the interfacial film,
34
the more difficult
the oil/water emulsion is to disrupt, making it more
stable.
35
Considering the data in Figure 7and Table 3, it can
be seen that the absolute zeta‐potential values for the
fermentation stock broth, 7% fermentation broth, and
petroleum sulfonate increase successively, and the
emulsifying effect becomes worse, which is contrary to
previous research results. Therefore, zeta potential is not
the main factor effecting the emulsification of crude oil
with a surfactant.
Combining the results shown in Figures 7and 8,it
can be seen that the interfacial shear viscosity for the
biosurfactant is greater than that for the chemical
surfactant, that is, the interfacial film strength is greater
and the emulsifying effect is better, which is consistent
with previous studies. Thus, it can be concluded that the
interface film strength is one of the important factors
affecting emulsifying stability.
3.3.2 |Artificial core testing of fermentation
broth
To simulate the microbial oil displacement process,
artificial core tests were carried out in the laboratory.
As can be seen from Figure 9, the addition of xanthan
gum increases the pressure inside the core, leading to a
larger ripple volume, which expands the action range of
the fermentation broth. The saturated oil volume is
6.2 ml. After primary water flooding, 53.2% of the crude
oil can be extracted from the rock core. When the water
cut reaches 98%, the prepared system was used for
secondary oil flooding, and subsequent water flooding
was carried out after 1 PV flooding. Injection system
flooding and subsequent water flooding displaced a total
of 1.16 ml of oil. The fermentation broth preparation
system increases oil recovery by more than 18.7% and
thus has good oil displacement potential for in‐the‐field
use. Xanthan gum alone only improves the oil displace-
ment efficiency by 8%, so 7% fermentation broth
improves oil displacement efficiency by 10.7%.
Artificial core tests have certain disadvantages. An
artificial core is different from natural rock in terms of
structure and uniformity, and because the core is small,
FIGURE 6 Contact angle test results. (A–C) The results for the
fermentation broth, 7% fermentation broth, and water
2072
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WANG ET AL.
even a small error will have a significant impact on the
oil‐displacement effect. However, the natural core of a
target reservoir is not easy to obtain. Although an
artificial core cannot completely replace the natural core,
it can imitate its porosity, permeability, and other
parameters. The experimental results obtained using an
artificial core can reflect the oil displacement ability of a
surfactant. Accordingly, this is the standard experimental
method for simulating oil displacement in the laboratory.
Liu and Feng
36
and many others have carried out oil‐
displacement experiments with artificial cores. Liu et al.
carried out binary composite flooding and ASP flooding
with artificial cores, which shows that this method is
widely used.
37
4|CONCLUSIONS
The following conclusions can be drawn from the results
of this study:
FIGURE 7 Emulsifying effect of different
surfactant systems on hexadecane and
simulated oil
TABLE 3 Zeta‐potential results
Emulsifier
Fermentation
broth
7% Fermentation
broth
Petroleum
sulfonate
Potential (mV) −14.6 −22.5 −29.6
Emulsifier
Fermentation
broth
7% Fermentation
broth
Petroleum
sulfonate
Potential (mV) −14.6 −22.5 −29.6
FIGURE 8 Relationship between shear viscosity and shear
speed
FIGURE 9 Relationship between injection pressure and
injection volume
WANG ET AL.
|
2073
(1) Bacillus subtilis fermentation broth contains lipopep-
tide biosurfactants, and its surface tension can be as
low as 25.84 mN/m, and the interfacial tension
between 7% fermentation broth solution and crude
oil can be as low as 1.24 mN/m.
(2) Even at a temperature of 120°C and a salinity of
50 g/L, the biological fermentation broth still exhibits
good activity and the capacity to act upon crude oil,
demonstrating its excellent temperature and salt
tolerance.
(3) Compared with that for a chemical surfactant, the
interface film strength for an oil–water emulsion
formed by the biological surfactant is higher,
resulting in a crude oil emulsion with higher
stability.
(4) The results of simulated core oil displacement
experiments showed that oil displacement efficiency
is increased by 18.7% using the 7% fermentation
broth, demonstrating its field application potential.
(5) Compared with purified biosurfactant, the biological
fermentation broth is lower in cost and thus has
better prospects for field application.
However, the results of our laboratory‐based research
need to be verified in the field to confirm the practical
value of this strategy.
ACKNOWLEDGMENTS
This study was financially supported by the National key
R & D projects of China (2018YFA0902104).
ORCID
Jianlong Xiu http://orcid.org/0000-0003-3340-0599
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How to cite this article: Wang H, Xiu J, Huang
L, Yu L, Wu B. Study on the application potential
of lipopeptide fermentation broth in oil recovery.
Energy Sci Eng. 2022;10:2065‐2075.
doi:10.1002/ese3.1116
WANG ET AL.
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