Research and Application of Microbial Enhanced Oil Recovery
Technology in High Waxy Oil Reservoirs
Rui Wang
1a
, Guan Wang
1
, Pei Wang
2
, Shasha Liu
1
, Chao Wang
1
, Jizhe Jing
1
, Ying Liu
1
,
Yajuan Tang
1
, Jinxiu Du
1
and Dong Xuan
3
1
Engineering Technology Research Institute, Huabei Oilfield Company of PetroChina, Renqiu, Hebei, China
2
The Forth Exploitation, Huabei Oilfield Company of PetroChina, Lang Fang, Hebei, China
3
Production Management Department, Huabei Oilfield Company of PetroChina, Renqiu, Hebei, China
Keywords: High Waxy Oil Reservoir, Microbial Oil Recovery, Compound Bacteria, Nutrition System.
Abstract: To solve the problems of high wax content and high freezing point in block Q, the compound strain which
could reduce wax content by 40% was selected through laboratory experiment and performance evaluation.
The nutrition system formula suitable for the target reservoir was obtained. After the formulation system
was applied to block Q, the colloid asphaltene and wax content of crude oil decreased, which was directly
reflected in the decrease of viscosity and solidifying point of crude oil. The solidifying point decreased by
12℃. The oil well fluid production increased and watercut decreased, achieving oil-increasing effect.
1 INTRODUCTION
1
The average porosity of block Q is 28.8% and
average permeability is 197.1mD, which is a high
porosity and medium permeability reservoir. The
high waxy content (32.1%) and high solidifying
point (40.1℃) leaded to poor liquidity and serious
paraffin precipitation in wellbore. After water
flooding development, the temperature of
near-well-bore area decreased. The precipitation and
deposition of wax blocked near-well-bore area and
reduced the permeability. The wax precipitation in
well shaft, string and borehole is serious. It seriously
affected the normal production and restricted the
efficient development of oil fields.
In order to solve the problems of high wax
content and poor fluidity of block Q, the degradation
of paraffin in crude oil by microorganisms and the
improvement of rheological properties by
metabolites were studied. The microorganisms for
wax removal generally use wax, colloid and
asphaltene as carbon sources (Qin 2015, Chen 2004,
Yi 2009), which can actively degrade the heavy
components, thus reducing the viscosity and
improving the fluidity of crude oil (Wang 2017,
Wang 2017). Microbial oil recovery technology is
a
https://orcid.org/0000-0001-7876-3954
simple in construction and has a long validity
period. It can avoid damage to oil layer caused by
hot washing with non-toxic and odor-free. It is safe
and environmentally friendly, and has good
economic, social and environmental benefits.
2 BACTERIA SCREENING
Experimental conditions: Crude oil, produced water
and injected water from block Q, temperature of
52℃.
Experimental methods: 100ml of produced water
was taken by 2% of the bacteria solution. 10g of oil
sample was added. After mixing, the sample was put
into a constant temperature shaker and cultured at
52℃. A blank test was conducted at the same time.
After 72 hours, the change of crude oil performance
was evaluated (Liu 2001, Shi 2008).
2.1
Adaptability Evaluation of Strain
Species and Reservoir
Environment
The strains were inoculated into the produced and
injected water for fermentation and culture, and then
the concentration of bacteria was observed with a
counter. The results showed that 11 selected strains
Wang, R., Wang, G., Wang, P., Liu, S., Wang, C., Jing, J., Liu, Y., Tang, Y., Du, J. and Xuan, D.
Research and Application of Microbial Enhanced Oil Recovery Technology in High Waxy Oil Reservoirs.
DOI: 10.5220/0011190200003443
In Proceedings of the 4th International Conference on Biomedical Engineering and Bioinformatics (ICBEB 2022), pages 127-131
ISBN: 978-989-758-595-1
Copyright
c
2022 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved
127
grew well in formation and injection water. The
bacteria concentration was from 2.1×10
8
to 5.4×10
8
/mL, showing perfect adaptability.
Table 1: Comparison of bacterial concentration in different
production environments (10
8
/ml).
Bacterial Produced wate
r
Injected wate
r
1903 3.00 3.12
HB3 5.28 5.07
BB2 2.96 3.45
1906 2.52 2.67
DM-2 3.43 3.12
1665 3.54 3.77
5S 5.44 5.37
5BQ 3.47 3.62
6H 2.89 3.37
6B 3.22 3.47
5BZ 2.14 2.66
2.2 Emulsification Effect Evaluation
The selected strains had different degrees of
emulsification effect after acting with crude oil,
among which 6H, 6B, 5S, 5BQ and 5BZ had the best
emulsification effect, and oil and water were
completely mixed without obvious stratification.
Table 2: Oil emulsification comparison.
Bacterial Emulsification level
1903 4
HB3 3
BB2 4
1906 4
DM-2 4
1665 4
5S 5
5BQ 5
6H 5
6B 5
5BZ 5
The level is based on < Q/SY HB 0209-2016>.
2.3 Viscosity Reduction Evaluation
According to the experimental results, 5S, 6H and
6B had better viscosity reduction effect.
Table 3: Comparison of viscosity reduction effects of
different strains.
Bacterial Viscosity, mPa.s Reduction rate, %
Blan
k
39.8
/
1903 29.1
26.85
HB3 35.6
10.58
BB2 42.1
-5.80
1906 32.1
19.34
DM-2 43.2
-8.57
1665 33.5
15.65
5S 25.4
36.02
5BQ 30.2
24.10
6H 25.8
35.17
6B 27.4
31.02
5BZ 32.3
18.76
3 NUTRITIONAL SYSTEM
SCREENING AND
EVALUATION
3.1 Nutritional System Screening
The selection of nutrients follows these principles:
(1) Five nutrient elements for strain growth are
basic. (2) The cost is low. (3) A good effect of strain
proliferation and viscosity reduction is needed. (4)
The compatibility with reservoir formation water is
well with no precipitation reaction.
Crude oil is the main carbon source, and glucose
and sucrose are added as supplements. Nitrogen
sources are mainly nitrate, ammonium salt, urea, etc.
Inorganic salts are phosphate, sulfate and
compounds containing sodium, potassium and other
metallic elements. Growth factors are mainly
vitamin, amino acid, purine and pyrimidine. Yeast
extract and peptone contain production factors.
Based on the above principles, six formulas in Table
4 are formed.
Table 4: Six different microbial formulations (unit: %).
Component F-1 F-2 F-3 F-4 F-5 F-6
Nitrogen source a 0.25 0.20 * * * *
Nitrogen source
b
* * * 0.45 0.45 0.45
Sodium 0.10 0.10 0.10 * * *
Growth factors 0.20 0.20 0.20 0.10 0.15 *
Inorganic salt a * 0.35 0.35 0.01 0.01 *
Inorganic salt
b
0.35 0.35 * * 0.35 0.35
Inorganic salt c 0.35 * 0.50 0.40 * 0.35
Nitrogen source c * * 0.45 0.45 0.45 0.45
ICBEB 2022 - The International Conference on Biomedical Engineering and Bioinformatics
128
Inorganic salt
d
0.03 0.03 0.03 * * *
Microelement 0.17 0.17 0.17 * * *
Carbon source 0.10 0.10 0.10 * * *
3.1.1 Emulsifying and Dispersing Effect
After being activated for 24 hours, 2% of selected
strains were transferred to the corresponding
nutritional formula added with 10% of crude oil. The
culture medium was carried out on a 150rpm shaker
at 52℃ for 5 days. Then the dispersion performance
was evaluated by using NIR Turbiscan with the
instability coefficient. The higher the instability
coefficient was, the better the dispersion
performance was. The results showed that 6H, 6B
and 5S of the selected strains had strong emulsifying
and dispersing effect in two different formulations.
But the emulsifying and dispersing effect was better
when the three strains were mixed in equal
proportion.
(a) F-3
(b) F-6
Figure 1: Dispersion effects comparison of different
strains.
3.1.2 Surface Activity of Microbial
Fermentation Broth
The culture solution was centrifuged (at 5000rpm for
20min), and the residual crude oil and cells were
removed by extraction and filtration to obtain a clear
liquid sample. The surface tension was measured
after standing at 25℃ for 1 hour. The results showed
that the combination strain could better reduce the
surface tension.
Figure2: Comparison of surface activities of different
strains.
3.1.3 Viscosity Reduction Effect
The strains were inoculated into a mixture of crude
oil sample and nutrient solution at a ratio of 3:7, and
cultured on a shaker for 5 days. Then the samples
were dehydrated to test the crude oil viscosity. The
experimental results were shown in Figure 3. The
results showed that the compound formula had
better viscosity reduction effect.
Figure 3: Comparison of viscosity reduction effects of
different formulas.
The wax content and freezing point of crude oil
were measured after dehydration. The experimental
result showed that F-3 had better effect.
Table 5: Comparison of wax content and freezing point of
different strains.
Wax
content
%
Decline rate
%
Freezing
point
℃
Blan
k
30.84
/
41.3
F-3 18.47 40.1 28.2
F-6 24.27 21.3 32.5
Research and Application of Microbial Enhanced Oil Recovery Technology in High Waxy Oil Reservoirs
129
3.2
Evaluation of Formula
Optimization
In order to further reduce the field injection cost, the
formulation 3 and 6H, 6B and 5S were selected for
further optimization. By comparing the properties of
different formulas, N-2 had better effect of
emulsifying, reducing wax content reducing and
crude oil viscosity decline.
Table 6: Optimized system formula (unit: %).
Component F-3 N-1 N-2 N-3
Microorganism 2.00 2.00 2.00 2.00
Sodium 0.10 0.08 0.05 0.03
Growth factors 0.20 0.15 0.10 0.05
Inorganic salt a 0.35 0.30 0.25 0.20
Inorganic salt c 0.50 0.35 0.25 0.20
Nitrogen source c 0.45 0.35 0.20 0.10
Inorganic salt d 0.03 0.02 0.01 0.01
Microelement 0.17 0.10 * *
Carbon source 0.10 0.10 0.10 0.10
Table 7: Performance parameters comparison of optimized
systems.
Formula Blank F-3 N-1 N-2 N-3
Viscosity
mPa.s
39.8 17.2 17.5 17.9 18.9
Surface tension
mN/m
56.50 38.15 40.12 40.65 42.31
Wax content
%
30.84 18.47 18.67 17.95 19.34
4 FIELD APPLICATION EFFECT
From 2019 to 2020, microbial oil recovery was
carried out in 2 well groups in block Q. After the
measures, the total bacterial concentration was
effectively increased from 10
4
/mL to 10
7
/mL. The
surfactant content was increased from 12.1mg/L to
60.4mg/L, which was conducive to crude oil
recovery. After microbial action, the gelatinous
asphaltene content and wax content decreased,
which was directly reflected in the decrease of the
viscosity and freezing point of crude oil. The
freezing point decreased by 12℃. The ascending
current of oil well decreased significantly and the
load was reduced.
Figure 4: Changes of microbial concentration of well Q53.
Table 8: Changes of crude oil properties before and after
the microbial measures of Q53.
Time
Before Afte
r
Viscosity, mPa.s 16.1 9.8
Wax content, % 40.3 30.1
Freezing point, ℃ 40.0 28.0
Colloid asphaltene content, % 8.6 8.3
Saturated hydrocarbon content, % 62.2 54.2
After the implementation of huff and puff, the
liquid production of well Q53 increased and
watercut decreased. The daily production of liquid
increased from 2.1t/d to 5.3t/d. The daily production
of oil increased from 0.8t/d to 3.2t/d, watercut
reduced by 22.3%. The accumulative oil was 266t.
Figure 5: Production curve of well Q53.
5 CONCLUSION
1. Aiming at high waxy oil reservoirs, the selected
strains have good compatibility with the target
reservoir. After the compound strains act with crude
oil, miscible emulsification can occur in oil and
water. The surface tension is reduced by 32.47%, the
wax content is reduced by 40.1%, the viscosity of
crude oil is reduced by 56.7%, and the fluidity of
crude oil is improved.
2. The microbial recovery measures in block Q
take effect significantly, which suggest that MEOR
can improve oil displacement efficiency. This
technology provides the theoretical and practical
ICBEB 2022 - The International Conference on Biomedical Engineering and Bioinformatics
130
support for MEOR of high waxy reservoir and can
become one of the effective means to increase
production in the late waterflood development.
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