Research on Efficient Microbial Enhanced Oil Recovery Technology Based on Low-Temperature Heavy Oil
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Research on Efficient Microbial Enhanced Oil Recovery Technology Based on Low-Temperature Heavy Oil Gang Wu 1, a , Fuping Ren 1,b , Jing You 1,c , Jiliang Yu 1,d , Yatuo Pei 1,e , Shasha Liu 1,f 1 ,Petroleum Production Engineering Research Institute of Hubei Oilfield Company, Renqiu Hebei 062552, P R of China a [email protected], b [email protected], c [email protected], d [email protected], e [email protected], f [email protected] Key words: Low-Temperature and heavy oil, Microbial oil recovery, Huff and puff with single well, Field trial. Abstract: Based on the low- temperature and heavy oil reservoir of conventional injection well pattern separated two strains of oil degradation bacteria LC and JH which had satisfactory compatibleness with BaoLige oill field. In order to study the feasibility of enhancing oil recovery rate of the two strains, the experiment of huff and puff with 15 wells were carried out. The average concentration of bacteria increase from 4.7×10 2 cells/ml to 8.1×10 6 cells/ml. The average reduction of surface tension and viscosity is 33.1% and 31.9%. The accumulative total was 1163.2t. The ratio of input to output was 1:2.12. Microbial enhanced oil recovery can improve the low- temperature and heavy oil production status, which provide a effective method for the similar oil field. Foreword Petroleum is a non-renewable energy. After primary and secondary oil recovery, 60 to 70 percent crude oil in formation remains undeveloped. How to enhance oil recovery has always been one concern in oil production sector. At present, tertiary oil recovery technologies for oil recovery enhancement mainly include: thermal physical treatment, chemical method, gas injection, microbial enhanced oil recovery as well as such new methods as seismic method, ultrasonography method and electromagnetic field excitation method [1] . By contrast, microbial enhanced oil recovery technique has such advantages as lower production cost, simpler construction process, easier operation with varying means, control ease, no damage to the formation and recycle service. Besides, formation contaminant impossibly occurs because of biodegradation of metabolic products and bacterium. This method can improve oil recovery ratio for a longer duration [2] . Microbial enhanced oil recovery(MEOR) is one oil production technology for improving oil recovery ratio by reducing crude viscosity and oil/water interfacial tension as well as lifting formation pressure through interaction of microbe and metabolic products with crude oil in formation. This technology includes two methods: surface fermentation (surface method) and subsurface fermentation (reservoir method). In a narrow sense, microbial oil production technology generally discussed is the second method, i.e. subsurface microbe fermentation [3] . By using this technology, microbe and nutrient medium, selected and evaluated, are injected into reservoir, making oil-bearing reservoir a large fermentation vessel through microbe growth and breeding. Such metabolic products as organic acid, biogas, bio surfactant, bio zyme and biological polymer will be produced to change the rock passages and oil physical and chemical properties so as to enhance oil recovery. During Middle East War in the 1990s, most of American oil companies sponsored their research organizations to develop new techniques including microbial oil production technology with greatest potential. Estimated American crude reserve is 6,490 hundred million barrels, 3,750 hundred million barrels of which is planned to be produced by microbial technology, which accounts for about 58 percent of total reserves [4] . It is thus evident that microbial oil production technology is greatly prospective. Currently, most of domestic oilfields enter production tail with rapid rise of water cut. And chemical method will worsen the pollution of formation and produced water. Microbial oil Advanced Materials Research Vols. 734-737 (2013) pp 1434-1439 Online available since 2013/Aug/16 at www.scientific.net © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.734-737.1434 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 130.207.50.37, Georgia Tech Library, Atlanta, USA-16/11/14,08:24:47)
Transcript of Research on Efficient Microbial Enhanced Oil Recovery Technology Based on Low-Temperature Heavy Oil
Research on Efficient Microbial Enhanced Oil Recovery Technology
Based on Low-Temperature Heavy Oil
Gang Wu1, a, Fuping Ren1,b, Jing You1,c, Jiliang Yu1,d, Yatuo Pei1,e, Shasha Liu1,f
1,Petroleum Production Engineering Research Institute of Hubei Oilfield Company, Renqiu Hebei
062552, P R of China
Key words: Low-Temperature and heavy oil, Microbial oil recovery, Huff and puff with single well, Field trial.
Abstract: Based on the low- temperature and heavy oil reservoir of conventional injection well
pattern separated two strains of oil degradation bacteria LC and JH which had satisfactory
compatibleness with BaoLige oill field. In order to study the feasibility of enhancing oil recovery rate
of the two strains, the experiment of huff and puff with 15 wells were carried out. The average
concentration of bacteria increase from 4.7×102cells/ml to 8.1×10
6cells/ml. The average reduction of
surface tension and viscosity is 33.1% and 31.9%. The accumulative total was 1163.2t. The ratio of
input to output was 1:2.12. Microbial enhanced oil recovery can improve the low- temperature and
heavy oil production status, which provide a effective method for the similar oil field.
Foreword
Petroleum is a non-renewable energy. After primary and secondary oil recovery, 60 to 70 percent
crude oil in formation remains undeveloped. How to enhance oil recovery has always been one
concern in oil production sector. At present, tertiary oil recovery technologies for oil recovery
enhancement mainly include: thermal physical treatment, chemical method, gas injection, microbial
enhanced oil recovery as well as such new methods as seismic method, ultrasonography method and
electromagnetic field excitation method[1]
. By contrast, microbial enhanced oil recovery technique
has such advantages as lower production cost, simpler construction process, easier operation with
varying means, control ease, no damage to the formation and recycle service. Besides, formation
contaminant impossibly occurs because of biodegradation of metabolic products and bacterium. This
method can improve oil recovery ratio for a longer duration[2]
.
Microbial enhanced oil recovery(MEOR) is one oil production technology for improving oil
recovery ratio by reducing crude viscosity and oil/water interfacial tension as well as lifting formation
pressure through interaction of microbe and metabolic products with crude oil in formation. This
technology includes two methods: surface fermentation (surface method) and subsurface
fermentation (reservoir method). In a narrow sense, microbial oil production technology generally
discussed is the second method, i.e. subsurface microbe fermentation[3]
. By using this technology,
microbe and nutrient medium, selected and evaluated, are injected into reservoir, making oil-bearing
reservoir a large fermentation vessel through microbe growth and breeding. Such metabolic products
as organic acid, biogas, bio surfactant, bio zyme and biological polymer will be produced to change
the rock passages and oil physical and chemical properties so as to enhance oil recovery. During
Middle East War in the 1990s, most of American oil companies sponsored their research
organizations to develop new techniques including microbial oil production technology with greatest
potential. Estimated American crude reserve is 6,490 hundred million barrels, 3,750 hundred million
barrels of which is planned to be produced by microbial technology, which accounts for about 58
percent of total reserves[4]
. It is thus evident that microbial oil production technology is greatly
prospective. Currently, most of domestic oilfields enter production tail with rapid rise of water cut.
And chemical method will worsen the pollution of formation and produced water. Microbial oil
Advanced Materials Research Vols. 734-737 (2013) pp 1434-1439Online available since 2013/Aug/16 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.734-737.1434
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 130.207.50.37, Georgia Tech Library, Atlanta, USA-16/11/14,08:24:47)
production technology, which complies with friendly environmental protection and sustainable
development proposed in “twelfth five-year” program, is compatible with reservoir and metabolic
product prevents from polluting the formation. Meanwhile, this technology enables to improve
ultimate recovery of oilfield and will not bring difficulties to later production.
Baolige oilfield, with high content of crude gum bitumen and poor water flooding efficiency, is
low-temperature heavy crude reservoir developed by conventional water flooding. In view of this,
strains LC and JH, which can produce grease peptide bio surfactant and degradation gum, are selected
within reservoir. Laboratory experiment proves that these bacteria are better compatible with
reservoir and viscosity breaking rate reaches 60.1 percent[5]
. To further verify whether they are
practical or not, these two bacteria are injected in 15 wells in Baolige oil filed. After treatment, oil
physical property is obviously improved, surface tension of produced water reduces and oil-aqueous
interface is improved, which shows better stimulation effect.
Baolige Oill Field Description
In this field, oil-bearing area is 6.37 km2, geologic reserve is 1238.97×10
4t and recoverable
reserve is 186×104t. Depositional environment is fan delta deposit system. In this block fault, worse
crude oil physical property appears. Mean wax content is 10.6 percent, average gum asphaltene is
48.4 percent, mean oil density is 0.9078g/cm3, average oil viscosity is 402mPa·s, freezing point
ranges from 28 to 30˚C, reservoir depth ranges from 853 to 1043m, average reservoir depth is 1000m,
average reservoir temperature is 38˚C, total salinity is 7813.5mg/l and formation pressure is 9.93Mpa.
Oil physical property and formation conditions provide the conditions for microbial enhanced oil
recovery. Therefore, for shooting the troubles in development of Baolge oil field, two bacteria species
are selected by laboratory experiment for efficiently breaking viscosity and are applied in 15 wells.
Experimental Materials and Methods
3.1 Experimental Materials. For this experiment, the materials include GC-112A gas
chromatograph （ Agilent ） , constant temperature incubator (SANYO MIR-262), microscope
(OLYMPUS BX43), rotational viscosimeter (BROOKFIED, DV-III+pro), surface tensiometer
(model QBEY, Chinese), centrifugal machine and bacteria LC and JH. For characteristics of bacteria,
see Table 1.
Table 1 Bacteria Species Characteristics
Code Number Genus Metabolization Property
LC Bacillus subtilis sp. Gas Production
JH Pseudomonas sp. Grease-Peptide Surfactant
Nutrient solution formula is as follow: 0.25 percent glucose, 0.25 percent molasses, 0.15 percent
ammonium chloride, 0.1 percent albumen peptone, 0.15 percent zyme cream and 0.1 percent
ammonium dihydrogen phosphate.
3.2. Experimental Method . Bacteria concentration measurement: Dilution Coating Plate Method
Crude oil viscosity measurement: After heated, free water is removed from crude oil at
2000r/min for 20 minutes of centrifugation. And then, keeping at 50˚C constant temperature for 10
minutes, oil viscosity can be measured by Brookfield viscometer at 0.6rpm.
Surface tension measurement: Crude oil is removed from produced fluid. Surface tension can be
measured by surface tensiometer at ambient temperature.
Field Application Analysis of Microbian Huff and Puff
4.1. Treatment Fluid Injection Rate for Single Well. Bacteria is finalized for use based on
laboratory experiment for individual wells. Fermentation liquor of LC and JH is mixed by 1:1 to
prepare mixed bacteria. Bacteria solution concentration is 2.0 percent and adding nutrient solution
Advanced Materials Research Vols. 734-737 1435
concentration is 1.0 percent. The solution is injected into the formation through the casing by
cementing truck at wellhead. All wells in this field are treated by fracturing, therefore, injected
bacteria liquor and nutrient solution will flow into the formation along the fracture length direction
and diffuse horizontally to shape one cuboid swept area. Flooded liquid volume should be calculated
for covering this swept area. The length and width of swept area are 50m and 1m, respectively. The
thickness is determined by pay zone: For individual bed, the thickness of swept area is reservoir
thickness; for multiple zone, the thickness is one third of gross pay affected by water flooding. The
rectangle volume is defined by the method above mentioned. Treatment fluid injection rate is
calculated by the Eq.1:
Vc = fc×L × H×Φ (1)
In which, Vc: basic volume of injected microbial solution, m3;
L: treated area length, 50m;
H: net pay thickness, m;
Φ: reservoir porosity;
fc: comprehensive factor.
Injection volume and bacteria applied in every single well are shown in Table 2.
Table 2 Injection Volume and Bacteria Applied in Every Single Well
Well No.
Reservoir
Thickness
[m]
Treated
Length
[m]
Porosity
[%]
Designed Treatment
Fluid Volume
[m3]
Bacteria
Species
B51-11 2.5 50.0 19.0 23.6 LC+JH
B51-14 7.8 50.0 20.1 26.1 LC
B51-17 4.2 50.0 18.25 38.3 LC+JH
B51-19 12.2 50.0 22.3 45.3 JH
B51-43 14.3 50.0 11.7 27.9 LC+JH
B51-50 4.5 50.0 12.4 26.1 LC
B51-28 9.6 50.0 15.7 25.1 LC+JH
B51-73 7.8 50.0 20.2 78.8 JH
B51-49 10.8 50.0 19 34.2 LC
B51-33 15.4 50.0 17.8 45.7 LC+JH
B51-79 16.8 50.0 14.9 41.7 LC+JH
B51-24 16.5 50.0 20.3 55.8 JH
B51-34 4.5 50.0 24.7 55.6 LC
B51-32 6.8 50.0 12.5 42.5 LC
B51-3 8.3 50.0 13.8 57.3 LC
Note: Upon completion of treatment, fresh water should be injected as displacement fluid.
4.2. Produced Fluid Monitoring. After treatment, the well is shut in for five days followed by
startup. The production stays in normal state. Three days later, cell concentration of produced fluid is
monitored. Comparison of cell concentration, produced fluid surface tension and oil viscosity are
respectively shown in Fig. 1, 2 and 3.
1436 Resources and Sustainable Development
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
B51-11 B51-14 B51-17 B51-19 B51-43 B51-50 B51-28 B51-73 B51-49 B51-33 B51-79 B51-24 B51-34 B51-32 B51-3
Oill wells
lg(C
on
ce
ntr
ati
on
,CF
U)
Pre-Treatment
Post-T reatment
Fig.1 Cell Concentration Comparison Between Pre-Treatment and Post-Treatment
After treatment, cell concentration increase to 8.1×106cells/ml from 4.7×10
3 cells /ml before
treatment, which shows that microbe growth in formation stays in sound state and the microbe is
greater compatible with formation.
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
B51-11 B51-14 B51-17 B51-19 B51-43 B51-50 B51-28 B51-73 B51-49 B51-33 B51-79 B51-24 B51-34 B51-32 B51-3
Oill wells
Surface tension,mN/m
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
Reduced rate,%
Pre-Treatment
Post-Treatment
Reduced Rate
Fig.2 Surface Tension Comparison Between Pre-Treatment and Post-Treatment
After treatment, surface tension drops by 33.1 percent, which shows that bio surfactant is
produced during the course of mycrobial growth and breeding in formation.
0.0
500.0
1000.0
1500.0
2000.0
2500.0
3000.0
3500.0
B51-11 B51-14 B51-17 B51-19 B51-43 B51-50 B51-28 B51-73 B51-49 B51-33 B51-79 B51-24 B51-34 B51-32 B51-3
Oill wells
viscosity,mPa.s
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
Reduced rate,%
Pre-Treatment
Post-Treatment
Reduced rate
Fig.3 Crude Oil Viscosity Comparison Between Pre-Treatment and Post-Treatment
After treatment, average crude viscosity drops by 31.9 percent, which shows that microbe does
play the role in thinning out the crude and boosting crude flowability.
4.3. Crude Oil Component Analysis. B51-49 is selected as representative well to analyze the crude
oil component before and after microbial huff and puff with GC-112A gas chromatograph
(chromatographic column: PEG-20M capillary chromatographic column, 30 m×0.25 mm×0.33 µm).
Gas chromatography conditions are as follows: initial temperature of column is 40˚C and temperature
rise rate is 2˚C/min. When the temperature reaches 200˚C, the temperature will keep rising to 290˚C
at 6˚C/min rise rate. The constant temperature will remain unchanged until no more peak value
appears. Total hydrocarbon analysis of produced oil before and after microbial huff and puff is shown
in Fig.4.
Advanced Materials Research Vols. 734-737 1437
Fig.4 Crude Oil Component Comparison Between Pre-Treatment and Post-Treatment
Total hydrocarbon gas chromatograph analysis tells us that the relative content of different oil
components changes obviously after microbial huff and puff, i.e., the relative content of heavy
component decreases while that of light component increases.
The relative content change of crude oil components after microbial huff and puff is shown in
Fig.5.
It can be seen from Fig. 5 that microbial breeds in the formation and interacts with crude oil.
Bacteria for MEOR has biodegradation against crude heavy component in Well B 51-49. The relative
content of long chain hydrocarbon decreases and that of light component increases. Therefore,
bacterial species which degrades heavy component should be selected.
4.4. Production Curve. Microbe grows in the formation and thins out the crude to improve oil
physical properties. Baolige oilfield production curve is shown in Fig.6.
Fig.6 Liquid Production Capacity of Baolige Oil Field
M
E
O
R
1438 Resources and Sustainable Development
After treatment, accumulative stimulation reaches 1163.2t calculated by critical point method.
Treatment expense for 15 wells is totally 2.25 million RMB calculated by 4100RMB/t of crude oil.
Input/output ratio is 1:2.12.
Conclusions
(1)Through cyclic injection in single well, two bacteria are selected to reduce average crude
viscosity by 31.9 percent and average surface tension by 33.1 percent. Mycobiont can grow and breed
in the formation for the purposes of improving crude physical property, increasing light component
and decreasing heavy component.
(2)Through field experiment, accumulative stimulation of 15 wells is 1163.2t with input/output
ratio 1:2.12.
(3)The case history of microbial enhanced oil recovery technology in low-temperature heavy
crude provides a solution to similar reservoir and settles the theorical foundation for application of
environment friendly technology MEOR in oilfields.
References
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2009, Vol 24 ,No 4. Pg58-61. In Chinese.
[2] Shiwei Huang, Tingshan Zhang, Jin Huo etc. Petroleum Geology and Engineering, Vol 20 ,No 1,
Jan 2006. Pg46-49. In Chinese.
[3] Mutai Bao, Bozhong Mu, Xiulin Wang etc. Journal of basic Sience and Engineering,Vol 8,No 3,
Sep 2000. Pg236-245. In Chinese.
[4] Information on http: //www. net.l doe. gov/scngo/Petroleum /Explora-tion% 20&% 20Production/
[EOR /eor. htmlS, 2008-05-01.
[5] Qing Li, Gang Wu, Gang Xie etc.Oill Drilling &Production Technology, Vol.33 No.2,Mar.2011.
Pg114-116.
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