research on microbial restoration of methane deposit with

- 1 -

Research on Microbial Restoration of Methane Deposit

with Subsurface CO2 Sequestration

into the Depleted Oil Fields

Kazuhiro Fujiwara*, Yoshiyuki Hattori

*, Hiroshi Ohtagaki

*, Takamichi Nakamura

*, Takahiro

Asano* and Komei Okatsu

**, Yuichi Sugai

***

* Chugai Technos Corp.

** Japan Oil, Gas and Metals Natl. Corp.

*** Kyushu Univ.

Abstract

Research into the microbial restoration of methane deposits (MRMD) system has

been carried out since 2003. The final objective of this research is to developing

microbial restoration system of methane deposits using subsurface sequestered CO2 and indigenous

anaerobes in depleted oil fields. As the past findings, some hydrogen-producing thermophilic

bacteria (HPTB) and methane-producing thermophilic archaea (MPTA) which

participate in the microbial restoration of natural gas have been detected at the DNA

level in some of producing water and successfully isolated. After hydrogen and methane

production from indigenous anaerobes inhabiting a reservoir have ascertained, feasibility of

MRMD system has estimated by primitive economic assessment. Furthermore, detailed

studies of accelerating conditions for hydrogen and methane production have been conducted

under real reservoir condition. Through this research, it has been shown that the velocity of

hydrogen and methane production have been enhanced respectively by adding some

unique inorganic additives. These data indicate that depleted oil reservoirs are potentially good

candidates to become subsurface microbial reactors and the productivity of hydrogen and methane

by indigenous anaerobes in oil reservoir may have controlled artificially.

1. Introduction

It is well known that CO2 is considered to be the major factor of global warming. Due to the

increased emissions of CO2 throughout the world, the CO2 in our atmosphere is at its highest levels

since record keeping began. Against this background, industries and governments are increasingly

looking into subsurface CO2 disposal and storage technologies as potential methods to reduce

greenhouse gas emissions in the atmosphere. On the other hand, consumption of natural gas has

been rising significantly worldwide. This means that development of sources of perpetual natural

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gas will take place incrementally over the short term.

The ongoing research on Microbial Restoration of Methane Deposits (MRMD) system provides

the twin dividend of reducing CO2 emissions and improving production of natural gas. This

technology has expected closer to reality because recent geochemical considerations and

geomicrobiological data1-6) have indicated that the anaerobic biodegradation of hydrocarbon and

conversion to methane in the deep subsurface may proceed by anaerobic microbial consortium.

From the viewpoint of resource recovery, the MRMD system presented in this study has regarded as

one of enhanced gas recovery (EGR) technique associated with the microbial gasification process

from crude oil. Namely, this MRMD system may also lead to give incentive to CO2 sequestration

technologies such as CCUS-EOR (Carbon dioxide Capture, Utilization and Storage with enhanced

oil recovery).

2. Microbial restoration process

We have been researching the sustainable carbon recycling system (Fig. 1) since 20036). The

final objective of our research is to develop the MRMD system using subsurface sequestered CO2

and indigenous anaerobes in depleted oil fields. This technology has the potential not only to

dispose of CO2, but to produce methane (Fig. 2).

On the MRMD system, we have been focusing on hydrogen production by hydrogen-producing

thermophilic eubacteria (HPTB) which can utilize a variety of carbon source such as hydrocarbones.

This hydrogen and the injected CO2 into the reservoir have also used as substrate for methane

production by Methane-producing thermophilic archaea (MPTA). (Fig. 3)

There are two approaches to the field operation technique of this MRMD system (Fig. 2). One

operation involves injecting only nutrient into the oil reservoir and allowing indigenous anaerobes to

produce the methane. The other operation involves injecting nutrient and anaerobes simultaneously

into the oil reservoir. In the present study, we are especially focusing on the latter operation,

because it can be used in oil reservoirs around the world regardless of the presence or absence of

hydrogen and methane producing anaerobes.

3. Approaches of our research

Over the coming years, we have been considering some subjects shown in below as the urgent and

extremely important issues for the practical use of MRMD system. In these issues, we have already

conducted on the Step 1 to 8 and the outlines of these results are overviewed in this paper.

(Step 1) Analysis of microbial diversity in the oil reservoir (reservoir brine and crude oil).

(Step 2) Ascertainment of hydrogen and methane production by indigenous anaerobes.

(Step 3) Feasibility study of MRMD system by priliminary economic assessment.

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(Step 4) Evaluation of hydrogen and methane production potential under real reservoir condition

and estimation of microbial methane producing pathway.

(Step 5) Direct verification of microbial conversions (crude oil to hydrogen and CO2 to CH4).

(Step 6) Detailed studies of accelerating conditions for the velocity of hydrogen production by

HPTB.

(Step 7) Detailed studies of accelerating conditions for the velocity of methane production and

conversion efficiency to methane by MPTA

(Step 8) Construction of suitable numerical simulation model for MRMD system in order to

evaluate experimental results step1 to 7..

(Step 9) Design of a field operation for MRMD system (including the injectivity of HPTB and

MPTA cells into porous media, and the design of state of CO2 that can become the

substrate of the methane production).

(Step 10) The grasping of microbial diversity related to MRMD system in the domestic and

overseas oil reservoir.

(Step 11) Ascertainment of conditions for methane production by indigenous anaerobes in reservoir

based on the field operation tests.

(Step 12) Economic assessment of MRMD system with high accuracy based on the field operation

test.

4. Previous research and major results

(1) Analysis of microbial diversity in the oil reservoir

In 2004, geological, reservoir engineering and microbiological studies have conducted at the

laboratory level to collect data which has been suggested a technological possibility of MRMD

system (Table 1). In particular, hydrogen and methane producing microbes which participate in

MRMD system have been investigated in detail using some microbial gene engineering techniques.

In order to use above investigation, some reservoir samples such as reservoir brine and crude oil

have taken from well head or bottom hole of oil/gas wells. As the results, it becomes clear that the

MRMD system could have applicable to some domestic oil/gas field (Table 2, 3)6). In addition,

some HPTB and MPTA have been detected and isolated successfully (Fig. 4). These different

kinds of microbes have participated in the MRMD system.

(2) Ascertainment of hydrogen and methane production through the accelerated tests

Hydrogen and methane producing experiments, using carbohydrates, such as glucose, as a carbon

source, have been conducted at the laboratory level to estimate the potential for microbial methane

production under actual reservoir pressure (5MPa), temperature (50°C) and the rock pore as micro

culture space6). Results of some experiments, using the isolates from reservoir samples and

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reservoir brine including active anaerobes which participate in the MRMD system have indicated

that microbial hydrogen and methane producing efficiency and velocity are relatively high even in

various reservoir conditions.

(3) Feasibility study of MRMD system with primitive economic assessment

The economic viability of the MRMD system in the case of after CCS process have evaluated

preliminary at the Yabase oil field in Japan (Table 4). Based on the maximum velocity of methane

generation obtained in the accelerated tests using carbohydrates as a carbon source, sum of the

incomes from methane selling and CO2 emissions rights trading exceeds the CO2 separation and

sequestration costs, even when molasses is used as the carbon source for the MRMD system6). The

data indicate that depleted oil reservoirs are potentially good candidates to become subsurface

microbial reactors.

(4) Evaluation of hydrogen and methane production potential under real reservoir condition

If the crude oil is available as a suitable and economical carbon source, depleted oil reservoirs are

potentially good candidates to become subsurface microbial reactors using the HPTB. To estimate

the possibility of an actual system in the deep subsurface, a lot of experiments, namely, productivity

of hydrogen from crude oil by the HPTB and productivity of methane by MPTA have been

conducted under real reservoir conditions. Through this research, it has shown that hydrogen has

been produced by HPTB from crude oil and CO2 has also been converted to methane by MPTA

under the conditions of actual reservoir circumstances such as pressure (5MPa) and/or temperature

(75°C) (Fig. 5). In addition, microbial methane producing pathway comprised of some kinds of the

HPTB and MPTA has able to demonstrate successfully based on these results7)(Fig. 6).

(5) Direct verification of microbial conversion

Through the culture experiments under the reservoir condition using hexadecane labeled by stable

isotope (13C), it has shown that

13C of hexadecane has been taken in some HPTB’s DNA. Hence,

this result has directly indicated that some HPTB can use the crude oil as a carbon source and

produce hydrogen.

Up until now, there is a little study concerned with examining the conversion efficiency of

injected CO2 to CH4. Then, lots of data on methane productivity by MPTA from CO2 injected into

the culture system have been also collected to estimate the possibility of an actual reaction of

methane production taking place in the deep subsurface. This research applying CO2 labeled by

stable isotope (13C) has shown that methane has been produced using CO2 injected into the head

space of culture system by a MPTA (such as consortium MYH-4 including Methanothermobacter

thermoautotrophicum). On that occasion, the conversion efficiency of CO2 gas to CH4 is 56.5%

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while the conversion efficiency of HCO3- to CH4 is low. These data have indicated that gaseous

CO2 in the subsurface reservoir can be used preferentially by the MPTA8). To evaluate the

economical viability of the MRMD process, the methane conversion rate is indispensable.

(6) Development of accelerating technique by additives

The experiments that accelerated methane production through the addition of certain compounds

have been conducted at the laboratory level9). Enhancing the velocity of hydrogen production has

achieved by combining the multiple HPTB, adding inorganic additives (such as, electric accepter,

active center of hydrogenase) and MPTA as a consumer of hydrogen. The present results imply the

hydrogen generation speed have able to promote up to 10~100 times. In addition, these data also

have made some anticipation, such as the discovery of other additives to speed up hydrogen

generation.

Enhancing the velocity of methane production has also been achieved by adding gaseous CO2 at

20% volume of head-space into the culture system. In some cases, the methane generation speed

has made the target of approximately 700% achievable on the results of evaluating the valuable

additives, such as vitamin, nitrogen source and phosphorus.

These data indicate that the productivity of hydrogen and methane by indigenous anaerobes in oil

reservoir may have controlled artificially.

(7) Development of accelerating technique by cells adsorption

Adsorption of HPTB and MPTA cells on the surface of reservoir rock (silica sand) has also

studied by measuring their zeta potentials and observing their adsorption in porous media with

fluorescent staining method (Fig. 7). Consequently, zeta potentials of the HPTB, MPTA and

reservoir rock are all negative and adsorption ratio of HPTB and MPTA on the surface of reservoir

rock has able to change by the decrease in pH value and the increase in salinity. In the case of the

culture experiments of the HPTB and MPTA in porous media with reservoir brine, almost all

microbial cells have adsorbed into the reservoir rock. Moreover, it is assumed that the ability of the

hydrogen production by the HPTB and methane production by MPTA adsorbed on the rock surface

has become higher than that of free bacteria in porous media.

5. Future challenges

The MRMD system presented in this paper may meet an important component of the global

energy economy. Hence, it is indispensable that residual challenges such as step 9 to 12 described

in the section on “Approaches of our research” will accomplish for the practical use of the MRMD

system, as well as detailed studies of step 1 to 8.

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6. Conclusion

To summarize the data, the following conclusion can be drawn.

(1) The MRMD system may lead to give incentive to CO2 sequestration technologies such as

CCUS-EOR (Carbon dioxide Capture, Utilization and Storage with enhanced oil recovery).

(2) In the past findings, indigenous anaerobes in oil reservoir which participate in MRMD system

have been isolated.

(3)The pathway and the accelerating conditions of microbial methane generation have also been

elucidated.

(4) But then, there are many obstacles to be resolved for the field operation and the practical use of

MRMD system.

References

1) Head, I. M., Jones, D. M. and Larter, S. R.:” Biological activity in the deep subsurface and the origin of heavy

oil“, Nature, 246 p.344 2003

2) Larter, S. R., Wilhelms, A, Head, I, Koopmans, M., Aplin, A., Diprimo, R., Zwach, C., Erdmann, M. and Telnaes,

N.:”The controls on the composition of biodegraded oils in the deep subsurface –part 1: biodegradation rates in

petroleum reservoirs”, Org. Geochem., 34 p.601 2003.

3) Anderson, T. R. and Lovley, R. D.:”Hexadecane decay by methanogenesis”, Nature, 404 (2000) 722.

4) Bonch-Osmolovskaya, A. E., Miroshnichenko, L. M., Lebedinsky, V. A., Chernyh, A. N., Nazina, N. T., Ivoilov,

S. V., Belyaev, S. S., Boulygina, S. E., Lysov, P. Y., Perov, N. A., Mirzabekov, D. A., Hippe, H., Stackebrandt,

E., Stéphane Haridon, L. S. and Jeanthon C.:”Radioisotopic, Culture-Based, and Oligonucleotide Microchip

Analyses of Thermophilic Microbial Communities in a Continental High-Temperature Petroleum Reservoir”,

Appl. Envir. Microbiol. 69 p.6143 2003

5) Townsend, T. G., Prince, C. R. and Suflita, M. J.:”Anaerobic Oxidation of Crude Oil Hydrocarbons by the

Resident Microorganisms of a Contaminated Anoxic Aquider” Environ. Sci. Technol. 37 p.5213 2003.

6)K. Fujiwara, T. Mukaidani, S. Kano, Y. Hattori, H. Maeda, Y. Miyagawa, K. Takabayashi, K. Okatsu, Research

Study for Microbial Restoration of Methane Deposit with Subsurface CO2 Sequestration into Depleted Gas/Oil

Fields, Proceeding of Society of Petroleum Engineers, Asia Pacific Oil and Gas Conference and Exhibition,

Adelaide, Sep. 11-13, 101248, 2006

7) S. Kano, T. Mukaidani, Y. Hattori, K. Fujiwara, Y. Miyagawa, K. Takabayashi, H. Maeda, Diversity of indigenous

anaerobes and methane conversion system from reservoir oil indigenous anaerobes in depleted oil fields, J. Jpn.

Petrol. Inst. 52 (6) : p.297-306, 2009

8) H. Otagaki, K. Fujiwara, Y. Hattori, Y. Sugai, K.Okatsu、Verification of Microbial Activities for Microbial

Restoration of Methane Deposit with Subsurface CO2 Sequestration into the Depleted Oil Fields、SPE Asia Pacific

Oil and Gas Conference and Exhibition held in Jakarta, Indonesia, 4–6 August 2009

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9) K. Fujiwara, Developing microbial restoration of methane deposit with subsurface CO2 sequestration into depleted

oil fields. Abstract of International Symposium for Subsurface Microbiology, Shizuoka, Japan. 2008.

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Fig.1 Sustainable carbon recyclingFig.1 Sustainable carbon recyclingFig.1 Sustainable carbon recyclingFig.1 Sustainable carbon recycling system by subsurface anaerobes system by subsurface anaerobes system by subsurface anaerobes system by subsurface anaerobes

Fig.2 Over view of Microbial Restoration of Methane Deposits (MRMD) systemFig.2 Over view of Microbial Restoration of Methane Deposits (MRMD) systemFig.2 Over view of Microbial Restoration of Methane Deposits (MRMD) systemFig.2 Over view of Microbial Restoration of Methane Deposits (MRMD) system

CH4

CH4CO2

CO2 ③③③③CCS (CO2 capture

and Storage)

①①①①Production

resources (CH4)

②②②②Combustion

・・・・Emission

④④④④Microbial

conversion

(CO2 to CH4)

圧入井圧入井圧入井圧入井栄養源栄養源栄養源栄養源（（（（塩塩塩塩））））のみのみのみのみ

栄養源栄養源栄養源栄養源（（（（塩塩塩塩））））のみのみのみのみ

キャップロックキャップロックキャップロックキャップロック（（（（不透水層不透水層不透水層不透水層））））

土着土着土着土着のののの油層常在油層常在油層常在油層常在微生物群微生物群微生物群微生物群のののの活用活用活用活用有用微生物有用微生物有用微生物有用微生物

のののの圧入圧入圧入圧入

栄養源栄養源栄養源栄養源（（（（塩塩塩塩））））+

有用菌有用菌有用菌有用菌



分離










分離

Injecting

Microbes

IndigenousMicrobes

Injection

wellNutrientNutrient

MicrobesMicrobes＆＆＆＆

Additives

Microbes CHCH44

Methane

Restoration

OilOil

GasGas

Oil/Gas

production

Oil

Reservoir

COCO22

CO2

Sequestration

Additives

Microbes CHCH44

Methane

Restoration

OilOil

GasGas

Oil/Gas

production

Oil

Reservoir

COCO22

CO2

Sequestration










分離










分離

Injecting

Microbes

IndigenousMicrobes

Injection

wellNutrientNutrient

MicrobesMicrobes＆＆＆＆

Additives

Microbes CHCH44

Methane

Restoration

OilOil

GasGas

Oil/Gas

production

Oil

Reservoir

COCO22

CO2

Sequestration

Additives

Microbes CHCH44

Methane

Restoration

OilOil

GasGas

Oil/Gas

production

Oil

Reservoir

COCO22

CO2

Sequestration

- 9 -

Fig.3 The Mechanism of Microbial ConversionFig.3 The Mechanism of Microbial ConversionFig.3 The Mechanism of Microbial ConversionFig.3 The Mechanism of Microbial Conversion

Fig.4 Fig.4 Fig.4 Fig.4 Form of MYHForm of MYHForm of MYHForm of MYH----4444 consortiumconsortiumconsortiumconsortium

Injection

* Inorganic reaction of thermal water and

reducing agent (i.e. Fe) of rock

*Hydrogen production with rock formation

(i.e. serpentine rock)

DDepletedepleted

oiloil/gas field/gas field

Organic

matter(i.e.carbohydrate,

hydrocarbone)

H２２２２Hydrogen-producing

thermophilic eubacteria

Methane-producing

thermophilic archaea

CO２２２２ CH4 2H２２２２O4H２２２２+ +

Injection

* Inorganic reaction of thermal water and

reducing agent (i.e. Fe) of rock

*Hydrogen production with rock formation

(i.e. serpentine rock)

DDepletedepleted

oiloil/gas field/gas field

Organic

matter(i.e.carbohydrate,

hydrocarbone)

H２２２２Hydrogen-producing

thermophilic eubacteria

Methane-producing

thermophilic archaea

CO２２２２ CH4 2H２２２２O4H２２２２+ +

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FigFigFigFig.5 Methane production by indigenous anaerobes .5 Methane production by indigenous anaerobes .5 Methane production by indigenous anaerobes .5 Methane production by indigenous anaerobes under reservoir under reservoir under reservoir under reservoir temperaturetemperaturetemperaturetemperature

BES: inhibitor for methanogens

Fig.Fig.Fig.Fig.6666 Microbial methane producing pathway in real reservoirMicrobial methane producing pathway in real reservoirMicrobial methane producing pathway in real reservoirMicrobial methane producing pathway in real reservoir

Acetic acid

Acetoclast methane

producing archaea

Methanosaeta sp.

Methane

Hydrocarbon degrading

hydrogen producing bacteria

Thermotoga sp.

Petrotoga sp.

Thermoanaerobacter sp.

SRB（Thermodesulfobacterium commune）

Hydrocarbons

(Chain-alkane,

Aromatic hydrocarbon)

Hydrogenotroph methane producing archaea

Methanoculleus sp.

M. thermautotrophicus

Hydrogen

Hydrogen producing bacteria

Soengenia saccharolytica

Metabolic

intermediate

Acetoclast hydrogen

producing bacteria Thermaacetogenium phaeum

Thermoanaerobacter sp.

Sintrophomonas sp.

Fig.2. Methane production from reservoir water (#AR-39)

0.0

50.0

100.0

150.0

200.0

250.0

0 50 100 150 200 250Incubation time （day）

Meth

ane (N

ml/

L-re

serv

oir w

ater)

#AR-39

#AR-39+BES

Incubation period (days)

Methane production (Nml/L-reservoir brine) 0.13 Nml/L-med/h

- 11 -

Fig.Fig.Fig.Fig.7777 AAAAdsorption dsorption dsorption dsorption of bacterial cells of bacterial cells of bacterial cells of bacterial cells in poin poin poin porous media rous media rous media rous media

(visualizing by (visualizing by (visualizing by (visualizing by fluorescent staining methodfluorescent staining methodfluorescent staining methodfluorescent staining method))))

10μm

Bacterial cells

- 12 -

Table 1 Table 1 Table 1 Table 1 Characters ofCharacters ofCharacters ofCharacters of Gas & Oil Fields Gas & Oil Fields Gas & Oil Fields Gas & Oil Fields

Table 2 Eubacteria discovered fromTable 2 Eubacteria discovered fromTable 2 Eubacteria discovered fromTable 2 Eubacteria discovered from reservoir brine and crude oil reservoir brine and crude oil reservoir brine and crude oil reservoir brine and crude oil

at Japan oil/gas fields at Japan oil/gas fields at Japan oil/gas fields at Japan oil/gas fields

3-51851615Current Pressure（MPa)

50-751036912040

Res.Temp（℃）

2600-12000700013,00010,00019,600Salinity conc. (ppm)

Non associatedGas

Gas-dissolvedin Water

Oil FieldsGas Fields

Depth

（ｍ）

Type Of

Sample

SampleOrigin

2200

Water

Minami-aga

（Niigata）

Oil

1200

Water

Yabase

（Akita）

Oil

2200250016711600

waterwaterRockCore

water

Iwaki(Fukushima)

Higashi-Kashiwazaki

（Niigata ）

Naruto（Chiba ）

3-51851615Current Pressure（MPa)

50-751036912040

Res.Temp（℃）

2600-12000700013,00010,00019,600Salinity conc. (ppm)

Non associatedGas

Gas-dissolvedin Water

Oil FieldsGas Fields

Depth

（ｍ）

Type Of

Sample

SampleOrigin

2200

Water

Minami-aga

（Niigata）

Oil

1200

Water

Yabase

（Akita）

Oil

2200250016711600

waterwaterRockCore

water

Iwaki(Fukushima)

Higashi-Kashiwazaki

（Niigata ）

Naruto（Chiba ）

-Delftia acidovoransIwaki-oki

-

Desulfotomaculum sp.Desulfovibrio alaskensis

Acetobacterium wieringae

Higashi-

kashiwazaki

Non-associated

gas field

-Clostridium sp.NarutoWater dissolved

gas field

Methylobacterium sp.Pseudomonas iners

Propionibacterium acnes

Streptcoccus thermophilus

Streptmyces avermitilis

Corynebacterium diphteriae

Clostridium sp.

Minami-aga

Anaerobaculum thermoterrenum

Petrotoga mobilis

Clostridium perfingens

Geobacter metallireducens

Nitrobacter winogradskyi

Desulfotomaculum thermobenzoicum

Desulfitobacter alkalitolerans

Thermotoga sp.Petrotoga mobilis

Thermoanaerobacter sp.Anaerobaculum sp..Thermoacetogenium

phaeum

Thermodesulfobacterium sp.Clostridium sp.

YabaseOil field

From Crude oilFrom Reservoir brineName of field

-Delftia acidovoransIwaki-oki

-

Desulfotomaculum sp.Desulfovibrio alaskensis

Acetobacterium wieringae

Higashi-

kashiwazaki

Non-associated

gas field

-Clostridium sp.NarutoWater dissolved

gas field

Methylobacterium sp.Pseudomonas iners

Propionibacterium acnes

Streptcoccus thermophilus

Streptmyces avermitilis

Corynebacterium diphteriae

Clostridium sp.

Minami-aga

Anaerobaculum thermoterrenum

Petrotoga mobilis

Clostridium perfingens

Geobacter metallireducens

Nitrobacter winogradskyi

Desulfotomaculum thermobenzoicum

Desulfitobacter alkalitolerans

Thermotoga sp.Petrotoga mobilis

Thermoanaerobacter sp.Anaerobaculum sp..Thermoacetogenium

phaeum

Thermodesulfobacterium sp.Clostridium sp.

YabaseOil field


- 13 -

Table 3 Archaea discovered fromTable 3 Archaea discovered fromTable 3 Archaea discovered fromTable 3 Archaea discovered from reservoirreservoirreservoirreservoir brine and crude oil at Japan oil/gas fields brine and crude oil at Japan oil/gas fields brine and crude oil at Japan oil/gas fields brine and crude oil at Japan oil/gas fields

TableTableTableTable 4 Parameters of 4 Parameters of 4 Parameters of 4 Parameters of primitive primitive primitive primitive economic assessmenteconomic assessmenteconomic assessmenteconomic assessment

1. Reservoir condition 2. CO2 injection (expenditure)

Mean reservoir area (m2) CO2 injection volume (t)

Effective thicknese (m) CO2 injection period (y)

Porosity (%) Cost of separation and injection ($/t)

3. Methane restration (expenditure) 4. Income

Velocity of methane production (ml/L-med/h) Price of CO2 emissions rights trading (€/t CO2)

Efficiency of methane conversion (%) Methane selling price (realized price) ($/t CO2)

Methane production period (y)

Quantity of methane production (million t)

Cost of methane production ($/t)

-Methanobacterium formicicumIwaki-oki

-Methanocalculus halotoleransHigashi-

kashiwazaki

Non-associated

gas field

-Methanocalculus halotorerance

Methanocalculus pumilusNaruto

Water dissolved

gas field

Methanoculleus sp.Methanosaeta sp.


Minami-aga

Methanoculleus sp.Methanocalculus halotorerance

Methanoculleus sp.Methanobacterium

thermoautotrophicum

Methanocalculus halotorerance

Methanosarcina mazeii

YabaseOil field


-Methanobacterium formicicumIwaki-oki

-Methanocalculus halotoleransHigashi-

kashiwazaki

Non-associated

gas field

-Methanocalculus halotorerance

Methanocalculus pumilusNaruto

Water dissolved

gas field



Minami-aga

Methanoculleus sp.Methanocalculus halotorerance

Methanoculleus sp.Methanobacterium

thermoautotrophicum

Methanocalculus halotorerance

Methanosarcina mazeii

YabaseOil field


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