Fundamental study of the effect of using Fundamental study of the effect of using carbon dioxide in methane hydrate carbon dioxide in methane hydrate

developmentdevelopment

Kentaro FukudaKentaro Fukuda

Yujing JiangYujing Jiang

Yoshihiko TanahashiYoshihiko Tanahashi

Nagasaki UniversityNagasaki University

Geoenvironmental LabGeoenvironmental Lab

Methane Hydrate (MH)

Petroleum and Natural gas are main energy resources.

The development of new energy resources

Now

Future

Limit of the quantity of resources

Methane Hydrate (MH)

Background of Research

MH

A material that Methane’s molecule is surrounded in the crystallization of the caged Water’s molecule forms

Equilibrium conditions: Low temperature and High pressure

① Sediment of sea beds

② Eternal frozen ground area

Distribution area

Triangle：Methane’s molecule　 Ball：Water’s moleculeCrystal structure of MH

Background of Research

Background of ResearchThe confirmation of existence of MH in sea area around Japan

The amount of the resource : About 7.4 trillions cubic meters

Equivalent to about 100 years of the amount of annual natural gas consumption in Japan(1999)Possibility of supplying energy for long term in Japan

Distribution area 1. The Nankai Trough

2. Kuril Islands3. Sea of Okhotsk4. Tataru Trough 5. Okushiri submarine ridge6. West Tsugaru basin

Gathered MH(White ice)

The gathered MH in Niigata offing

However

Background of Research

MH has the possibility to become the next generation energy

The influence on sea beds in the production of MH (Buckling of winze, Landslide etc.)

The necessity of developing MH considering the environment problems

Problem

More stable than MH

Disposal of greenhouse gases

Low cost

Background of Research

The suggestion of developing MH with Carbon Dioxide

The formation of Carbon Dioxide Hydrate (CO2-Hyd)

Advantage

Global environment problem

Energy problem Solution at the same time

Background of Research

Ocean

Lower layer

MH layer

Upper layerCO2-Hyd layer

Production of MH

CO2-Hyd layer

CO2 injection

Construction of artificial roof

Stabilization of soft stratum

CO2-Hyd layer

CO2 injection

Construction of artificial prop

Maintenance of artificial roof

Immobilization of CO2

Purpose of Research

Evaluate the property by doing triaxial compression test on the specimen with CO2 gas and mixture gas (emphasizing the latter one)

Comparison of the strength on the simulated specimen with each of CO2-Hyd and MH

Evaluation of utilization possibility of CO2

Organization of Collaboration ： Methane Hydrate lab, National Institute of Advanced industrial Science and Technology

Close-packedClose-packed

Sample Manufacture

Mold of pillar shape (Caliber:50mm, Height:100mm)

Water + Toyoura sand

Freeze with refrigerator Drain

Adjustment of the saturation

Set of Frozen sample

Sample Set

Triaxial Compression Test Apparatus

Set of Frozen sample

Installation of Rubber sleeve

Installation of lid of pressure container

Injection of antifreeze solution

Pressure Container

Formation of CO2-Hyd Establishment of formation conditions

Pore pressure (Formation pressure) : 8MPa

Lateral pressure : 9, 10 , 12MPa

Temperature in the cell : 6, 2.5 ℃

Penetration of mixture gas in the void of the specimen

Formation of CO2-Hyd Adjustment of formation time

Control with outside computers

Triaxial Compression Test

In situ conditionsTest conditions

Water depth 700m

The layer with the thickness of 100m under see beds

Undrain conditions

Back pressure : 0MPa

Pore pressure : 8MPa

Lateral pressure : 9, 10, 12MPa

Temperature in cell : 6, 2.5℃Establishment of the

conditions close to in-situ Enforcement of

loading test

Decomposition of CO2-Hyd

The sample after decomposition

Decomposition of CO2-Hyd by decompression

Measurement of the amount of CO2 gases with the gas meter

Calculation of CO2-Hyd saturation degree

Constitution of Sample

Core manufacture CO2-Hyd formation

V

ガス

水

標準砂

Vg

Vw

Vs

Vv

ガス

ハイドレート水

標準砂

V

Vg

Vh

Vw

Vs

Vv

Sand Sand

WaterWater

Gas

HydratePore

volume

Gas

Hydrate

CO2-Hyd saturation degree

％　 　100v

hh V

VS

Stress-Strain relation (mixture gas)

0

2

4

6

8

10

0 2 4 6 8 10 12 14 16 18

Axial strain　 （％）

Axi

s di

ffer

ence

str

ess

（MP

a）

Sh=33.0％(2.5℃)

Sh=25.4％(2.5℃)

Sh=20.1％(6℃)

Sh=14.6％(6℃)

Only N2(6℃)

Only sand(5.3℃)

0

2

4

6

8

10

0 2 4 6 8 10 12 14 16 18

Axial strain　 （％）

Axi

s di

ffer

ence

str

ess

（MP

a）

Sh=33.0％(2.5℃)

Sh=25.4％(2.5℃)

Sh=20.1％(6℃)

Sh=14.6％(6℃)

Only N2(6℃)

Only sand(5.3℃)

The strength at the same level as N2

The influence of formation of Hydrate: small

0

2

4

6

8

10

0 2 4 6 8 10 12 14 16 18

Axial strain　 （％）

Axi

s di

ffer

ence

str

ess

（MP

a）

Sh=33.0％(2.5℃)

Sh=25.4％(2.5℃)

Sh=20.1％(6℃)

Sh=14.6％(6℃)

Only N2(6℃)

Only sand(5.3℃)

Increase of the saturation degree of Sh than that in 6℃ Increase of the strength

9MPa

σ

σmax

σmax/2

ε50 ε

50max50 /2)( ε／σ＝E

Deformation modulus

E50 ： Secant elastic modulus in axis difference stress 50 percent

σmax ： Maximum axis difference stress

ε50 ： Strain in axis difference stress 50 percent

0

100

200

300

400

500

600

700

0 10 20 30 40

Degree of CO2-Hyd saturation (％)

Def

orm

atio

n m

odul

us E

50

（MPa

）

Lateral pressure 9MPa

Lateral pressure 10MPa

Lateral pressure 12MPa

Deformation modulus

May depend on the saturation degree of Sh

Lateral pressure 9MPa

→ Linear increase of deformation modulus

CO2 gas Mixture gasFormation pressure 8MPa 3.0，3.5MPa 8MPa

Temperature 5℃ 2℃ 6℃，2.5℃Lateral pressure

MHCO2-Hyd

9MPa

Ｉtem

Formation conditions

Concentration degree

CO2 gas, Methane 　→ 100 ％

Mixture gas 　→ The ratio of 50 ％ of CO2 and N2

CO2 gas Mixture gasNo water substitution

UndrainTemperature 6℃，2.5℃

Back pressure 0MPaLateral pressure

Pore pressure

Item MHCO2-Hyd

8MPa9MPa8MPa

Load conditionWater substitution

Drain5℃

Loading conditions

0123456789

10

0 20 40 60 80 100

Degree of saturation （％）

Max

imu

m a

xis

dif

fere

nce s

tress

（Ｍ

Ｐa）

CO2（3MPa)CO2（3.5MPa)Mixture gas(8MPa)

MH（8MPa)Only sand

Formation pressure

Maximum axis difference stress

Linear strength increaseMixture gas: The strength is high.

The strength at the same level with MH is shown although their conditions are different.

0123456789

10

0 20 40 60 80 100

Degree of saturation （％）

Max

imu

m a

xis

diff

eren

ce s

tres

s （ＭＰ

a ） CO2（3MPa)CO2（3.5MPa)Mixture gas(8MPa)

MH（8MPa)Only sand

Formation pressure

Maximum axis difference stress

The strength at the same level with MH despite at low saturation degrees

The possibility that N2 was mixed in the hydrate

ConclusionEvaluation of the mechanical property of CO2-Hyd

CO2 gas

Mixture gas

Low

High

Formation pressure Strength

Low

High

MH

Mixture gas

Drain

Undrain

Strength at the same level

The utilization possibility of CO2 is confirmed

Drain conditions Strength

Future problem

Applying the triaxial compression test under the conditions more close to in-situ

Realization of MH development by using CO2

Elucidation of the change of hydrate saturation degree by the influence of Nitrogen when using the mixture gas

END