Evaluation of the Compression Strength and Deformation Behaviour

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Evaluation of the Compression Strength and
Deformation Behaviour of Methane Hydrate
Simulation Specimen
Nagasaki University J.Nagaeki Y.Jiang Y.Tanaba
si
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Research background
Energy resource
There is a limit at the resources of the fossil
energy.
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Methane Hydrate
MH

• Cage state structure that the methane
• gas is surrounded for water molecule.

• Equilibrium under the condition of low
  temperature and high pressure .

Rangeland

• The permafrost area
• In the sedimentary layer of sea bed

Distributed in the nearby sea area in Japan
About 100 times of the natural gas consumption
per year of Japan
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Production of MH
Production method

• Thermal stimulation method

• Decompression method

Problem
Ground deformation
Interference of the production activity
Elucidation of mechanical characteristic and
deformation characteristic of MH sedimentary
layer
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Purpose of the research
Purpose
To obtain basic data of MH sedimentary
layer,which are necessary for further calculation
and development.
Test outline

• Temperature
• pressure
• Sand blend ratio

• Compression strength
• Deformation characteristic

The manufacture of the dynamics test equipment
Ttriaxial compression tests are carried out in
low temperature,using the artificial material
which has the same properties with the sample.
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The layout of test equipment
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?heat storage layer ?pressureproof
container ?low-pressure pump ?high-pressure
pump ?flocon ?safety valve ?actuator ?air
pressure line ?return line
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The appearance of test equipment
?heat storage layer ?pressureproof
container ?low-pressure pump ?high-pressure
pump ?flocon ?safety valve ?actuator ?air
pressure line ?return line
temperature range -30?20? normal loading
capacity 100kN lateral pressure loading
capacity 10MPa pore pressure capacity 10MPa
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Gap sensors and the pressure vessel
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Pressure and temperature control
?heat storage layer ?pressureproof
container ?low-pressure pump ?high-pressure
pump ?flocon ?safety valve ?actuator ?air
pressure line ?return line
low-pressure line
high-pressure line
return line
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Trial test-piece
Sandy soil is used to simulate the sedimentary
layer where MH stored.
Geologic material
Toyoura standard sand fine powder ice ( screen
passing material of 250 µm )
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The test-piece manufacture
Laboratory Temperature -5?
Sand fine powder ice
The molding cylinder
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?????1/min
Experimental method
Mass ratio of Toyoura sand and fine powder ice
Sand blend ratio
Testing condition and number of sample
Shaft loading rate 1/min
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Test result Relationship between stress
difference and axial ? strain Lateral pressure
6MPa ?
Sand blend ratio
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Test result Relationship between sand blend ratio
and largest stress difference
Largest stress difference ?(s1-s3)max?(MPa)
Sand blend ratio ()
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Test result Relationship between axial strain
and sand blend ratio
Axial strain ?ea?()
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Test result Relationship between sand blend ratio
and distortion calculation
EtTangent modulus EsSecant coefficient
Lateral pressure
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Test result Relationship between sand blend ratio
and shear strength
Shearring stress?t?(MPa)
Normal stress?s?(MPa)
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Conclusions

• Low temperature triaxial compression test
• apparatus was manufactured.

• Manufacturing method of the MH simulation
• test-piece and test procedure were
  established.

• The triaxial compression test which set test
• temperature at -5? was carried out.

• The relationship between sand blend ratio and
• distortion calculation and strength constant
  of
• the trial test-piece was examined.

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Conclusions
Sand blend ratio

• Take great effect on the relation between
• axial strain and stress difference.

• Take great effect on the change of distortion
• calculation.

Lateral pressure dependence

• Lateral pressure dependence is high for the
• sample of the 85 sand blend ratio.

• Lateral pressure dependence is very low for
• the sample of 70 sand blend ratio or less.

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Conclusions
Shear strength and sand blend ratio
?Internal frictional angle? Sand blend ratio 70
or less f 1
From these results
It was possible to obtain the part of basic data
of the MH sedimentary layer,which are necessary
for the development of the consolidation
calculation module.
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Future prospect
?????
Test temperature -1? -10?
Trial test-piece containing actual MH
Temperature dependency of deformation
characteristic and strength constant
Dependence by the existence of the methane of
distortion calculation and strength constant
Development of the consolidation calculation
module
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END
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