GasHydrates- KMuralidhar
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Transcript of GasHydrates- KMuralidhar
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EXPLOITATION OF GAS
HYDRATES AS AN ENERGYRESOURCE
K. Muralidhar
Department of Mechanical Engineering
Indian Institute of Technology Kanpur
Kanpur 208016 India
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Organization of the talk
Energy scenario
What are gas hydrates Resource availability
Exploitation of gas hydrates
Environmental aspect
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Assessing energy sources
1. Demand
2. Availability3. Technology
4. Efficiency
5. Environmental impact6. Cost
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The 21st century imbalance
Annual population increases at 2%.
Energy use per capita increases at 2%per year.
As a result, energy consumptionincreases at 4% per year.
Doubles every 36 years!
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0
500
1000
1500
2000
2500
3000
3500
4000
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52
World fossil consumption (1950-2003)
Source: World Watch Institute, 2003
Coal
Oil
NaturalGas
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Projected world energy supply
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H y d r o
G a s - C o m b i n e d c y c l e
C o
a l
G a s T
u r b i n e c y c l e
N u c l e a r
W i n d
S
o l a r T h e r m a l
S o
l a r - P V
G e o t
h e r m a l
B i o m a
s s
0
10
20
30
40
50
60
70
80
E l e c t
r i c a l E f f i c i e n c y
( % )
.
1 810
15
25
33
38
43
58
8080
Efficiencies of power technologies
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W i n d
N u c l e a r
S o l a r - P
V
B i o m a s
s / S t e a m
N a t u r a l G a s
C o a l
G e o t h e r m a l
H y d r o
0
0.2
0.4
0.6
0.8
1
1.2
1.4
C O 2 E m i s s i o n s ( k g C O 2 / k W h )
0.025
0.47
0.0040.060.025
0.38
1.18
0.02
0.1
0.790.58
1.04
CO2 emissions [includes Construction/Operation/Fuel
Preparation]
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50-75
12
53
2 2
56
2
19
14
4 4
10
8 7
17
S o l a r - P V
N u c l e a r
G a s
C o a l
H y
d r o
W i n d
B i o m a s s
G e o t h e r m
a l
S o l a r T h
e r m a l
0
5
10
15
20
25
30
35
C o s t o f E l e c t r i c i t y ( c e n t s / k
W h )
Cost of electricity (global average, 1998)
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Equipment cost in IRs/kWh for electricity
generation
Solar Thermal 6 - 8
Nuclear 5 - 9
Natural Gas 5 - 9Hydro 5 - 18.5
Wind 4.5 - 7
Coal 3.5 - 7Geothermal 4.25 - 7
Biomass 4.15 - 8
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Operations and maintenance costs IRs/kWh
Wind 1.3
Coal 2
Nuclear 2.2Geothermal 2.7
Gas 3.1
Wood 3.1
Oil 4.1
Waste 4.5
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Hydrogen substitution
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Summary
Using every yardstick: availability,
efficiency, environment, and cost,the 21st century will see an
irrevocable shift towards gas-based
energy generation
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Large scale power production from gas
Energy production from gas relies on the following
technologies:
Gas turbines
Fuel cells (futuristic)
Gas hydrates are a source of methane and can be
integrated with these technologies.
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Indian scenario
With no major findings of gas reserves it is essential to
look for other alternative resources such as gas
hydrates.
Vast continental margins with substantial sediment
thickness and organic content, provide favorable
conditions for occurrence of gas hydrates in the deepwaters adjoining the Indian continent.
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Indian scenario (continued)
Caution: Gas hydrates hold the danger of naturalhazards associated with sea floor stability, release of
methane to ocean and atmosphere, and gas hydratesdisturbed during drilling pose a safety problem.
Research: Development of a field model is quitenecessary before the installation of a full scale setup inthe sea bed.
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What are gas hydrates
A gas hydrate consists of a water lattice in which light
hydrocarbon molecules are embedded resembling dirty
ice.
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What are gas hydrates (continued)
Naturally occurring gas hydrates are a form of waterice which contains a large amount of methane withinits crystal structure.
They are restricted to the shallow lithosphere (2000-4000 m depth)
With pressurization, they remain stable at
temperatures up to 18°C.
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What are gas hydrates (continued)
The average hydrate composition is 1 mole of methanefor every 5.75 moles of water.
The observed density is around 0.9 g/cm3.
One liter of methane clathrate solid would contain 168liters of methane gas (at STP).
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It is present in oceanic sediments along continental margins and in polar
continental settings.
Where are gas hydrates located?
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The ocean scenario
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Various issues related to extraction of gas hydrates
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Recovery of Methane Gas from Gas Hydrates
Modifying the equilibrium conditions by
1. Depressurization
2. Inhibitor injection
3. Thermal stimulation
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Phase equilibrium diagram
stable
unstable
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Decomposition of hydrates by depressurization,
thermal, and chemical techniques
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Exploitation schemes
1. DEPRESSURISATION: At fixed temperature,
operating at pressures below hydrate formation
pressure.
2. INHIBITION: Inhibition of the hydrate formationconditions by using chemicals such as methanol and
salts.
3. HEAT SUPPLY: At fixed pressure, operating at
temperatures above the hydrate formationtemperature. This can be achieved by insulation or
heating of the equipment.
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Schematic representation of production from a
hydrate reservoir with underlying free gas
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Hydrate dissociation and formation
Molecular structure
Phase equilibrium diagram
Flow, transport, and chemical reactions in a complex
pore network
Research aspects
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Schematic drawing of gas exchanges
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Mass transfer at constant pressure and
temperature
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Mathematical Model
uuuuu
K
f
K p
dt
d
2
u
uuu
.
t dt
d
Fluid flow
is the porosity and K, the
permeability.
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Mathematical Model
s f f eff f p QT k T
t
T C
,
..
u
s f seff s p QT k t
T C
,.1
Heat transfer
Solid
Fluid
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Species transport equation
Mathematical Model
g
ji
n
j
g
ijii
i
M t
g
1..
Ju
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List of undetermined parameters
• Dispersion coefficient
• Permeability tensor
• Inter-phase transport coefficient
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Unanswered questions
Stability boundary
Destabilization dynamics
Flow and transport in a hierarchical porenetwork
System development
Disaster management
Cost considerations
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Environmental impact
Carbon
sequestration
Carbon capture
and storage Carbon trap
technologies
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Conclusions
1. Irreversible shift towards gaseous fuels.
2. Gas hydrates are secondary gas sources(internationally) but are primary, in the
national context.
3. Safe exploitation of methane from hydrate
reservoirs calls for a massive research
program.
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Thank you!