GasHydrates- KMuralidhar

7/29/2019 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



Organization of the talk

Energy scenario

What are gas hydrates Resource availability

Exploitation of gas hydrates

Environmental aspect



Assessing energy sources

1. Demand

2. Availability3. Technology

4. Efficiency

5. Environmental impact6. Cost



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!



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



Projected world energy supply



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



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]



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)



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



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



Hydrogen substitution



Summary

Using every yardstick: availability,

efficiency, environment, and cost,the 21st century will see an

irrevocable shift towards gas-based

energy generation



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.



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.



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.



What are gas hydrates

A gas hydrate consists of a water lattice in which light

hydrocarbon molecules are embedded resembling dirty

ice.

http://en.wikipedia.org/wiki/Hydrocarbon

http://en.wikipedia.org/wiki/Molecule

http://en.wikipedia.org/wiki/Molecule

http://en.wikipedia.org/wiki/Hydrocarbon



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.



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).



It is present in oceanic sediments along continental margins and in polar

continental settings.

Where are gas hydrates located?



The ocean scenario



Various issues related to extraction of gas hydrates



Recovery of Methane Gas from Gas Hydrates

Modifying the equilibrium conditions by

1. Depressurization

2. Inhibitor injection

3. Thermal stimulation



Phase equilibrium diagram

stable

unstable



Decomposition of hydrates by depressurization,

thermal, and chemical techniques



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.



Schematic representation of production from a

hydrate reservoir with underlying free gas



Hydrate dissociation and formation

Molecular structure

Phase equilibrium diagram

Flow, transport, and chemical reactions in a complex

pore network

Research aspects



Schematic drawing of gas exchanges



Mass transfer at constant pressure and

temperature



Mathematical Model

uuuuu

K

f

K p

dt

d

2

u

uuu

.

t dt

d

Fluid flow

is the porosity and K, the

permeability.



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



Species transport equation

Mathematical Model

g

ji

n

j

g

ijii

i

M t

g

1..

Ju



List of undetermined parameters

• Dispersion coefficient

• Permeability tensor

• Inter-phase transport coefficient



Unanswered questions

Stability boundary

Destabilization dynamics

Flow and transport in a hierarchical porenetwork

System development

Disaster management

Cost considerations



Environmental impact

Carbon

sequestration

Carbon capture

and storage Carbon trap

technologies



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.



Thank you!

GasHydrates- KMuralidhar

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