gas hydrates

1. ENERGY FROM GAS
HYDRATES
Guided by:
Pro: Gigi Sebastian
Submitted by:
AFSAL AMEEN C

2. INTRODUCTION
 Gas hydrates are cage-like structures of water
molecules, surrounding molecules of gas, primarily
methane.
 Methane is the principal component of natural gas.
 They form when water and natural gas combine at
sufficiently low temperatures and high pressures.
 They seen in the regions of permafrost and in
subseafloor sediments.
 Theoretically estimated that maximum of 270 million
trillion cubic feet of natural gas exist in hydrate deposits.

3. HISTORY
 Russian scientists in the late 1960s were the first to
propose that gas hydrate might occur naturally in marine
and onshore locations (Makogon and Medovskiy,1969)
 In the early 1970s, scientists found that gas hydrate
existed below the permafrost and in marine sediments
(Stollet al., 1971; Bily and Dick, 1974).
 Deep sea drilling expeditions confirmed that gas hydrate
occurred naturally in deepwater sediments along outer
continental margins (Paull et al., 1996; Tréhu et al.,
2003;Riedel et al., Proceedings of the ODP, 2006).

4. OCCURANCE
 Natural gas hydrates are solid, crystalline, ice-like
substances composed of water, methane, and usually a
small amount of other gases,
 With the gases being trapped in the interstices of a
water-ice lattice.
 They form under moderately high pressure and at
temperatures near the freezing point of water.
 In the United States, very large methane hydrate
deposits are located both on- and offshore northern
Alaska.

5. OCCURANCE
Fig:3 Location of known and inferred gas hydrate
occurrences
Kvenvolden and Rogers, 2005)
Reproduced with permission from Keith Kvenvolden and Bruce Rogers.

6. HYDRATE STABILITY
 stability of the gas hydrate mostly depends on pressure
and temperature.
 the mechanical properties of gas hydrate are similar to
those of ice because gas hydrate contains about 85 %
water by mass.
 It may look like ice, it does not behave like ice — for
example, it burns when lit with a match.
 colder temperatures and/or higher pressures — the gas
hydrate is stable.

7. HYDRATE STABILITY Cont…
Gas Hydrate Occurrence Zone and Stability Zone

8. NATURAL GAS HYDRATES
 Gas hydrates form when water and natural gas combine
at low temperatures and high pressures.
 Gas hydrates are cage-like structures of water
molecules.
 surrounding molecules of gas, primarily methane.
Methane is the principal component of natural gas.
 They are members of a highly varied class of substances
called clathrates.

9. NATURAL GAS HYDRATES cont..
 Natural gas hydrate is a potentially vast source of
hydrocarbon energy that is currently unexploited.
 They are seen in the regions of permafrost and in marine
subseafloor sediments.
 They substances composed of water, methane, and
usually a small amount of other gases.
 It has been estimated that a maximum of 270 million
trillion cubic feet of natural gas could theoretically exist in
hydrate deposits

10. NATURAL GAS HYDRATES cont..
It is highly inflammable and are called "Fiery ice"
or ―Ice that burns‖

11. STRUCTURE
Fig: 2 structure of gas hydrate

12. PRODUCTION METHODS
 There are three mainly used production methods are
1. DEPRUSSURIZATION.
2. THERMAL STIMULATION
3. CHEMICAL INHIBITION

13. PRODUCTION METHODS Cotd..
1. DEPRUSSURIZATION.
 Its objective is to lower the pressure in the free-gas
zone immediately beneath the hydrate stability zone,
causing the hydrate at the base of the hydrate stability
zone to decompose and the freed gas to move toward
a wellbore.
.

14. PRODUCTION METHODS Cotd..
2. THERMAL STIMULATION.
 which a source of heat provided directly in the form of
injected steam or hot water or another heated liquid, or
indirectly via electric or sonic means.
 It is applied to the hydrate stability zone to raise its
temperature, causing the hydrate to decompose.
 The direct approach could be accomplished in either of
two modes: a frontal sweep similar to the steam floods
that are routinely used to produce heavy oil, or by
pumping hot liquid through a vertical fracture between
an injection well and a production well.

15. PRODUCTION METHODS Cotd..
3. CHEMICAL INHIBITION.
 It is similar in concept to the chemical means presently
used to inhibit the formation of water ice.
 This method seeks to displace the natural gas hydrate
equilibrium condition beyond the hydrate stability
zone’s thermodynamic conditions through injection of a
liquid inhibitor chemical adjacent to the hydrate.

16. PRODUCTION METHODS Cotd..
Fig:3 Schematic of proposed gas hydrate production
methods: (a) thermal injection (b) depressurization, and (c)
inhibitor or other additive.

17. TRANSPORTATION
There are at least three ways to transport the gas
ashore;
 by conventional pipeline;
 by converting the gas hydrates to liquid middle distillates
via the newly-improved Fischer-Tropsch process and
loading it onto a conventional tanker or barge; or
 by reconverting the gas into solid hydrate and shipping it
ashore in a close-to-conventional ship or barge

18. SAFETY &ENVIRONMENTAL
CONCERNS
 Normal drilling can generate enough downhole heat to
decompose surrounding hydrates, possibly resulting in
loss of the well.
 While large volumes of oceanic natural gas hydrate
deposits are known to have decomposed in the past
absent human influence.
 It is clear that the release of large quantities of methane
into the atmosphere, can cause increase its greenhouse
capability since methane is 21 times more potent a
greenhouse gas than is CO2.

19. APPLICATIONS
used in power generation.
urea fertilizer production.
room heating& cooking .

20. CHALLENGES
 During drilling wells as part of the development of gas
hydrate will produce significant amount of cuttings
containing methane gas.
 CO2 produced when methane is burned as a fuel.
 methane itself is a greenhouse gas with 21 times than of
carbon dioxide.
 High cost for long pipe lines across unstable continental
slops.

21. COMPARISONS
 The natural gas is found is gaseous state, while gas
hydrate is a solid .
 When natural gas is burned, it emits CO2, leads to
global warming. But the amount released is less than
that of coal or oil is burned.
 Oil and coal, emit air pollutants like SO2 & nitrogen
oxides. But in natural gas no such emissions.
 Methane gas is the cleanest fuel, because it emits
minimum residue in the environment.

22. CONCLUSION
 exploration and quantification of gas- hydrates are very
much required for evaluating the resource potential and
hazard assessment.
 Proper exploitation of methane at one hand can meet
the ever-increasing demand of energy and on the other
hand will reduce the environmental and submarine geo-
hazard.
 There are several technical problems in extracting and
producing gas from gas-hydrates at this moment.
 The recoverability of gas from gas hydrate may be
evaluated if the hydrate occurs in unfrozen sandy
sediments

23. REFERENCES
 Sain, K., ZeIt, C.A., and Reddy,P.R., 2002.Imaging of subvolcanic
Mesozoics using traveltime inversion of wide-angle seismic data in the
Saurastra peninsula of India, Geophysical Journal International, 150,
 Global Resource Potential of Gas Hydrate – ANew Calculation By Arthur H.
Johnson (Hydrate Energy International) ,vol 11,issue 2,methane hydrate
news letter .
 The 2nd South Asain Geoscience Conference and
Exhibition,GEOIndia2011, 12-14th Jan,2011,Gearter Noida,New Delhi,India
,Asit Kumar Samadder, Petrophysist, ONGC , Mumbai,India Exploration of
Gas Hydrate and the present global scenario.
 Gas Hydrates Resource Potential of South Asia, Published by SAARC
Energy Centre Plot No. 18, Street No. 6, Sector - H9/1 Islamabad,
Pakistan ,Mr .m .jamaluddin, Mr .malcolm v. lall.
 Alternative energy sources: Methane hydrates – in from the cold By Michael
Richardson For the Straits Times, 12 April 2010.