ENERGY FROM GAS HYDRATES

Guided by:

Pro: Gigi Sebastian

Submitted by:AFSAL AMEEN C

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.

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).

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.

OCCURANCE

Fig:3 Location of known and inferred gas hydrate occurrences

Kvenvolden and Rogers, 2005)Reproduced with permission from Keith Kvenvolden and Bruce Rogers.

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.

HYDRATE STABILITY Cont…

Gas Hydrate Occurrence Zone and Stability Zone

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.

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

NATURAL GAS HYDRATES cont..

It is highly inflammable and are called "Fiery ice" or “Ice that burns”

STRUCTURE

Fig: 2 structure of gas hydrate

PRODUCTION METHODS

There are three mainly used production methods are

1. DEPRUSSURIZATION.

2. THERMAL STIMULATION

3. CHEMICAL INHIBITION

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.

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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.

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.

PRODUCTION METHODS Cotd..

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

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

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.

APPLICATIONS

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

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.

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.

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

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.

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