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Review article
Natural gas hydrates A promising source of energy
Yuri F. Makogon*
Texas A&M University, Petroleum Engineering, 3116-TAMU-721 Richardson Building, College Station, TX 77843, United States
a r t i c l e i n f o
Article history:
Received 30 November 2009
Received in revised form
11 December 2009
Accepted 12 December 2009
Available online 21 February 2010
Keywords:
Gas hydrates
Energy source
Messoyacha field
Hydrate distribution
Hydrate kinetics
Morphology of gas hydrates
a b s t r a c t
Gas hydrates are clathrate physical compounds, in which the molecules of gas are occluded in crystalline
cells, consisting of water molecules retained by the energy of hydrogen bonds. All gases can form
hydrates under different pressures and temperatures. The crystalline structure of solid gas hydrate
crystals has a strong dependence on gas composition, pressure, and temperature. Presently, threecrystalline structures are known (Sloan, 1990, 2007) to form at moderate pressure, and nearly ten
structures in the pressure range above 100 MPa. For example, methane hydrate can be stable at a pres-
sure of 20 nPa to 2 GPa, and at temperatures changing from 70 to 350 K (Makogon, 1997). Formation of
gas hydrate occurs when water and natural gas are present at a low temperature and a high pressure.
Such conditions often exist in oil and gas wells, and pipeline equipment.
Hydrate plugs can damage gas transport system equipment. The petroleum industry spends about one
billion US dollars a year to prevent hydrate formation in wells, pipelines and equipment. Natural deposits
of gas hydrates also exist on Earth in colder regions, such as permafrost, or sea bottom areas. Natural gas
hydrates are an unconventional energy resource. Potential reserves of gas in hydrated posits distributed
offshore and on land are over 1.5 1016 m3 (Makogon, 1982). About 97% of natural gas hydrates have
been located offshore, and only 3% on land.
At present time, there are several successful federal research programs in a number of countries for
research and development of gas hydrate deposits. Over 230 gas hydrate deposits were discovered, over
a hundred wells drilled, and kilometers of cores studied. Gas hydrate resource is distributed conveniently
for development by most every country. Effective tools for the recovery of gas from hydrate deposits, and
new technology for development of gas hydrate deposits are being developed. There is a commercialproduction of natural gas from hydrates in Siberia. Researchers continue to study the properties of
natural gas hydrates at reservoir conditions, and develop new technologies for exploration and
production of gas from hydrate deposits in different geological formations.
2009 Published by Elsevier B.V.
1. Introduction
A huge potential resource of hydrated gas, estimated at over
151012 toe, exists on our planet. If we will produce only 17 to 20%
of this resource, it can be a sufficient supply of energy for 200 years.
Gas hydrate deposits exist on land in the polar region, and offshore
around the globe. Over 230 Gas Hydrate Deposits (GHD) have been
found. A map of the discovered GHD is shown inFig. 1.
1.1. A brief history of the discovery of natural gas hydrates
Gas hydrates were first obtained by Joseph Priestley in 1778,
while in his laboratory, bubbling SO2 through 0 C water at
atmospheric pressure, and low room temperature (Priestley, 1778).
However, when describing the crystals he obtained, he did not
name them hydrates. About 33 years later, in 1811, similar crystals
of aqueous chlorine were named hydrates of gas by Humphrey
Davy. Some scientists consider Davy to be the discoverer of gas
hydrates; however, Priestley was the first to create gas hydrates in
the laboratory. The results by Davy did not draw the attention of
contemporaries, and studies of hydrates did not seriously develop
for almost a century. Within the first period of purely academic
studies of gas hydrates from 1778 to 1934, only 56 papers from 16
authors were published. There was not much interest in gas
hydrates from the industry prior to the 1930s.
The second period of gas hydrates study began in 1934, when
Hammerschmidt published the results of the inspection of the
U.S. gas pipelines. It was noted that the inspection was compli-
cated by the formation of solid plugs in the winter time. It was
assumed that they encountered ice plugs due to the freezing of
liquid water and condensed water. Hammerschmidt (1934),* Tel.: 1 979 845 4066.
E-mail address:[email protected]
Contents lists available atScienceDirect
Journal of Natural Gas Science and Engineering
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j n g s e
1875-5100/$ see front matter 2009 Published by Elsevier B.V.
doi:10.1016/j.jngse.2009.12.004
Journal of Natural Gas Science and Engineering 2 (2010) 4959
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relying on his laboratory investigations, showed that the solid
plugs consisted not of ice, but of hydrate from the transported
gas. The urgency with which gas hydrates were studied grew
sharply. It was necessary to investigate in detail the conditions of
the formation of gas hydrates, and to find an effective means of
preventing solid hydrate plugs from forming in pipelines. In the
mid-thirties of the last century,Nikitin (1936)hypothesized that
gas hydrates were clathrate compounds. A few years later, Von
Stackelberg (19491954) confirmed this experimentally. There
were 144 papers on gas hydrates published between 1934 and1965. The third period in the history of studying gas hydrates is
tied to the discovery of natural gas hydrates, which become an
unconventional source of energy in the coming decades. The
existence of gas hydrates in nature was proven in the 1960s
(Makogon, 1965, 1966). Over 9000 papers on natural gas hydrates
have been published over the past forty-plus years. Now we
know that gas hydrates exist in nature, and they are present both
on our planet, and in the universe. Hydrates played an important
role during the formation of planets, and the atmosphere and
hydrosphere of Earth.
The problem of development and production of gas from GHD is
an important problem for the twenty first century. A number of
countries, including the USA, Japan, India, China, Korea, and
Germany, have national programs for studying hydrates, and
industrial production of natural gas from hydrates. Furthermore, inmany other countries, including Russia, Canada, and England,
important studies of gas hydrates are conducted in many labora-
tories. However, even the basic review of publications on gas
hydrates shows that most of the research projects are conducted
separately, at different scientific levels, and the published results
frequently are unnoticed by the energy industry. The scientific
community should be more focused on an effort to improve the
technologies necessary to locate, measure, and produce gas from
gas hydrate deposits.
The first example of natural gas production from hydrates came
from Siberia. The Markhinskaya well drilled in 1963, in the north-
western part of Yakutia to a depth of 1830 m, revealed a section of
rocks at 0 C temperature at a depth of 1450 m, and permafrost
which ended at approximately 1400 m. The conditions of rock
formations matched those of hydrate formation. This match led me
to hypothesize the possibility of finding gas hydrate accumulations
in cold layers (Makogon, 1965). The natural hydrate hypothesis was
seriously doubted by the experts. The idea needed an experimental
confirmation. Hydrates of natural gas were then formed in a porous
medium, and in core samples at the Gubkin Institute of Oil and Gas
in Moscow (Makogon, 1966).
The results have shown the possibility of formation and stableexistence of naturally occurring gas hydrates in rocks, and were
recorded as a scientific discovery of natural gas hydrates. After
a comprehensive international examination, the discovery of
natural hydrateswas recordedin the USSR State Registerof scientific
discoveries asN 75 with the following statement: The previously
unknown property of natural gases to form deposit in the solid
gas hydrate state in the Earths crust at specific thermodynamic
conditions was experimentally established (Moscow, 1969).
Soon thereafter, a group of young geologists named Mark Sapir,
Alexandr Benyaminovich and Anatoly Beznosikov (1970) found the
first gas hydrate deposit in the Messoyakha field in the Transarctic
region on the eastern border of West Siberia. Comprehensive
geophysical and thermodynamic studies performed in the Mes-
soyakha wells showed that gas in a hydrated state exists in the
upper part of the deposit. The underlying part of the deposit con-tained gas in a free state. The Messoyakha field, with original
reserves of about 30 billion m3, was dwarfed by the giant Urengoy,
Yamburg and Medvezhye gas fields in Siberia. However, the Mes-
soyakha production of gas from hydrates was a catalyst in the
growth of research on natural gas hydrates. The field provided gas
to an important metallurgy factory in the Transarctic, and allowed
the factory to replace costly imported coal with the clean, cheap
natural gas. The Messoyakha field was the first confirmation of the
presence of gas hydrate deposits, and introduced the possibility of
their commercial development. The discovery of natural gas
hydrates coincided with the peak of an energy crisis. Studying gas
hydrates became more important as energy prices increased in the
Fig. 1. Distribution of discovered gas hydrate deposits. BSR deposit located by seismic refraction.
Y.F. Makogon / Journal of Natural Gas Science and Engineering 2 (2010) 495950
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1970s. The basic stages of gas hydrate discovery and subsequent
development are as follows:
1778 Priestley obtained SO2 hydrate in the laboratory.
1811 Davy obtained Cl2 hydrate in a laboratory and called it
a hydrate.
1934 Hammerschmidt studied gas hydrates in industry.
1965 Makogon showed that natural gas hydrates exist and
represent an energy resource.1969 Official registration of scientific Discovery of Natural Gas-
Hydrates (24 Dec. 1969)
1969 Start of gas production from the Messoyakha gas hydrate
deposit in Siberia (Dec. 24).
1.2. Characteristics and morphology of gas hydrates
Gas hydrates may formally be referred to as chemical
compounds, because they have a fixed composition at a certain
pressure and temperature. However, hydrates are compounds of
a molecular type. They form as a result of the Van der Waals
attraction between the molecules. Covalent bonds are absent in the
gas hydrates, because no pairing of valence electrons and no spatial
redistribution of electron cloud density occurs during their
formation. Gas hydrates can be stable over a wide range of pres-
sures and temperatures (Fig. 2).
Fig. 3 shows the cell of methane hydrate in structure I. A few
structures exist at pressures above 1000 bar.
Hydrates of gases are widespread in nature, and easily form
during systems (equipment) of production, transportation, and the
processing of gases and a number of volatile liquids. Gas hydrate is
a mineral of the clathratehydrate group.Hydrates have sixdifferent
forms: (1) Molecular sieves, characterized by interconnected
trough cavities and/or passages; (2) Channel complexes when
hydrate forming molecules form a crystalline lattice with tubular
cavities; (3) Layered complexes which form clathrates with inter-
laced molecular layers; (4) Complexes which form with large
molecules having concavities, or niches in which an inclusionmolecule resides; (5) Linear polymeric complexes form by tube
like-shaped clathrate molecules; (6) Clathrates form in cases when
inclusion molecules fill in the closed cavities, creating a shape
similar to a sphere. Hydrates of gases and volatile liquids are related
to the latter type of clathrates.
Four conditions must be met simultaneously, and within one
region in order for the gas hydrate to form: presence of gas, water,
high pressure and low temperature. Pressure and temperature
conditions for some gases known to form hydrates are shown in
Fig. 4. The hydrate formation process is exothermal.
Several properties of gas hydrates are unique. For example, 1 m3
of water may tie up 207 m3 of methane to form 1.26 m3 of solid
hydrate; whereas without gas, 1 m3 of water freezes to form
1.09 m3 of ice. One volume of methane hydrate at a pressure of 26
bar, and temperature of 0 C contains 164 volumes of gas. In
hydrate, 80% (by volume) is occupied by water, and 20% by gas.
Thus, a volume of 0.2 m3 of hydrate contains 164 m3 of gas. The
dissociation of hydrate by increasing the temperature in a constant
volume will be accompanied by a substantial increase in pressure.
For methane hydrate formed at a pressure of 26 bar and temper-ature of a 0 C, it is possible to obtain a pressure increase of up to
1600 bars. Hydrate density depends on its composition, pressure
and temperature. Depending on the composition of gas, pressure,
1
10
100
1000
10000
-25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60
Temperature, C
Pressu
re,
Mpa
Gas-Hydrate-Ice
Gas-Hydrate-Water
Gas-WaterGas-Hydrate-Ice
AB
C
D
E
F
G
Gas-Ice
Fig. 2. Pressuretemperature equilibrium curves for methanewater system for hydrate formation. Presently, only three structures are known at moderate pressure: namely, the
structures I and II (Stackelberg, 19491954;Davidson, 1983), and structure H (Ripmeester et al., 1994).
Fig. 3. Cell of MethaneHydrate Str. I, (T. Y. Makogon, PersonalCommunication,2002).
Y.F. Makogon / Journal of Natural Gas Science and Engineering 2 (2010) 4959 51
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and temperature, the density of hydrate changes from 0.8 to
1.2 g cm3. Density of some gas hydrates is reported inTable 2at
equilibrium pressure, and a temperature of 273 K. However, density
of hydrates changes depending on pressure and temperature, as
shown in Table 2 and Fig. 5. Composition of gas hydrates also
strongly depends on free gas composition, pressure, and temper-
ature (Tables 1 and 3).
The morphology of gas hydrate crystals depends on water and
gas compositions, pressure, temperature, and the phase state of
water (liquid, vapor or solid) and gas. More than ten thousand
different forms of crystals were studied. Nuclei of hydrate crystals
usually start to form at a gas-water interface, and grow to a total
coverage of the interface (grow to totally cover the interface?).
Following that, crystals grow in free gas phase or in water. There are
three basic morphologic forms of hydrate crystals: massive, whis-kery and gel-like, as shown in Fig. 6-a through d (Figs. 7 and 8).
2. Natural gas hydrates hydrates formed in nature
Natural gas hydrates are metastable minerals, where the
formation and dissociation depend on the pressure and tempera-
ture, composition of gas, salinity of the reservoir water, and the
characteristics of the porous medium in which they were formed.
Hydrate crystals in reservoir rocks can be dispersed in the pore
space without the destruction of pores; however, in some cases, the
rock is affected. Hydrates can be in the form of small nodules (up to
12 cm in size), in the formof small lenses, or in the form oflayers up
to several meters thick (Fig. 9).
Gas hydrates may have also formed in space, and helped to form
planets of the solar system, as well as the hydrosphere and atmo-sphere of Earth. In order to release gas from a gas hydrate deposit,
one has to heat the entire mass of rock containing the gas hydrate.
The amount of energy required will depend on the heat capacity of
the hydrate, the heat capacity of the hydrate-saturated rock, the
specific concentration of hydrate in the rock pores, and the degree
of supercooling, which caused the formation of the gas hydrate
deposit. Hydrates possess a high acoustic conductivity and low
electrical conductivity (Makogon, 1966), which are used for the
effective methods of finding and evaluating a gas-hydrate deposit.
Dissociation of hydrate in rock, especially at offshore conditions,
can be accompanied by a significant change in strength of hydrate-
bearing rocks cemented by gas hydrates.
2.1. The location of gas hydrate zones
The mechanism of how gas hydrate deposits are formed and
where hydrates are located has been affected by numerous factors,
such as thermodynamic conditions in the region; the intensity of
generation and migration of hydrocarbons; the composition of gas;
degree of gas saturation and salinity of reservoir water; structure of
porous medium; lithology of reservoir; geothermal gradients in the
zone of hydrate formation, and in the basement rocks; and by the
phase state of hydrate formers. The Hydrate Formation Zone (HFZ)
represents the thickness of sediments in which the pressure and
temperature correspond to the thermodynamic conditions of stably
existent hydrate. These HFZs arefound where the earth is cold, such
as the Arctic (Fig. 10) and at the bottom of oceans (Fig. 11).
With an increase in the salinity of water, the thickness of theHFZ decreases. The thickness and the temperature of the HFZ in the
offshore strongly depend on the sea bottom temperatures, and
temperature gradient in the sediments. With an increase in sea
bottom temperatures, the size of the HFZ decreases. In the regions
with permafrost, the thickness of sediment in which gas hydrate
deposits exist can reach 400 to 800 m. The HFZ in the ocean is
found in the deep-water shelf and the oceanic slope at depths of
200 m, or deeper for the conditions of polar oceans, and from 500
to 700 m or deeper for the equatorial regions. The upper boundary
of the HFZ offshore is located near the seafloor.
Permeability of hydrate-saturated deposits is very low. If
hydrate saturation of pore space is over 20 to 25%, then the rocks
Temperature,
Pressure
atm
0
100
200
300
400
500
600
700
800
900
1000
0 5 10 15 20 25 30 35
CO2CH4
H2S
C3H8
Nat.Gas
Fig. 4. Equilibrium PT hydrate formation for different gases.
0.88
0.9
0.92
0.94
0.96
0.98
1
1.02
1.04
1.06
1.08
10 1000
Pressure, atm
100
H2S
Orenburg
Shebelinka
CH4
Density,g
/cm
3
Fig. 5. Relationship between the density of gas hydrates and equilibrium pressure.
Table 1Heat of dissociation of gas hydrates.
Gas Formula Dens ity g/cm3 Mole volume
cm3/mol
Heat of dissociation
T>0 C T
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can be considered impermeable. Resistivity and sonic velocity of
hydrate-saturated layers is very high. These characteristics can be
used for the discovery of gas-hydrate deposits.
2.2. Characteristics of gas hydrate deposits (GHD)
There are two basic forms of GHD: primary and secondary. A
primary deposit is one which does not melt after its formation.Primary deposits are usually found in deep water, where temper-
atures do not change rapidly over time. They are formed by the
gases dissolved in the reservoir water, and are located in the near
seafloor sediments, characterized by high porosity, low tempera-
ture, and low rock strength. Frequently, a primary GHD does not
have good barriers or seals. The hydrate begins to form in the pore
space and eventually plugs the migration paths which trap more
hydrate.
The hydrate can also act as cement holding the rock together.
After the decomposition of hydrate, the porous media may revert
back to a permeable, unconsolidated state.
For a primary GHD, the gas can be found over large areas that do
not depend on the presence of structures. Free oil or gas may be
present in the case of primary GHD.
Secondary GHD are usually located in the Arctic onshore. Theyare associated with natural gas reservoirs, located under the
impermeable cap rocks in structural, or stratigraphic traps. Upon
temperature decrease in the formation (lower than the equilibrium
temperature for the existing gas of this composition), hydrates may
form. The temperature of rock layers on the continents is cyclic
during the geologic time. During these cycles, the gas hydrates in
the rocks will form and melt repeatedly. Often, there is a free gas or
oil under the hydrate layers.
An example of this kind of field is the Messoyakha field in
Siberia, which is now in the decomposition stage due to an increase
in temperature. About two thousand years ago, the Messoyakha
was a 100% gas hydrate field, in which there was no gas in the free
state. The layers are warming and some of the gas is now present as
free gas. Thus, GHD areforming and melting over geologic time. The
most promising regions to look for commercial deposits of gas
hydrate are the deep-water shelves, continental slopes, and conti-
nental abyssal trenches, with depths of water ranging from 700 to
2500 m. However, the most promising resources of gas hydrate are
concentrated in only 9 to 12 % of the ocean floor ( Fig. 12).
In many sediments and rocks, the pressure and temperature arefavorable for the formation of gas hydrates. However, in most of the
rocks the saturation of gas hydrate is too low to be commercially
developed. For example, in Messoyakha Field only 40 m of hydrate
has been identified in the HFZ layers that are 600-m thick. This
corresponds to 6.6% of thickness of the HFZ. In the Nankai Trough
(offshore Japan) there are 505 m of overall thickness of the sedi-
mentary rocks in which thermodynamic conditions were favorable
for the formation, and stable existence of GHD. However, only 17 m
of formation contains gas hydrates at reasonable saturations, which
constitutes only 3.4% of the total HFZ thickness. At Blake Ridge (East
Cost of the USA), the hydrate formation zone is 440-m thick.
However, only 7.5 m (i.e., only 1.7% of the thickness of the HFZ)
contains natural gas hydrates. Fig. 13 shows the pressure and
temperature conditions of some GHD located offshore. It is clear
that the majority of the GHD are in the supercooled state; i.e., the
temperature of the hydrate-saturated layers is considerably lower
than equilibrium temperature/pressure. In this case, pressure in
GHD should exceed equilibrium by more than several tens of bars,
and up to over one hundred bars. This does not normally occur in
offshore regions, and greatly increases the reservoir temperature.
It is important to emphasize that geology, thermodynamic
conditions, depth of water and GHD, infrastructure of region, etc.,
can strongly influence and dictate the adequate technology for the
development of GHD. To rapidly improve the technology, the
industry should form an International Coordination Board to help
solve the vital problems associated with the development of GHD.
The board should provide guidance for the acquisition of research
money from different organizations, and for various projects. The
world needs energy concentrated in natural gas hydrates. However,the technology must be developed as soon as possible in order to
produce GHD in the near future.
2.3. Composition of natural gas hydrates
The composition of natural gas hydrates is determined by the
composition of gas and water, and the pressure and temperature at
which they existed during formation. Over geologic time, there will
be changes in the thermodynamic conditions, and the vertical and
lateral migration of gas and water; therefore, the composition of
hydrate can change both due to the absorption of free gas, and the
recrystallization of already-formed hydrates. Based on cores taken
while drilling in GHD, hydrate usually consists of methane with
small ad mixtures of heavier components. However, in a number of
cases, hydrate contains a significant volume of heavy gases (seeTable 3). The presence of heavy hydrocarbons in the hydrates is an
indicator of the presence of oil reservoirs in the formations below
the GHD.
3. Methods of developing gas hydrate deposits
The following properties are useful in exploration for GHD: (1)
high sonic velocity; (2) high electrical resistance; (3) low density;
(4) low thermal conductivity; and (5) low permeability to gas and
to water. One can evaluate GHD by using seismic data, gravimetric
surveys, the measurement of heat and diffusion fluxes above the
GHD, and the measurement of the dynamics of electromagnetic
Table 2
Some properties of gas hydrates.
Gas Molecular
Weight
g/mole
Dissociation
pressure at
t 273 K,
MPa
Lattice
constant,
nm
Specific volume
of water in
hydrate state at
t 273 K, cm3/g
Hydrate
density at
t 273 K,
g/cm3
CH4 16.04 2.56 1.202 1.26 0.910
C2H6 30.07 0.53 1.203 1.285 0.959
C3H8 44.09 0.172 1.740 1.307 0.866
i-C4H10 58.12 0.113 1.744 1.314 0.901CO2 44.01 1.248 1.207 1.28 1.117
H2S 34.08 0.096 1.202 1.26 1.044
N2 28.01 14.3 1.202 0.995
Ar 39.95 8.7 1.202 1.26
Kr 83.8 1.46 1.202 1.26
Xe 131.3 0.156 1.200 1.252
Table 3
Composition of gas of natural gas hydrates (After Taylor, 2002).
Gas hydrate deposit Gas composition, mol %
CH4 C2H6 C3H8 iC4H10 nC4H10 C5 CO2 N2
Haakon Mosby Mud
volcano
99.5 0.1 0.1 0.1 0.1 0.1
Nankai Trough, Japan 99.3 0.63
Bush Hill White 72.1 11.5 13.1 2.4 1 0
Bush Hill Yellow 73.5 11.5 11.6 2 1 0.3 0.1
Green Canyon White 66.5 8.9 15.8 7.2 1.4 0.2
Green Canyon Yellow 69.5 8.6 15.2 5.4 1.2 0
Bush Hill 29.7 15.3 36.6 9.7 4 4.8
Messoyakha, Russia 98.7 0.03 0.5 0.77
Mallik, Canada 99.7 0.03 0.27
Nankai Trough -1, Japan 94.3 2.6 0.57 0.09 0.8 0.24 1. 4
Blake Ridge, USA 99.9 0.02 0.08
Y.F. Makogon / Journal of Natural Gas Science and Engineering 2 (2010) 4959 53
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field in the region being investigated. The most common method is
seismic surveying at frequencies of approximately 30 to 120 hertz(1 hertz 1 s1) with a resolution ranging from 12 to 24 m, and
high-frequency over 400600 hertz with a resolution of 12 m.
One can use standard two-dimensional (2D) seismic to locate the
lower boundary of the hydrate-saturated formation by looking for
BottomSeismic Reflectors (BSR). In GHD, BSR areformed by free gas
underneath the hydrate layer. Unfortunately, 2D seismic surveying
does not answer many important questions, and in particular, it
does not provide information about the degree of hydratesaturation.
The results of high-resolution, three-dimensional seismic
surveying are more informative, and make it possible to determine
lower and upper boundaries of the hydrate-saturated layers. It is
necessary to learn how to evaluate the concentration of hydrate in
the rocks, which will make it possible to determine the amount of
Fig. 6. a. Methane hydrate film formed on the free gaswater surface (Makogon, 1960). b. CO2-Sw Hydrate Mono Crystals (Makogon, 2000). c. Secondary black methane hydrate
crystals with transformation of color. d. Secondary black natural gas hydrate crystal formed in water.
Fig. 7. After whiskery crystals of gas hydrate formed erosion of stainless steel.
Fig. 8. Solid gashydrate plug formed in an offshore gas pipeline, diameter 16 in.
(Courtesy of Petrobras).
Y.F. Makogon / Journal of Natural Gas Science and Engineering 2 (2010) 495954
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gas trapped in GHD.Fig. 14illustrates the seismic profile of a GHD
located in the Caspian Sea. Detailed evaluation of GHD is accom-
plished by combining seismic data with well log, and core data
obtained from wells. However, much more research is required to
perfect these methods.
To eventually produce natural gas economically from GHD, it is
important to determine notonly the potential gas-in-place, but also
what amount can be extracted economically. The effectiveness of
Fig. 9. Cores of natural gas hydrates (Collett, 2000).
Fig. 10. Gas hydrate stable zone onshore (AfterMakogon, 1965). Fig. 11. Gas hydrate stable zone offshore (After Makogon, 1970).
Y.F. Makogon / Journal of Natural Gas Science and Engineering 2 (2010) 4959 55
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the extraction is determined by the geological and thermodynamic
conditions, and by the concentration of gas hydrate in the deposit.
To produce the free gas, the hydrate must be first changed from
a solid to a fluid.
Thus, it is necessary to use much of the energy contained in the
GHD for heating the rock layers near the GHD. Preliminary esti-
mates show that the coefficient of extraction of the gas hydrate can
be as high as 50 to 70%. However, from total world potential
resource it has been estimated that the coefficient of extraction
should average from 17 to 20%.
For offshore conditions, with the depths of water ranging from
0.7 to 2.5 km, effective production of gas from GHD in the majority
of the cases may occur when hydrate saturation of porous media
exceeds 30 to 40%. However, each geologic region will have to be
studied in detail to establish the minimal hydrate saturation that is
required. To change GHD to natural gas, it is necessary to (1)
decrease reservoir pressure to lower than equilibrium one; (2)
increase the temperature to higher than equilibrium one; (3) inject
active reagents; which facilitate the decomposition of hydrate; and(4) use some new technology. The easiest method is to lower the
reservoir pressure in GHD. Clearly, this method is only feasible
when free gas is found below the GHD.
3.1. General characteristic of the Messoyakha gas hydrate field
The Messoyakha field was discovered in 1967 in the north-
western portion of East Siberia, in the almost inaccessible region of
the Trans-arctic, on the west side of the Yenisey River. Its coordi-
nates are 68.5 to 68.7 N and 84 to 85 W. The lowest outsidetemperatures reach 55 C in January, while the average for the
month is28 C. The average temperature in July is10C, and the
average annual temperature is 18C. The thickness of the
permafrost in the field ranges from 420 to 480 m. Cross-section of
Messoyakha GHD is presented inFig. 15
The cyclic supercooling of the gas hydrate deposit during
geological time contributed to the active process of formation and
dissociation of hydrates, which led to the destruction of the mineral
cement between the sand particles in the GHD. Thus the productive
layers of the GHD are characterized by low rock strength. The
maximum permissible reduction in pressure cannot exceed 2 to 4
bars, above which formation collapse can occur. Development
began in December 1969, against the background of two giant
Siberian gas fields called Urengoy and Yamburg. However, Mes-
soyakha played the role of catalyst in the development of natural
gas hydrates studies. First of all, it ensured the replacement of
expensive imported coal to the region. Secondly, the field
confirmed the presence of gas hydrate deposits, and the real
possibility of their commercial development.
The Messoyakha structure is 12.519 km on the top of the
Dolganskoy Formation of AlbianCenomanian age with amplitude
of 84 m. The geological section, revealed by deep drilling, is the
sandy argillaceous deposits of Middle Jurassic, and lower and Upper
Carboniferous age, overlapped by Quaternary sediments. The
deposit is located in part of the Dolganskoy formation; the floor of
the gas-bearing capacity is equal to 75 m, and it measures 730 m
from minimum depth to the topof the layer. The depth of gas-water
contact is located at a depth of approximately 850 m. The porosity
varies from 16 to 38% with an average value of 25%. Residual watersaturation varies from 29 to 50%, averaging 40%. The permeability
Fig. 12. Most effective zone for development of GHD.
Fig. 13. Real pressuretemperature conditions for gas hydrate deposits with different gas composition.
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varies over wide limits from several mD to 1D, with a 125 mD
average. Initial reservoir pressure was 78 bar. The initial composi-
tion of the free gas was: C1-98,6%; C2 0,1%; C3 0,1%; CO2 -0,5%;
N2 0,7%. The salinity of reservoir water does not exceed 1.5 %,
which confirms the presence of active dissociation of hydrates in
the deposit.
The initial reserves of gas, without taking into account the
presence of hydrates were 24109 m3. The reserves of gas in the
hydrated state prior to the beginning of field development were
estimated at about 12109 m3.
Fig. 16shows the pressure and temperature in Messoyakha; the
equilibrium curve of gas hydrate under in situ conditions is also
included in this figure.The boundary of phase transition passesover
the conditional interface with a temperature near 10 C. Productive
layersare divided into twodeposits: (1)freegas that is located lower
than equilibrium surface; and (2) gas hydrate, which is located
higher than equilibrium surface. The geothermal gradient (GTG) in
the interval of the frozen layers is around 1 C per 100 m. The GTG
under the permafrost layers is of 3.0C per 100 m. The temperature
atthe top ofthe deposit is8 C,whereas atthe bottomit is12C.The
GTG in the productive part of the deposit is 4.2 C per 100 m.
There is an absence of lithological trap. The thermodynamic
interface of the gas hydrate and free gas deposits does not have
a lithological trap. The hydrate-saturated intervals are located in
the layers where the thermodynamic equilibrium exists, and free
gas is present. As such, conventional oil and gasmethods can be
used to develop the GHD. Hydrate saturation of pore space in the
initial stage was about 20%. The maximum degree of supercooling
in the reservoir prior to the beginning of development did not
exceed 2 C (at the top of the productive layer). The average degree
of supercooling was 1 C. Low supercooling contributed to the
decomposition of hydrate by insignificant lowering in the deposits
reservoir pressure. This prevented the formation of hydrate during
Fig. 14. High resolution seismic cross-section with gas hydrate deposit (After Diaconescu et al., 2001).
Fig. 15. Cross-section of Messoyha Gas-Hydrate Deposit in East Siberia.
Fig. 16. Thermodynamic cross-section of Messoyakha gas-hydrate field. Black area
represents hydrated layer, gray free gas saturated layer.
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the drilling. The composition of the drilling mud, containing
calcium salts, prevented the formation of hydrates.Fig. 17presents
the gas production, and actual and calculated reservoir pressure
during the production and shut-in periods.
On 31 December 2008, the gas production from the Messoyakha
Deposit was 13.3109 m3, of which 6.9109 m3 were produced as
a resultof dissociationof hydrates. There wasa decreasein reservoir
pressure.The reservoir pressure,after 35 years of development, was
reduced from 78 bar to 60 bar. In the absence of hydrate, the reser-
voir pressure should have been 36 bar. In the first years of devel-
opment, with high rates of gas production, the reservoir pressurewas lowered to 50 bar, which was below the equilibrium one by 16
bar. In this case, the active process of decomposition of hydrate
began, and continued for manyyears. After the field had been shut-
in foran extendedperiod (from1979 to1982), thereservoir pressure
increased to 60 bar; i.e., back to equilibrium one. Currently, the gas
production does not exceed 175106 m3 per year, and the reservoir
pressure has remained practically constant. The volumes of the gas
produced from the deposit, approximately corresponded to the
volumes of hydrate gas entering due to dissociationof hydrates. The
position of gas-water contact did not change as gas was produced.
4. Conclusions
The energy concentrated in natural gas hydrates can serve as an
unconventional energy source very important to sustain thegrowing energy needs for several decades. Natural gas hydrates are
more evenly distributed on the planet than sources of hydrocar-
bons. The production of gas from GHD will be accessible to many
countries. Many existing technologies can be used to find and
develop GHD. However, significant Research and Development will
be necessary before GHD can be developed economically. The
economic and ecological aspects of producing a GHD must be
evaluated. Both the economics and the ecological aspects depend
upon developing technologies. In addition, each GHD will be
different, so different technologies may have to be employed.
Experience in Messoyakha field showed that the cost required to
produce the GHD was about 15 to 20% higher than a conventional
gas field in the same area. Expendituresfor drilling wells in GHD are
considerably lower than the cost of drilling wells in natural gas
reservoirs, because GHD are located at shallow depths. A better
formation evaluation technology is needed to better define a GHD
in order to improve the economics of its development. The most
important problem is the creation of highly-effective technologies
of the transfer of natural gas from its solid state into free gas.
Studies of natural gas hydrates must be coordinated on a world-
wide scale which could speed up the technology development.
Acknowledgement
The author is grateful to Professor Academician Dr. Michael J.
Economides for reviewing the manuscript and making some valu-
able suggestions.
References
Collett, T., 2000. Ladd detection of gas hydrate concentration on the Blake RidgeODP. Rep.164.
Davidson, D.W., 1983. Gas hydrates as clathrate ices. In: Cox, J. (Ed.), Natural GasHydrates.
Diaconescu, C.C., Kieckhefer, R.M., Knapp, J.H., 2001. Geophysical evidence for gashydrates. Marine Petroleum Geol. 18.
Hammerschmidt, E.G., 1934. Formation of gas hydrates in natural gs transmissionlines. Ind. Eng. Chem. 26, 851855.
Makogon, Y.F., 1960. Hidtrates of Natural Gases. J. Gas Technik 3, 1041.Makogon, Y.F., 1965. A gas hydrate formation in the gas saturated layers under low
temperature. Gas Indus. 5, 1415.Makogon, Y.F., 1966. Peculiarities of Gas-Field Development in Permafrost. Nedra,
Moscow.Makogon, Y.F., 1982. Perspectives for the development of Gas Hydrate deposits. In:
Fourth Canadian Permafrost Conference, Calgary, March 26, 1981.Makogon, Y.F., 1997. Hydrates of Hydrocarbons. Penn Well, Tulsa, USA, 516 p.Nikitin, B.A., 1936. Gas hydrates. Z. Anorg. Allg. Chem. 227, 81.Priestley, J., 17781780. Versuche und Beobachtungen Uber Verrshiedene Gattun-
gen der Luft, Th. 1-3, 3:359362. Wien-Leipzig.Ripmeester, J., Ratclife, C., Klug, Tse, J., 1994. II-nt. GHC, N-Y.Sloan, E.D., 1990. Clathrate hydrates of natural gases, Sec. Ed. N-Y.Sloan, E.D., Koh, C.A., 2007. Hydrates of Natural Gases, third ed. NY.Taylor, C., 1954. Formation studies of methane hydrates with surfactants. In: 2nd
International Workshop On Methane Hydrates. October 2002, Washington.Von Stackelberg, M., 19491954. Solid gas hydrates. Zeitschrift Elektrochem 58, 104.
Fig. 17. Reservoir pressure during development of Messoyakha GHD.
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Further reading
Makogon, Y.F., 1972. Natural Gases in the Ocean and the Problems of Their Hydrates.In: VNIIEGasprom. Express-Information, No.11, Moscow, p. 43.
Makogon, Y.F., 1974. Hydrate of Natural Gas NEDRA, Moscow, 1981. PennWell, Tulsa,237 p.
Giavarini, Carlo, 2007. Hydrate of Methane. University of La Sapienza, Roma, 192 p.Makogon, Y.F., Trebin, F.A., Trofimuk, A.A., 1971. Finding of a pool of gas in the
hydrate state. Moscow, DAN SSSR 196 (1), 197206.Makogon, Y.F., Holditch, S.A., Makogon, T.Y., 2004. Proven Reserves and Basics for
Development of Gas Hydrate Deposits. AAPG, Vankouver.Makogon, Y.F., Holditch, S.A., Makogon, T.Y., 2005. Development of G-H deposits oil
and gas J Nos. 7.II., and 14.II.Sapir, S.H.,Beniaminovich, A.F.,1973.Messoyakhygashydrate Field. GeolOil Gas 6, 26.
Glossary
Gas Hydrates:Solid clathrate physical compounds, formed by molecules of gas andwater.
Natural Gas Hydrates: Gas Hydrates formed in nature.Kinetics of hydrates: Dynamics of formation and dissociation of gas-hydrate crystals
at different pressures and temperatures.
Prof. Makogon is a world-renowned expert on gas hydrates. He is the author ofScientific Discovery of Natural Gas-Hydrates (1965). He has authored eight mono-graphs, including six books on gas hydrates and over 260 scientific papers. He holds27 patents, and has over 50 years of experience in education and research for the oiland gas industry. Yuri F. Makogon graduated with honors from the KrasnodarTechnical School in 1951 and from the Gubkin Petroleum Institute in Moscow in1956. Dr. Makogon a Member of the Russian Academy of Natural Science (RANS)since 1990. Prof. Makogon served as the first Chairman of the SPE International,Russian section (199193). Dr. Makogon joined Texas A&M University in 1992. Hesheaded the gas-hydrate laboratory of Texas A&M University since 1995. He wasnominated International Distinguished SPE Lecturer for 20022003. He is currentlythe US Section Regional Secretary of the RANS. Dr. Y.F. Makogon received anHonorary Doctorate from the Nikolaev Institute of Inorganic Chemistry RussianAcademy of Science in 2005. His awards include the Gubkin StatePrize in 1989;Lifetime Achievement Award of Honor by the Sixth International Conference on GasHydrates in 2008; and many international Honor Awards.
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