This was the report of a project in natural gas engineering (PGE 403).A short literature review on the developments of marine gas hydrates. We have previously uploaded a powerpoint presentation of the project, This is the final report. Hope it might be helpful.Thank you and good luck.

1. NEAR EAST UNIVERSITY ENGINEERING FACULTY
PETROLEUM AND NATURAL GAS ENGINEERING
DEPARTMENT
DEVELOPMENTS IN MARINE GAS HYDRATES
Project
PGE 403
Submitted of the Petroleum and Natural Gas Engineering Department
in Partial Fulfillment of the Requirements for the Degree of Bachelor
of Science
Prepared By
Modou JARJU (20157408)
Near East University
Nicosia
April 2018

2. i
NEAR EAST UNIVERSITY ENGINEERING FACULTY
PETROLEUM AND NATURAL GAS ENGINEERING
DEPARTMENT
DEVELOPMENTS IN MARINE GAS HYDRATES
Project
PGE 403
Submitted of the Petroleum and Natural Gas Engineering Department
in Partial Fulfillment of the Requirements for the Degree of Bachelor
of Science
Prepared By
Modou JARJU (20157408)
Near East University
Nicosia
April 2018

3. ii
YAKIN DOĞU ÜNİVERSİTESİ
MÜHENDİSLİKİ FAKÜLTESİ
PETROL VE DOĞAL GAS MÜHENDİSLĞİ
BÖLÜMÜ
DENİZ GAZ HİDRATLARINDA GELİŞMELER
Proje
PGE 403
Lisans Derecesi Gerekliliğinin Kısmi Yerine Getirilmesinde Petrol ve
Doğal ğaz Mühendisliği Bölümüne Sunulmuştur
Hazırlayan
Modou JARJU (20157408)
Near East University
Nicosia
Nisan, 2018

4. iii
MODOU JARJU: DEVELOPMENT IN
MARINE GAS HYDRATES
Approval of Chairman of Undergraduate School of Faculty of
Engineering
Prof. Dr. Cavit ATALAR
Chairperson
We certify this thesis is satisfactory for the award of the degree
of Bachelors of Science inPetroleum and Natural Gas
Engineering
Examining Committee in Charge
Title, Name and Surname Department
Prof. Dr. Cavit ATALAR Committee Chairman, Department of Petroleum and
and Natural Gas Engineering, NEU
Dr. Ersen ALP Department of Petroleum and Natural
Gas Engineering, NEU
MSc. Serhat CANBOLAT Department of Petroleum and Natural
Gas Engineering, NEU

5. iv
ABSTRACT
Hydrates also known as gas clathrates are ice-like mixtures of natural gas and water in which
gas molecules are trapped within the crystalline structures of frozen water. They exist in arctic
regions of Soviet Siberia, Canada, and the North Slope of Alaska where temperatures low as
low as 32°F exist far beneath the earth's surface. The hydrates, which are of importance to the
petroleum industry, are composed of water and eight molecules which includes methane,
ethane, propane, isobutane, normal butane, nitrogen, carbon dioxide and hydrogen sulfide.
Recent evaluations, which had been conducted on the energy potential of gas hydrates, proves
that the extraction of methane from marine gas hydrates is soon to become a promising option
for many nations around the globe. Over the past years, the hydrate exploration prospects
have steadily stirred away from the confirmation of the presence of gas hydrate to a more
sophisticated issue of anticipating for specific accumulations of highly concentrated gas. In
general, the ideas for gas hydrate exploration has advanced from a search for bottom
simulating reflectors to a process which is similar to that of the conventional oil gas
exploration that accommodates direct detection of gas hydrate accumulations in seismic data
supported by integrated geophysical/geochemical studies that tackles the subject of gas supply
and reservoir distribution. Gas hydrates resource types Gas hydrate as pore fill in intrinsically
permeable sediments “Chimney” structures. Disseminated gas hydrates in muds. The marine
gas hydrate is commonly theorized as low-to-moderate saturation deposits broadly
disseminated in clay matrix often near the base of gas hydrate stability.

6. v
ÖZET
Gaz klatratları olarak da bilinen hidratlar, gaz moleküllerinin donmuş suyun kristal yapıları
içinde tutulduğu, buz benzeri doğal gaz ve su karışımlarıdır. Sovyet Sibirya, Kanada ve
Alaska'nın Kuzey Yamacının kutup bölgelerinde, 32 ° F gibi düşük sıcaklıkların yeryüzünün
çok altında olduğu yerlerde var. Petrol endüstrisine önem veren hidratlar su ve metan, etan,
propan, izobütan, normal bütan, azot, karbondioksit ve hidrojen sülfür içeren sekiz
molekülden oluşmaktadır. Gaz hidratlarının enerji potansiyeli üzerine yapılan son
değerlendirmeler, metan gazının deniz hidratlarından çıkarılmasının dünyanın dört bir
yanındaki pek çok ulus için umut verici bir seçenek haline geldiğini kanıtlamaktadır.
Geçtiğimiz yıllarda, hidrat keşif umutları, gaz hidratının varlığının doğrulanmasından, yüksek
konsantrasyonda gazın spesifik birikimlerini öngören daha sofistike bir soruna doğru giderek
karışmıştır. Genel olarak, gaz hidrat araştırması için fikirler, entegre jeofizik / jeokimyasal
çalışmalarla desteklenen sismik verilerdeki gaz hidrat birikimlerinin doğrudan algılanmasını
sağlayan geleneksel petrol gazı araştırmasınınkine benzer bir yönteme yansıtıcı alttan
yansıtıcıların araştırılmasıyla ilerlemiştir. Bu, gaz tedariki ve hazne dağıtımı konusunu ele
alır. Gaz hidratları kaynak tipleri • Doğal olarak geçirgen tortularda gözenek dolgusu olarak
gaz hidratı • “Baca” yapıları • Çamurlarda yayılmış gaz hidratları Deniz gazı hidratı
genellikle, genellikle tabanın yakınındaki kil matrisinde yaygın olarak yayılan düşük ila orta
doygunluk yatakları olarak kuramlaştırılır. gaz hidrat kararlılığı.

7. vi
ACKNOWLEDGEMENTS
We would love to express our utmost and most honorary gratitude to our supervisor Serhat
CANBOLAT for whose helpful aid, comments and suggestions made this project possible.
My since gratitude to my colleagues Imran Abdulhameed and Believe Weli for their
contribution towards the project. Finally, to our colleagues and anyone who helped us with
advices, their knowledge based on practical experiences and materials that aided our project,
we offer our most sincere gratitude.

8. vii
TABLE OF CONTENTS
Contents
ABSTRACT .....................................................................................................................................................................iv
ÖZET...............................................................................................................................................................................v
ACKNOWLEDGEMENTS.................................................................................................................................................vi
TABLE OF CONTENTS ...................................................................................................................................................vii
LIST OF FIGURES .........................................................................................................................................................viii
LIST OF ABBREVIATIONS ...............................................................................................................................................ix
CHATER 1 .......................................................................................................................................................................1
INTRODUCTION .............................................................................................................................................................1
1.1Gas Hydrate Exploration Target............................................................................................................................1
1.2 Types of primary resources of gas hydrates ........................................................................................................2
1.2.1 Gas Hydrate as Pore fill in inherently (Naturally) Permeable Sediments .....................................................2
1.2.2 “Chimney” Structures ...................................................................................................................................3
1.2.3 Disseminated gas hydrates in muds .............................................................................................................3
CHAPTER 2 .....................................................................................................................................................................4
EXPLORATION PROCESS.................................................................................................................................................4
2.1Recommended Exploration Process.....................................................................................................................4
2.1.1 BSR (Bottom simulation reflectors) ..............................................................................................................4
2.1.2 Limitation of BSR (Bottom simulation reflectors).........................................................................................5
CHAPTER 3 .....................................................................................................................................................................6
3.1 Approaches..........................................................................................................................................................6
3.1.1 Establishment of the extent of the gas hydrate stability zone (GHSZ) .........................................................6
3.1.2 Prospect for “direct” indicators of gas hydrate occurrence within the GHSZ ..............................................7
3.1.3 Mitigate geologic risk through evaluation of occurrence of reservoir facies ...............................................8
3.1.4 Risk through evaluation of gas presence and migration ..............................................................................9
3.2 Status of BSRs in Gas Hydrate Exploration ..........................................................................................................9
CHAPTER 4 ...................................................................................................................................................................10
PRESENCE OF GAS HYDRATES IN THE ALASKAN ARTIC................................................................................................10
4.1 Log Evaluation....................................................................................................................................................11
CHAPTER 5 ...................................................................................................................................................................12
SUMMARY AND CONCLUSION.....................................................................................................................................12
REFERENCES.................................................................................................................................................................13

9. viii
LIST OF FIGURES
Figure 1: Gas hydrate pyramid variety of forms after (Boswell, 2014)..........................................................................1
Figure 2: delineation of the GHSZ through reference to the BSR after (Boswell, 2014). ..............................................6
Figure 3: Nomogram for determination of methane-hydrate-stability zone after Godbole, 1988)............................11

10. ix
LIST OF ABBREVIATIONS
GHSZ Gas Hydrate Stability Zone
BSR Bottom Simulator Reflectors
JOGMEC Japan Oil Gas and Metals National Corporation
BGHS Base of Gas-Hydrate Stability
SMI Sulfate-Methane Interface
NPHI Neutron Porosity
SPHI Sonic

11. 1
CHATER 1
INTRODUCTION
Gaseous petrol hydrates are ice-like blends of flammable gas and water in which gas atoms are
caught inside the crystalline structures of solidified water. They exist in ice areas of Soviet
Siberia, Canada, and the North Incline of The Frozen North where low temperatures exist far
underneath the world's surface. To deliver petroleum gas from hydrate zones, it is important to
decay the hydrates into gas and water by different techniques, for example, depressurization, 15
steams 16 or high temperature water infusion, 17 or infusion of such chemicals as methanol,
glycols, and brackish waters, 18 that are inhibitors of hydrate (Godbole et al, 1988).
1.1Gas Hydrate Exploration Target
The extraction of methane from marine gas hydrate has currently been assessed as having a
vitality potential for alternative energy around the world. There is high expectation on the
increment of gas hydrate exploration. Gas hydrate is notable to exist in an assortment of
structures that stance diverse openings and difficulties for vitality asset investigation and
generation process. Original Hydrate resources in-place, as well as numerical simulations have
indicated that only high saturation of hydrate inn permeable reservoirs are considered
economically and technically recoverable. Expectantly in search for more hydrates resources,
difficultly to recover resources will be encountered especially in well-developed gas hydrates
“chimney” structures. is likely that these structures will be produced as technology advances.
(Max et al, 2006).
Figure 1: Gas hydrate pyramid variety of forms after (Boswell, 2014).

12. 2
Gas hydrate resource pyramid demonstrating general occurrence-types based on lithology (left)
of the encasing sediment and associated estimates of natural gas resources (right). The change
from silts to muds is likely additionally degree, with key differentiation (dashed red line) being
the shift from predominantly pore-fill to predominantly grain-displacing mode of gas hydrate
occurrence. This figure does not include sea-floor mound deposits, as they remain an ugly huge
resource target. (Boswell, 2014).
1.2 Types of primary resources of gas hydrates
1.2.1 Gas Hydrate as Pore fill in inherently (Naturally) Permeable Sediments
The use of reservoir simulations to make geological models and suggest potentially recoverable
hydrates has help in determining viable producible gas hydrate-bearing sand-rich sediments. The
major deciding factor in this kind of hydrate resources is 1.Grain size
2. Intrinsic permeability
However, the intrinsic (during sedimentation, or before accumulation) permeability is the major
deciding factor on the reservoir quality. Sediments of high natural (intrinsic) permeability have
the potential to accumulate hydrates in high saturations of (50% to 90% of pore space), and are
much responsive depressurization production of gas. However, grain size is major or closest
factor for permeability; it is also influenced by porosity sediment sorting grain texture and other
factors. In all around arranged sediments, high characteristic porousness might be kept up in
dregs well into the sediment estimate rang; along these lines, the normal qualification made in
talks of gas hydrate repository quality between "coarse-grained" and "fine-grained" stores isn't
really at the ostensible sand/sediment cut-off (62 microns), however some place inside the center
to-bring down sediment measure go. Additionally, comprehension of the idea of this change will
be imperative, as it can be normal that numerous deep-water supplies will comprise of very fine
sands and silts and therefore may fall within this grey area. (Boswell, 2014)
For a case sample, a Japanese company (Japan Oil Gas and Metals National Corporation
(JOGMEC) in 2013 conducted a production test which successfully demonstrated gas extraction
via reservoir depressurization from gas hydrate reservoir. in the Nankai Trough, extending
findings established earlier in arctic field production experiments. While reservoir quality is
expected to increase with increasing grain size, the primary control of importance may be
intrinsic permeability. (Yamamoto et al, 2014).

13. 3
1.2.2 “Chimney” Structures
Worldwide, it is most likely that ‘chimney’ structures are predominantly abundant in most gas
hydrate reservoirs. In basins in which gas hydrate-bearing sands and coarse silts are not present,
or where their occurrence is well constrained, assessment of the occurrence of gas-hydrate cored
“chimney” structures is warranted. (Boswell, 2014)
Structure:
1. Generally cylindrical accumulations
2. Roughly equal width and thickness (typically 100s of m).
3. Largest features often being much more wide than tall.
4. Elongated vertically; hence, the name “chimney” structures (vertical exaggerations used in
displays of seismic data)
5. Chimney characteristic: 1. amplitude reduction (“blanking”) 2. Vertical displacement of strata
along the lateral margins.
Hydrates in the western deep-water Ulleung basin, East Sea of Korea. J. Marine Pet. Geol
Gas hydrate occurrence in saturations (10-40%) has been confirmed by drilling and coring
operations within chimneys. (Ryu et al, 2009).
In any case, the showed advances of innovation that has empowered creation from a scope of
"unpredictable" inland assets gives motivation to question that the building difficulties will stay
the way they are. There is surety of advancement in the gas hydrate production. (Ryu, B-J et al,
2009).
1.2.3 Disseminated gas hydrates in muds
Clay-Matrix are commonly known to be the host for most marine gas hydrate in low-to moderate
saturation deposits., often near the base of gas hydrate stability. It is indistinct whether such
events, exemplified maybe best by the Blake Edge stores off the eastern shoreline of North
America, are pore-filling or grain-dislodging at little scales yet regardless, the saturations are
commonly low (10% and regularly less) (Collett et al, 2009).

14. 4
CHAPTER 2
EXPLORATION PROCESS
The least difficult and fastest strategy for recognizing the zone of conceivable gas hydrate event
is to look at the gas-hydrate-stability zone. The basic condition for gas hydrate security at a given
profundity is that the genuine earth temperature at the profundity is lower than the balance
temperature of hydrates comparing to the weight and gas organization conditions. The thickness
of a potential hydrate zone can be an imperative variable in boring activities where penetrating
through hydrates requires exceptional precautionary measures. It additionally can be of
criticalness in deciding districts where hydrate events may be adequately thick to legitimize gas
recuperation. The presence of a gas-hydrate-solidness condition. However, it does not guarantee
that hydrates exist in that area, but rather just that they can exist. Nevertheless, if gas and water
exist together inside the hydrate-steadiness zone, at that point they should exist in gas hydrate
for. (Johnson, A., 2012).
2.1Recommended Exploration Process
There has been enormous evolution around the evaluation of marine gas hydrate through the
years.
2.1.1 BSR (Bottom simulation reflectors)
The connection between the manifestation of “bottom simulating reflectors” (BSRs) and gas
hydrates were greatly elaborated in Tucholke et al (1977) and Shipley et al (1979) in the late
1970s. Field confirmation of this connection was provided through well logging and sampling
across a prominent BSR on the Blake Outer Ridge, offshore eastern North America. The
successful discovery of high concentration gas hydrates in sand-rich marine reservoirs in the
Nankai Trough in 1999 prepared for another setting for gas hydrate investigation that
recommended De-accentuation of BSRs and development of more reliable indicators of sand-
facilitated, high saturation occurrences. This trend was accelerated as continued study of the
nature and generation of BSRs uncovered. (Boswell, 2007)
1) that their sign in seismic information is exceedingly touchy to the quality and nature of the
information
2)That the idea of BSRs is extremely sensitive to the event of free gas and correspondingly,
exceptionally unfeeling to the plenitude of gas hydrate. Inside industry, profound water shallow
danger evaluation yielded knowledge into already unrecognized geophysical signs of the base of
gas hydrate solidness. (Boswell, 2014).

15. 5
2.1.2 Limitation of BSR (Bottom simulation reflectors)
The limitations of BSR was confirmed after multi- well exploration drilling and coring program
prior to completion of an extensive seismic data acquisition in 2004 in the Nankai trough. The
limitation of BSRs in exploration 1, high-concentration, sand-hosted hydrates, Saeki et al. The
approach for gas hydrate exploration that integrates investigation of BSRs was further extended
by DOE-Chevron Gas Hydrates Joint Industry Project and the Bureau of Ocean Energy
Management’s in Gulf of Mexico and the success of this resulted success of these efforts in
delineating a number of gas-hydrate-bearing deep water sands provided confirmation that viable
gas hydrate exploration can be conducted prior to drilling using existing industry 3-D seismic
data. (Jones et al 2008).

16. 6
CHAPTER 3
3.1 Approaches
Viable gas hydrate exploration can be conducted prior to drilling using existing industry 3-D
seismic data. The following outlines the approach
3.1.1 Establishment of the extent of the gas hydrate stability zone (GHSZ)
The appraisal of marine districts for gas hydrate potential (or siting of areas for gas hydrate asset
assessment through boring and coring programs) begin with the diagram of the level of the
GHSZ through reference to all available seismic and well data. The acknowledgment of a
"BSR", paying little respect to its inclination, is for the most part adequate to do this, despite the
nearness of a BSR, elucidation of the profundity to the base of the GHSZ can be evaluated or
refined utilizing known or assessed water profundities, base water temperature, subsurface
weight and temperature inclinations, and gas and water geochemistry. (Boswell, 2014).
Figure 2: delineation of the GHSZ through reference to the BSR after (Boswell, 2014).

17. 7
figure 2 shows planned gas hydrate events as perceived in seismic information: Left: Seaward
Colombia, indicating outline of the GHSZ through reference to the BSR, and solid amplitudes
inside overlying residue. "Time-cut" maps through the amplitudes stamped "channels"
demonstrated crooked morphology characteristic of submarine channels, which can be relied
upon to be sand-inclined. Appropriate: from the southwestern Bay of Mexico, indicating
comparable highlights including an unmistakable BSR signifying the degree of the GHSZ, solid
amplitudes inside the GHSZ, checked change in the character of seismic occasions as they cross
the base of the GHSZ, and proof of gas nearness and movement, counting high-abundance
occasions beneath the BSR and likely ocean depths expulsion highlights.
3.1.2 Prospect for “direct” indicators of gas hydrate occurrence within the GHSZ
Any log information accessible from the district ought to be checked on for the event of high
resistivity zones inside sand-rich units inside the GHSZ. In light of earlier boring outcomes from
various areas around the world, the most encouraging "direct" seismic markers of gas hydrate at
high immersions in supply facies are irregular, high abundancy, reflections that are of an
indistinguishable extremity from the ocean bottom and that happen inside the GHSZ. All else
being equivalent, such occasions will be most planned where they happen at generally more
noteworthy sub-ocean profundities as water-immersed sands encased in exceptionally permeable,
uncompact muds at shallow sub-ocean profundities will likewise create positive plentifulness
irregularities. The prospectively of high-plentifulness occasions depends on the idea that the age
of the adequate impedance contrasts is just liable to happen where gas hydrate-immersion
achieves the levels for the most part managed just by sand dominated have lithology’s. (Boswell,
2014).
An extra convincing "direct" marker of gas hydrate event is lifted interim speed inside the area
between the construed best of gas hydrate and either the BGHS or the relating surmised base of
gas hydrate. The expression "coordinate" is utilized here not to propose that any seismic sign can
be convincing, however rather to mean seismic highlights that are believed to be created by the
gas hydrate events themselves. This is rather than a scope of other important "aberrant" markers,
for example, the basic nearness of BSRs or the nature and wealth of ocean depths includes that
assistance set up the geologic conditions for gas hydrate event yet don't fundamentally identify
with a particular planned gas hydrate event). The age of noteworthy positive-abundancy
abnormalities inside mud-rich dregs by the amassing of gas hydrate is far-fetched accordingly
residue have not been seen to help adequately high immersions of gas hydrate.

18. 8
In any case, a typical geophysical trait of the aggregation of gas hydrate in mud-rich silt is
acoustic "blanking", in which amplitudes diminish due, clearly, to the amassing of low to direct
immersions of gas hydrate. Plentifulness concealment is additionally extremely normal in
smokestack structures where the disturbance of unique depositional texture by vertical gas
relocation likely assumes a part (Saeki and Fujii, 2008).
3.1.3 Mitigate geologic risk through evaluation of occurrence of reservoir facies
The atypical amplitudes portrayed above are not really identified with gas-hydrate-bearing sand-
rich facies. Such highlights just show a skyline that denotes a solid differentiation in acoustic
speed, which can have a scope of causes. Along these lines, to alleviate the geologic hazard
natural in such prospects, it is basic to outline circulation of amplitudes related with that skyline
for confirm that backings that the abundancy is driven by an adjustment in pore fill (instead of
general lithological factors). For instance, if the appropriation of the sufficiency shows control
by geologic structure (which would be construed to post date or generally be disconnected to
lithological variety, for example, irregular terminations against shortcomings as well as
conformance to auxiliary height, at that point prospectively is expanded. Additionally, if the
dissemination of the plentifulness is reliable with the normal morphology of sand-rich deep-
water depositional facies, for example, sinuous channels or lobate fans, prospectively is
enormously expanded. Additional confirmation that the sufficiency reaction is driven by pore fill
is a stamped change in abundancy as the skyline is followed beneath the derived BGHS. Most
forthcoming in such manner are occasions where the adequacy can be appeared to switch
extremity along a solitary skyline. Conversely, amplitudes that are inescapable and steady
finished expansive regions, or that do not change character as the skyline is followed out of the
GHSZ, are substantially less. (Shedd et al 2012).

19. 9
3.1.4 Risk through evaluation of gas presence and migration
The assessment depicted above gives solid confirmation to the event of gas hydrate in sand-rich
dregs. In such cases, it might be to some degree disputable to freely affirm gas nearness or gas
conveyance pathways. Nevertheless, where significant geologic hazard remains, prove that
backings the nearness of gas or portrays obviously pathways in which gas is probably going to
have relocated into the GHSZ, are profoundly profitable. Such proof can incorporate the
nearness of 1) gas fireplaces (solid confirmation of gas age at profundity and upward movement
into the GHSZ); 2) BSRs (coordinate affirmation of gas nearness and conveyance to the BGHS);
3) negative-extremity sufficiency abnormalities beneath the BGHS; 4) ocean bottom highlights
that are reliable with dynamic gas motion, and 5) geochemical proof of hoisted gas transition as
acquired through shallow ocean depths examining, for example, shallow profundities to the
sulfate-methane interface (SMI). Earlier examinations have upheld both thermogenic and
biogenic hotspots for gas housed in gas hydrates. Thermogenic gas can require generally long-
separate relocation from more profound sources, and thusly then presence of more profound
ordinary oil/gas aggregations are ideal for the event of gas hydrate. Additionally, while privately
produced microbial gas can specially fill sand-rich supplies, there might be restrains with regards
to how much such sources can charge sand units to high-degrees of immersion, especially those
of adequate amount (thickness) to be for the most part viewed as forthcoming for vitality asset
potential. (Bryan, 1974).
3.2 Status of BSRs in Gas Hydrate Exploration
The search for BSRs dominated the early stages of global gas hydrate evaluation. As field
evaluation of gas hydrate resource potential has progressed, the relevance of BSRs became less
clear. The presence of a BSR, regardless of its nature, is certainly not sufficient to indicate the
occurrence of prospective accumulations. In fact, a well-developed, regionally pervasive BSR is
very likely a contra-indicator of prospectively as it suggests a diffuse (unfocused) gas flux within
a homogeneously fine-grained stratigraphic succession. Nonetheless, BSRs remain critical to gas
hydrate exploration. Primarily, the identification of a BSR (as defined broadly to include
associated seismic features that mark the base of the gas hydrate stability zone) enables
delineation of the BGHS and insight into local temperature gradients. Further, where variable
stratigraphy includes a mix of muds and potentially-prospective reservoir-quality units, the
impact of traversing the BGHS (including phase reversals and other events that are commonly
considered to be a form of BSR) can provide insight into the nature of prospective horizons
(Boswell, 2014 and Boswell, 2007).

20. 10
CHAPTER 4
PRESENCE OF GAS HYDRATES IN THE ALASKAN ARTIC
The study of gaseous petrol hydrates is not a new concept rather its study was done so that its
forming is avoided in the oil and gas pipelines (Hammer Schmidt, 1934). The exploration of
large petroleum gasoline sources on the Northern Slope of Alaska initially developed enthusiasm
around the periods of 1971. Katz who conducted a study in 1972 suggested that the stabilization
of gaseous petrol hydrates around the Northern region of the Alaskan slope could reach the
depths of about 1200m (3940ft). He proposed this suggestion after the successful exploration of
the region and confirmation of the hydrates presence in Alaska on March 1972 by Exxon and
Acro. The oil companies used pressurized core barrels to retrieve the core samples of the gas
hydrate at depths ranging between 570 - 780m from Prud Hoe Bay oil field in Northwest of
Eileen and since then, a lot of research and works have been carried out solely for the purpose of
identification and quantification of the Alaskan gas hydrate resources (Collett et al, 1984).
During the course of the research, which Collett et al conducted, in 1983, they studied a total of
125 wells in the Alaskan region and developed some techniques, which involved the use of data,
which were gotten from well logs. Positive results were yielded showing about a 100-absolute
hydrate occurrence in 32 wells. In addition, Kammath et al in 1987 investigated 46 wells in the
same region and concluded that about 10 of the wells among the tested showed the possibility of
gas hydrate deposits in them. An estimate, which was later done on the Eileen, showed the
amount of gas trapped in the hydrates was about 192 x 106
to 412 x 106
m3
/Km2
(Matthews,
1986).
Collett et al during their studies in 1984 employed the concept of the Pickett cross plotting
technique together with the neutron porosity (NPHI) and sonic porosity (SPHI) to decide the
thicknesses, depths, porosities and saturations in situ of another field in the Alaskan region,
which was known as the Kapurak Field. Estimates of the natural gas trapped in gas hydrates of
the Kapurak field region was estimated to be about 579 x 106
m3
/km2
(Collett et al, 1984).

21. 11
4.1 Log Evaluation
Collett et al as mentioned earlier developed some techniques to distinctly differentiate hydrates
and ice and the quantification of the deposits of hydrates. The technique requires the application
of NPHI transit time cross plot correlated with a Pickett cross plot (Collett et al, 1984).
Figure 3: Nomogram for determination of methane-hydrate-stability zone after Godbole, 1988).
They presented a correction factor based on hydrogen atom density in water with respect to
hydrates. The ratio of hydrogen present in l cm3
of water is compared to the hydrogen present in
1 cm3
of Structure I hydrate, which is 0.93 and could be used as a correction factor to the neutron
porosity within the hydrate zone. It is necessary to use a compensated neutron log to minimize
the effect of increased borehole. In addition, the increased wellbore resulting from thawing might
contain drilling fluids and free gas, and hence should be carefully considered. The porosity
measurements in cased holes should be considered only semi quantitative (Collett et al, 1983).
The case study discusses the effect of geothermal properties and the gas composition relating to
the thickness of the hydrate-stability zone in such regions as the North Slope of Alaska. A
nomogram was developed to determine the zone of methane hydrate stability for specific
geologic conditions and this proved to be successful.

22. 12
CHAPTER 5
SUMMARY AND CONCLUSION
As field evaluation of gas hydrate resource potential has progressed, the relevance of BSRs
became less clear. The presence of a BSR, regardless of its nature, is certainly not sufficient to
indicate the occurrence of prospective accumulations. In fact, a well-developed, regionally
pervasive BSR is very likely a contra-indicator of prospectively as it suggests a diffuse
(unfocused) gas flux within a homogeneously fine-grained stratigraphic succession. Nonetheless,
BSRs remain critical to gas hydrate exploration. Primarily, the identification of a BSR (as
defined broadly to include associated seismic features that mark the base of the gas hydrate
stability zone) enables delineation of the BGHS and insight into local temperature gradients.
Further, where variable stratigraphy includes a mix of muds and potentially prospective
reservoir-quality units, the impact of traversing the BGHS (including phase reversals and other
events that are commonly considered a form of BSR) can provide insight into the nature of
prospective horizons. (Tsuji et al, 2004).
Spurred by continuing favorable research and development results related to gas hydrate
occurrence and recoverability, the assessment of offshore areas for the likely presence of
potentially recoverable gas hydrate accumulations is expected to increase. It is recommended
that effort initially focus on assessment of potential occurrences in sand-hosted sediments, as
field data and numerical simulation indicate that such deposits are amenable to recovery using
known drilling and production concepts. An approach, which has proven to be effective in the
past, is to
1) prospect initially for potential direct indicators of gas hydrate occurrence within the
defined gas hydrate stability zone and then
2) mitigate the geologic risk inherent in such prospects through evaluation of
geological/geophysical/geochemical evidence that associate those prospects with sand-
rich reservoir facies and that may be connected those facies with gas sources through
recognized migration pathways (Boswell, 2014).

23. 13
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