Natural gas hydrates - from the microstructure towards a geological understanding [Elektronische Ressource] / vorgelegt von Stephan A. Klapp

Stephan A. Klapp

Informations

• Publié par: universitat_bremen
• Publié le: 01 janvier 2009
• Nombre de lectures: 28
• Langue: English
• Poids de l'ouvrage: 31 Mo

Extrait

Natural Gas Hydrates – from the Microstructure
towards a Geological Understanding



Dissertation



Zur Erlangung des
Doktorgrades der Naturwissenschaften
(Dr. rer. nat.)

im Fachbereich Geowissenschaften
der Universität Bremen



vorgelegt von
Stephan A. Klapp


Bremen, August 2009






















Gutachter:
Prof. Dr. Gerhard Bohrmann
Prof. Dr. Werner F. Kuhs





“If there is magic on this planet, it is contained in water.”
Loren Eiseley, The Immense Journey, 1957
PREFACE

This PhD thesis was written at the ‘MARUM – Center for Marine Environmental Sciences’ and
Department of Geosciences at the University of Bremen, Germany. The thesis work has been carried
out from September 2006 until August 2009. The thesis was funded by a private scholarship of the
'HGM Energy GmbH’ in Bremen. The graduate education was embedded into ‘GLOMAR – Bremen
International Graduate School for Marine Sciences’. The gas hydrate samples researched in this
thesis were retrieved during the R/V SONNE Cruise SO 174 in the Gulf of Mexico in 2003, R/V
PROFESSOR LOGACHEV Cruise TTR 15 in the Black Sea in 2005, R/V METEOR Cruise M67/2 in the Gulf
of Mexico in 2006 and R/V METEOR Cruise M72/3a+b in the Black Sea in 2007. The collaborating
institutes and laboratories are the ‘Abteilung Kristallographie’ of the ‘Geowissenschaftliches Zentrum’
at the University of Göttingen (GZG), Germany, the ‘Deutsches Elektronen-Synchrotron’ (DESY) and
‘Hamburger Synchrotronstrahlungslabor’ (HASYLAB) in Hamburg, Germany, the Geochemistry Group
from the Department of Geosciences at the University of Mainz, Germany, the Paul-Scherrer-Institute
(PSI) and Swiss Light Source (SLS) in Villigen, Switzerland, and the Monterey Bay Aquarium
Research Institute (MBARI), California, USA.
The thesis comprises six research papers in the main text attempting to better understand gas
hydrates in natural submarine environments. Accordingly, the Introduction Chapter is subdivided into a
geological part and a mineralogical part, both focusing on gas hydrates. The motivation for this thesis
is given after the introduction on hydrate mineralogy. The second Chapter briefly describes the
analytical methods and sampling locations. The research papers start in Chapter 3 with a
methodological paper describing the technique for obtaining crystal sizes of gas hydrates. The results
of these investigations are interpreted in the geological context in Chapter 4. The relations of gas
chemistry, crystallographic structure, microstructure and thermodynamic stability for hydrates from the
Gulf of Mexico are presented in Chapter 5. -computer tomography is introduced as a novel
technology for gas hydrate research with first results in Chapter 6. Chapter 7 reports on the co-
existence of two gas hydrate structures at the Chapopote asphalt volcano in the southern Gulf of
Mexico. In Chapter 7 the assessment of the gas hydrate inventory of the Batumi gas seep in the
eastern Black Sea is presented along with a discussion on possible transport mechanisms to the sea
surface. The thesis closes with a Chapter drawing conclusions from the outcomes of the research
presented here and offering future perspectives.
CONTENTS

Abbreviations IV
AbstractV
KurzfassungVII

CHAPTER 1 INTRODUCTION 1
1.1 Gas hydrates in marine sediments 1
1.1.1 Introduction 1
1.1.2 Gas hydrates on Earth 2
1.1.2.1 Gas hydrate occurrence 2
1.1.2.2 Hydrocarbon gas sources 3
1.1.3 Parameters for hydrate formation in marine sediments 4
1.1.3.1 Pressure and temperature 4
1.1.3.2 Methane solubility 5
1.1.3.3 Influence of salinity
1.1.3.4 Effect of methane oxidation on the gas hydrate interface in sediments 6
1.1.4 Marine environments promoting gas seepage and gas hydrate formation 6
1.1.4.1 Cold seeps 6
1.1.4.2 Gas seepage – is there an effect on the atmosphere? 7
1.1.5 Occurrence of gas hydrates in marine sediments 9
1.1.5.1 Hydrate fabric and relation to burial depth 9
1.1.5.2 Shapes of shallow gas hydrates in marine deposits 11
1.1.6 Gas hydrates and energy industry 12
1.2 Mineralogical aspects of gas hydrates 13
1.2.1 Structure of gas hydrates 13
1.2.1.1 Crystallographic structures 13
1.2.1.2 Hydration number 14
1.2.1.3 Relation of gases and hydrate structures 16
1.2.1.4 Incipient structure and long-term stability 18
1.2.1.5 Volatility 19
1.2.2 Microstructure 20
1.2.2.1 Sub-micrometer-sized porosity
1.2.2.2 Microstructuand anomalous self-preservation 21
1.2.2.3 Microstructure imaging of decomposing hydrates 21
1.2.2.4 Developments for microstructure characterization of hydrates 22
1.2.3 Grain growth 23
1.2.3.1 Ostwald ripening
1.2.3.2 Static grain growth 24
1.3 Motivation and main questions 25

CHAPTER 2 METHODS AND SAMPLING LOCATIONS 27
2.1 Methods 27
2.1.1 Recovery of samples 27
2.1.2 Gas chemistry
3.1.3 X-ray diffraction 28
2.1.3.1 Phaseanalysis
2.1.3.2 Crystallite size analyses 29
2.1.4 X-ray computer tomography 31
I 2.1.4.1 Medical computer tomography 31
2.1.4.2 Microscalecomputerized tomography
2.1.5 FE - Scanning Environmental Electron Microscopy 33
2.1.6 Raman spectroscopy 34
2.2 Sampling locations35
2.2.1 Gulf of Mexico
2.2.1.1 Northern Gulf of Mexico 36
2.2.1.2 Southern Gulf of Mexico 37
2.2.2 Study sites offshore Georgia in the eastern Black Sea 37

CHAPTER 3 MANUSCRIPT 1: Crystallite size distributions of marine gas hydrates. 39
Klapp, S.A., S. Hemes, H. Klein, G. Bohrmann, W.F. Kuhs, Abegg, F.
(2008) In: Englezos, P. and Ripmeester, J., Eds., Proceedings of the 6th
International Conference on Gas Hydrates (ICGH 2008), July 6-10, 2008,
Vancouver, BC, Canada, 13 pp.
CHAPTER 4 MANUSCRIPT 2: Grain size measurements of natural gas hydrates. 53
Klapp, S.A., Hemes, S., Klein, H., Bohrmann, G., MacDonald, I.R., Kuhs,
W.F. (submitted May 5, 2009) Marine Geology.
CHAPTER 5 MANUSCRIPT 3: Microstructures of structure I and II gas hydrates from 67
the Gulf of Mexico.
Klapp, S.A., Bohrmann, G., Kuhs, W.F., Murshed, M.M., Pape, T., Klein,
H., Techmer, K.S., Heeschen, K.U., Abegg, F. (in press) Marine and
Petroleum Geology, doi:10.1016/j.marpetgeo.2009.03.004.
CHAPTER 6 MANUSCRIPT 4: Natural gas hydrate investigations by synchrotron 83
radiation X-ray cryo-tomographic microscopy.
Murshed, M.M., Klapp, S.A., Enzmann, F., Szeder, T., Huthwelker, T.,
Stampanoni, M., Marone, F., Hintermüller, C., Bohrmann, G., Kuhs, W.F.,
Kersten, M. (2008) Geophysical Research Letters, 35, L23612,
doi:10.1029/2008GL035460.
CHAPTER 7 MANUSCRIPT 5: Mixed gas hydrate structures on the Chapopote asphalt 91
volcano, southern Gulf of Mexico.
Klapp, S.A., Murshed, M.M., Pape, T., Klein, H., Bohrmann, G., Kuhs,
W.F., Brewer, P.G., manuscript in preparation.
CHAPTER 8 MANUSCRIPT 6: High-intensity gas seepage feeds shallow gas hydrate 111
deposits in the eastern Black Sea.
Pape T., Bahr A., Klapp S.A., Abegg F., Bohrmann G. (submitted June 25,
2009) Earth and Planetary Science Letters.

CHAPTER 9 CONCLUSIONS AND PERSPECTIVES 127
9.1 Conclusions 127
9.1.1 sI/sII structure co-occurrence
9.1.2 Relation between the gas chemical composition, crystallographic
structure and microstructure
9.1.3 Crystallite sizes and size distributions of hydrates 128
9.1.4 Dissociation of gas hydrates 129
9.1.5 Gas hydrate occurrence at a constrained seep site and possible 129
transport mechanisms to the sea surface
9.2 Perspectives 130
9.2.1 Porosity and grain boundaries of different hydrate structures
9.2.2 Crystallite sizes
II 9.2.3 Co-occurrence of two structures 131
9.2.4 Hydrate transport through water by means of seafloor rafting 132

References 133

Acknowledgements 155

APPENDICES 157
Appendix I Feseker, T., Pape, T., Wallmann, K., Klapp, S.A., Schmidt-Schierhorn, F.,
Bohrmann, G. (in press) The thermal structure of the Dvurechenskii mud
volcano and its implications for gas hydrate stability and eruption dynamics.
Marine and Petroleum Geology. doi:10.1016/j.marpetgeo.2009.01.021
Appendix II Sahling H., Bohrmann G., Artemov Y.G, Bahr A., Brüning M., Klapp S.A.,
Klaucke I., Kozlova E., Nikolovska A., Pape T., Reitz A., Wallmann K. (2009)
Vodyanitskii Mud Volcano, Sorokin Trough, Black Sea: Geological
characterization and quantification of gas bubble streams. Marine and
Petroleum Geology. doi:10.1016/j.marpetgeo.2009.01.010
Appendix III Pape T., Bahr A., Rethemeyer J., Kessler J.D., Sahling H., Hinrichs K.-U.,
Klapp S.A., Reeburgh W.S., Bohrmann G. (in revision) Molecular and
isotopic partitioning of low molecular weight hydrocarbons during migration
and gas hydrate precipitation in deposits of a high-flux seepage site. Marine
Chemistry.
Appendix IV Bohrmann, G., Kuhs, W.F., Klapp, S.A., Techmer, K.S., Klein, H., Murshed,
M.M., Abegg, F. (2007) Appearance and preservation of natural gas