Seismoacoustic Study of the Shallow Gas Transport and ... - E-LIB

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Chapter 2 along the feeder channel from the deeper sources, e.g. the Maikopian Formation (Dimitrov, 2002). Biogenic gas is widely produced and concentrated above and beneath the BGHSZ. 2.7. Conclusions Four types of pathways for gas and fluid migration can be recognized: feeder channels of mud volcanoes, columnar zones, acoustic curtains and faults. Also three types of gas reservoirs in the central Black Sea are identified: a) Large gas/gas hydrate reservoirs around the feeder channels of mud volcanoes (BSZA); b) Large gas/gas hydrate reservoirs located above the acoustic curtains (BSZB); c) Small gas/gas hydrate reservoirs at the top or sides of the faults and columnar zones (BSZC). No regional BSR exists in the central Black Sea. A BSR is difficult to identify and absent in most parts of the study area, possibly due to the nearly parallel sedimentary layers to the seafloor and the local gas supply. Only a few local BSR segments can be recognized. The BGHSZ is found at a depth of ~650 ms TWT bsf, which suggests a geothermal gradient of 23°C/km. Bright spots occur in a depth range between ~400 and ~650 ms TWT bsf within the GHSZ. A few bright spots with reverse polarity indicate the free gas, while most of the bright spots with positive polarity may suggest an increase in impedance, which we interpret as charging with gas hydrates only. Our age model suggests that seismic Unit U1 has been deposited since ~900 ka, representing Danube and Dniepr fan sediments, with an upward increase in grain size/reflectivity due to fan progradation. Unit U2 is related to coarser material particularly from the Paleo-Don River, while the early Quaternary Unit U3 consists of uniformly layered sediment, probably made of distal finer grained turbidites. Unit U4 is of Pliocene age. Overall grain size variations distinctly influence porosity and potential for the presence of gas accumulations and gas trapping. All the BSZAs of relatively wide lateral extent appear at the boundary between Units U1 and U2, which is marked by a change from supposedly more sandy material to fine-grained turbidites, providing a seal for gas migration due to lower (vertical) permeability, forming a reservoir-seal combination. The bright spots Zones BSZB and BSZC are more probably formed by massive gas hydrate layers, converted originally from free gas, which are associated with normal polarity reflections. 65
Chapter 2 Mud volcanoes are composed of wide and deep feeder channels, showing several wide mud chambers, residing on collapsed sediment strata in the center. They show both gas and gas hydrate accumulations near the feeder channel, where gas may be of biogenic and thermogenic origin and from hydrate decomposition during eruptive phases. Kornev, Goncharov Malyshev, MSU and Vassoevitch mud volcanoes reveal three major eruption episodes, while at Yuzhmorgeologiya mud volcano only two major eruption episodes can be interpreted. All of the eruptive episodes of the mud volcano might be related to distinct sea level falls, which seem to be one of the main trigger factors of the mud volcano eruptions in the central Black Sea. Acknowledgements We thank the crew and the participating scientists of the Meteor cruise M52/1 for their hard work and assistance in data. We also thank Christian dos Santos Ferreira for kind help on generating the bathymetric grid. Thanks to Dr. Noemi Fekete and Dr. Benedict Preu for revising the manuscript. References Barg, I., 2007. Age and origin of the Kerch Strait and the Sea of Azov. Doklady Earth Sciences 412 (1), 17–18. Bega, Z., and Ionescu, G., 2009. Neogene structural styles of the NW Black Sea region, offshore Romania. The Leading Edge, September 2009, 1082-1089. Cohen, K.M., Finney, S., and Gibbard, P.L., 2013. International Chronostratigraphic Chart, International Commission on Stratigraphy. Damuth, J. E., and Kumar, N., 1975. Amazon Cone: morphology, sediments, age, and growth pattern. Geological Society of America Bulletin, v. 86, pp. 863-878. Dimitrov, L.I., 2002. Mud volcanoes - the most important pathway for degassing deeply buried sediments. Earth-Science Reviews, 59: 49-76. Finetti, I., Bricchi, G., Del Ben, A., Pipan, M., and Xuan, Z., 1988. Geophysical study of the Black Sea. Bolletino di Geofisica Teorica ed Applicata, 30: 197-324. Gay, A., Lopez, M., Cochonat, P., Sultan, N., Cauquil, E., and Brigaud, F., 2003. Sinuous pockmark belt as indicator of a shallow buried turbiditic channel on the lower slope of the Congo Basin, West African Margin. Geological Society, London, Special Publications, 216 (1), 173-189. Gaynanov VG, Bouriak SV, Ivanov MK, 1998. Seismic evidence for gas accumulation related to the area of mud volcanism in the deep Black Sea. Geo-Mar Lett 18:139–145. Ginsburg, G.D., Kremlev, A.N., Grigor, M.N., Larkin, G.V., Pavlenkin, A.D. and Saltykova, N.A., 1990. Filtrogenic gas hydrates in the Black Sea (21st voyage of the research vessel 66
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Seismoacoustic Study of the Shallow
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Table of contents Table of contents
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Abstract Abstract In recent years,
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Outline of the Dissertation Outline
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Chapter 1 Chapter 1. Introduction 1
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Chapter 1 reflections, interpreted
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Chapter 1 Submarine gas seeps, pock
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Chapter 1 which have documented act
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Chapter 1 fluid migration related t
Page 20 and 21: Chapter 1 Evidence of gas seepage
Page 22 and 23: Chapter 1 The three main different
Page 24 and 25: Chapter 1 from deeper sources in th
Page 26 and 27: Chapter 1 numerous countries such a
Page 28 and 29: Chapter 1 1.5 Geological setting of
Page 30 and 31: Chapter 1 main sequences consist of
Page 32 and 33: Chapter 1 craterlike depressions wi
Page 34 and 35: Chapter 1 Jurassic - Paleogene, Upp
Page 36 and 37: Chapter 1 respectively, and one wat
Page 38 and 39: Chapter 1 During the seismic data p
Page 40 and 41: Chapter 1 1.6.2 The Parasound sedim
Page 42 and 43: Chapter 1 Caress, D.W., and Chayes,
Page 44 and 45: Chapter 1 Hovland, M., Gardner, J.V
Page 46 and 47: Chapter 1 Luo, X.R. and Vasseur, G.
Page 48 and 49: Chapter 1 Schroot, B.M., Klaver, G.
Page 50 and 51: Chapter 2 Chapter 2. Shallow Gas Tr
Page 52 and 53: Chapter 2 times. Seismically imaged
Page 54 and 55: Chapter 2 spike noise were marked a
Page 56 and 57: Chapter 2 The 2D high resolution se
Page 58 and 59: Chapter 2 Figure 4 A close-up of se
Page 60 and 61: Chapter 2 within the upper sediment
Page 62 and 63: Chapter 2 volcanoes between 66 and
Page 64 and 65: Chapter 2 Figure 7 Geo-seismic sect
Page 66 and 67: Chapter 2 In the study area, many b
Page 68 and 69: Chapter 2 volcanism could be calcul
Page 72 and 73: Chapter 2 Evpatoriya). Soviet Geol
Page 74 and 75: Chapter 3 Chapter 3. Sedimentary Ev
Page 76 and 77: Chapter 3 South (Fig. 2). The water
Page 78 and 79: Chapter 3 Figure 3 (a) Uninterprete
Page 80 and 81: Chapter 3 Seven seismic facies type
Page 82 and 83: Chapter 3 Seismic Unit 5 ranges in
Page 84 and 85: Chapter 3 3.4.3.5. Seismic Unit 2 A
Page 86 and 87: Chapter 3 Figure 11 (a) Uninterpret
Page 88 and 89: Chapter 3 Figure 13 (a) Uninterpret
Page 90 and 91: Chapter 3 boundary between the Plio
Page 92 and 93: Chapter 3 Seismic Unit 6 belongs to
Page 94 and 95: Chapter 3 subsidence was coincident
Page 96 and 97: Chapter 3 Acknowledgements We thank
Page 98 and 99: Chapter 3 Tugolesov, D.A., Gorshkov
Page 100 and 101: Chapter 4 study area at ~900 m wate
Page 102 and 103: Chapter 4 Figure 2 Bathymetry of th
Page 104 and 105: Chapter 4 University of Bremen). At
Page 106 and 107: Chapter 4 and Ridge R2 (GeoB07-139)
Page 108 and 109: Chapter 4 flares location. Anticlin
Page 110 and 111: Chapter 4 GeoB07-145. Green arrows
Page 112 and 113: Chapter 4 4.4.3.2.3. Other anomalou
Page 114 and 115: Chapter 4 Slope fan deposits with f
Page 116 and 117: Chapter 4 Figure 12 Possible locati
Page 118 and 119: Chapter 4 bulk hydrate or even high
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Chapter 4 may add to gas accumulati
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Chapter 4 The narrow-beam Parasound
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Chapter 4 River fan deposits. Being
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Chapter 4 Klaucke, I., Sahling, H.,
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Chapter 4 Wagner-Friedrichs, M., 20
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Chapter 5 deposited; during lowstan
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Chapter 5 accumulations. An acousti
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Acknowledgements Acknowledgements I
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