Sediments of the accretionary prism, present along the continental margin of the Peninsula Antarctica SW of Elephant Island, are filled by gas hydrates as evidenced by a strong BSR. A multidisciplinary geophysical dataset, represented by seismic data, multibeam, chirp profiles, CTD and core samples, was acquired during three oceanographic cruises. The estimation of gas hydrate and free gas concentrations is based on the P -wave velocity analysis. In order to extract a detailed and reliable velocity field, we have developed and optimized a procedure that includes the pre-stack depth migration to determine, iteratively and with a layer stripping approach method, the velocity field and the depth- migrated seismic section. The final velocity field is then translated in terms of gas hydrate and free gas amounts by using theoretical approaches. Several seismic sections have been processed in the investigated area. The final 2D velocity sections have been translated in gas-phase concentration sections, considering the gas distribution within sediments both uniformly and patchly distributed. The free gas layer is locally present and, consequently, the base of the free gas reflector was identified only in some lines or part of them. The hydrate layer shows important lateral variations of hydrate concentration in correspondence of geological features, such as faults and folds. The intense fluid migration along faults and different fluid accumulation in correspondence of geological structures can control the gas hydrate concentration and modify the geothermal field in the surrounding area.

Correlation betwee geological structures and gas hydrate amount offshore the South Shetland Island-Preliminary results

Tinivella U;Accaino F;Giustiniani M
2008

Abstract

Sediments of the accretionary prism, present along the continental margin of the Peninsula Antarctica SW of Elephant Island, are filled by gas hydrates as evidenced by a strong BSR. A multidisciplinary geophysical dataset, represented by seismic data, multibeam, chirp profiles, CTD and core samples, was acquired during three oceanographic cruises. The estimation of gas hydrate and free gas concentrations is based on the P -wave velocity analysis. In order to extract a detailed and reliable velocity field, we have developed and optimized a procedure that includes the pre-stack depth migration to determine, iteratively and with a layer stripping approach method, the velocity field and the depth- migrated seismic section. The final velocity field is then translated in terms of gas hydrate and free gas amounts by using theoretical approaches. Several seismic sections have been processed in the investigated area. The final 2D velocity sections have been translated in gas-phase concentration sections, considering the gas distribution within sediments both uniformly and patchly distributed. The free gas layer is locally present and, consequently, the base of the free gas reflector was identified only in some lines or part of them. The hydrate layer shows important lateral variations of hydrate concentration in correspondence of geological features, such as faults and folds. The intense fluid migration along faults and different fluid accumulation in correspondence of geological structures can control the gas hydrate concentration and modify the geothermal field in the surrounding area.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.14083/3654
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