caa a22 4500 463216229 CHVBK 20180405153157.0 cr unu---uuuuu 170326e20070601xx s 000 0 eng 10.1007/s00367-007-0071-5 doi (NATIONALLICENCE)springer-10.1007/s00367-007-0071-5 Analysis of shallow gas and fluid migration within the Plio-Pleistocene sedimentary succession of the SW Barents Sea continental margin using 3D seismic data [Elektronische Daten] [Karin Andreassen, Espen Nilssen, Christian Ødegaard] Three-dimensional (3D) seismic data acquired for hydrocarbon exploration reveal that gas accumulations are common within the 2-3km thick Plio-Pleistocene stratigraphic column of the south-western Barents Sea continental margin. The 3D seismic data have relatively low-frequency content (<40Hz) but, due to dense spatial sampling, long source-receiver offsets, 3D migration and advanced interpretation techniques, they provide surprisingly detailed images of inferred gas accumulations and the sedimentary environments in which they occur. The presence of gas is inferred from seismic reflection segments with anomalously high amplitude and reversed phase, compared with the seafloor reflection, so-called bright spots. Fluid migration is inferred from vertical zones of acoustic masking and acoustic pipes. The 3D seismic volume allows a spatial analysis of amplitude anomalies inferred to reflect the presence of gas and fluids. At several locations, seismic attribute maps reveal detailed images of flat spots, inferred to represent gas-water interfaces. The data indicate a focused fluid migration system, where sub-vertical faults and zones of highly fractured sediments are conduits for the migration of gas-bearing fluids in Plio-Pleistocene sediments. Gas is interpreted to appear in high-porosity fan-shaped sediment lobes, channel and delta deposits, glacigenic debris flows and sediment blocks, probably sealed by low-permeability, clayey till and/or (glacio)marine sediments. Gas and fluid flow are here attributed mainly to rapid Plio-Pleistocene sedimentation that loaded large amounts of sedimentary material over lower-density, fine-grained Eocene oozes. This probably caused pore-fluid dewatering of the high-fluid content oozes through a network of polygonal faults. The study area is suggested to have experienced cycles of fluid expulsion and hydrocarbon migration associated with glacial-interglacial cycles. Springer-Verlag, 2007 Andreassen Karin Department of Geology, University of Tromsø, 9037, Tromsø, Norway aut Nilssen Espen Department of Geology, University of Tromsø, 9037, Tromsø, Norway aut Ødegaard Christian Department of Geology, University of Tromsø, 9037, Tromsø, Norway aut Geo-Marine Letters Springer-Verlag 27/2-4(2007-06-01), 155-171 0276-0460 27:2-4<155 2007 27 367 https://doi.org/10.1007/s00367-007-0071-5 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00367-007-0071-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Andreassen Karin Department of Geology, University of Tromsø, 9037, Tromsø, Norway aut NATIONALLICENCE 700 1- Nilssen Espen Department of Geology, University of Tromsø, 9037, Tromsø, Norway aut NATIONALLICENCE 700 1- Ødegaard Christian Department of Geology, University of Tromsø, 9037, Tromsø, Norway aut NATIONALLICENCE 773 0- Geo-Marine Letters Springer-Verlag 27/2-4(2007-06-01), 155-171 0276-0460 27:2-4<155 2007 27 367 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer