000			02075nab a2200193 4500
005			20260520001933.0
008			260224s2005 xxu
245	0	0	_aIndications for an active petroleum system in the Laptev Sea, NE Siberia
260			_a _b _coct. 2005
270			_a23/05/2011 ; 23/05/2011
300			_a16 p. ; 369-384
520			_aTranscripción del resumen del autor. The shallow shelf of the Laptev Sea offshore NE Siberia is characterized by a number of rift basins more than 10 km deep. These basins are filled with sedimentary rocks of predominantly Cenozoic age and are likely sites for petroleum generation and accumulation. One objective of the BGR97 Arctic cruise to the Laptev Sea was to explore for near-surface indications of petroleum, and for this purpose water samples and near-surface sediments were collected for geochemical analysis. Gaseous hydrocarbons adsorbed in near-surface sediments include thermally-generated gas which has probably migrated upwards from deeper sedimentary strata. The hydrocarbons’ compositions together with stable carbon isotope ratios indicate an origin from a marine source rock at a maturity of between 0.9 and 1.3% vitrinite reflectance. On reflection seismic profiles, zones of poor reflectivity were observed locally, also suggesting the presence of ascending gas. These geophysical indications for gas occur most frequently in the northern part of the Laptev Sea; here, seepages of thermogenic methane were detected in the sea water at two locations. Refraction seismic and multichannel data indicate the existence of sub-sea permafrost down to a depth of 500m, which probably prevents gas from escaping into the water column in most areas. The greater water depths at the northern edge of the shelf may have prevented the formation of the permafrost layer, allowing the upward migration of hydrocarbons to occur.
581			_a4
773	0		_tJournal of Petroleum Geology _g28
942			_cARTICULO
100	1		_aCramer, B. _99723
100	1		_aFranke, D. _947776
999			_c181930 _d181930