HR: 0800h
AN: OS51B-02    [Abstracts]
TI: A conceptual model for hydrocarbon accumulation and seepage processes inside Chapopote asphalt volcanism site, Southern Gulf of Mexico: from high resolution seismic point of view
AU: * Ding, F
EM: dingfeng@uni-bremen.de
AF: Research Center Ocean Margins, FB5, Geo Universität Bremen Klagenfurter Str., Bremen, D-28359, Germany
AU: Spiess, V
EM: vspiess@uni-bremen.de
AF: Research Center Ocean Margins, FB5, Geo Universität Bremen Klagenfurter Str., Bremen, D-28359, Germany
AU: Fekete, N
EM: nfekete@uni-bremen.de
AF: Research Center Ocean Margins, FB5, Geo Universität Bremen Klagenfurter Str., Bremen, D-28359, Germany
AU: Keil, H
EM: hanno.keil@uni-bremen.de
AF: Research Center Ocean Margins, FB5, Geo Universität Bremen Klagenfurter Str., Bremen, D-28359, Germany
AU: Bohrmann, G
EM: gbohrmann@uni-bremen.de
AF: Research Center Ocean Margins, FB5, Geo Universität Bremen Klagenfurter Str., Bremen, D-28359, Germany
AB: As part of the German R/V Meteor M67/2 expedition in 2006 to the southern Gulf of Mexico, a set of 2D high resolution seismic profiles was acquired across the Chapopote knoll to study sea floor asphalt occurrences and their origin. Based on regional seismic stratigraphy studies, correlated to DSDP sites, a higher reflective coarse grained sediment unit of Late Miocene age is identified as a potential shallow gas reservoir, overlain by a low permeability fine grained Pliocene and Pleistocene cover. As a result of salt diapirism, local uplift has caused reduced accumulation rates above the diaper since the late Pliocene, while the rates had been uniform throughout the area before. This has further improved the seal properties, since more fine grained material deposited in elevated locations. Nevertheless, on the crest of Chapopote, sediments above the coarse sediment unit are only around 150-75 m thick. Since oil and gas production can well be expected at depth in Jurassic and Tertiary source rocks, the presence of high amplitude reflector packages within the reservoir unit is interpreted as a result of the presence of hydrocarbons. This interpretation is further supported by the observation that some reflectors are cross-cutting and/or reveal a drop in instantaneous frequency. But, the thin seal above the reservoir unit, located directly underneath a widespread occurrence of asphalts at the sea floor, probably facilitates the leakage of hydrocarbons trapped inside the reservoir through a ~ 750 m wide acoustically chaotic zone partly aided by faulting. Since the top of Chapopote shows a high structural complexity, more seepage sites may exist beyond where seafloor asphalts have been found so far. Evolution and structure of the migration and reservoir system, which may be deep rooted, will be discussed both with respect to shallow gas and asphalt occurrences.
DE: 3004 Gas and hydrate systems
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly