Open AccessConstraints on a shallow offshore gas environment determined by a multidisciplinary geophysical approach: The Malin Sea, NW Ireland
Author(s) -
Garcia Xavier,
Monteys Xavier,
Evans Rob L.,
Szpak Michal
Publication year - 2014
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2013gc005108
Subject(s) - geology , seabed , submarine pipeline , structural basin , geophysics , proxy (statistics) , bathymetry , geomorphology , petrology , seismology , oceanography , machine learning , computer science
During the Irish National Seabed Survey (INSS) in 2003, a gas related pockmark field was discovered and extensively mapped in the Malin Shelf region (NW Ireland). In summer 2006, additional complementary data involving core sample analysis, multibeam and single‐beam backscatter classification, and a marine controlled‐source electromagnetic survey were obtained in specific locations.This multidisciplinary approach allowed us to map the upper 20 m of the seabed in an unprecedented way and to correlate the main geophysical parameters with the geological properties of the seabed. The EM data provide us with information about sediment conductivity, which can be used as a proxy for porosity and also to identify the presence of fluid and fluid migration pathways. We conclude that, as a whole, the central part of the Malin basin is characterized by higher conductivities, which we interpret as a lithological change. Within the basin several areas are characterized by conductive anomalies associated with fluid flow processes and potentially the presence of microbial activity, as suggested by previous work. Pockmark structures show a characteristic electrical signature, with high‐conductivity anomalies on the edges and less conductive, homogeneous interiors with several high‐conductivity anomalies, potentially associated with gas‐driven microbial activity.