Sub-basalt imaging - new insight from investigations of petrophysical and seismic properties of Faroes basalts (SeiFaBa project)

The development of methods of seismic imaging beneath basalt is still hindered by a lack of knowledge about the elastic properties of basaltic sequences and the degree of three-dimensional heterogeneity. The SeiFaBa project (2002- 2005) is funded by the Sindri Group as part of the programmes for licensees within the Faroese area and will address these issues. The first year included drilling of a new 700-m deep well, Glyvursnes-1, near Tórshavn with full core, reaming of the existing 660 m deep Vestmanna-1 well farther north, and the acquisition of a wide range of wireline logs in both wells. The two wells represent almost half of the exposed lava sequence and are central to a number of co-ordinated experiments. These are targeted at creating firm data-derived models for seismic wave propagation through basalt by combining detailed analysis at core, log and seismic scales. After initial tests in 2002 the main part of the seismic programme was carried out June to September 2003. The work was centred on Glyvursnes-1 and included both VSP, offset-VSP and surface seismic experiments. Detailed studies of well logs and core material from the above and other wells have been initiated. The aim is to better understand the sonic response of basalt lavas in terms of physical and compositional properties and thus also seismic signatures of flood basalt successions.