This paper (SPE 51828) was revised for publication from paper SPE 38503, first presented at the 1997 SPE Offshore Europe Conference, Aberdeen, 9-12 September. Original manuscript received for review 9 September 1997. Revised manuscript received 6 July 1998. Paper peer approved 10 July 1998.
Summary
Fundamental geological and environmental differences exist between the basins of the North Sea and the basins of the northwest European continental margin, and strategies for success in the North Sea have not necessarily transferred directly to the continental margin. As a result, exploration outcomes to date have been somewhat disappointing, with one or two notable exceptions.
Furthermore, a change in the approach to acreage evaluation places increasing levels of reliance on seismic data, specifically three-dimensional (3D) data, to tie down prospects before drilling. This approach focuses down rapidly to the prospect scale, and, although allowing detailed analysis of target structures, there is a risk of creating a gap in understanding between the geological processes observed at the basin scale and those at the prospect scale.
A strategy to bridge this gap has drawn upon the wider family of geophysical data, namely gravity and magnetic data, in conjunction with a conventional, broad, regional grid of two-dimensional (2D) seismic data. These data have been worked together to construct a basin scale framework into which 3D seismic data acquisition can be planned and the results interpreted.At the regional scale, satellite-derived gravity coverage has enabled the removal of the effects of Tertiary seafloor spreading, allowing structures on the northwest European continental margin to be viewed in context with the geology of East Greenland.At the basin scale, basinal elements have been identified and correlated among seismic, gravity, and magnetic data. Controlling faults have been mapped, and the timing of basin formation inferred from trend and geometry, with implications for source rock distribution.At the license block scale, the segmentation of basin margins has been revealed by high spatial resolution magnetic data with implications for both trapping potential and the control of sediment supply into the basins.
The fusion of interpretations made from the different types of geophysical data creates a scale of observation range that stretches from tectonic plates to prospective structures. The resulting geological framework has sufficient scale overlap to relate immediately to the level of detail available from 3D seismic data. Moreover, the broader perspective may ensure that those seismic data are acquired in the correct part of the basin in the first place.
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Precambrian tectonic inheritance control of the NE Brazilian continental margin revealed by Curie point depth estimation
