Conical sandstone injection structures imaged by 3D seismic in the central North Sea, UK
S. Molyneux, J. Cartwright and L. Lonergan
Journal name: First Break
Issue: Vol 20, No 6, June 2002 pp. 383 - 393
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The improved imaging and resolution potential of 3D seismic data has been demonstrated in many recent case studies (e.g. Weimer & Davis 1996). The improved resolution of 3D often allows the interpreter to recognize features that would not previously have been mapped using conventional 2D grids because of spatial aliasing (Clausen & Huuse 1999; Stewart 1999). In some cases this has led to the discovery of new types of deformational or sedimentary structures (e.g. Cartwright 1994; Davies et al. 1999). We consider the origin of some enigmatic amplitude anomalies recognized and mapped on a 3D seismic survey from the central North Sea. These anomalies are characterized by their conical geometry, and are localized in a specific stratigraphic unit, the Lower Eocene. Initial lithological calibrations from wells aimed at deeper targets suggest that these structures are intrusive sand sheets, with thicknesses of up to 30 m. If this interpretation is correct, these conical sand sheets would be the largest form of clastic sedimentary intrusion yet reported. The paper describes the evidence supporting this interpretation of the amplitude anomalies, reviews alternative models for their origin, and concludes with a brief discussion of the wider importance of this interpretation for hydrocarbon exploitation in deepwater sandstone reservoirs.