CRONIN, BRYAN T., ADRIAN J. HARTLEY, and ANDREW HURST, University of Aberdeen, Aberdeen

Abstract: Deep-Water Clastic Depositional Geometry in Small, Sandy, Topographically Constrained Systems: Analogues for Basins without Sinuous Deep-Water Channels

Over 85% of published data on modern deep-sea clastic systems are still confined to large, passive margin settings.The last 12 years have seen an explosion in the acquisition of more high resolution, deep-towed sidescan images of deep-water sedimentary environments from smaller, more tectonically active areas.These small basins are characterised by erratic sea floor topography which control turbidite sediment pathways and sedimentation. The new data provide virtual "optical" images of the planform expression of deep-water clastics, with dimensions and geometry, directly analogous to subsurface gravity flow deposit hydrocarbon plays, as well as smaller salt withdrawal filland-spill basins.The sidescan sonar records clearly show channels, canyons and lobes but also a significant amount of sedimentary bodies that do not have these geometries. Such components are visible on a sub-seismic scale and include: fairway deflection around seafloor topography, bedform fields, asymmetric channel levees, thalweg channels, slump scars, debris flows, non-lobate stringer depositional bodies, sheet sand systems and distributary channels on lobes.These features are correlatable on an inter-well scale and overlap significantly in scale with data from a large number of outcrop analogues. Once formatted in spreadsheets the data can be used to constrain stochastic modelling of specific parts of analogous reservoirs.The limitations that can then be placed on reservoir genetic element size, shape and lateral extent improves the deterministic models enormously by constraining what turbidite system component is most likely to occur for a given set of physiographic parameters.

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England