3-D Stratigraphic Modeling
in a Space-Time Framework Using
Sequence Stratigraphy
Kedzierski, Pierre, Jean-Jacques Royer, Jean-Laurent Mallet, INPL-CRPG, Vandoeuvre, France
Mostly used in the early stage of oil exploration,
three-dimensional stratigraphic models help
subsurface data interpretation, evaluation and understanding of complex
interactions of sedimentary depositional systems. These models give
quantitative information about geometry, continuity, location and dimensions of
sedimentary units and also characterize their sedimentary facies.
This paper suggests a numerical approach based on sequence stratigraphy concepts, which interpret transgressive/regressive
shifts, the timing of all system tract and sequence boundaries (e.g. maximum
flooding surface, correlative conformity, or conformable transgressive
surface) as the interplay of sedimentation and base-level fluctuations. The
presented model integrates well data, seismic
survey and geologic knowledge to
model sedimentary units architecture, sequence
boundaries geometry and facies proportions in three
dimensions.
This solution simplifies the initial problem by modeling
singly
the geometry in the geological space (x,y,z)
and the properties in the geochronological space (u,v,t). A forward model accounting for well data and
geological knowledge is computed in the geochronological
space where isochroneous surfaces are strictly
horizontal. A quality control of the sequence boundaries geometry is done in
the geological space in order to fit to the
seismic
reflector. After the
quality control, properties (facies, sand/shale
ratio, depositional water depth, ...) are painted from
the geochronological space to the geological space.
Last, by
modeling
the sedimentary units in time layers, this approach opens some doors
to complex geostatistical analyses such as
compositional trends in sediments.