Sequence
Stratigraphic Organization of Architectural Elements
Architectural elements control fluid flow
in reservoirs and many datasets exist on likely geometries and (less commonly)
shapes. Datasets include both modern and ancient outcrop examples and, under
optimal conditions, high resolution shallow seismic examples. However, a
crucial and sometimes forgotten aspect of architectural element applications to
reservoir modelling is the degree of preservation of original depositional
geometries. We argue that these datasets must be collected within a robust high
resolution sequence stratigraphic framework, so that correct analogues are
used. Long term accommodation trends impose a predictable control on the nature
of high frequency sequences such that in fluvial reservoirs, long term base
level fall results in very net:gross but ‘leaky' reservoirs, with many elements
not preserved. Periods of long term base level rise produce less incision at
high order sequence boundaries hence reduced vertical connectivity and
preservation of a wider range of elements. Deepwater basin floor fan reservoirs
are commonly composite lowstand bodies of high order sequences that stack in a
predictable forward-stepping to aggradational to landward-stepping manner.
Different mixes of architectural elements are preserved in the different
stacking positions and this architecture strongly affects vertical/horizontal
connectivity. Accurate linking of architectural elements of position in
sequence and in sequence hierarchy allows for forward prediction of proportions
of element types and preservation of these elements, thus allowing a greater
degree of determinism in 3-D reservoir models.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California