Print this pageGeomorphology: A Key to Filling Gaps and Increasing Realism in Reservoir Descriptions
R. S. Tye
Combining core and wireline 
data
with geomorphic analogs facilitates the
quantification of geologic information for the numerical characterization of
subsurface strata. Traditional three-dimensional geologic descriptions are
limited by one- and two-dimensional data sources (outcrop or well data).
Geomorphic analyses of fluvio-deltaic systems reveal log-normal distributions of
discrete depositional environments. These provide statistical constraints for
conditioning the area (X and Y dimensions), shape, placement, and preferred
orientation(s) of geologic facies in three-dimensional models.
Accurate stratigraphic and facies-association representations built from
subsurface and analog data are integral parts of geologic modeling. Seismic,
outcrop, and vertically oriented well data provide structural and
chronostratigraphic information. Moreover, core and wireline-log data give
lithofacies type and thickness (Z dimension), in addition to petrophysical
trends. The distribution of facies in the X and Y directions (between wells) is
realistically accomplished by using geomorphic guidelines to distribute
lithofacies or facies- associations as three-dimensional objects. Furthermore,
geomorphic analogs aid the distribution of a lithofacies within a facies
association. This is beneficial where individual beds contain permeability
extrema. Given a relationship between facies and p rmeability, a
three-dimensional rendition of facies becomes a proxy for reservoir quality.
Geomorphic data from appropriate modern fluvio-deltaic analogs are linked
with core and wireline-log data
to render conditioned, three-dimensional,
geologic models. Model accuracy relies upon bed-thickness and
chronostratigraphic constraints imposed by cores and stratigraphic correlations,
as well as, the lateral extent of facies associations governed by geomorphology.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California