Dakota Aquifer Program--Geologic Framework--Stochastic Modeling
The future of the model
The stochastic, or probabilistic, nature of the modeling process provides
us with several models. Currently, the geologist interprets these models,
selecting those that are most likely. For each of these models, flow
analysis can be conducted to determine the overall flow regimes within
the aquifer.
Geologically, future work will concentrate on usage of paleocurrent,
lithofacies, and geometric data to gain better controls on the 3D geometry
and linear stacked behavior of elements. For example, paleocurrent and
geometric data will be used for better calculation of sinuosity of channel
elements. Also, subsurface work is being conducted to constrain the
relative abundance of various elements and to further analyze element
geometry, size and behavior.
There is, of course, refining work that needs to be conducted with the
mathematical model. The sophistication of the probability generators will
increase as more model runs are performed. The initialization step will
also improve with the inclusion of subsurface (well log) data. Also, the
stacking of consecutive layers is still being developed, and this will
provide three-dimensional models that can be input into existing
postprocessing programs.
There are also two significant improvements that are currently being developed:
- Channels tend to run from border to border, but are currently treated as
an element just like all of the others. We are now treating the channels
first, in the initialization phase, separately from the other elements.
They will be allowed to grow border to border, then the other elements will
grow and be introduced stochastically in the generation phase of the modelling.
- Rather than relying on the geologist to determine whether a model is
reasonable, we will let the model determine this. After several models
are generated, statistics will be computed on them and compared to the
field statistics. The initialization ("p") probabilities will then be
adjusted in an attempt to conform the model to the field data. For the
non-channel elements, the introduction ("r") probabilities are also adjusted
since they are closely related to the "p" probabilities. The result will
still be a set of plausible models that can be put into a flow analysis
package, but the advantage will be that these models will match the field
data without the interpretation of the geologist, giving additional
relevance to the modeling procedure.
We have provided preliminary studies of central Kansas outcrop data,
and a prototype model which used the collected data. From here, we
will proceed to incorporate fill possibilities into elements produced
by the model. Packaging model outputs into paleovalleys will also be
incorporated. As this study continues, the results will provide an
accurate set of possible models of the Dakota aquifer.
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Start of the Stochastic Modeling Report
Kansas Geological Survey, Dakota Aquifer Program
Updated July 5, 1996.
Scientific comments to P. Allen Macfarlane
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The URL for this page is HTTP://www.kgs.ku.edu/Dakota/vol1/geo/stoch10.htm