Large-scale 3-D modeling by integration of resistivity models and borehole data through inversion
Other literature type, Article
Marker, Pernille Aabye
Christiansen, A. V.
Høyer, A. S.
- Publisher: Copernicus GmbH
We present an automatic method for parameterization of a 3-D model of the
subsurface, integrating lithological information from boreholes with
resistivity models through an inverse optimization, with the objective of
further detailing of geological models, or as direct input into groundwater
models. The parameter of interest is the clay fraction, expressed as the
relative length of clay units in a depth interval. The clay fraction is
obtained from lithological logs and the clay fraction from the resistivity
is obtained by establishing a simple petrophysical relationship, a
translator function, between resistivity and the clay fraction. Through
inversion we use the lithological data and the resistivity data to determine
the optimum spatially distributed translator function. Applying the
translator function we get a 3-D clay fraction model, which holds information
from the resistivity data set and the borehole data set in one variable.
Finally, we use <i>k</i>-means clustering to generate a 3-D model of the subsurface
structures. We apply the procedure to the Norsminde survey in Denmark,
integrating approximately 700 boreholes and more than 100 000 resistivity
models from an airborne survey in the parameterization of the 3-D model
covering 156 km<sup>2</sup>. The final five-cluster 3-D model differentiates between
clay materials and different high-resistivity materials from information held
in the resistivity model and borehole observations, respectively.