Presentation by Peter Vermeulen (Deltares) at the iMOD International User Day, during Delft Software Days - Edition 2017. Tuesday, 31 October 2017, Delft.

1. 5 december 2017
Geo-Modelling in iMOD using VOXELS
Swiss-Case
Peter Vermeulen

2. 5 december 2017
Geo-Modelling in iMOD
 Translation of point-,
vector- and image data
together with expert
knowledge into a 3D grid
representation of the
subsoil

3. Geo-Modelling in iMOD
5 december 2017
 iMOD has the ability to construct interfaces of geo-bodies with the
iMOD Solid Tool – simply connect the boreholes …

4. Geo-Modelling in iMOD
5 december 2017
 In reality it is often less obvious; boreholes might be of different length
and/or irregular spaced to simply draw cross sections between each
?
?

5. Geo-Modelling in iMOD
5 december 2017
 Gain more insight by including more boreholes by projecting
boreholes from an increased distance to the cross section
?
?

6. Geo-Modelling in iMOD
5 december 2017
 Solid Tool offers the ability to construct a subsurface system via
cross sections in which interfaces of geo-bodies need to be
identified;
 Challenge is the determination of the connectivity of the different
geo-bodies in an objective and reproducible manner
Option:
 Generate a voxel model that shows the probability of different
lithology's per depth to support the identification of geo-bodies in
the 2D cross sections

7. Geo-Modelling in iMOD
5 december 2017
 iMOD Batch has a function XYZTOIDF to generate a voxel model
based on Lithology

8. Geo-Modelling in iMOD – Swiss Case
5 december 2017
 Visp – Canton Wallis (Switzerland)

9. Geo-Modelling in iMOD – Swiss Case
5 december 2017
Kimmeier, F., 3-D Groundwater Flow Modeling in
Heterogeneous Geologic Media : Integrated Approach
Using Spatial and Temporal Database, Geostatistics
and GIS. Thèse, Université de Neuchâtel, 2001.
 Visp – Canton Wallis (Switzerland)

10. Geo-Modelling in iMOD – Swiss Case
 Example of the iMOD
Batch function
XYZTOIDF to
compute the voxel
model
5 december 2017
Lithology’s for which the
probability will be be
computed
Anisotropy definitions
Definition of the layering
of the Voxel model –
yielding 75 layers
(x 8 lithology’s and stdev)

11. Geo-Modelling in iMOD – Swiss Case
5 december 2017
r
r’
s
s’
r  Points effected
by anisotropy
(ellips) are
converted to
isotropy (circle)

12. Geo-Modelling in iMOD – Swiss Case
5 december 2017
 Anisotropy is 2000 meter for the major axis and 250 meter for the
minor axes. The angle of the anisotropy is equal to the angle of the
valley. Alluvium fans doesn’t have anisotropy and a radius of 250
meter

13. Geo-Modelling in iMOD – Swiss Case
 Methodology
5 december 2017
0.10 1.00
0.10
1.00
0.40
0.30
zi
zi+1
VOXEL Layer i
A B

14. Geo-Modelling in iMOD – Swiss Case
 Methodology
5 december 2017
0.10 1.00
0.10
1.00
0.40
0.30
zi
zi+1
VOXEL Layer i
A B
0.10 1.000.50
probably clayprobably something else

15. Geo-Modelling in iMOD – Swiss Case
 Methodology
5 december 2017
0.10 1.00 0.10+
0.20=
0.30
0.20+
0.20=
0.40
0.40+
0.30=
0.70
0.10
1.00
0.10
0.20
0.20
0.20
0.40
0.30
zi
zi+1
VOXEL Layer i
A B C D D’

16. Geo-Modelling in iMOD – Swiss Case
 Probability(0.0-1.0) of
SwaD (Swampy) deposists
in between 624 - 626
m+MSL

17.  Probability of SwaD (Swampy Deposits)
Probability (0-1)
Geo-Modelling in iMOD – Swiss Case

18. Geo-Modelling in iMOD – Swiss Case
 Final lithology at each
pixel is the one with the
highest probability
5 december 2017
Probability of SwaD
(Swampy) Deposits)
Probability of FluD
(Fluvial) Deposits)
0.33 (SwaD)
0.74 (FluD)

19.  Main lithology per pixel
Geo-Modelling in iMOD – Swiss Case

20.  Usage of VOXEL model to construct 3D model with limited number of
layers
Geo-Modelling in iMOD – Swiss Case
Aquitard1
Aquitard2
Aquitard3
Aquitard4

21.  Usage of VOXEL model to construct 3D model with limited number of
layers
Geo-Modelling in iMOD – Swiss Case
Aquitard1
Aquitard2
Aquitard3
Aquitard4
Using boreholes only, might define the aquitard differently – more or less

22.  Usage of VOXEL model to construct 3D model with limited number of
layers
Geo-Modelling in iMOD – Swiss Case
Aquitard1
Aquitard2
Aquitard3
Aquitard4
Ignore local phenomena

23. Conclusions
5 december 2017
 Solid Tool offers the ability to construct a subsurface system via
cross sections in which interfaces of geo-bodies need to be
identified;
 Challenge is the determination of the connectivity of the different
geo bodies in a objective and reproducible manner
Solution:
 Generate a voxel model that shows the probability of different
lithology's per depth supports the identification of geo-bodies in the
2D cross sections – assists you to decide differently in the
determination of the interfaces
 Next speaker shows how to use a voxel as is in a model