layer-based models
DESCRIPTION
Hydraulic parameterization of 3D subsurface models: from measurement-scale to model-scale Jan L. Gunnink, Jan Stafleu, Denise Maljers and Jan Hummelman TNO – Geological Survey of the Netherlands. Layer-based models. n ation-wide (~ 41,000 km 2 ) upper 500 m ArcGIS raster layers - PowerPoint PPT PresentationTRANSCRIPT
Hydraulic parameterization of 3D subsurface models: from measurement-scale to model-scale
Jan L. Gunnink, Jan Stafleu, Denise Maljers and Jan Hummelman
TNO – Geological Survey of the Netherlands
Layer-based modelsnation-wide (~41,000 km2)upper 500 mArcGIS raster layersresolution 100 x 100 m(hydro) geological units with:
top, base, thicknessuncertaintieshydraulic parameters
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Voxel models
nation-wide (~41,000 km2)upper 30 mresolution 100 x 100 x 0.5 meach voxel contains:
stratigraphic unit + uncertaintylithology (sand, clay, peat) + uncertainty
15 km
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Anthropogenic
Clay
Peat
Fine sand
Medium sand
Coarse sand
Clayey sand
Parameterization of Voxel models
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Stratigraphy
Lithology and sand grain-size
Hydraulic conductivity
Groundwaterflow models
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Measuring hydraulic conductivity
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How?Measure from samplesPumping testsSlug testsEmpirical relationships linking lithology and grain-size to conductivity
Measuring hydraulic conductivity
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Systematic sampling of stratigraphic units and lithologies in the Netherlands
Application: hydraulic resistance map
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days
Calculated directly from measured values
70 km
Scale difference between measurement and model
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100 m
0.1 m
Small-scale heterogeneity
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0.1 m
Alternating sand and clay layers in a tidal environment
low high
Hydraulic conductivity (m/day)
100 m
1 m
100
m
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Sand
Clay 50 realizations of sand-clay distribution
Block composed of small voxels of 0.5 x 0.5 x 0.05 m
1 m
100 m100 m
Step 1: Model the spatial distribution of sand and clay within a single voxel
Sand-clay proportion
80%
20%
5 different sand-clay proportions
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Sand
Clay 50 realizations of sand-clay distribution
Block composed of small voxels of 0.5 x 0.5 x 0.05 m
100 m
1 m
100 m
40%
60%
Step 1: Model the spatial distribution of sand and clay within a single voxel
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Block composed of small voxels of 0.5 x 0.5 x 0.05 m
5 * 50 realizations of vertical hydraulic conductivity
5 * 50 different sand-clay distributions
Step 2: Model the spatial distribution of vertical hydraulic conductivity
100 m
1 m
100 m
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5 * 50 different distributionsof vertical hydraulic conductivity
Block composed of small voxels of 0.5 x 0.5 x 0.05 m
Effective vertical hydraulic conductivity of the entire block (m/day)
Step 3: Apply Modflow-model
Vertical flow
Results
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Clay
Sand
N=50
Effective vertical hydraulic conductivity of a heterogeneous sand-clay voxel
40%
60%
Application: hydraulic resistance map
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70 km
days
Calculated from upscaled hydraulic resistance
Application: hydraulic resistance map
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days
Calculated from measured hydraulic resistance, without upscaling
70 km
Conclusions
Systematically measure hydraulic conductivity from samplesNew procedure to assign effective hydraulic conductivity values to each voxel in our modelsProcedure accounts for:
difference in scale between laboratory measurements and voxelssmall-scale heterogeneity within voxels
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Thank you for your attention
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Stratigraphy
Lithology and sand grain-size
Hydraulic conductivity
Groundwaterflow models
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Keff = Kg * (1 + variance(ln(k)/6)) for 3D effective conductivity
This applies for the sandy facies, with almost no heterogeneity
Kg=exp(E[ln(K)])
Gutjahr, 1978; Desbartes, 1992