3D Geological Modelling at BRGM

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C. Truffert
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3D Geological Modelling at BRGM
Main axis and application fields of 3D geological modelling in BRGM
Softwares and methods
Examples of applications
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1. Two main axis
Construction of 3D geological models (geometry + properties)
Models are often the input for the simulation of a process (water or CO2 flow, seismic, …)
Research
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Aquifer inventory; input model for flow simulation
Urban geology
Seismic risk
Assessment of geothermal potential
1. Application fields
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geophysical inversion
EARTH VISION (commercial software)
ISATIS (commercial geostatistical software)
2. Softwares & methods
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2D geostatistical interpolation
Data: boreholes, full geological map, cross sections, 3D passage points
Several thousands of data points can be taken into account
Main advantages
Full set of data consistency checks (hole-DEM, hole-hole, hole-geological map, histogram, geostatistical cross validation)
Stratigraphic pile
3D Constraint points digitized on 2D maps or cross sections (in GDM)
Automatic contour maps (with scale, axis, …), logs
But no direct 3D visualisation
export of result grids to other softwares (Arcview, Mapinfo, EarthVision)
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3D potential field interpolation
A geological interface is a particular isovalue V0 of a 3D field V=f(X,Y,Z)
Data: boreholes, points from the geological map, digitized cross sections, 3D boundaries points + orientation data
(Number of data limited to max 2000 to 3000 per geological unit)
Main advantages
Geological pile
3D constraint points digitized on 2-D map or cross sections
True 3D model (geological formation known at every 3D point)
Full 3D visualisation (surface+volume)
Geophysical inversion
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Complex 3D geometry and fault network
Spline type interpolation for layer-cake geometry, or 3D function for 3D objects
Data: 3D passage points from boreholes, geological map, digitized cross sections, seismic data
Main advantages
geological pile
3D visualisation (surface+volume)
But more difficult to use, does not handle inequalities, expensive
More adapted for oil-industry data (many seismic, few holes)
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2D-3D Interpolation (geometry or rock properties)
2D-3D Simulation (facies simulation, pixel-based methods or object-base methods)
Main advantages
3D visualisation (surface+volume)
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3. Examples
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Basic geological knowledge
Marine geology (GEOMODELLER)
Understand relationships between the Messinian phase and the regional tectonic context
Describe the markers of the Messinian Salinity Crisis in the marginal basin
Main objectives :
3. Examples
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Infra-Toarcian aquifer
Poitiers region
3. Examples
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Nice model (alluviums) : model used to simulate
the ground behaviour during a seismic event
3. Examples
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Bordeaux (2006) : Geometry (GDM+ISATIS); Geotechnical and hydrogeological properties (ISATIS)
3D probability map of being in a low permeability terrain
in the alluviums of a sector of Bordeaux city
Size of model: approx 7 km * 6 km * 15 m
3. Examples
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Mineral water (2007): Geometry (GEOMODELLER) + double phase flow simulation
3. Examples
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Dogger in Paris Basin : geometry (EARTHVISION)
Dogger in Paris Basin: facies and flow properties (ISATIS)
CO2Net project
Permability model
(Cmos software – GEUS)
3. Examples
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3. Examples
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Improving construction of models
More data in Geomodeller
More realistic geological models
Improve imports and exports
Links with further processing
Public
Geo-scientists, …
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4. Projects in R&D
Final objective: to give the geologist an integrated interface on his PC, enabling :
search and display available data (drill holes, geol maps …)
download + pre-process this data
build a geometrical model
mesh this model according to the final objective of the work
populate the meshes of the model with the appropriate properties
simulate a physico-chemical process in this model
display results in 1D, 2D, 3D, 4D …
Web server for models and results
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BRGM is involved in 3D geological modelling since 10 years
3D modelling is the key issue for geology and forward applications (ground-water, risk assessment, land-use, mineral resources and oil exploration …)
Continue Research & Developpement are needed to implement a workflow from data acquisition to 3D dynamic modelling
Different 3D modelling softwares are needed
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3D Geological Modelling at BRGM

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