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A Review of Geological Modeling

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Title: A Review of Geological Modeling


1
A Review of Geological Modeling
Short Course 503 Three-Dimensional Geologic
Mapping for Groundwater Applications October 27,
2007
  • A. Keith Turner
  • Colorado School of Mines
  • Carl W. Gable
  • Los Alamos National Laboratory

2
Why Is Modeling Visualization Important?
The World of the Geoscientist Is
Multi-dimensional
  • Current interpretation methods limit this view
  • Digital versions of traditional maps are not
    sufficient
  • Increased efficiency demands computer-based
    methods to
  • Integrate and Manage the data
  • Interpret geological features
  • Visualize attributes spatially and temporally
  • Model dynamic Earth processes

3
Importance of This Topic
  • 3-D subsurface modeling first became feasible in
    late 1980s with the introduction of
    high-performance Unix-based graphical
    workstations
  • Developing digital representations of the
    subsurface does not ensure high-quality and
    efficiently managed projects
  • Society is increasingly demanding
  • multi-scale, multidisciplinary, integrative
    projects
  • a shift from passive data collection and
    archiving to dynamic information management and
    dissemination

4
Over The Past DecadeEnormously more powerful
computers anddata storage have vastly reduced
costs!
  • Continuing, rapid advances in computer HARDWARE
    and SOFTWARE technologies
  • Modeling visualization increasingly integrated
  • Increasingly realistic models possible

5
Problems in Subsurface Investigation are
Unique...
  • Subsurface information is often incomplete and
    conflicting
  • The subsurface is naturally complex and
    heterogeneous
  • Sampling is most often insufficient to resolve
    all uncertainties and
  • Scale effects on rock , fluid, and other
    properties are usually unknown.

6
Why We Need Special Modeling and Visualization
Tools and Not Just CAD
GEO-OBJECT
ENGINEERING OBJECT
7
A Typical Modeling Project
8
Geometry (Descriptive) Modeling
  • Definition Geometry (Descriptive) Modeling
    involves visually describing, through various
    means such as computer graphics and modeling
  • The geologic framework
  • Distribution and propagation
  • of attributes

9
3-D Model Involves Two Stages
  • Framework Definition
  • Borehole and isolated sample data
  • Triangulated surfaces
  • 2-D grids and meshes
  • Iso-volumetric models
  • from triangulated surfaces
  • from cross-sections
  • from grids and meshes
  • parametric (NURBS, etc)
  • Boundary Representations
  • Discretisation and
  • Property Distribution
  • 3-D grids and meshes
  • regular hexahedral
  • octree variable
  • geocellular
  • tetrahedral unstructured
  • meshes

10
Modeling Often Begins with Borehole Data
(Lynx Geosystems)
11
Geometry Models can be Constructed Using
Cross-Sections
12
3-D Solid Models can bedeveloped from Multiple
Surfaces
(Lynx Geosystems)
13
Layered Models may involve many surfacesComplex
channels and pinch-outs are difficult to model
14
Regional (Volumetric) SubdivisionFeasible for
Non-stratigraphic Cases
(C. Gable LANL)
15
Framework Models require Grids or Meshes to
assign Property Distributions
16
Geological Framework Defined First then Grid
Resolution
(C. Gable LANL)
17
Discretisation may involvestructured and
unstructured meshes
18
Geocellular Volumetric Model
19
Yucca Mountain Represented by a Tetrahedral Mesh
Model
(C. Gable LANL)
20
Accurately Modeling Faults is a Challenge
  • Near-horizontal thrust faults form additional
    surfaces
  • Steeply inclined Faults commonly shown as
    vertical

Edwards Aquifer Model In Texas by USGS
21
Advanced Fault Modeling
22
Models may be Nestedfrom Regional to Local
Scales
23
Purpose of Modeling is Prediction
  • Prediction has an extrapolative rather than
    interpolative character
  • Involves risk
  • Leads to Decision-making

24
Predictive Modeling
  • Examples
  • economic simulations,
  • reservoir performance,
  • fluid migration and transport models,
  • seismic velocity modeling,
  • structural restoration
  • Definition Predictive Modeling involves
    prediction and/or simulation of events, dynamic
    and other types of processes occurring in the
  • geological subsurface
  • Solve equations, or other
  • numerical analyses
  • Forward and inverse
  • modeling techniques

25
The geologic framework controls the application
modeling
26
Contamination plume model shown within geology
27
Full contamination plume model
28
The Bottom Line Trends in 3-D Modeling
  • Continuing, rapid advances in computer
    technologies
  • Increasingly realistic models possible
  • Coarse- vs. Fine-scale Models
  • Cannot easily incorporate geologic knowledge
    (i.e. geologic interpretations)
  • Difficulties representing uncertainties
  • Hampered by imprecise data and inability to
    adequately sample the prototype

29
The Modeling Challenge
How Can We Do Better?
  • Build 3-D models from isolated bore data and
    soft information
  • Connect known conditions between the boreholes
  • Model real-world complexity
  • Verify the resulting models
  • Represent the uncertainties of the geologic
    framework
  • Reduce cost and time of model development

30
An Integrated Data Management Process
31
What Benefits will an Integrative Approach
Provide??
  • To the Individual Scientist
  • To the Scientists Organization
  • To the Client Organizations and Their Staff
  • To Society at Large

32
Benefits to the Individual Scientist
  • More time for science, so.
  • More interactions with colleagues
  • More interesting projects/studies
  • More job satisfaction
  • More publications
  • More rapid promotions

33
Benefits to the Scientists Organization
  • Society
  • Maximize Organizations
  • Value to Customers
  • Maximize Strategic Value BETTER!
  • Maximize Financial Value CHEAPER!
  • Maximize Operational Effectiveness FASTER!

34
Benefits to the Client Organizations and Their
Staff
  • Model Consistency
  • Data versioning, audit trail, documentation
  • QA compliance
  • Improved Predictive Capability Model
    Maintenance
  • Efficiency streamlining processes, updating
    databases
  • Auto-updating decision support tools

35
Benefits to Society at Large
  • Relevant science that supports decision-making
  • Clearly communicated results
  • Cost reductions

36
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