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PSFrom collection to
utilization: Outcrop analog 
data
in a 3D world*
By
John B. Thurmond1
Search and Discovery Article #40126 (2004)
*Adapted from poster presentation at AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.
1University of Texas at Dallas ([email protected])
The collection of
three-dimensional data from outcrops is playing an increasingly important role
in reservoir characterization studies. There are a variety of techniques that
can be used to acquire three-dimensional data from outcrops, and each should be
applied individually or in concert to collect data in specific circumstances.
The current suite of emerging methods typically used in outcrop-scale
measurement includes traditional surveying, direct GPS measurement, laser
scanning (LIDAR), photogrammetry, and photorealistic mapping (texture draped
geometry). Depending on the morphology, setting, and particular data needs of a
specific outcrop, different methods can be used to acquire data. Case studies of
individual outcrops will be shown to illustrate the problems and benefits of
several of these methods.
Once
three-dimensional data is collected, utilizing the data can present its own set
of challenges. Each collection method produces a different type of data, each of
which requires a variety of processing and interpretation methods to utilize
effectively. In most cases, there is also the need to integrate data from a
variety of sources into a single interpretable data set. Again, case studies
provide specific illustrations of effective methods that have been used in
various projects to produce reservoir models from a variety of environments,
including deep-water channel systems, heavily faulted fluvial environments, and
carbonate build-ups.
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uAbstractuPhotorealistic outcrop capture
uAbstractuPhotorealistic outcrop capture
uAbstractuPhotorealistic outcrop capture
uAbstractuPhotorealistic outcrop capture
uAbstractuPhotorealistic outcrop capture
uAbstractuPhotorealistic outcrop capture
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Figure Captions
MethodsThe most
straightforward method for Normally, Real-Time Kinematic GPS systems are used, which provide an accuracy of approximately 2cm. Due to the practicalities of efficiently walking on a geologic surface, the normal accuracy is about 50 cm.
Advantages: High accuracy (50 cm or less).
Accurate
Disadvantages: Slow (5-10 km per day).
Re-interpretation can require
re-
Laser Rangefinder Often, it
is not physically possible to “walk” on a stratigraphic surface, so
other techniques are required. Reflectorless Laser Rangefinders, coupled
with high-precision GPS receivers, provide the opportunity to capture
Advantages: Fast.
Disadvantages: Lower accuracy (varies with distance). Encourages interpolation/extrapolation.
Re-interpretation can require
re-
Photorealistic Outcrop Capture (Figures 7 and 8) Using a
scanning laser system, coupled with a high-accuracy GPS system, it is
possible to scan the topography of an outcrop with a high degree of
accuracy. Digital photographs can then be accurately mapped to the
topography, which provides an accurate, three-dimensional model of the
outcrop. This model can then be interpreted in 2D (on the photographs)
or in 3D (on the model), and re-interpreted as often as necessary. Some
laser systems provide the capability of scanning color simultaneously
with distance, but the
Advantages: Fast. High accuracy (5-10cm pixel error (!)).
Provides images with
Disadvantages: Expensive equipment required. Processing can be intensive.
CarbonatesLocation: Last Chance Canyon, Guadalupe Mountains, New Mexico (Figures 5 and 6) Problem:
Excellent 3D exposures of a mixed carbonate and siliciclastic system.
Antecedent topography is an important control on subsequent facies
deposition.
Techniques: Currently, only GPS Results: Current: 3D geologic model of (hydrodynamic?) mud-mounds. Model provides evidence for re-interpretation of processes controlling mud-mound deposition. Future:
Interpreted photorealistic model of Last Chance Canyon. This will
provide a framework for building a 3D geologic model of the canyon,
which will be an excellent research and teaching
SiliciclasticsLocation: Eocene Ainsa II deepwater channel and lobe complex of the South-Pyrenean Foreland Basin, Spain (Figures 7, 8, 9, 10, and 11) With: Ole J. Martinsen and Tore M. Løseth, Jan Rivenaes, and Kristian Soegaard, Norsk Hydro Research Centre Problem:
These deep-water siliciclastics are an excellent analog for active
production fields in offshore Angola. Accurate 3D Techniques: Numerous integrated photorealistic models were used to collect accurate 3D representations of the outcrop. Surfaces were interpreted in an immersive visualization environment (a CAVE) and, combined with spatially accurate 3D structural models, produced by the University of Barcelona. Results:
A reservoir model was produced from the 3D
Fault
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