Raster Data Enhancement and Tectonic Element Interpretation

in ArcMap

Vsevolod Egorov

ESRI Petroleum User Group ConferenceHouston, TX

2005

Abstract

ArcMap Spatial Analyst provides quick, but powerful tools for the geoscientist. Digital elevation models and a variety of geophysical data are utilized in raster grid format. ArcMap Spatial Analyst allows us to enhance these data and map lineament features (e.g., faults, dykes, and drainage patterns), which are necessary components oftectonic interpretation. The interpreted tectonic elements are output in vector format (e.g., shape files) and may be incorporated in many GIS products. This methodology may be applied to both topographic and geophysical (gravity, magnetic, and seismic) data. These data complement each other and enable a more complete interpretation.

This presentation covers an easy-to-implement approach to enhance raster grid data in ArcMap environment, and the subsequent mapping of geomorphologic and geologic features.

The examples are presented from the oil and gas exploration areas of North America and Africa.

Outline

• Objectives

• Data

• Raster Data Enhancement Basics

• Paradox Basin: Salt-Cored Anticlines and Igneous Intrusions

• Drainage Pattern as a Geological Indicator

• Conclusions

Objectives

• Introduce basic theory of raster data enhancement in ArcMap Spatial Analyst

• Demonstrate enhancements of data used in oil and gas exploration

• Demonstrate use of enhanced data for geomorphologic and geologic features mapping

(Note: This work is not intended to be a complete interpretation project, but rather illustrates some techniques that may be utilized by the interpreter in theArcMap environment.)

Data• Terrain Data

SRTM30 data available from U.S. Geological Survey, EROS Data Center, Sioux Falls, SD:http://seamless.usgs.gov/

• Aeromagnetic DataCourtesy of Fugro Airborne Surveys Corp.http://www.fugro.comhttp://www.fugroairborne.com

• Gravity DataUTEP-USGS-NGA-NOAA Gravity DatabaseGeoNet - US Gravity Data Repository System:http://paces.geo.utep.edu/gdrp/default.aspx

Outline

• Objectives

• Data

• Raster Data Enhancement Basics

• Paradox Basin: Salt-Cored Anticlines and Igneous Intrusions

• Drainage Pattern as a Geological Indicator

• Conclusions

INPUTRaster

(Terrain, Gravity,Magnetic,

Seismic HorizonGrids)

EnhancementsRaster

(Computational and Visual)

InterpretationRaster to Vector

(Terrain and Geologic Features

Mapping)

IntegrationRaster to Vector(Cross-Reference between Different

Enhancements)

OUTPUTVector

(Tectonic ElementMap)

Interpretation Workflow

Enhancements

Computational Visual

-Low Pass Filter-High Pass Filter-Horizontal Gradient/Maximum Slope-Vertical Gradient-2nd Vertical Gradient-etc.

-Aspect/Dip Direction-Color Schemes-Hillshade

Gravity/Magnetic Field Observed over the Body

Terrain

Maximum Slope of the Field(Amplitude of Horizontal Gradient)

Maximum Slope of Terrain

Slope enhances edges of the subsurface body or terrain feature.

ArcMap Spatial Analyst slope and aspect calculated over the model.

Slope anomalies (top) over the model (bottom).

Aspect (top) shows dip direction of the model surfaces (bottom) in colors (yellow – flat, red – east, blue – west).

Outline

• Objectives

• Data

• Raster Data Enhancement Basics

• Paradox Basin: Salt-Cored Anticlines and Igneous Intrusions

• Drainage Pattern as a Surface and Deep Geology Indicator

• Conclusions

Paradox Basin: Terrain.

Paradox Basin: Slope of terrain calculated in Spatial Analyst.

Paradox Basin: The slope of terrain map is used to map salt-cored anticlines. Mapped features are saved in vector data format - a polygon shape file.

Paradox Basin: The slope of total magnetic field calculated in Spatial Analyst. (Data are courtesy of FAS Corp.)

Paradox Basin: The slope of total magnetic field is used to map high-gradient zones – indicators of possible igneous intrusions. Note that salt-cored anticlines are not high-gradient magnetic zones. (Data are courtesy of FAS Corp.)

Paradox Basin: The slope of Bouguer gravity anomaly calculated in Spatial Analyst overlain on the shaded terrain.

Paradox Basin: The slope of Bouguer gravity anomaly confirms positions of the salt-cored anticlines and shows their subsurface extent. Note that gravity data primarily reflect sedimentary structures.

Paradox Basin: Hillshade of terrain is another visual enhancement of Spatial Analyst. The mapped features previously saved as shape files are overlain on the raster image.

Paradox Basin: Spatial Analyst terrain enhancements of the Upheaval Dome – a fascinating geologic feature of Utah.

Shaded Terrain Hillshade

Slope Aspect of Slope

Paradox Basin: Spatial Analyst terrain enhancements of the Disappointment Syncline.

Hillshade Slope

Outline

• Objectives

• Data

• Raster Data Enhancement Basics

• Paradox Basin: Salt-Cored Anticlines and Igneous Intrusions

• Drainage Pattern as a Geological Indicator

• Conclusions

Drainage Pattern Analysis: Hillshade function applied to terrain data in Spatial Analyst.

Drainage Pattern Analysis: Aspect of Slope function applied to terrain data to enhance surface fabric.

Drainage Pattern Analysis: Drainage pattern and possible faults/contacts are mapped based on Aspect of Slope map.

Conclusions• Tools available in ArcMap Spatial Analyst provide useful

computational and visual enhancements of raster data.

• Terrain, gravity, magnetic and any other raster data (e.g., seismic horizons) important for geological interpretation can be imported into ArcMap and enhanced using these tools.

• Different data (and their enhancements) complement each other in identifying geomorphologic and geologic features.

• ArcMap editing tools allow mapping of these features in vector format, and storing the results as shape files that may be incorporated in the tectonic element map and other interpretive map products in GIS applications.

Acknowledgments:

Fugro Robertson Inc. for the opportunity to present this work, and personally Robert Pawlowski and Rao Yalamanchili for their help and encouragement.

Fugro Airborne Surveys Corp. for the opportunity to use and present its aeromagnetic data. My special thanks to Jeffrey Rowe, Leanne Isaac, and Ron Lyall.

Dr. Randy Keller, University of Texas at El Paso, for his cooperation and introducing me to the great gravity dataset compiled by his group.

Selected References

Keller, G. R., T. G. Hildenbrand, R. Kucks, M. Webring, Allen Briesacher, Kristine Rujawitz, A. M. Hittelman, D. Roman, D. Winester, R. Aldouri, R. Torres, W. J. Hinze, A. Gates, and J. Seeley, 2005, A community effort to construct a gravity database for the United States and an associated web portal: Contribution to Geological Society of America Special Paper on Geoinformatics, accepted pending minor revision.

Author Information

Vsevolod EgorovGeophysicistFugro Robertson Inc.6100 Hillcroft, 5th FloorHouston, TX 77081Direct : 713-369-6114Main : 713-369-6100Fax : 713-369-6110E-mail: vegorov@fugro.com