Raster Data Enhancement and Tectonic Element Interpretation in ArcMap

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1 Raster Data Enhancement and Tectonic Element Interpretation in ArcMap Vsevolod Egorov ESRI Petroleum User Group Conference Houston, TX 2005

2 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 of tectonic 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.

3 Outline Objectives Data Raster Data Enhancement Basics Paradox Basin: Salt-Cored Anticlines and Igneous Intrusions Drainage Pattern as a Geological Indicator Conclusions

4 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 the ArcMap environment.)

5 Data Terrain Data SRTM30 data available from U.S. Geological Survey, EROS Data Center, Sioux Falls, SD: Aeromagnetic Data Courtesy of Fugro Airborne Surveys Corp. Gravity Data UTEP-USGS-NGA-NOAA Gravity Database GeoNet - US Gravity Data Repository System:

6 Outline Objectives Data Raster Data Enhancement Basics Paradox Basin: Salt-Cored Anticlines and Igneous Intrusions Drainage Pattern as a Geological Indicator Conclusions

7 Interpretation Workflow INPUT Raster (Terrain, Gravity, Magnetic, Seismic Horizon Grids) Enhancements Raster (Computational and Visual) Interpretation Raster to Vector (Terrain and Geologic Features Mapping) OUTPUT Vector (Tectonic Element Map) Integration Raster to Vector (Cross-Reference between Different Enhancements)

8 Enhancements Computational Visual -Low Pass Filter -High Pass Filter -Horizontal Gradient/ Maximum Slope -Vertical Gradient -2 nd Vertical Gradient -etc. -Aspect/Dip Direction -Color Schemes -Hillshade

9 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.

10 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). ArcMap Spatial Analyst slope and aspect calculated over the model.

11 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

12 Paradox Basin: Terrain.

13 Paradox Basin: Slope of terrain calculated in Spatial Analyst.

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

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

16 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.)

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

18 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.

19 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.

20 Shaded Terrain Hillshade Slope Aspect of Slope Paradox Basin: Spatial Analyst terrain enhancements of the Upheaval Dome a fascinating geologic feature of Utah.

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

22 Outline Objectives Data Raster Data Enhancement Basics Paradox Basin: Salt-Cored Anticlines and Igneous Intrusions Drainage Pattern as a Geological Indicator Conclusions

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

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

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

26 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.

27 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.

28 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.

29 Author Information Vsevolod Egorov Geophysicist Fugro Robertson Inc Hillcroft, 5 th Floor Houston, TX Direct : Main : Fax : vegorov@fugro.com

Horizontal gradient and band-pass filter of aeromagnetic data image the subsurface structure; Example from Esh El Mellaha Area, Gulf of Suez, Egypt.

Horizontal gradient and band-pass filter of aeromagnetic data image the subsurface structure; Example from Esh El Mellaha Area, Gulf of Suez, Egypt. Essam Aboud 1, Serguei Goussev 2, Hassan Hassan 2, Suparno