Author: Mike Cline, T/X Resources
Have you ever had to plan a seismic survey, or determine a well location prior to drilling? If so, did you use a paper map? Wouldn’t it be better to utilize something more accurate, informative, and realistic-looking, such as a shaded Digital Ortho-Quad (DOQ), similar to the image below?
See the larger Adobe Reader pdf file.
What is a DOQ? It’s nothing more than high resolution aerial photographs which have been rectified (corrected for camera distortions), merged, and calibrated to match the real-earth xy locations. Global Mapper is the Geographic Information System (GIS) tool that I currently use to merge DOQ’s into larger areas, drape these over a Digital Elevation Model (DEM), convert the original geographic coordinates (for example, USGS UTM to a Texas State Plane Zone), and overlay planned source and receiver locations on the image to see how terrain, culture, or hydrologic features may affect the operations of a 3D seismic survey, or determine a well location. You can also export the final shaded DOQ from Global Mapper as a GeoTiff file, to import into SMT’s 2d/3dPak for future requirements.
For example, the image below is a hypothetical 3D survey plan (inside the red rectangle) within the larger area of about 20 square miles. You can tell immediately that the northeastern quarter of the proposed 3D survey is going to be impacted by the somewhat rugged topography of the gully system that feeds the river on the eastern side of the aerial photo. Having the ability to move the source locations positioned in the gullies, during the pre-planning stage (so that you can minimize affect on the 3D survey), is a real time saver.
Another benefit, is the ability to export the DEM data from Global Mapper as an ascii xyz file and then import this file into SMT as a grid. You can then hold the cursor over any point on this map and directly read the surface elevation–good for checking the 3D or well surveying for transposed numbers, or estimating the ground/KB elevation for a proposed (or existing well without KB info).
Copyright © T/X RESOURCES, 1995-2008. All Rights Reserved.