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Merging Rocks and Lasers: Bringing 3-D Outcrop Geology to the Workstation

David C. Jennette, Bureau of Economic Geology, Austin, TX

Outcrop analog studies have long served as a benchmark tool to convey geologic relationships of subsurface reservoirs and to improve the modeling of hydrocarbon recovery. One limiting feature of outcrop research is that its "language" is analog based, typically relying on cumbersome photomosaics and geologic cross sections.The exchange, archiving, and/or retrieval of information and knowledge have been challenging. Because today's subsurface geologist works mainly in a workstation environment, it is highly desirable to develop a medium by which interpreters can readily access and share the outcrop knowledge that has been gained from decades of study. New developments in lidar technologies are bringing about such change by providing a direct link between the outcrop and the workstation. Advances in acquisition technology, data handling and processing, and visualization now bring kilometer-long and complexly faceted rock exposures into navigable 3-D volumes.

Researchers at the Bureau of Economic Geology are targeting several clastic and carbonate outcrops from a variety of depositional settings for quantitative study. We combine conventional field study methods with laser-generated imagery to create a 3-D digital framework for the outcrop. We can interrogate the exposures by positioning ourselves in an infinite number of "virtual" vantage points and observe relationships not visible or apparent while on foot. Bounding surfaces, lithofacies types, and faults can be interpreted on the laser-generated point cloud of the outcrop, similar to the interpretation of 3-D seismic data volumes. Digital photographs are draped onto the 3-D outcrop models, providing geologists the ability to take virtual tours of the rock face using simple VRML (virtual reality modeling language) technology. Simply put, we can ask questions and seek answers at a pace and accuracy that were not previously possible.

Laser-generated models and visualization software offer geologists a quantitative 3-D medium to interact with and share outcrop observations. The archiving and retrieval of a large volume of data are possible. The combination of rocks and laser technology has exciting potential for use in stratigraphic research, structural analysis, analog modeling, and education and information exchange.

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