By DIANE FREEMAN
EXPLORER Correspondent

Outcrops Get Close-Up Look

Lasers Taking 3-D to Next Level

SEE RELATED STORY

Graphics courtesy of the Bureau of Economic Geology

Click on images to enlarge.

Two posters and a paper involving lasers and 3-D views of outcrops will be presented at and AAPG Annual Meeting in Salt Lake City in May.

Those technical works are:

"Textural Mapping with Lidar and Real-Time Kinematic GPS on the Flow-Unit Scale: An Example from the Pipe Creek Early Albian Rudist Buildup, Central Texas," a poster presented by Jerry Bellian, Charles Kerans and Ted Playton, also of the University of Texas at Austin. It will be offered Monday morning, May 12, in the session "From Outcrop to Simulation I: Using Outcrop Data to Build Reservoir Models."

"Dual-Purpose Geologic Analysis Using Airborne and Ground-Based Lidar, Coastal Southern California: Quantitative 3-D Characterization of Modern Coastal Erosion and Ancient Reservoir Architecture," another poster by Bellian, David Jennette and Roberto Gutierrez, all of the University of Texas at Austin. It will be offered Monday afternoon, May 12, in the session "From Outcrop to Simulation II: Using Outcrop Data to Build Reservoir Models."

"3-D Modeling of Deepwater Carbonate Outcrops Using Laser Technology (Lidar)," a paper presented by Kerans (co-authored by Bellian and Playton), to be presented at 1:50 p.m. Wednesday, May 14, in the session "3-D Interpretation Techniques Using 3-D Visualization Software."

Research and technological advances have made it possible for geologists to get a better view -- and understanding -- of outcrops. Click on image for a better view.

Lasers have been synonymous with rock shows for years -- but they are about to become important for their rock shows.

Or, in the words of Scott Tinker (and his co-authors Jerry Bellian, Charlie Kerans and Dave Jennette), lasers will play a critical role in the 3-D seismic interpretation because lasers will offer geoscientists the ability to see -- and better understand -- outcrops in the same way that we currently examine 3-D seismic surveys and derivative geologic models on workstations.

Tinker, director of the Texas Bureau of Economic Geology, spoke in Denver at the recent annual 3-D Seismic Symposium, sponsored by the Rocky Mountain Association of Geologists and the Denver Geophysical Society.

He did more than just talk, of course: He demonstrated through a slide presentation how Bellian, Kerans, Jennette and other BEG researchers have been using laser data to allow geologists to appear to fly into a rock outcrop for an elevated view, or gain a perspective not physically possible by removing canyon walls or obstructions.

"We're able to get into this world and fully interpret the 3-D outcrop data," Tinker said, adding that working with 3-D outcrops will revolutionize subsurface modeling.

"With this capability, we have a lot more understanding of exactly what we're seeing."

Researchers' near-term goals are to use the high-frequency 3-D outcrop models to:

• Derive realistic 3-D synthetic seismic data that can be used to examine seismic response as a function of frequency.
• Test a range of seismic attribute sensitivities to small changes in lithology, fluid and gas saturation.
• Create a portfolio of analogs for siliciclastic and carbonate outcrop settings worldwide that give geoscientists the ability to examine rock systems with clarity and precision from their desktop.

The best news: Three-D outcrop studies that incorporate land- and air-based laser, radar, electromagnetic and other remote sensing technology will have a significant impact on subsurface exploration and production success.

"The decades ahead promise a 4-D world of instrumented producing fields and real-time data streaming," he said.

"Advanced recovery processes on producing fields will require an even greater knowledge of the reservoir," he added, "and new discoveries will be developed with fewer wells requiring an increased understanding from remote sensing data."

'That's Fine Resolution'

Until now, photo panoramas have provided the best means available for studying outcrops -- but their "retrieval capabilities are limited," Tinker said, bringing mixed results.

However, the portable, solar-powered Light Detection and Ranging systems(LIDAR), built by Optech, can now scan 2,000 points per second for each point record x, y, z, and reflected intensity values for outcrop faces up to one kilometer away, he said.

"We can shoot digital photos, (and) you can make remarkably accurate renditions of canyon walls by patching it all together and merging them to get continuous coverage of an outcrop wall," he said. "This is just the beginning."

With this technology, tightly gridded reflection intensity data are draped as a texture onto an optimized laser surface model. These data can be interpreted directly as one would interpret a black and white photopan, but the user can rotate the image to achieve optimal perspective and accurately map the geology in real space while still in the field.

"We are researching a range of information sources that enhance the outcrop image, many of which may not be obvious or even visible to the human eye," he said.

"That's a whole lot of information before you even take a step on the rock."

Tinker's talk represented BEG research in progress in laser technology applications and its 3-D analysis of carbonate systems conducted by the Bureau's Reservoir Characterization Research Laboratory (RCRL), and clastics systems conducted by the Clastics Reservoirs Group.

Several major oil companies, large state oil companies and independents currently sponsor the Bureau's Lidar studies.

These high frequency studies have yielded some remarkable results, he said. Moreover, high-frequency laser data can be collected and processed for most outcrop settings in just a few weeks, greatly reducing post-processing and interpretation cycle time from conventional photopan-based field methods.

"Most importantly," he added, "we retain the true spatial relationships of the outcrop."

The initial product is a 3-D digital elevation model with vertical resolution on the centimeter scale, which can be used to:

• Visualize topography -- and plan field work, optimizing sampling strategies.
• Merge with digital photographs or other remote sensing data.
• Interpret stratigraphic horizons, joints, faults, macroscale diagenetic processes and bed-scale sedimentology.
• Drape and interpolate measured section data.
• Calculate first derivative, second derivative, reflection strength and other properties to help characterize such things as faults and fractures, solution features and lithology.
• Provide the framework for input into 3-D modeling.

Tinker backed up his words with slides of a channel complex collected and interpreted by co-authors Bellian and Jennette in northern Spain with an elevated view, proving the point that "you can get different, sometimes incorrect, information by looking at it on foot from the canyon floor.

"You can fly into the cliff," he said. "You're there on that outcrop. It can make the field work a lot more intelligently designed."

Even in a distant photo of an outcrop with some buildings on top, the viewer can zoom in on details as small as the wristwatch of a person standing on a balcony of a building.

"That's fine resolution," he said.

Jennette and Bellian will be presenting papers on their research at the AAPG annual and international meetings in Salt Lake City and Barcelona, Spain.