It seems that every once in a while a new idea comes along that makes people slap themselves in the forehead saying, “We’ve been doing this wrong for HOW long?” When it comes to multicomponent seismic, a new company named VertiShear might just set the forehead-slapping into motion.
Let’s look at standard multicomponent seismic acquisition. To acquire the true full elastic wavefield, contractors have been combining three-component geophones with three sources at every source station. This creates a true nine-component dataset. And it’s ridiculously expensive. But it’s still considered the only way to get a true full elastic wavefield dataset.
Dr. Bob Hardage at the Bureau of Economic Geology at the University of Texas-Austin had a different idea. After years of looking at vertical seismic profile (VSP) data, which is typically acquired using a standard vertical vibrator, he began to notice an additional wave embedded in the data along with the downgoing compressional (P) wave.
“The way to figure out where that wave came from was not easy because rarely did anyone record VSP data where the receivers went all the way to the earth’s surface,” Hardage said. “There was always an interval of a couple thousand feet or so where you had no data. You just had to speculate what went on.”
He began to collect data in which the receivers did go all the way to the surface and found that the downgoing P wave and shear (SV) waves converged at the source point. Was it possible that vertical vibrators could generate shear energy?
To test his theory Hardage used the university’s test site to use every kind of source available to the industry. The results were impressive. “What the test data show is that every source we call a P-wave source generates far, far more shear wave energy than P-wave energy,” he said. “We’re talking factors of five.”
This discovery roughly coincided with a love note from the president of the university asking his research folks to start commercializing more of their technologies. Hardage applied for several patents (he’s received four so far) and released VertiShear, a commercial technology company that works with seismic processing companies to apply the new technique.
The beauty of the discovery, of course, is that there are enormous databases full of legacy 3-D data. “That shear wave information is embedded in those data, and it’s ripe for the picking,” Hardage said. “If you want to lower the cost, then I don’t know of any way to get the cost lower than not even recording the data, just leasing it out of a data library.”
For more information, visit vertishear.com.
Contact the author, Rhonda Duey, at firstname.lastname@example.org.