Downhole photonics

Gail Overton   Senior Editor   Laser Focus World   gailo@pennwell.com

I was reading an article this week in the July 2011 issue of Physics Today on natural gas fracking called "Shale-gas extraction faces growing public and regulatory challenges." It's fascinating to me that horizontal drilling, blasting, and high-pressure fracking chemicals loosen the rock thousands of meters below ground, liberating the natural gas and forcing it to the surface. Though opinions may differ on the environmental soundness of natural gas fracking and other oil-extraction methods such as steam-assisted gravity drainage (SAGD) and tar sands conversion, one thing is certain: the thirst for energy means that ALL sources will continue to be exploited until truly "sustainable" energy generation methods are widely deployed (or until the atmosphere becomes so toxic that you can't breathe).

To minimize environmental issues and improve yields and drilling safety in fossil-fuel extraction (NOTE: I never have been a fan of the term "fossil fuel" since there is conflicting research that says perhaps the earth's crust itself generates oil--see "Laser heating shows that petroleum could have non-dinosaur origins" in Laser Focus World's May 2010 issue), I'm all for using photonics in any way possible. For a review on downhole photonics applications and the tremendous strides that have been made in sending optics into one of the hottest, dampest, harshest environments on the planet, see "Downhole sensing puts fiber optics to the test" in our April 2011 issue.



IMAGE: A fiber-optic sensor is being loaded downhole to monitor temperature and pressure. Courtesy Intelligent Fiber Optic Systems (IFOS; Santa Clara, CA)

One of the fascinating aspects of downhole petroleum sensing that I neglected to cover in my recent article is the need to monitor seismic activity in both terrestrial and especially, marine environments; oddly enough, if you read the Physics Today fracking article you'll see that fracking has even been linked to earthquakes! Our sister media company PennEnergy covered a very interesting fiber-optic geophone that improves over electronic-based technology for downhole seismic monitoring. As the number of fracking sites increases throughout the United States, I certainly would like to know if there is a fracking/earthquake link. As a California native, earthquakes are a big deal and a big concern; any help we can get from photonics and optics in learning more about them is surely appreciated!