A hydrocarbon differential absorption lidar system is expected to help Laser Exploration Inc. in Midland, Texas, to find stratigraphically trapped oil and gas fields. Ophir Corp. in Littleton, Colo., and Chimera Geophysical Corp. in Reno, Nev., recently completed successful field testing of the mid-infrared laser technology. Within a 1-mile laser-to-reflector distance, the lidar system can detect ethane, methane and potentially propane at about 1 ppm. It is believed that these gases are leaking upward from pressurized oil and gas fields. A Raman-shifted Cr:LiSAF laser generates the spectroscopic probe beam, and an extended-cavity solid-state diode laser performs spectral tuning.