THE ENERGY DEPT. FIGURES the U.S. still has twice as much oil underground as has been extracted. Much of it is even near existing wells. But until recently, the best way to find it was to drill a fresh hole, an expensive and environmentally destructive task. Now, ParaMagnetic Logging Inc. in Palo Alto, Calif., is licensing a system that can prospect for overlooked deposits by looking through the half-inch-thick steel casings that line existing oil wells.
The key: Rock containing oil and gas resists an electrical current much more than rock that has been saturated with the salt water used to squeeze out oil. So PML's equipment runs a current from electrodes deep in the well to electrodes on the surface. Engineers spot oil deposits by carefully measuring how much current leaks through the steel into the surrounding rock--using sensors that can detect changes as minute as a billionth of a volt, even when under intense heat and pressure. Oil-field giant Schlumberger Ltd. patented a similar concept four decades ago but lacked today's ultrasensitive microcomponents. Schlumberger has licensed PML's system, which was developed with support from the Gas Research Institute in Chicago and the Energy Dept. It has won high marks from companies such as Arco and Mobil Oil.