An Electromagnetic Induction Tomography Field Experiment At Lost Hills, Ca

We have collected borehole to surface electromagnetic induction field data for a shallow steam<br>injection that is underway at Mobil Oil’s Lost Hills-3 field in San Joaquin Valley. Earlier<br>work had been done at the same site by Wilt et al. (1996). This site is an interesting test<br>for techniques under development for environmental engineering, because it can be viewed as<br>an excellent analog of a shallow environmental remediation using steam injection. Surface<br>magnetic field data (vertical and radial fields, magnitude and phase) were collected using 18<br>receiver stations along two profiles which ran radially from the EM transmitter well from 5<br>m to 120 m. The data at each surface station were collected while the EM transmitter was<br>raised slowly from a depth of 120 m to a final depth of 20 m. As part of this experiment, a<br>calibration of the EM transmitter was also performed. Magnetic field data from Lost Hills were<br>successfully collected, including both vertical and horizontal (surface radial) magnitude and<br>phase data along a northerly profile and along a westerly profile. We have observed that the<br>radial receiver data appear to be better behaved than the vertical receiver data, suggesting that<br>these data may be less sensitive to environmental clutter (numerous metallic pipes crisscrossing<br>the site at the surface) than are the vertical data. Some simple 1-D modeling has been done to<br>confirm that the expected conductivity change in the steam zone should produce an observable<br>anomaly in the measured data when comparing the pre-steam to the post-steam conditions.<br>Results of this test were positive. Further analyses of these data making use of a new code<br>developed in a companion paper are in progress and will presented separately.