Three-dimensional massively parallel electromagnetic inversion—II. Analysis of a crosswell electromagnetic experiment

A 3-D electromagnetic inversion scheme has been successfully applied to crosswell electromagnetic data collected at the Richmond Field Station near Berkeley, California. By comparing images of data collected before and after the injection of 50000 gallons of salt water, a 3-D image of the plume has been developed, which shows the location of zones of maximum permeability surrounding the injection well through which the salt water has migrated. A resolution analysis has determined that the location of the plume is fairly accurate. However, the image of the geology will be distorted due to incomplete data coverage. This latter problem is further complicated by the fact that data residuals indicate that the wells deviate from the vertical. These deviations have been shown to cause artefacts within the images and thus further reduce the accuracy of the images with respect to the geology.