Mapping Of A Hydrocarbon Plume And The Geometry Of An Abandoned Petroleum Storage Reservoir

Geophysical data were collected over an abandoned petroleum storage reservoir in Norwalk,<br>California. The storage tank is a bowl-shaped structure that is approximately 600 feet in<br>diameter. The walls of the structure are approximately 2 to 8 feet below the surface and achieve<br>a maximum depth of 25 feet. The reservoir was used as a storage facility in the 1920s and has<br>since been back filled. The location of the reservoir, the continuity of its walls, and the<br>locations of possible concentrations of hydrocarbons within and outside the reservoir were the<br>objectives of the geophysical survey. Geophysical methods used included electromagnetic<br>terrain conductivity, and magnetics. Positioning was obtained using differential GPS. Terrain<br>conductivity highs not associated with in-phase and magnetic anomalies were interpreted as<br>possible concentrations of hydrocarbons. Magnetics and electromagnetics were used to map the<br>perimeter of the reservoir and locate any possible breaches in the wall of the structure.<br>Magnetic data were collected remotely with GPS positioning. A test in which magnetic field<br>data were collected continuously (5Hz) and transmitted to a remote data acquisition system<br>compared favorably to data collected in a more traditional discrete mode. Magnetic data were<br>modeled at locations along the perimeter of the reservoir to estimate the depth to the top of the<br>structure’s wall, using electromagnetic in-phase data for tank edge control.