Study of Petroleum Contaminated Sites In Mexico With Resistivity and Em Methods

Hydrocarbons are among the main factors of geological medium contamination. We differentiate long-term contaminations lasting years or decades of years and short-term contaminations or single accidents. The first produces give more evident geophysical anomalies, whereas anomaly strength of the second depends on the time since the accident occurred. After 6-12 months following the accident this type of contamination gives measurably low resistivity anomalies. Our experience with contaminated sites characterization in Mexico shows that low resistivity<br>anomalies caused by hydrocarbon contamination is possible to localize with the help of vertical electrical sounding (VES) or with electromagnetic profiling (EMP). Such contamination gives low resistivity anomaly as a result of petroleum biodegradation at shallow depth in the earth. It is more difficult to characterize the second type of contaminated sites because the anomalies are not as intensive. Short-term contamination is more abundant in the oil industry.