EPR and magnetic susceptibility studies in well samples from some Venezuelan oil fields

Electron Paramagnetic Resonance (EPR) and Magnetic Susceptibility (MS) meas urements were carried out in near-surface samples of 6 wells (producers and non-producers) from some Venezuelan oil fields. EPR measurements were perf ormed to determine the organic matter free radical concentration (OMFRC) in the samples. MS anomalous levels, where the restrictive presence of micros copic framboidal magnetic minerals has been recognized, were found only at the producer wells. Moreover for these same wells, anomalies of OMFRC were observed at depths close to MS anomalous levels. These preliminary results seem to suggest a relationship between the presence of OMFRC and MS anomali es, possibly associated with the underlying reservoir. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.