HR: 0800h
AN: GP31C-03    [Abstracts]
TI: Surface Reservoir Characterization and Stratigraphic Studies Using Rock Magnetism and EPR in Venezuela: A Review
AU: * Aldana, M
EM: maldana@usb.ve
AF: Departamento de Ciencias de la Tierra, Universidad Simon Bolivar, Valle de Sartenejas, Baruta, 89000, Venezuela
AU: Diaz, M
EM: marisel@ivic.ve
AF: Centro de Fisica, Instituto Venezolano de Investigaciones Cientificas, IVIC, Km. 14, Carretera Panamericana, Altos de Pipe, Los Teques, 21827, Venezuela
AU: Costanzo-Alvarez, V
EM: vcosta@usb.ve
AF: Departamento de Ciencias de la Tierra, Universidad Simon Bolivar, Valle de Sartenejas, Baruta, 89000, Venezuela
AB: During the last years, the Paleomagnetic and Rock Magnetic Laboratory at the Simon Bolivar University has incorporated studies of rock magnetism and non conventional techniques in geophysics (as Electronic Paramagnetic Resonance or EPR) to solve diverse problems at the Venezuelan oil industry. Particularly, surface reservoir characterization and EPR-Magnetostratigraphic studies have been performed. At some Venezuelan oil fields (Guafita, La Victoria and Furrial) rock magnetic properties studies (e.g. Magnetic Susceptibility (MS)), extractable organic matter (EOM) and organic matter free radical concentration (OMFRC obtained via EPR) analysis have been applied trying to identified, at shallow levels, the "oil magnetic signature" of subjacent reservoirs. The results obtained in non consolidated samples from the first 1500 m of producers and non producers wells, show the existence of MS, EOM and OMFRC anomalies at shallow levels that are associated with an underlying reservoir and/or oil migration. Authigenic spherical aggregates of submicronic FE-rich magnetic crystals, observed by Scanning Electron Microscopy (SEM), are responsible for the detected MS anomalies. These studies allowed to establish a set of criteria (i.e. EPR, EOM and SEM) in order to link, with a minimum uncertainty, near-surface MS anomalies with the underlying reservoir. We have also explored the application of EPR, combined with petrographic, MS analysis, Qn and S-ratios, to characterize stratigraphic facies and identifying depositional environments at various sections in southwestern Venezuela. The different paramagnetic species that have been identified (e.g. manganese, free radicals and different Fe forms) together with the rock magnetic parameters, seem to give valuable information regarding the lithological characteristics of the studied sections. According to our results, as manganese content is related with the redox conditions, it can be used as a paleoenvironmental change index in stratigraphic columns with large lithological contrasts. For stratigraphic sections that present similar lithologies, the presence and concentration of distinct Fe species could be useful to characterize different depositional environments. The results obtained indicates that this kind of integrated analysis can be used as powerful tool for stratigraphic and environmental studies.
DE: 1517 Magnetic anomalies: modeling and interpretation
DE: 1520 Magnetostratigraphy
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly