Non-Seismic Methods Used to Delineate Hydrocarbon Deposits in Hungary

CSOGEI, J., F. LADA, Eotvos Larand Geophysical Institute, Budapest, Hungary, B. BEKE, CS. Formanne-Gulyas, T. NAGY, and Z. NAGY, Hungarian Geophysical Exploration Company, Budapest, Hungary

Chemical and physical alterations of rocks within and above reservoirs allow application of geoelectric methods for detection and delineation of hydrocarbon deposits.

Deep-penetration time-domain-induced polarization measurements (with AB up to 3200 m) were carried out, and factoring of decay curves provided useful information on the location of deposits.

The WEGA-D electromagnetic method can be used to detect any type of alteration connected to hydrocarbon deposits (resistivity of induced polarization anomalies). The field equipment uses a flexible transmitter array, and observed data can be interpreted by an expert system, multidimensional cluster analysis, and pattern recognition.

Controlled-source electromagnetic frequency sounding was carried out in a grid or along profiles in a frequency range corresponding to the depth of deposits. Results were plotted as resistivity or phase pseudosections and maps for different depths. By means of mathematical procedures, regional and residual pseudosections and maps can be constructed; residual anomalies coincide with boundaries of deposits.

Shape and size of magnetotelluric impedance and magnetic polar diagrams vary with frequency. Behavior of these polar diagrams can be used to detect nonstructural hydrocarbon deposits. Mathematical modeling of the magnetotelluric response of 2-D and cylindrical objects seems to justify this idea.

Methods are illustrated with case histories from from Hungary.

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)