STATISTICAL ANALYSIS OF DIPMETER LOGS FROM EXPLORATION WELLS IN THE DRAVA DEPRESSION, NORTHERN CROATIA

J.  Velic1, T.  Malvic1,2, M. Cvetkovic1* and M. Bošnjak 3

1 Faculty of Mining, Geology and Petroleum Engineering, Department of Geology and Geological Engineering, Pierottijeva 6, 10 000 Zagreb, Croatia.

2 INA-Industry of Oil Plc., Sector for Geology and Reservoir Management, Subiceva 29, 10 000 Zagreb, Croatia.

3 Croatian Natural History Museum, Demetrova 1, 10 000 Zagreb, Croatia.

*corresponding author, email:  marko.cvetkovic@rgn.hr

Stratal dip and azimuth data from dipmeter logs recorded at wells in the western Drava Depression (northern Croatia) were analysed in order to assist with subsurface structural interpretations. The dipmeter data came from the Miocene Moslavacka gora, Ivanic-Grad and Kloštar Ivanic Formations at wells Virovitica-3, Rezovacke Krcevine-1 istok, Rezovacke Krcevine-2 and Orešac-1, located near the town of Virovitica. In contrast to conventional dipmeter interpretations in which dip patterns are represented by “colour trends” (e.g. red represents increasing dip with depth), statistical methods of analysis were used in this study, and consisted of the interpretation of regression curves of dip and azimuth variations with depth. Interpretation of the dipmeter data in this way assisted with the structural interpretation of this folded and faulted part of the Drava Depression.

Also discussed are techniques for the selection of typical regression curves which can help in the identification of lithologically similar intervals based on stratal dip and azimuth data. A total of six such curves can be used for structural and depositional interpretation of such intervals.

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