Open Conference Systems / RGNF, Mathematical methods and terminology in geology 2020

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Geological model of the A field in the Sava Depression
Kristina Novak Zelenika, Ana Majstorović Bušić

Last modified: 2020-09-12


The oil field A is situated about 50 km to the southeast from Zagreb, in the Sava basin. The seismic attributes analyses allowed the revision of whole depositional concept. The previously drilled wells (A-1, A-2, A-2Al) defined this area as non-commercially saturated with hydrocarbons due to very small thickness or even complete absence of the sandstones (A-2 well). The interpretation of seismic attributes, primarily amplitude anomalies reveals the existence of distinct depositional unit with depositional direction different from the regional. It is as typical stratigraphic trap, and represents sandstone series with dominant local source of material (transport direction NE-SW). The sandstones of local source supposed to have a short transport from the northeast direction and they are considered independently as isolated sandstone bodies. The reservoirs belong to Miocene period (Upper Pannonian) and consist of sandstone bodies interbeded with sandy marls and marls. X reservoir is proved as the most productive and it is the target of this paper.

Geological model was constructed in PetrelTM software. Structural model was built using a simple grid (cell dimension 50x50 m). Laterally, seismic anomaly and oil/water contact represent reservoir borders. Vertically, five reservoir zones were established by the well to well correlation. Porosity in the model was distributed by Moving Average method using seismic attribute as trend. OHIP was estimated in two ways; deterministic (volumetric method) and probabilistic. P50 realization of the probabilistic estimation confirmed deterministically calculated OHIP with difference of approximately 1%.


geological model; stratigraphic trap; sandstone reservoir; Upper Pannonian; Sava Depression

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