## 2 Geological Background  
The Drava Basin is an elongated WNW-ESE trending, tectonically subsided basin with a maximum thickness of Neogene and Quaternary sediments of about 7000 m [22; 23]. Lithost stratigraphic division for the western part of the Drava Basin corresponds to the one in the Sava Basin due to similar depositional processes [24], while it is somewhat different in the eastern part of the basin.  
According to [22; 25], the Neogene sedimentary sequences in the western part of the Drava Basin were formed during three depositional megacycles. The first megacycle started during the Early Miocene and is composed of Lower to Middle Miocene syn-rift and early post-rift sediments. Terrestrial sandstones, coastal precias, conglomerates, and sandstones were deposited, and they are overlain by shallow to deep marine marks and shales with thin sandy intercalations, while biogenic and bioclastic limestones were deposited in the coastal zone [26] (Figure 2). The end of the megacycle is characterized by the deposition of fine-grained sediments in the brackish water basin. The Sarmatian/Pannonian boundary is marked by decreased salinity and the sediments of a brackish water environment [27]. The second megacycle is associated with the thermal subsidence of the Pannonian Basin during the Late Miocene. The sedimentary sequence begins with littoral limestones and a nearshore transgressive layer overlain by hemipelagic calcareous and clayey marks [27]. The western part of the Drava Basin was filled to lake level and the youngest deposits of this megacycle were formed in fluvial environments. In the eastern part of the Drava Basin, deposition continued on the delta front [28; 29]. The third megacycle lasted from the Pliocene to the Quaternary and was characterized by the shallowing of the large lake environment and the transition to marsh and then terrestrial environments [27; 30], accompanied by a compressional type of tectonics [25].  
In the western part of the Drava Basin, the main hydrocarbon reservoirs are located within conglomerates and sandstones of the Lower and Middle Miocene (first megacycle) and Lower Pannonian sandstones (lower part of the second megacycle). However, Upper Pannonian sandstones also have good reservoir properties [22].  
The main target of this research is the Upper Miocene sediments of the Gola Field, located in the southwestern Pannonian Basin near the Croatian-Hungarian border and the Drava River (Figure 1). The Neogene sediments represent important reservoir rocks and form a sequence of sandstone, siltstone, marl, and their transitional lithofacies due to the depositional conditions in this area. These deposits were formed in a brackish lake environment in the zone of the lake littoral and part of the sublittoral and represent sediments of channel fill and underwater delta, deposited by turbidites [31].  
They mostly occur in lenticular forms, which makes their accurate identification and spatial correlation challenging [31]. The problem is particularly emphasized when there is a lack of well logging data. Any approach to estimating lithology, such as geophysical modeling, the application of various statistical methods, or artificial intelligence methods, would provide more reliable results if the input data are consistent and complete.