Lithofacies definition in the subsurface is an important factor in modeling, regardless of the scale being at reservoir or basin level. In areas with low exploration level, modeling of lithofacies distribution presents a complicated task as very few inputs are available. For this purpose, a case study in the Požega Valley was selected with only one existing well and several seismic sections within an area covering roughly 850 km2. For the task of expanding the input data set for lithofacies modeling, neural network analysis was performed that incorporated interpreted lithofacies (sandstone, siltite, marl, and breccia-conglomerate) in a single well and attribute data gathered from a seismic section. Three types of different neural networks were used for the analysis: multilayer perceptron, radial-basis function, and probabilistic neural network. As a result, three lithofacies models were built alongside a seismic section based upon predictions acquired from the neural networks. Three lithofacies were succe...

Soil gas measurements of radon (²²²Rn), CO₂, and hydrocarbon concentrations, as well as gamma-ray spectrometry, were conducted at two separate locations to estimate the measurement results for known locations of hydrocarbon accumulations in the subsurface and oil seepage on the surface. The aim of the study was to confirm the applicability of the method for identifying migration pathways (e.g., faults) and to detect possible seepages of hydrocarbons to the surface as well as to investigate possible health issue potential about the soil gas analysis results. Site A investigations were performed with a large number of sampling points to provide sufficient spatial coverage to capture the influence of subsurface lithologic variability as well as the influence of the migration pathway on the measured parameters. For the investigation of site B, sampling points were positioned to reflect the situation between the area above producing hydrocarbon fields and areas with no confirmed accumulation. The results presented show that it is possible to distinguish the near-surface lithology (gamma-ray spectrometry), characterize the migration pathway, and indicate the area of oil seepage at the surface. Areas above the known hydrocarbon accumulations generally have elevated radon concentrations and detectable heavier hydrocarbons with sporadic methane in soil gas, which contrasts with the lower radon levels and lack of detectable heavier hydrocarbons in soil gas in the area with no confirmed hydrocarbon accumulation in the subsurface.

Presented work focuses on the importance of unconformity that separates the Neogene infill from older Palaeozoic and Mesozoic rocks in the Croatian part of Pannonian Basin. Structure map of this horizon nearly represents the thickness map of the Neogene and Quaternary basin fill. Rock formations just below the unconformity are significantly weathered, which results in favourable petrophysical properties, making them interesting from the aspect of geoenergy potential. The pre-Neogene surface was constructed in 1:400,000 scale using publicly available subsurface maps of different scale and different level of detail. Harmonization and compilation of these maps enabled construction of a structured surface with near-vertical fault planes. Supplemental maps were constructed via basin modelling, showing the temperature distribution in the subsurface, potential source rock maturity near the mapped horizon, surface heat flow and geothermal gradient distribution. Constructed maps illustrate the importance of the mapped interval for regional planning of future geoenergy-related research..

Every country with a history of petroleum exploration has acquired geological knowledge of its sedimentary basins and might therefore make use of a newly emerging resource—as there is the potential to decarbonise energy and industry sectors by geological storage of CO₂. To reduce its greenhouse gas emissions and contribute to meeting the Paris agreement targets, Croatia should map this potential. The most prospective region is the SW corner of the Pannonian basin, but there are also offshore opportunities in the Northern and Central Adriatic. Three “geological storage plays” are suggested for detailed exploration in this province. Firstly, there are three small gas fields (Ida, Ika and Marica) with Pliocene and Pleistocene reservoirs suitable for storage and they can be considered as the first option, but only upon expected end of production. Secondly, there are Miocene sediments in the Dugi otok basin whose potential is assessed herein as a regional deep saline aquifer. The third option would be to direct future exploration to anticlines composed of carbonate rocks with primary and secondary porosity, covered with impermeable Miocene to Holocene clastic sediments. Five closed structures of this type were contoured with a large total potential, but data on their reservoir properties allow only theoretical storage capacity estimates at this stage.