engleski

Radon, CO2 and hydrocarbon concentrations in soil gas and gamma dose rate investigations for the purpose of geological model improvement

Several soil gas parameters were measured at two different locations near the city of Kutina (Sava depression). The first location was selected based on historically known locations of the surface oil seepage (site A) and the second because of known hydrocarbon accumulation in the subsurface (site B) (Cvetković et al, 2021). Measured parameters were radon (222Ra), thoron (220Ra), CO2, CH4, PID (photoionization detector - volatile organic compound), and TP (total petroleum - volatile hydrocarbon component) concentrations. Since radon concentrations are very variable and it is difficult to conclude which parameters affect them, measurements of natural radioactivity were also performed to evaluate local lithology's influence on the results. The results show that it is possible to distinguish the shallow subsurface lithological composition (by measuring natural radioactivity), to characterize the migration path and to indicate the area of oil seepage on the surface and its correlation with Radon, Thoron, CO2 and hydrocarbon concentrations in soil gas. Areas above known hydrocarbon accumulations generally have elevated radon concentrations and measured higher hydrocarbons in soil air with sporadic methane occurrences, in contrast to lower radon levels and lack of higher hydrocarbons in soil air in the area without confirmed underground hydrocarbon accumulation. These parameters were spatially presented for site A. Additionally, self-organizing neural networks were used for the classification of the measured data to highlight the zone of hydrocarbon migration. Further soil gas monitoring will be carried out in potential areas with migration pathways which should contribute to geological modelling.

Soil gas monitoring, Radon, Carbon dioxide, Hydrocarbon exploration

Rad predstavlja dio rezultata dobivenih u sklopu projekta HRZZ-UIP-2019-04-3846 - GEODEP (GEOloška karakterizacija podzemlja istočnog dijela Dravske depresije s ciljem procjene Energetskog Potencijala) financiranom od strane Hrvatske zaklade za znanost (HRZZ).