engleski

Heat flow and hydrocarbon reservoirs in Croatia

Vertical conductive heat flow on the territory of Croatia has been determined on the basis of temperature measurements in deep exploration and production hydrocarbon wells corrected on static conditions, ground temperature measurements performed at meteorological stations, and heat conductivities of rocks calculated from interval seismic velocities. Hydrocarbon reservoirs can be associated with the positive heat flow anomalies, although, as can be seen from this paper, they are not necessarily connected with the maximum heat flow values. Heat convection by means of ground water, oil and gas migration, as well as tectonics and the appearances of rocks with different heat conductivities, are the main causes of local heat flow anomalies. The phenomenon that in many cases hydrocarbon reservoirs are located on the margins of the maximum heat flow values can be explained by the idea of the separation of hydrocarbons within favourable traps, during the migration of fluid mixture in the geologic past. Small or even negative temperature gradients in deeper intervals of the wells VC-1 south-east from Bjelovar and KBNZ-1A south from Zagreb, as well as higher temperature gradients above those intervals, indicate that within the water-bearing layers there is still an active process of heat transfer by means of convection, i.e. vertical migration of ground water, which is probably a consequence of the thermosyphonic circulation along the fracture systems in formations having good thermal conductivities.

heat flow; hydrocarbon reservoirs; heat conduction and convection; Croatia

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