Heat flow in oligocene sediments at Szentendre

Summary

In an exploration borehole of 500 m depth at Szentendre detailed geothermal measurements were made for the determination of the terrestrial heat flow. The hole crossed porous Oligocene sandstone containing clay minerals. 40 rock samples were collected but the cores lost a considerable part of their pore-water while taking ont of the borehole and transporting into the laboratory. Resaturation was not possible owing to desintegration of the samples due to swelling of clay minerals.

The author presents a method for overcoming this difficulty. It there exist a suitable model of pore distribution, the approximatein situ conductivity can be established. At first the rock specimen is completely dired out and the dry conductivity is measured. Then the specimen is saturated with some organic liquid or mineral oil with known conductivity and the conductivity is measured again. From these two values and from the conductivities of the air and liquid, with help of the pore structure model, thein situ conductivity can be approximated.

After comparing his results to other investigators experiments, the heat flow is computed using the method described for the determination of thein situ conductivity. The heat flow amounts to

$$2.01 \cdot 10^{ - 6} cal/cm^2 ,\sec $$

which is consistent to other results in the Hungarian basin.