The story of medical oil – Naphtalan

The area around Ivanić-Grad is one of the oldest Croatian oil and gas provinces. This is a place which is better known as “Croatian Kuwait”. But that’s not all. People don’t use the oil and gas only for transportation and industry here. They use it as a medicine, because it really is!

Upper photo: The original well Križ-1 into the oil Croatian field. (source: Marko Špelić, 2015). Lower photo: Naphtalan as used for medicinal purposes (source:

This is a story of Naphtalan, a name given to a natural crude oil with a very particular composition, and which has healing properties. Everything started in the cold winter of 1949 when the first well, Križ-1 penetrated to the several hundreds meters deep reservoir saturated with oil. This was one of the first Croatian oil fields where the first big oil and gas company was founded. The pioneering job was done by the hands of local people who used to be farmers. They then became roughnecks, drivers, electricians, engineers and they built roads, schools and theaters. But, most important in this story, their teamwork and the unique geological features of this region gave rise to a new branch of industry: health tourism.
The oil source rocks in this region were deposited in anoxic conditions during the evolution of the Pannonian basin system. Small organisms that lived in the Pannonian sea and lake fell on the bottom and were buried without decomposition. As more and more sediments accumulated above, these deposits with remains of organisms were buried deeper and deeper. Finally, they came into temperature and pressure conditions which changed them forever. They became natural crude oil. But this is just the beginning of the journey. Crude oil started to leave the source rock through small pores, fractures and faults. Finally, it came to the old fragmented crystalline basement and the conglomerates above it. But the oil was not anymore the same as it was in the beginning. Although the precursors of this oil may have predestinated it, its uniqueness is also a consequence of the various rocks that it met on its journey. Several millions of years had passed when this unique crude oil came back to the surface of the Earth at the oil well. When it was examined in the lab, it was figured that it is heavy oil with middle sulphur content but enriched in a special type of cyclic hydrocarbons. After it is refined, this oil is very suitable for the healing of various types of diseases and medical problems. Therefore, the Naftalan hospital opened its doors at the town of Ivanić-Grad in 1989. It is a place where local people and tourists from various countries all over the world can be healed with Naphtalan products while they can swim in the thermal waters from the long gone Pannonian lake.

And here I am, standing after a short jogging in the forest where the mentioned oil field  Križ is situated. In front of me is the famous well Križ-1. Almost 70 years have passed since the first crude oil came to the surface. I’m wondering if anyone in those days had an idea that the oil they were looking for, would be used as a medicine. What a journey for this ancient organism, crude oil, industry and society in this region of Croatia!

Marko Špelić, Marko Budić and Tomislav Kurečić
Croatian Gelogical Survey (HGI-CGS)



Galović, S., 1953: Prilog geološkom poznavanju poznavanju strukture Križ (Contribution to geological knowledge of the Križ structure). Geološki vjesnik, 1951-1953, 255-272.

Alajbeg, A., Donelli, D., Srića, V., Podolski, Š., Alajbeg, I., Šegudović, N., 2001: Usporedba fizičkih svojstava i sastava Naftalana (Comparison of some physical propertis of Naphtalan). XVII. Hrvatski skup kemičara i kemijskih inženjera, Vicković, I., Hrvatsko kemijsko društvo i hrvatsko društvo kemijskih inženjera (Book of Abstract XVII. Croatian Meeting of Chemist and Chemical Engineers), 173-173.


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