Abstract: Kukersite Oil Shale in Estonia: Basin Geology, Resources and Utilization

Heikki Bauert

Kukersite is the name given to exceptionally carbon-rich Middle Ordovician oil shales found in the Baltic Oil Shale Basin. The basin is administratively divided into the Estonia and Leningrad fields, comprising two currently mined (Estonia and Leningrad) deposits and the prospective Tapa deposit. At present, the Estonia deposit supports the largest commercial oil shale industry in the world, with the proven reserves of more than 770 million tons. The deposit has been mined continuously since 1916 and, during the last two decades, the average annual output has been over 20 million metric tons.

In the central part of the Estonia field, the oil shale-bearing sequence is 20-30 m thick and contains up to 50 individual kukersite beds alternating with argillaceous biomicritic limestone. Most of these kukersite beds are 10-40 cm in thickness, but some are as thick as 2.4 m. Individual kukersite beds are laterally continuous and can be traced over 250 km in an east-west direction. The most organic-rich beds (B and E) may contain as much as 40-45% TOC. Semiquantitative XRD analyses reveal that calcite and dolomite form the main mineral phases in kukersites, while the amount of silt-size clastics, composed chiefly of quartz, feldspars and illite, does not usually exceed 15%.

Kukersite is a major fossil fuel in Estonia. About 90% of mined oil shale is burned directly for electricity production in two power plants (1,600 and 1,400 MW). The rest of the oil shale is retorted into shale oil which is consumed by the chemical industry.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994