ABSTRACT: Assessment of the Zent Coal Field, Southeastern Costa Rica

J. N. Weaver, G. Cubilla, R. Samuels

The Zent coal field is one of nine coal fields in Costa Rica that were investigated by the Refinadorra Costarricense de Petroleo (RECOPE) and the U.S. Geological Survey, under the auspices of the Government of Costa Rica and the U.S. Agency for International Development. Estimated resources of lignite and subbituminous coal in the nine fields are more than 49 million metric tons, of which almost 15 million metric tons are in the Zent coal field. In the Zent coal field, which has an areal extent of about 100 km², two major coal beds of Miocene age were sampled and analyzed, the Capa del Indio and Capa Segunda. A total of 58 samples were collected from drill cores from the Capa del Indio coal bed, and 13 samples were collected from the Capa Segunda coal bed. On a as-received basis, coal from the Capa del Indio bed has an average heat-of-combustion value of 5700 Btu/lb, 12.15% ash, 41.36% moisture, and 0.98% sulfur. Coal from the Capa Segunda bed has a heat-of-combustion value of 3200 Btu/lb, 16.38% ash, 41.20% moisture, and 0.74% sulfur.

As of February 1989, the estimated reserves of the Zent coal field are 777,500 metric tons of coal with as much as 50 m of overburden. The estimated resources of the Capa Segunda bed, about 10 m above the Capa del Indio bed, are 247,200 metric tons. Combined reserves for these two coal beds in the Zent coal field total an estimated 1,025,000 metric tons.

Uses for the coal from the Zent coal field range from production of heat for drying coffee and making sugar and cement to primary generation and co-generation of electricity.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990