Coal Seam Gas Emissions from Ostrava — Karvina Collieries in the Czech Republic during Mining and after Mines Closure

Abstract

The Ostrava-Karvina part (OKR) of the Upper Silesian coal basin is the most important hard coal basin in the Czech Republic. This basin extends over an area of 1,600 km². The Carboniferous basin fill contains 255 seams with a net coal thickness of 150 m. In the north-western part of the basin, the coal seam gas contains methane and carbon dioxide. But in the remaining part it contains only methane. The gas content in the coal is estimated between 4.4 to 20 m³/t. The seams of the western and south collieries are prone to outbursts of coal and gas.

In the active mines, a system of methane drainage is operating to ensure mine safety. Other safety measures are taken in the mines which exploit the seams susceptible to outbursts of coal and gas to predict and to prevent their occurrence.

Some of the collieries are already closed or being closed. Coal mines closure does not mean that methane liberation into the underground abandoned areas would be stopped. After closure water level in the mines would rise. During this stage some mine gas may leak uncontrollably to the surface via old mine shafts and natural migration channels. This migration is greatly influenced by rapid drops in atmospheric pressure. A risk of explosion or fire would occur in the basements of buildings or industrial plants in the densely populated city of Ostrava. A complete system of gas extraction, gas monitoring and safety measures in the buildings is being built to prevent the gas emissions to the atmosphere and to ensure the inhabitants safety.