Recovery and utilisation of coal seam gas : impetus by the German hard coal mining industry

In Europe, the epoch of systematic seamgas drainage began in the early 1940s, when two German mining engineers filed for a patent after successful borehole tests in Mansfeld colliery of the Ruhr basin. Shortly after World War II, the coal mining industry in other European countries started to benefit from that achievement with Belgium quickly reaching a top position regarding both volumes of drained gas and percentage of its utilisation. In line with declining hard coal production in western Europe during the two last decades, seam gas drainage fell in absolute figures, while R & D efforts continued to improve recovery and utilisation. By lawyers abroad already quoted as German declaration, the recent decision on the fundamental question concerning ownership of coalseam gas provides a sound legal base for seam gas production by surface holes as well as for coal mining operations and associated underground gas drainage. Application of well stimulation techniques, like hydraulic fracturing, can be traced back to the 1960s when the first surface test wells for seamgas had been treated in the Saar basin. For the last 20 years, special drilling techniques for exploration by surface and underground boreholes had been developed by the coal mining industry. So far, more than 700 surface wells have been drilled in the Ruhr basin, characterised by slime hole technique, deviated and horizontal holes. Experience and skills connected with that performance provide a unique and valuable base for the planned commercial projects related to seamgas Dependent on mining operations, underground drained seam gas is subject to changes in quality and quantity. This fact can complicate long-term utilisation or requires gathering systems for balanced supply of defined volumes and certain range of methane content to customers. Examples from different German coal fields are introduced, underlining the influential meaning of gas availability, infrastructure and demand. Current utilisation of seam gas in Germany ranges from chemical feedstock to different kinds of heat and power generation. Some recent developments are explained in more details.