Main factors controlling coalbed methane distribution in the Ruhr district

Abstract: The Carboniferous coal deposits in the Ruhr District of Germany have been evaluated for their coalbed methane (CBM) potential utilizing data from more than 600 wells collected uring the last 20 years of coal exploration. It can be shown that the distribution of methane (and other gases) and therefore the commercial value of the deposit are controlled by several factors that are a result of a combination of processes related to burial during the Carboniferous, ubsequent phases of erosion/exposure and, finally, re-burial. Therefore, th distribution and accumulation are not only a function of coal petrology and geochemistry, but also of basin configuration (e.g. tectonics, hydrology, stratigraphy). Thus the assessment of the CBM potential of the basin requires a multidisciplinary approach. Coals of Carboniferous age have been mined for centuries in western and eastern Europe. Although the mining activity has frequently been associated with disastrous accidents caused by underground gas explosions, and European Carboniferous coals are known to have provided the hydrocarbon source for a large number of gas fields (e.g. the giant Groningen Field, the fields in the southern UK gas basin), only limited interest has in the past been given to coal bed methane (CBM) as a potential energy resource. However, the success of CBM production in the USA has resulted in a significant interest in European coals as a potential future source of natural gas and several coal basins have been studied extensively, including the Ruhr Basin in Germany (see Fig. 1), to establish the CBM potential within these basins. Although the mining industry in the Ruhr District has collected a considerable volume of gas content data, little (Teichmfiller et al. 1970; Hinderfeld et al. 1989) has been done to determine regional variations in the gas content and the reason for such variations. The objective of this paper is to characterize the gas distribution and present a model that accounts for some of the vertical and lateral variations in gas content within the Ruhr Basin