Coalbed methane prospect of Jamalganj coalfield, Bangladesh

Five major Gondwana coalfields have been discovered in the half-graben type basins in the subsurface in the Precambrian platform area of northwest Bangladesh. The Jamalganj coalfield, with an estimated reserve of about 1053 million tons of coal, has seven coal seams in the depth range between 640 to 1158 m below the ground surface. Compared to the other coalfields of the area, with coal occurring at 150 to 500 m depth, Jamalganj coal is considered to be too deep to be exploited by conventional underground or open pit mining. Instead, developing coal bed methane from Jamalganj coalfield may be considered as a viable option for its exploitation. The positive factors of Jamalganj coal bed methane development include high net thickness of coal with at least one very thick (40 m+) and widely developed seam, coal seam burial depth within optimum range, large coal reserves, indication of significant gas content from drilling data, and poor permeability in the rocks above and surrounding the coal layers. The thickest seam III can be a primary target for CBM development especially where it combines with seam IV in the eastern part of the coalfield. However, there are a number of unknown factors like actual gas content of coal, the coal permeability, and in-seam pressure that need to be evaluated before deciding the viability of the project. An initial attempt to collect these baseline data should include drilling test well or wells in the primary target area where seam III is most thick and widely developed.