Beyond Desorption Testing on Coal Bed Methane Exploration (CBM). Colombia Case

Abstract

Due to the decrease of natural gas reserves and the high death toll from explosions in coal mines, Colombia has been carrying out preliminary explorations of coalbed methane (CBM). Until now, CBM exploration has focused on the gas content per tonne of coal from canisters desorption systems, but few additional tests have been done to determine coal gas saturation, gas origin, methane percentage and coalbeds permeability. The purpose of this research is to analyze recent information on the use of adsorption isotherms, C¹³ and deuterium isotopes analyses, gas chromatography and permeability modeling. Adsorption isothermal test indicates that coalbeds are subsatuated, isotopic results show that gas origin is mainly biogenic, that methane content would be below 77%, and that permeability values could be high. These results also indicate that more isotherms, isotopes, chromatography and permeability tests are required to clarify with greater precision methane saturation, gas origin, methane percentage and flow capacity that CBM deposits would have in Colombia, and in this way ensure that there is enough gas to achieve economic feasibility in future projects. It is also concluded that the exploration has been superficial and that it is necessary to investigate the CBM at depths greater than 500 m, at a prudent distance from mining works and away from highly fractured areas; preferably in structures such as synclines with low deep structures, which should include studies of fractures, diagenesis, and reservoir modeling.