Abstract:

Trial coalbed methane (CBM) production of the well group in Baode has achieved a relatively satisfactory result but the
CBM genesis is still unconfirmed. Based on the data of the components and stable isotope composition of the CBM sampled from
the producing wells, the genesis was discussed. Results showed that the CBM is mainly composed of the methane with little heavy
hydrocarbons. Carbon isotopic composition of the methane is obviously light, and partial data of the carbon and hydrogen isotopes
of the methane plot within the transitional range between the thermogenic and biogenic gases. Carbon isotopic composition of the
carbon dioxide of the samples is relatively heavy and is negatively correlated to the carbon isotopic composition of the methane. It
was suggested that the coalbed methane in the area has a mixed thermogenic and biogenic origin, but thermogenic gas is the main
with composition minor of biogenic gas. Biogenic methane was formed through the reduction of carbon dioxide. The chemistry
and hydrodynamics of the coalbed water and the porosity and permeability of the strata in the area were favorable of the active
population of the methanogenic bacteria.