Factors influencing biogenic gas production of low-rank coal beds in the Jiergalangtu Sag, Erlian Basin

Abstract

The study on the factors influencing the biogenic gas production of low rank coal beds is of great significance to the search of the favorable biogenic gas enrichment areas of similar coal beds and the guidance of the microbial stimulation technologies. In this paper, the lignite samples taken from the Jiergalangtu Sag in the Erlian Basin were selected to carry out the simulation experiment of biogenic coalbed methane under different temperatures, pH values, oxidation-reduction potentials (Eh) and trace element concentrations. Then, the influences on biogenic gas production were discussed and the optimal biogenic gas production condition was determined. And the following research results were obtained. First, in the simulation experiments, the biogenic gas production of coal beds increases first and then decreases with the increase of temperature, pH and trace element concentration and the decrease of Eh. Second, in the case of temperature 30–35 °C, pH 7.0–7.5 and Eh −225 mV, the metabolism of methanogen is the most active and the most favorable for the generation of biogenic gas, so biogenic gas production can be promoted by adding the trace elements (Fe2+ and Ni2+) of proper concentration. It is concluded that a proper burial depth (300–600 m), a weak runoff hydrodynamic condition and an anaerobic environment constitute the favorable conditions for the generation of biogenic gas in the Jiergalangtu Sag, Erlian Basin. Moreover, the addition of appropriate trace elements can be an effective means of microbial stimulation.