--> Abstract: Fractional Generation of Nitrogen and Methane in Northern Germany, by J. Frielingsdorf, B. Kroosz, R. Littke, and B. Muller; #90990 (1993).

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FRIELINGSDORF, J., B. KROOSZ, R. LITTKE, and B. MULLER, Forschungszentrum Julich GmbH, Julich, Germany

ABSTRACT: Fractional Generation of Nitrogen and Methane in Northern Germany

In northern Germany, nitrogen contents in gas fields in the deep subsurface range between 1 and 99%. As it is an open question whether nitrogen is sourced by the same precursor as methane, namely terrigenous organic matter in Upper Carboniferous sediments, a study was started to calculate the kinetics of nitrogen generation and the masses of nitrogen released under natural conditions from coals.

The kinetic study was performed with coals of different maturities (high volatile bituminous coals to anthracites) at a heating rate of 0.1 degrees C/min and in the temperature range between 50 and 1000 degrees C. One result of these experiments is that a low maturity coal (0.8% Rr) produces methane in a temperature range of 350-700 degrees C. Nitrogen, however, is only released at very high temperatures ranging from 580-l000 degrees C. A kinetic interpretation of

the generation curves leads to the prediction that methane and nitrogen release from coals in natural systems will occur at different temperatures (and times). In particular, these data indicate that significant amounts of nitrogen are only generated at temperatures greater than 300 degrees C.

A mass balance, based on the elemental composition (C, H, O, N) of coals supports the above interpretation that nitrogen is released at a late stage of maturation from coals. The total mass loss of the coals is close to 50% in the maturity range of 0.7-5% Rr. Nitrogen lost in this maturity range is about 1% of the original coal mass.

In view of the great abundance of coals in northern Germany, these data demonstrate that coals are an important source of nitrogen in the study area Also, the positive correlation of a high maturity of the Upper Carboniferous with high nitrogen/methane ratios supports the idea that fractional generation of both gases from coal has an important influence on the gas composition.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.