In situ CO2–coal reactions in view of carbon dioxide storage in deep unminable coal seams

Injection of CO2 in coalbed is considered to be an attractive option for storage. Large amounts of carbon dioxide are generated during the burial history of coal. In commercially produced coalbed gas, however, only small amounts of CO2 are found. This has motivated the present investigation of the long-term stability of sequestered CO2 in coal seams. Thus, the purpose of this study is to examine whether reactions with carbon dioxide can occur in coal at reservoir temperatures. The question is whether a relatively small decomposition of CO2 to form CO can become significant in periods of 10,000 years.High pressure high temperature static and dynamic experiments with CO2 and coal were performed, which led to the opinion that chemical reactions involving CO2 cannot be ruled out. All CO concentrations from CO2 dynamic pressure experiments appear elevated compared to the nitrogen dynamic pressure experiment. The experiments do strongly point towards the reactivity of CO2 to form CO but because of limited experimental data the chemical involvement cannot be articulated in detail.