Coal Chemistry for Mechanical Engineers: From Macromolecular Thermodynamics to Reservoir Simulation

Abstract

In pilot trials and commercial scale field demonstrations of CO2 storage in coal seams, quite often unexpected problems with coal swelling around injector and reducing injection efficiency (e.g., Allison unit in the San Juan Basin, RECOPOL in Poland, Hokkaido project in Japan, etc.) can stall or even terminate the site development. To avoid the costly mistakes with the prospective site evaluation, the state of the art in reservoir modeling needs to be improved by taking into account coal properties at the macromolecular level. The current models are based on the rock mechanics, which ignores decades of experimental and theoretical studies of interaction between coal and injected fluids. A pseudopolymer approach is introduced to the modelers as a viable alternative, especially, at medium to high fluid pressures. Further, it is discussed how the thermodynamics of CO2 dissolution in the macromolecular network of the coal matrix can be incorporated into geomechanical models.