Carbon dioxide sequestration in coal: the relationships between coal structure, texture, and mineralogy, and the role of mineral reactivity with carbonic acid

Dawson, Grant Kristofor Wayne (2012). Carbon dioxide sequestration in coal: the relationships between coal structure, texture, and mineralogy, and the role of mineral reactivity with carbonic acid PhD Thesis, School of Earth Sciences, The University of Queensland.

       
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Author Dawson, Grant Kristofor Wayne
Thesis Title Carbon dioxide sequestration in coal: the relationships between coal structure, texture, and mineralogy, and the role of mineral reactivity with carbonic acid
School, Centre or Institute School of Earth Sciences
Institution The University of Queensland
Publication date 2012-01
Thesis type PhD Thesis
Supervisor Sue Golding
Joan Esterle
Paul Massarotto
Total pages 235
Total colour pages 39
Total black and white pages 196
Language eng
Subjects 04 Earth Sciences
040309 Petroleum and Coal Geology
040202 Inorganic Geochemistry
Formatted abstract Injection of CO2 into coal seams, with or without enhanced coal bed methane recovery (CO2-ECBM), is one method for sequestering CO2 greenhouse gas emissions underground. Critical to this process is the permeability of the coal seam reservoir and its geochemical reactivity to carbonic acid as it moves through the coal matrix and its fracture network. This thesis conducted a series of linked studies to develop predictive relationships for the nature and occurrence of cleat and fracture, the degree and type of mineralisation within the fractures and the matrix and their potential response to injection for a range of coals. In reservoir modelling, permeability is dependent upon the coal fracture or cleat density, its interconnectivity and openness within a given stress field. The spacing between cleats of a given cleat class was found to be directly proportional to cleat height, and this bore a relationship to coal banding texture of vitrain and durain. The intersection angles between primary and secondary vitrain layer confined cleats were found to correlate with the intersection angles between master cleats, which will influence directional permeability upon injection. Multiple generations of mineralisation were evident within the studied coals, and the same minerals often occurred within both the fractures and matrix. Vein sulfide and carbonate mineralisation was most prevalent in samples taken from near the intersection of faults with anticline fold axes. Mineral matter in coal can occlude coal fractures and matrix pores, impeding fluid flow and gas sorption, unless it is reactive and able to be dissolved during CO2 injection. Geochemical batch reactor experiments were carried out with coal cubes and carbonic acid under simulated in situ temperature and pressure conditions. Significant mobilisation of elements occurred during the experiments. The major elements mobilised tended to be those commonly found in nature, for example calcium and magnesium, although comparable amounts of sulfur were also leached from the coals. The presence of chloride ions in the reaction waters caused significant enhancement of mobilisation of elements from coals relative to carbonic acid reactions in deionised water. Demineralisation of cleats and other coal fractures could enhance permeability, and demineralisation of matrix pore mineralisation could enhance CO2-sorption capacity of coal. Improved knowledge of cleat frequency and orientations in fields, as well as coal mineralisation and the type and context of reactions with CO2 acidified waters, will improve reservoir models for CO2 injection and ECBM.
Keyword Coal
Cleat
Joint
Fracture
Mineral paragenesis
Geochemical reaction
Carbonic acid
CO2 sequestration

 
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Created: Fri, 14 Sep 2012, 13:21:51 EST by Grant Dawson on behalf of Scholarly Publishing and Digitisation Service