The concept of storing carbon dioxide into coal seams is considered to be a safe and effective method for permanently storing it, with the potential added benefit of enhanced coal bed methane (ECBM) production. Recent field pilots have demonstrated the feasibility of CO2 sequestration in coal seams. In this context it is important to improve the understanding of fluid flow and storage processes taking place. Unlike conventional reservoirs, coal primarily stores methane or CO2 as adsorbed gas on the internal surface area of the matrix. Since the CO2 sorption capacity of coal is much higher than that for methane, injection of CO2 into coal beds can improve methane recovery. The objective of this study was to evaluate the impact of CO2 injection on a number of petrophysical properties of selected European coals. This paper presents experimental results on the matrix deformation and the simultaneous measurement of gas permeability and strain under varying stress-pore pressure conditions. The porous structure of the coals was characterised using NMR T2 relaxation on water saturated core plugs. The coals studied presented a multimodal pore size distribution in the matrix, where the larger population corresponded to the micropores. Coal matrix deformation (shrinkage or swelling) was measured at different sorption pressures under unconfmed conditions. The matrix swelling was found to increase with CO2 sorption pressure and displayed a positive correlation with coal rank. For a non-adsorbing gas, such as helium, an increase in net stress caused a reduction in permeability following a non-linear relationship. For the samples tested, matrix swelling due to CO2 adsorption had a severe impact on permeability resulting in a permeability decrease. The permeability-stress-strain trend for CO2 at constant pressure was similar to helium, indicating that it is the cleats that dominate gas flow. However, the permeability also decreased with rising CO2 pressure, suggesting a complex interaction between coal and CO2.


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    Title :

    Measurements of petrophysical properties of coal for CO2 sequestration


    Additional title:

    Messung petrophysikalischer Eigenschaften von Kohle für die CO2-Sequestrierung


    Contributors:
    Grattoni, C.A. (author) / Ahsan, M. (author) / Durucan, S. (author) / Jing, X.D. (author)


    Publication date :

    2006


    Size :

    12 Seiten, 10 Bilder, 1 Tabelle, 11 Quellen


    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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