Wettability determination by contact angle measurements: HvbB coal-water system with injection of synthetic flue gas and CO 2

Department of Geotechnology, Delft University of Technology, Delft 2628CN, The Netherlands.
Journal of Colloid and Interface Science (Impact Factor: 3.37). 08/2011; 364(1):237-47. DOI: 10.1016/j.jcis.2011.07.091
Source: PubMed


Geological sequestration of pure carbon dioxide (CO(2)) in coal is one of the methods to sequester CO(2). In addition, injection of CO(2) or flue gas into coal enhances coal bed methane production (ECBM). The success of this combined process depends strongly on the wetting behavior of the coal, which is function of coal rank, ash content, heterogeneity of the coal surface, pressure, temperature and composition of the gas. The wetting behavior can be evaluated from the contact angle of a gas bubble, CO(2) or flue gas, on a coal surface. In this study, contact angles of a synthetic flue gas, i.e. a 80/20 (mol%) N(2)/CO(2) mixture, and pure CO(2) on a Warndt Luisenthal (WL) coal have been determined using a modified pendant drop cell in a pressure range from atmospheric to 16 MPa and a constant temperature of 318 K. It was found that the contact angles of flue gas on WL coal were generally smaller than those of CO(2). The contact angle of CO(2) changes from water-wet to gas-wet by increasing pressure above 8.5 MPa while the one for the flue gas changes from water-wet to intermediate-wet by increasing pressure above 10 MPa.

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Available from: Narjes Shojai Kaveh, Mar 24, 2015
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    • "Under similar conditions, γ for CO 2 /water and CO 2 /brine show similar evolution with respect to temperature and temperature (Chun and Wilkinson, 1995; Chalbaud et al., 2010). It decreases with pressure at constant temperature and this is more significant at lower pressure near the critical region (Shojai Kaveh et al., 2011; Nielsen et al., 2012) especially at low temperature (Chalbaud et al., 2010). At higher pressure, plateau is reached at the value of γ for the system that slightly increases with salt concentration at constant temperature (Chalbaud et al., 2010). "
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    • "A large value of P a means that the surface is rough and a small P a factor indicates a smooth surface (i.e., the P a value of a glass surface is about 0.1 ␮m). A more detailed description on determination of P a value is given by Shojai Kaveh et al. (2011) "
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    ABSTRACT: The injection of carbon dioxide (CO2) or flue gas into coal layers enhances the coal bed methane production (ECBM) and offers an option for CO2-storage. The success of this process depends on different factors, among them wetting behavior of the coal plays an important role, which is a function of pressure, temperature, coal rank and composition of the gas.The wettability behavior of wet coal samples (semi-anthracite), with respect to injection of synthetic flue gas and pure CO2, was investigated in a modified pendant drop cell at a constant temperature of 318 K and pressures varying between 0.2 and 16 MPa. For the semi-anthracite Selar Cornish sample, the wettability alteration from intermediate-wet to gas-wet with CO2 injection was observed at pressures above 5.7 MPa. Experimental results with synthetic flue gas revealed that the wettability of Selar Cornish coal is intermediate-wet at all pressures and the contact angle only slightly increases with increasing pressure.Comparison between high rank (semi-anthracite) and medium (high volatile bituminous (hvBb)) coals confirms that hydrophobicity increases with the coal rank for samples with a similar bulk mineral content. The results of the contact angle experiments are input parameters for field scale reservoir modeling.
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