Effect of coal petrology and pressure on wetting properties of wet coal for CO_2 and flue gas storage

摘要

The injection of carbon dioxide (CO_2) or flue gas into coal layers enhances the coal bed methane production (ECBM) and offers an option for CC>2-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 investigatedin a modified pendant drop cell at a constant temperature of 318 K and pressures varying between 0.2 and 16MPa. For the semi-anthracite Selar Cornish sample, the wettability alteration from intermediate-wet to gas-wet with CO_2 injection was observed atpressures 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 highrank (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.