Effect of coal petrology and pressure on wetting properties of wet coal for CO2 and flue gas storage

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.

The wettability behavior of wet coal samples with different ranks (high volatile bituminous (hvBb) and 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.Figure optionsDownload as PowerPoint slideHighlights
► Determination of wettability behavior of wet coal surface with synthetic flue gas and pure CO2.
► Contact angle measurement at elevated pressures and temperature in saturated aqueous phase.
► Experiments on two different coal ranks, medium and high rank, with similar bulk mineral contents.
► Microscopic image analysis to determine the surface roughness.
► A Phoenix Nanotom™ micro CT-scanner was used to determine the void and mineral matter distribution.