Open AccessStudy of coal gas wettability for CO 2 storage and CH 4 recovery
Author(s) -
Saghafi A.,
Javanmard H.,
Pinetown K.
Publication year - 2014
Publication title -
geofluids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.44
H-Index - 56
eISSN - 1468-8123
pISSN - 1468-8115
DOI - 10.1111/gfl.12078
Subject(s) - coal , wetting , distilled water , contact angle , dissolution , bubble , chemistry , volume (thermodynamics) , mineralogy , materials science , chromatography , thermodynamics , composite material , mechanics , organic chemistry , physics
To quantify and rank gas wettability of coal as a key parameter affecting the extent of CO 2 sequestration in coal and CH 4 recovery from coal, we developed a contact angle measuring system based on a captive gas bubble technique. We used this system to study the gas wetting properties of an A ustralian coal from the S ydney B asin. Gas bubbles were generated and captivated beneath a coal sample within a distilled water‐filled ( pH 5.7) pressurised cell. Because of the use of distilled water, and the continuous dissolution and shrinkage of the gas bubble in water during measurement, the contact angles measured correspond to a ‘transient receding’ contact angle. To take into account the mixed‐gas nature ( CO 2 , CH 4 , and to a lesser extent N 2 ) of coal seam gas in the basin, we evaluated the relative wettability of coal by CH 4 , CO 2 and N 2 gases in the presence of water. Measurements were taken at various pressures of up to 15 MPa for CH 4 and N 2 , and up to 6 MPa for CO 2 at a constant temperature of 22°C. Overall, our results show that CO 2 wets coal more extensively than CH 4 , which in turn wets coal slightly more than N 2 . Moreover, the contact angle reduces as the pressure increases, and becomes < 90° at various pressures depending on the gas type. In other words, all three gases wet coal better than water under sufficiently high pressure.