Ash and sulphur are the two main variables that influence coal quality and are therefore very important contractual
parameters in a coal supply agreement. Coal which is low in ash yield and sulphur content is considered as ‘cleaned
coal’. Nonetheless, combustion of coal is also known to release toxic trace elements, which are known or suspected to
be carcinogenic and may also cause respiratory problems, pregnancy complications, premature mortality and possibly
a wide range of health problems. The two traditionally used coal quality parameters have proven to be insufficient for
defining ‘cleaned coal’. This is evidenced by the low ash and low sulphur Balingian coals that is seen as relatively safe
in environmental terms, but still contains high concentrations of potentially hazardous trace elements which may pose
health and environmental threats during coal combustion. Therefore, a comprehensive assessment of coal quality should
also include information on concentration, spatial distribution and modes of occurrence of trace elements, particularly
the 15 potentially hazardous trace elements identified by the United States Clean Air Act Amendments (1990).
The present study evaluates the petroleum source rock generation potential of the Neogene Bhuban shales from Bangladesh.
Organic geochemical and organic petrological methods were used for analyzing 11 drill core samples from 4 gas fields
in the basin. Source rock potential, maceral composition, organic matter abundance, biomarker distribution, thermal
maturity, hydrocarbon generation and depositional environment were evaluated. Kerogen in the studied shale samples
is classified mainly as Type III with lesser amounts of Type II. Vitrinite is the dominant maceral group observed in the
analyzed Bhuban samples followed by liptinite and inertinite. Vitrinite reflectance, Tmax and biomarker parameters
indicate the thermal maturity ranges from just pre-oil window to mid-oil window. Based on its total organic carbon
(TOC), extractable organic matter (EOM) and hydrogen index (HI), the analyzed Bhuban shales are ranked as mainly poor
to fair source rocks but with good gas generation potential. The dominant terrestrial environment prevailed during the
deposition of the studied Bhuban shales while the condition was sub-oxic as indicated by cross-plots of pristane versus
phytane and sterane versus pristane/phytane ratios.