The distribution and significance of dimethyldibenzothiophenes, trimethyldibenzothiophenes and benzo[b]naphthothiophenes in source rock extracts from offshore Niger Delta basin, Nigeria

The distribution of dimethyldibenzothiophenes, trimethyldibenzothiophenes and benzo[b]naphthothiophenes were investigated in rock extracts from Niger Delta, Nigeria, by gas chromatography-mass spectrometry. The dimethyldibenzothiophenes were characterized by the predominance of 4,6-dimethyldibenzothiophene and 3,6-dimethyldibenzothiophene while 2,4,6-trimethyldibenzothiophene was the dominant compound among the trimethyldibenzothiophenes. Among the benzo[b]naphthothiophenes, the abundance of benzo[b]naphtho[2,1-d]thiophene was higher than other isomers. The rock samples were found to have immature to early mature status. The dimethyl- and trimethyldibenzothiophene ratios showed good correlation with 4-/1-methyldibenzothiophen ratio, T-max (degrees C) and % Ro, indicating their dependency on maturity increase. The distribution and abundance of dimethyldibenzothiophenes and trimethyldibenzothiophenes were found to be effective in determining the thermal maturity of source rock extracts in Niger Delta basin.