The
hydrocarbon generation potential of the Carboniferous Batamayineishan
mudrocks has been overlooked for a long time. In this study, organic
petrology and geochemistry were used to determine the sedimentary
environments, organic matter (OM) type, and organic maturity of the
Carboniferous Batamayineishan source rocks, collected from outcrops,
Wulungu area, Junggar Basin, China. The maceral composition of the
studied samples is dominated by vitrinite and inertinite, ranging
from 40 vol % to 100 vol % and from 0 vol % to 60 vol % on a mineral
matter free basis, respectively. Liptinite macerals, mainly as lamalginites,
are only present in trace amounts in several sediments. Vitrinite
reflectance values are 0.67% to 2.78%. TOC values are high in these
samples, whereas the S1, S2, and HI are very
low. Pr/Ph ratios, the plot of Pr/n-C17 versus Ph/n-C18, DBT/P versus Pr/Ph, and ternary of fluorene, dibenzothiophene,
and dibenzofuran indicate that anoxic saline environments prevailed
during deposition of the Batamayineishan Formation. This is consistent
with the presence of β-carotane and high abundances of gammacerane
in the studied samples. The major biological source is from vascular
plants, and the kerogen type is humic (type III) as indicated by the
maceral composition and rock pyrolysis data. The samples from the
No. 4 and No. 6 sections occur in the oil window, whereas the other
samples are overmature in terms of hydrocarbon generation. The abundant
organic richness, humic kerogen, and high thermal maturity demonstrate
that these rocks are effective gas source rocks. The volcanics and
mudrocks in the Carboniferous Batamayineishan Formation collectively
constitute a self-generation and self-storage petroleum system, and
represent a main exploration target for gas discovery for the Carboniferous
in the Wulungu area.