Organic geochemistry of Carboniferous and Lower Permian source rocks, Turpan-Hami Basin, NW China

Abstract

Organic geochemistry characteristics of carbonate rock and mudstone samples are reported for cores in exploration wells and outcrops in the Carboniferous and Lower Permian, Turpan-Hami Basin. Extensive analyses include organic matter abundance, kerogen type, hydrocarbon generation and thermal evolution. The mudstone is higher in organic content, ranging from 0 – 4.45% TOC, suggesting relatively good source rock potential; whereas, the carbonate rock has a maximum TOC of 0.52% and is basically non-source rock. The matrix types of both carbonate rock and mudstone are grouped into Type III (dominant) and II2 (less). The carbonate rock is a bit better quality than the mudstone in organic types. The source rock from downhole samples can be early mature to highly mature. The maturity of outcrop samples range from mature to over-mature. The lower maturity of well samples is related to the shallower depth of the samples. The higher maturity of outcrop samples may be related to the tectonic movement and high geothermal gradient. Based on characteristics of thermal evolution, more effective Carboniferous-Lower Permian source rocks are distributed in the deeper location of the sag and can generate more natural gas. The igneous/volcanic rocks are better deep reservoirs in which natural gas accumulates. Key words: Organic geochemistry, Carboniferous, Lower Permian, source rock, Turpan-Hami Basin