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As a gas-rich region in the Tarim Basin, the northern Shuntuoguole area (also known as the Shunbei area) is an attractive prospect. Non-etheless, the debate about the origins of these natural gas continues. The analysis on the geological context, natural gas components, and the carbon and hydrogen isotope ratios prove that methane is the predominate component of alkane gases. Alkane gases’ carbon isotope fractionation (δ13C2 < −28‰ and δ13C3 < −25‰) shows that they are oil-associated gas, and their parent material type is I kerogen. Natural gas can be broken down further into three subgroups—Type I1, Type I2, and Type I3. Based on the link between the carbon number 1/n and δ13Cn of the gas. Modified plots of lnC1/C2 vs. lnC2/C3 reveal that kerogen cracking is the primary source of natural gas in the Shunbei area, and that this gas is combined with the contribution of oil cracking gas. Petroleum exploration and development in the Shunbei area can be justified on the basis that natural gas in the area originate primarily from Ordovician source rocks, as shown by carbon isotopic compositions.

In order to have a deeper insight into the accumulation mechanism of ultra-deep hydrocarbons, in this paper, the recently discovered ultra-deep Ordovician light oil and gas deposits (>7200 m) in the Shunbei No. 1 fracture zone are studied intensively, including maturity, source kitchens, the extent of secondary alterations, and possible migration directions, based on an analysis of the molecular compositions and stable carbon isotopes of crude oils and natural gases. The average equivalent vitrinite reflectance (Rc) of these oils, estimated from light hydrocarbons (H versus I), MDI, DNR, and MDR, are about 1.50%, 1.58%, 1.48%, and 1.51%, respectively, which suggests that most of the oils are in the late stages of crossing the oil window. The two maturity grades (1.06–1.25% and 1.36–1.67%) of the oil samples calculated from the aromatic compounds indicate the presence of at least two stages of hydrocarbon charge. In addition, the positive correlation plot of DNR and MDR (y = 3.59x − 12.84; R2 = 0.96) indicates that oils in the southwestern region of the F1 (S1-11–S1-16) are slightly more mature than oils in the northeastern region of the F1 and the well at SL1, far from the No. 1 main fault zone. In addition, the study shows that these hydrocarbons belong to the same source kitchen of a reduced marine sedimentary environment with mixed organic matter comprising benthic and planktonic algae, based on biomarker parameters, light hydrocarbons, and carbon isotope compositions. The oil–oil correlation analyses suggest that the studied oil samples are probably derived from the in situ Lower Cambrian Yuertusi formation source rocks. Various geochemical parameters consistently show limited significant hydrocarbon alteration processes, indicating favorable preservation conditions in the study area. The integrated geochemical characteristics of the hydrocarbons allow us to infer that they mainly migrate vertically from the in situ Lower Cambrian Yuertusi formation source rocks toward the Ordovician reservoirs, followed by a certain degree of lateral migration from southwest to northeast.