## 6 Conclusions  
1. The predominance of low molecular weight n-alkanes, the absence of odd-even dominance, and the predominance of C\({}_{20}\) TTs, rather than C\({}_{23}\) TTs, along with the dominance of C\({}_{21}\) pregnancies all show that the studied oils in the F1 zone are at a high maturity stage. The average equivalent vitrinite reflectance (Rc) of these oils, as estimated from light hydrocarbons (H versus I), MDI, DNR, and MDR, is in the vicinity of 1.50%, which indicates that most of the oils are in the late stage of crossing the oil window. In addition, the crude oils in the southwestern region of the F1 area (S1-11-S1-16) are slightly more mature than those in the northeastern region of the F1 and the well, SL1, far from the No. 1 main fault zone. The two maturity grades (1.06-1.25% and 1.36-1.67%) of the oil samples suggest the presence of at least two stages of hydrocarbon charge, with the late-stage charge predominating. Moreover, the natural gas in this study is dominated by kerogen cracking gas, with trace amounts of wet gas from the early stages of oil cracking, based on the gas compositions and component carbon isotopes.
2. This paper mainly investigates the secondary alteration effects of hydrocarbons in terms of biodegradation, thermochemical sulfate reduction, thermal cracking, and evaporative fractionation. The indicators of various geochemical parameters show the significant alteration processes of hydrocarbons to be limited, suggesting favorable preservation conditions in the study region.
3. On the basis of biomarker parameters, light hydrocarbons, and carbon isotope compositions, all findings suggest that these oils belong to the same source kitchen of a reduced marine sedimentary environment with mixed organic matter formed of benthic and planktonic algae. The oil-oil correlation analyses suggest that the oil samples are probably derived from the in situ Lower Cambrian Yuertusi formation source rocks. Additionally, according to the distribution of crude oil maturity and natural gas drying coefficient in the study area, it can be inferred that the hydrocarbons in this study area mainly migrate vertically from the in situ Lower Cambrian Yuertusi formation source rocks to the Ordovician reservoirs, followed by a certain degree of lateral migration from southwest to northeast along the Shunbei No. 1 fault zone.  
Figure 13: The cross-plot of Rc2 (Rc2(%) = 0.49 + 0.09 * DNR) of the studied oils and the depth of the Ordovician reservoir.  
**Author Contributions:** Conceptualization, J.B. and D.H.; data curation, J.B. and D.H.; formal analysis, J.B., D.H. and Z.J.; funding acquisition, D.H.; investigation, J.B., D.H., X.C. and Z.J.; methodology, J.B.; project administration, D.H.; resources, J.B. and D.H.; software, [PERSON] and D.H.; supervision, [PERSON], [PERSON], [PERSON] and Z.J.; visualization, [PERSON] and D.H.; writing--original draft, [PERSON] and D.H.; writing--review and editing, [PERSON] and D.H. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This study was financially supported by the Research Academy Key Special Project of Northwest Oilfield Company (Grant No. KY2021-S-046) and Shanxi Natural Science Foundation (Grant No. 201901D111050).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The datasets presented in this study can be obtained upon request to the corresponding author.  
**Acknowledgments:** The authors gratefully acknowledge the Northwest Oilfield Company for sample and data collection.  
**Conflicts of Interest:** The authors declare no conflict of interest.