ABSTRACT Multiple oil and gas fields have been discovered in the deep strata of the Penyijingxi Sag's surrounding tectonic belts. However, the origin and accumulation process of crude oils remain controversial or unclear. Geochemistry, basin modeling, and geological analysis were comprehensively employed to address these issues. The result shows that crude oils of the study area can be categorized into two types. Type 1 oils, derived from P 1 f source rocks, are primarily distributed in the Dinan Uplift, the southern area of the Mosuowan Uplift, and Mobei Uplift. Type 2 oils, sourced from P2w source rocks, are mainly found in the Qianshao Slope and the northern area of the Mosuowan Uplift, with discovered oils dominated by high‐maturity hydrocarbons from late‐stage charging. The study area had two hydrocarbon charging periods and two migration periods: P 1 f ‐sourced hydrocarbons charged reservoirs in the Middle‐Late Jurassic, then Yanshan tectonism destroyed paleo‐oil reservoirs in the Late Jurassic‐Early Cretaceous; P 2 w source rocks generated hydrocarbons extensively in the Late Cretaceous (mixing with earlier P 1 f secondary reservoirs), and finally Himalayan tectonism drove northward oil‐gas migration at the end of the Paleogene, leading to mixing, re‐accumulation in new traps, and the current distribution pattern.
Jiang et al. (Sun,) studied this question.