车排子凸起轻质油成熟度分析与烃源层再认识

Maturity assessment of light oils in Chepaizi Uplift and re-understanding of its source rock

通过对车排子凸起南部轻质油的甲基双金刚烷和甲基菲参数分析，发现其成熟度已达等效镜质组反射率约1.3％～1.6％的高过成熟阶段。结合周边凹陷烃源岩演化特征分析，认为该区轻质油来源于侏罗系烃源岩的可能性较小，来自二叠系高过成熟烃源岩的可能性较大。该区轻质油地球化学特征与二叠系烃源岩差异较大，而与白垩系和古近系烃源岩地球化学特征相似，推断该高过成熟油气中不含生物标志化合物或生物标志化合物含量极低，其现有特征是在运移过程中受成熟度较低而生物标志化合物含量丰富的烃源岩可溶有机质浸染所致。这一认识不但对揭示研究区的油气成藏规律具有重要的理论和实践意义，也将为准噶尔南部深凹区及山前坳陷区轻质原油及天然气来源的重新认识提供合理的参考依据。

Based on methyldiamantane and methylphenanthrene maturity parameters, the light oils in the southern Chepaizi uplift were found to be at a highly to over mature stage （equivalent vitrinite reflectance of about 1.3%-1.6%）. Combined with the evolution characteristics of potential sources rocks in the peripheral depressions, we suggested that these oils probably were generated from the Permian source rocks with high to over maturity, rather than the Jurassic source rocks. Geochemical characteristics of the light oils in this region were significantly different from that of Permian source rock, but similar to that of Cretaceous and Paleogene source rocks, inferring that aboundant biomarkers in these highly mature light oils probably sourced from the pollution of soluble organic matter in low mature source rocks during the migration process. This conclusion is not only significant for investigating the oil and gas accumulation in the Chepaizi Uplift, but also can provide a reasonable evidence for re-understanding the origin of light oils and natural gases from the deep sags and the foreland depression belts in the southern Junggar.