塔里木盆地北部哈拉哈塘凹陷海相油气特征与成因

哈拉哈塘凹陷作为塔北隆起西部的重要油气单元,其奥陶系碳酸盐岩储层中油气资源丰富,但呈现多相态分布,油气性质变化成因尚不明确。通过详细的地球化学分析揭示了该区油气特征与成因。油-油、油-岩对比表明,原油与中-上奥陶统烃源岩特征更为相近,指示具有成因联系;正构烷烃单体烃碳同位素对比显示,可能有寒武系烃源岩的成烃贡献。哈拉哈塘原油具有相对较高的硫芴含量,C₂₉和C₃₅藿烷相对含量也较高,暗示有碳酸盐岩烃源岩的成烃贡献。傅里叶变换离子回旋共振质谱(FT-ICR MS)分析表明,哈拉哈塘地区原油中低热稳定性硫化物含量不高,表明当前没有明显的TSR改造迹象。综合分析认为,源岩成熟度是控制深部高气油比原油形成的重要因素,而生物降解等次生作用是控制相对浅层重质油和H₂S形成的重要因素。

Characteristics and genesis of marine hydrocarbons in the Halahatang Sag in the northern Tarim Basin

The Halahatang Sag is an important oil and gas unit in the western part of the Northern Tarim Uplift. The Ordovician carbonate reservoir contains abundant petroleum resources with multiple phases, but the variable characteristics and genetic mechanism of the oil and gas are still unclear. Oil-oil and oil-rock correlations indicate that the crude oil has a close genetic relationship with the middle and upper Ordovician source rocks. The comparison of carbon isotopes for individual n-alkanes shows that the Cambrian source rocks might also contribute. Halahatang oils are rich in dibenzothiophenes, and also contain relatively abundant C₂₉-and C₃₀-hopane, which implies a contribution from carbonate source rocks. Based on the Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis, sulfides with low thermal stability have low concentrations, suggesting that TSR alteration is not significant. Source rock maturity is the major factor controlling the genesis of oils with high gas/oil ratios, while biodegradation is the major factor for heavy oil and H₂S formation in the relatively shallow reservoir.