Abstract:

Shengtuo Oilfield of Dongying Depression is ternary mixed oil derived from the multiple source rocks and multistage accumulation. The early-accumulated oil was from the upper Es₄, and it suffered biodegradation in the tectonic movement. The late-accumulated oil was from the lower Es₃ and the upper Es₄. Absolute quantitative analyses of biomarkers in the selected three typical end-members show that the average contribution of source rock in the upper Es₄ is 39% in the early accumulation, and the contribution rates of source rocks in the upper Es₄ and the lower Es₃ during the late accumulation are respectively 30% and 31% in the Es₂ reservoirs in Tuo 2 Block. In the Es₂ reservoirs of Tuo 3 Block, the contribution rate of the mixed oils in the upper Es₄ source rock is 41% in the early accumulation, and the contribution rates of source rocks in the upper Es₄ and the lower Es₃ in the late accumulation are about 33% and 26%, respectively. The contribution of the lower Es₃ source rock is reduced from Tuo 2 Block to Tuo 3 Block. The contribution rate of source rock in the upper Es₄ to the Es1 reservoir of Tuo 2 Block is 8% in the early accumulation and 24% in the late accumulation, the contribution rate of the lower Es₃ source rock is 68%. The mixing ratio of oils in this block differs from that in the main oil-bearing layers.

Key words: Shengtuo Oilfield, mixed oils, biomarker, oil-source correlation, hydrocarbon accumulation period, end-member oils, quantitative determination

摘要：

精细的原油组群划分、油源对比及成藏分析表明,东营凹陷胜坨油田主要含油层系沙二段的原油是由沙四上亚段烃源岩提供的早期降解原油与沙三下亚段、沙四上亚段两套烃源岩提供的晚期成藏原油形成的三元混合原油。选择两期成藏三个端元典型的原油样品,建立三角形判识图版,运用生物标志物绝对定量分析方法对胜坨油田的混源油进行了油源比例确定。结果表明:坨二区沙二段原油中,沙四上亚段源岩早期贡献为39%,晚期贡献为30%,沙三下亚段源岩的贡献为31%;坨三区沙二段原油中,沙四上亚段源岩早期贡献为41%,晚期贡献为33%,沙三下亚段源岩贡献为26%,即从坨二区到坨三区沙三下亚段烃源岩的贡献有减小的趋势。另外,坨二区沙一段原油中,沙四上亚段源岩早期贡献为8%,晚期贡献为24%,沙三下亚段源岩贡献为68%,混源比例不同于本区主要含油层系原油。

关键词: 胜坨油田, 混源油, 生物标志物, 油源对比, 成藏期次, 端元油, 定量计算