Abstract:

The south slope of Dongying sag is a favorable petroleum exploration target. The research results indicate that Es₄ oils show typical characteristics of mixed oils. The source inputs contain dual contributions of aquatic lives and high plants, thermal maturities are varied from low mature to mature, sedimentary environments are mainly reduction with different intensities, and part samples show characteristics of mixed oil charging before and after biodegraded. According to the geochemical correlation, for the east part of south slope with Niuzhuang sag as source kitchen, Le’an and Wangjiagang oil fields are Es₄sourced oils mixed with few Es₃-sourced. For the middle part with Niuzhuang and Lijin sag as source kitchens, Liangjialou oilfield is Es₃-sourced oils mixed with few Es₄-sourced, while Chunhua oilfield is reversed. For the west part with Boxing sag as source kitchen, Zhenglizhuang and Gaoqing oilfields are Es₄-sourced oils mixed with few Es₃-sourced, while Jinjia oilfield is Es₃-sourced. Mature oils generated from Es₄-Es₃ in the subsag center are mixed by the low mature oils generated from Es₄ in the slope, migrated along faults and unconformities, and accumulated on the high parts of the south slope.

Key words: mixed oil, oil/source correlation, contribution ratio, geochemistry, biomarker, south slope of Dongying sag