Research paperCharging of oil fields surrounding the northern end of Liaoxi uplift from multiple source rock intervals and generative kitchens, Bohai Bay basin, China

- The correspondence between C29 20S/(20S + 20R) sterane ratio and Ro in the Liaodong Bay sub-basin was calibrated.
- Maturity parameters of oils were used for tracing oil migration directions.
- The function of delta sandstone for oil migration and accumulation.

The Liaoxi uplift, one of the most petroliferous uplifts in the Bohai Bay basin, is sandwiched by two sags containing multiple mature source rocks. The origins of oil located on the northern end of this uplift, both in terms of source rock intervals and in terms of generative kitchens, were studied using biomarker distributions from 75 source rock extracts and 15 oils. Two oil families have been identified using 4 biomarker parameters and could be linked to the source rocks of the first and second members of the Shehejie formation (E2s1+2) and the third member of the Dongying formation (E3d3) respectively. E2s1+2- derived oils were found in the Liaoxi sag and on the Liaoxi uplift and were interpreted to originate primarily from the Liaoxi sag. E3d3-derived oils were found in the Liaozhong sag and originated from the Liaozhong sag. The Liaoxi uplift have not been charged by E2s3-drived oils from the Liaoxi sag mainly because it departed from the dominant migration direction of E2s3-drived oils. The Liaoxi uplift have not been charged by E2s3, E2s1+2 and E3d3-drived oils from the Liaozhong sag mainly because there were no delta sandstones developed on the slope between the Liaoxi uplift and the Liaozhong sag to serve as migration channels from source rocks to uplift in all three formations. The sandstone up-dip pinch out traps in E2s3 formation in the Liaoxi sag, traps within the Liaozhong sag and traps on the slope between the Liaozhong sag and the Liaodong uplift have a better chance to accumulating petroleum.