Overpressure water zone influence on hydrocarbon migration and oil reservoir distribution in low Cretaceous formations of Yinger sag,China

The low Cretaceous Zhonggou, Xiagou, and Chijinpu formations are major source rocks in Yinger sag, Jiudong Basin, China. Oil reservoirs were discovered in Zhonggou and Chijinpu formation, which were on the top and bottom of overpressure water zone, but no hydrocarbon was discovered within overpressure zone. The impact of overpressure zone on oil accumulation was indicated by reservoir fluorescence and oil-source correlation study through geochemical analysis. The result shows the overpressure zone reservoirs have less fluorescence display and reservoir extracts dissimilar to source rocks of Chijinpu or Zhonggou formation, implying the inexistence of oil migration in overpressure zone.