Abstract:

The oil in Shengbei structure belt of rich hydrocarbon Taibei sag in Tuha basin is sourced from Shuixigou Group and Qiketai Formation lacustrine facies rock resources, and the gas is coal-related gas. Above the hydrocarbon bearing interval of Qiketai Formation, the oil is mainly lacustrine facies oil and the gas is mainly coal-related gas. Below the hydrocarbon bearing interval of Qiketai Formation, the oil is mainly coal-related oil and the main accumulation stage is on Late Tertiary. Allocation relationship on reservoir-forming elements of Shengbei structural belt has controlled the distribution of different oil & gas types in this zone. By means of faults, the lacustrine facies oil of Qiketai Formation in Late Tertiary can preferentially accumulate in the well-physical property of Cretaceous reservoir. From Late Tertiary to Quaternary, the coal-related gas, in the progress of upward migration, can enter the sand with blocked up by heavy crude and short of physical property of reservoir in Kalazha Group and finally generates gas condensate reservoir. Because of the good sealing characteristics of the argillyte in the Middle-Upper Kalazha Group, some of gas migrate continually upward the oil reservoir of Lianmuqin Formation in Cretaceous. Above all, it has nowadays formed the distribution character of oil above and gas below in shallow layer of this area.

Key words: oil source, main accumulation stage, reservoir-forming factors, Tuha basin, petroleum gas