Timing of petroleum accumulation and the division of reservoir-forming assemblages, Junggar Basin, NW China

Timing of petroleum accumulations and distribution of vertical basin-scale sealing beds are important in the study of superimposed basins. This information can be used to divide petroleum accumulations of different times into different petroleum-forming assemblages vertically so as to reconstruct the petroleum accumulation process and distribution more accurately. The Mahu-West Well Pen 1 combination petroleum system in the Junggar Basin is taken as the case study. By isotopic K-Ar dating of authigenic illite, optical feature of organic inclusions, and fluid inclusion homogenization temperature, combined with burial and thermal history analysis, timing of petroleum accumulations is defined, i.e., P2–3, T3, J2—K1 and N. According to the vertical sealing mudstones of T3b, J1s1, and K1tg, four petroleum-forming assemblages were divided including C—T3, T3—J1, J2—K1, and K-N.