Abstract: In view of disputable adscription of geological era and petroliferous formation classification of Shinan-31 Wellblock in Junggar basin, the systematic analyses of existing data from paleontology, core sample and geophysical prospecting are conducted. The geologic era of the petroliferous strata is dated as Qingshuihe stage of Early Cretaceous, which is higher than the basal conglomerate of Cretaceous in horizon, through the correlation of sand layers and the identification and tracing of the seismic sequence boundary by means of sequence stratigraphy and sedimentary system theory. The reservoir type of Shinan-31 Wellblock belongs to the lithologic reservoir with upward pinchout sands.

Key words: Junggar Basin, Geological era, adscription, formation classification