High-resolution sequence stratigraphic analysis of the Upper Ganchaigou Formation in the Youshashan Oil Field, Qaidam Basin, Qinghai

In the light of the high-resolution sequence stratigraphic theory presented by Cross, and well logs and core observation in this study, the strata of the Upper Ganchaigou Formation in the Youshashan Oil Field, Qaidam Basin, Qinghai may be divided into 15 to 20 short-term, 6 medium-term and 1 long-term base-level cyclic sequences. The present paper focuses on the analysis of sedimentary facies and evolution within the individual cycles, construction of the high-resolution isochronous stratigraphic framework in the ascending and descending hemicycles of the medium-term cycles and sandstone distribution in the Upper Ganchaigou Formation. It is indicated that the early ascending hemicycles,late descending hemicycles and the delta system are interpreted to be the most favourable zones for the development of reservoir sandstones.