Abstract:

Formation thickness of Putaohua oil layer in Sanzhao depression, Songliao basin, reduces gradually from north to south, and the thinning mode is always controversial, result in understanding confusion of hydrocarbon vertical distribution. Log curves of 1 024 wells and core data of 10 wells analyzing formation structure of Putaohua oil layer and sedimentary features of reservoirs show formation of Putaohua oil layer is a process of gradually thinning by layers controlled by uplift of syndepositional structure at the end of deltas, and surfaces of sand-clay discontinuity at the top and bottom of Putaohua oil layer is a sand-clay interface formed by gradually changing from northern sand to southern clay rather than a genuine interfaces; shallow deltas typically developed in Putaohua oil layer, concentrated and continuous straightly-underwater channels and river-dominating extremity sheet sands are the main microfacies; Putaohua oil layer vertically develops sedimentary evolution of sequence with first fast dereliction then slowly transgression, the well developed distributary channel sand body is hydrocarbon preferential transporting channel of lateral migration and enriched layer in central Putaohua oil layer (lowstand).

Key words: Songliao basin, Sanzhao depression, Putaohua oil layer, sequence, sedimentary characteristics, petroleum gas