Abstract: Sifangtuozi area is the key project for Jilin Oilfield to submit reserves and raise efficiency recently, but there is no breakthrough of Yaojia Formation due to the poor knowledge of scientific theories. Based on the data from 147 exploration wells and 300 development wells, focused on core observation from 25 coring wells, combined with petrological characteristics, sedimentary structures, seismic sections and modern sedimentary cases, the formations, sedimentary features and exploration prospects of the shallow water delta of Upper Cretaceous Yaojia Formation in Sifangtuozi area were analyzed. The result shows that Yaojia Formation can be divided into two third-order sequences (SQY₁ and SQY₂₊₃)and six fourth-order sequences (RST). In the sedimentary period of Yaojia Formation, the paleo-topography grade is less than 3°, the paleo-depth is less than 20 m, and the dry and hot paleoclimate and opening of eastern Songliao Basin, jointly contributed to the development of shallow delta and shallow to semi-deep lacustrine sedimentary system. Specifically, the natural traits of the shallow water delta comprising features of traction current and short distanced depositional process with near-provenance, with the development of enforced hydrodynamics structures, are presenting as blanket shaped morphological characteristics and imbricated aggradations seismic facies. Integrated the delta of the Ganjiang River and the Mississippi River with the studied case, it is concluded that the large scaled bed-like sand bodies developed in depositional center, are with the characteristics of horizontal long distance propulsion and vertical extensive overlap in multistage. The above knowledge will be helpful to the exploration of subtle reservoirs in southern Songliao Basin scientifically.

Key words: residual moveout, dynamic time warping, shape context, prestack gather