Prediction technology and application for high-quality mid-deep reservoirs in the Pinghu Slope Zone, Xihu Sag

The Pinghu Slope in the Xihu Sag has developed tide-affected deltaic reservoirs in the Pinghu Formation. Sand bodies that formed in distributary deltaic channels, tidal sand bars, and tidal channels have fast changes in sedimentary facies and are difficult to identify. Meanwhile, due to large burial depth of target layer, the seismic response of reservoir shows mostly a “dark spot” seismic reflection with small impedance differences, which further increased the difficulty of identifying high-quality reservoirs. Therefore, we used technologies such as ancient landform restoration, AI artificial intelligence fault identification, high impedance sandstone wedge AVO forward simulation, and extended elastic impedance to clarify the gully slope system and determine high-quality reservoirs for hydrocarbon detection in this area. Results indicate that U-shaped, V-shaped, and W-shaped valleys are developed in this area. The W-shaped valley is the main channel for sediment diversion. Four identical fault-step–typed slope breaks were identified, and the segmented points controlled the input of sand bodies in the area. The gradient negative 90° phase rotation seismic body could effectively identify the “dark spot” reservoirs in this area. We found that the optimal coordinate rotation angle for extended elastic impedance in this area is 20°, by which the detection of major sand body hydrocarbons could be completed and favorable areas for oil and gas exploration be located.