Reservoir prediction of channel sublacustrine fan in faulted lacustrine basin: take the middle sub-member of the Third Member of Shahejie Formation in Laizhouwan Sag as an example

Large channel sublacustrine fan lithologic traps are in the Third Member of Shahejie Formation in Laizhouwan Sag, Bohai Bay Basin, with good reservoir forming background and great exploration potential. However, the sedimentary characteristics of sublacustrine fan are not clear, and the reservoir distribution is difficult to be delineated, which restrict the exploration process. Therefore, under the guidance of seismic sedimentology and sedimentology theory, a method of optimizing attributes based on seismic facies analysis of different gravity flow channel types was proposed, and the distribution of sublustrine fan was described in detail with plane section, and favorable reservoir development area was finally established. This study will provide favorable support for the exploration and deployment of sublacustrine fan lithologic reservoirs in the study area. It is recognized that the sublacustrine fan channel has the chaotic characteristics of medium and weak amplitude, which is obviously different from the parallel and continuous strong amplitude reflection of lacustrine mudstone. Based on this, the coherence attribute of frequency-divided dip coherency, seismic structure attribute based on gray level co-occurrence matrix and waveform classification technique of neural network were selected to characterize the boundary of sublustrine fan and the inner channel. The sandstone thickness of restricted channel complex and superimposed channel complex is large, and the two channel development areas are favorable reservoir areas in the study area. The restricted channel complex is distributed under the slope break zone of F1 fault, and the channel thickness and width are large. Superimposed channel complexes are distributed under the slope break zone of F2 fault.