Carboniferous-Permian stratigraphic thickness in northern Songliao Basin: Evidence from deep reflection seismic data

Based on the characteristics of the seismic phase on the section including the horizon reflection characteristics and the inphase axis characteristics and combined with the geological evolution process analysis, the authors established the seismic identification characteristics of the Carboniferous-Permian strata in the northern Songliao Basin. The Carboniferous-Permian strata were identified on six deep reflection seismic profiles of Song Ⅰ-Song Ⅵ based on seismic phase characteristics. The main phase characteristics are medium-strong reflection energy, existence of local high values and the continuous overall in-phase axis changing from south to north and from west to east. The time-depth conversion relationship of the study area was obtained by collecting the exploration data of the existing Carboniferous-Permian strata and the seismic wave propagation velocity. Based on the reflection time distribution of the Carboniferous-Permian phase tracing correlation in the study area, the authors calculated the travel time difference between the top and bottom interfaces of the Carboniferous-Permian strata on the deep reflection seismic time profile, and gave the thickness and distribution of the Carboniferous-Permian strata in the study area by time-depth conversion. The distribution of the whole area is not extremely uniform. There are mainly two areas with high thickness, namely, the eastern part of the central uplift zone and the western part of the fault depression zone. The whole strata can be divided into upper, middle and lower layers from shallow part to deep part, and the seismic phase characteristics are different from each other. The distribution of Carboniferous-Permian strata in the northern Songliao Basin provides a valuable basis for deep oil and gas exploration under the main oil layers in Northeast China.