Seismic Sedimentology Research on Shallow Water Delta Front Sandbodies: A case study on Member 3 of upper Cretaceous Qingshankou Formation in Qian'an area, south Songliao Basin, NE China

Key words: 
• subaqueous distributary channel /
• seismic sedimentology /
• qingshankou Formation /
• Qian'an area /
• Songliao Basin

Abstract: The shallow water delta-front sand bodies are one of the major exploration and development targets in the Songliao Basin, and the prediction of these sand bodies is difficult due to its characteristics of thin intersection of sandstone and mudstone. Integrated with the full-covered 3D seismic data, drilling and logging data, the framework of high-resolution sequence stratigraphy of the Member 3 of Qingshankou Formation in the study area is established, and then with the integrated research method of seismic sedimentology, "phase adjustment-seismic facies-strata slice", the type and character of the sand bodies and their evolution discipline in the frame of high resolution sequence stratigraphy is discussed. The results shows that the K₂qn³ can be divided into two 3rd-order sequences and twelve 4th-order sequences. The correlationship between seismic events and lithofacies has been established after the phase adjustment of seismic data, the red wave crest refers to partial sandstone lithofacies, and the black wave trough refers to partial mudstone lithofacies. From the typical strata slice extracted under the restriction of 4th-order sequence, three main types of sand bodies have been recognized, including the branch type of subaqueous distributary channel, meandering type of subaqueous distributary channel and terminal type of subaqueous distributary channel, of which each type has own characters of unique seismic facies. In the early stage of SQ1, there were mainly terminal type of subaqueous distributary channel sand bodies in the study area. In the late stage of SQ1, there were mainly branch type and meandering type of subaqueous distributary channel sand bodies. However, in the early stage of lake transgressive system tract of the SQ2, sand bodies in the study area were mainly branch type whereas mainly terminal type in the late stage. In the lake regressive system tract of the SQ2, there were mainly branch type and meandering type of subaqueous distributary channel sand bodies in the study area.