Seismic Sequence and Source Analysis of Typical Sandstone Reservoirs

In order to understand the problem of sediment sources in the Xujiahe Formation of the Central Sichuan Uplift, high-density two-dimensional seismic data was used, and LCS2 (the second section of the Xujiahe Formation) was taken as the research object. Combined with logging interpretation results, typical seismic facies were identified within the sequence, including clinoform seismic facies, progradational reflection seismic facies, and incised valley seismic facies. The progradational reflection seismic facies can be divided into two types: S-shaped and oblique progradational reflection facies. The oblique progradational reflection seismic facies representing the rapid filling environment of sediments are mainly distributed in the southeast of the study area, while the northwest mainly develops relatively low-energy sedimentary mechanisms of S-shaped seismic facies. The incised valley seismic facies are mainly distributed in the eastern and southeastern parts of the work area. On the plane, the incised valley seismic facies have a trend of gradually widening and shallowing towards the northwest direction. In addition, the distribution of sedimentary facies was analyzed using seismic attributes. The southeastern and central parts of the study area are mainly composed of proximal sand-rich braided river alluvial plains, while the northwestern part is mainly composed of distal mud-rich braided river alluvial plains. The distribution of sedimentary facies generally shows a southwest to northeast distribution. From southeast to northwest, the sedimentary facies show a clear trend of changing from sand-rich to mud-rich. Based on the comprehensive distribution characteristics of seismic and sedimentary facies, it is believed that the river in the Central Sichuan Uplift basically enter the region from the south or southeast, and transport sediments from southeast to northwest. Based on the above evidence, it is inferred that the sedimentary material of the Xujiahe Formation in the Central Sichuan Uplift mainly comes from the «Qianzhong Ancient Uplift» or «Fanjing Mountain Ancient Land» on the southern and southeastern of the Sichuan Basin.