Accurate Seismic Imaging Methods on Complex Fault Blocks of Subei Basin

Abstract

Subei basin is well-known for its complex fault block reservoirs and has wide growth of shallow igneous rocks. These inherent geological characteristics seriously affect the accurate seismic imaging of target layers. Pre-stack depth migration is an effective imaging method for complex structure and velocity field zones. In order to verify nice imaging ability of Kirchhoff’s pre-stack depth migration (KPSDM) and reverse-time migration (RTM), imaging tests were carried out based on the velocity model for complex fault block of igneous area in Subei basin. Experimental results showed that under the condition of reliable high-frequency velocity field, RTM had obvious advantage in imaging of fault blocks, otherwise, KPSDM was a viable option. In order to verify above experimental results, by selecting seismic data with higher signal to noise ratio (SNR), a reliable high-frequency velocity field was established, and the imaging processing was carried out. The results showed that RTM has obvious advantage over KPSDM in the aspect of improving imaging results of fault blocks and target layers under igneous rocks. Therefore, the choosing of imaging methods for complex fault blocks with igneous zone depends on SNR of seismic data. If seismic data has high SNR, a more accurate high frequency velocity field can be set up. Thus RTM can achieve precise imaging for target layers. If the seismic data has low SNR, KPSDM will become a good choice.
Key words: Subei basin; Complex fault block; Igneous rock; Velocity model; Reverse time migration