Seismic response characteristics of deep carbonate reservoirs with complex structures in the southwestern Tarim Basin

Abstract Seismic data in the Yubei region has a relatively low signal-to-noise ratio, with multiple interbed multiples developed in the Ordovician strata, significantly affecting the accurate imaging of complex structures and reservoirs, leading to considerable uncertainty in structural interpretation and reservoir prediction. This paper first determines the styles of complex structural belts influenced by interbed multiples through wave equation forward modeling. The parallel-layered reflection at the top of complex structures is due to the alteration of effective strata reflection caused by strong interbed multiples at the top. Second, integrating data from drilling, logging, and geological aspects in the region, seismic wavefield characteristic forward modeling analyses for different types of reservoir are conducted. The results show that factors such as the scale and spatial development position of fractured-vuggy reservoirs have significant impacts on seismic reflection characteristics, strong reflective interfaces may mask the reflection characteristics of the top reservoir, the development of fractured-vuggy reservoirs at different positions can weaken or enhance the reflection of strata interfaces; locally intensive development of fractures in the Ordovician manifests as weak bead anomalies, while large-scale fracture reservoirs exhibit chaotic reflections, and karst caves are characterized by distinct moderately strong bead or tabular amplitude anomalies. By comparing with actual seismic data, the correctness of the complex structural interpretation model is effectively verified, and seismic wavefield characteristics of various types of Ordovician reservoir are summarized, providing a certain basis for understanding the interpretation of complex structures and the reflection characteristics of fractured-vuggy reservoirs in the region.