Classification of Seismic Response Types for Tight Oil Sandbodies in the Fuyu Formation, Northern Songliao Basin Based on Forward Modeling

The tight oil reservoirs in the Fuyu oil layer of the northern Songliao Basin constitute a critical target for reserve enhancement and production increase in the Daqing Oilfield. These reservoirs are predominantly controlled by multi-provenance systems from the northern, western, and southern directions, where fluvial-deltaic sand bodies exhibit vertical multi-stage stacking patterns and lateral discontinuous distribution. The accurate prediction of sweet-spot target layers remains a persistent challenge, constraining horizontal well-based exploration and development of tight oil resources. Commencing with thin-layer theoretical modeling, this study establishes wedge-shaped forward models with variable sand body thicknesses and mudstone interlayer thicknesses. Through systematic analysis of amplitude variations and interface positioning induced by sand body development, we clarify the seismic forward response mechanism. Building upon drilling-validated sand body distributions, integrated with seismic data and typical geological dissection, we propose the first systematic classification framework for seismic response patterns of tight oil sandbodies in the northern Songliao Basin's Fuyu Formation. Results demonstrate that sedimentary facies belts can be categorized into four principal types: single-layer, dual-layer stacked, multi-layer stacked, and strong-reflection shielded configurations, with further subdivision into seven subtypes based on sand body thickness, interlayer thickness, and sand body development location. For target-layer prediction, we developed an integrated technical methodology comprising: Qualitative identification of sand-rich zones through multi-attribute fusion combined with seismic sedimentology interpretation and micro-paleogeomorphological analysis; Quantitative prediction via high-resolution seismic inversion techniques. Key technical innovations include: Systematic classification criteria for vertically superimposed sand body seismic responses; Forward modeling-guided seismic attribute optimization strategy; Thin interbedded reservoir identification technology integrating waveform decomposition and spectral inversion. The established theoretical framework and core technologies effectively address the long-standing challenges in sweet-spot prediction, providing critical technical support for reserve expansion and production capacity construction in the Fuyu tight oil reservoirs. This methodology demonstrates significant potential for application in analogous tight oil exploration domains characterized by complex depositional systems and strong heterogeneity..