Seismic Response Characteristics of Tight Oil Sweet Spots in Fuyu Reservoir Under the Source in the Northern Songliao Basin

The tight oil sweet spots in the Fuyu reservoir in the northern Songliao Basin are dominated by channel sand bodies, which are controlled by physical properties, and are vertically and horizontally discontinuous. The type, distribution, and seismic response characteristics of tight oil sweet spots are unusually complex, restricting the efficient exploration and development of tight oil. The seismic response characteristics of tight oil sweet spots were studied through seismic forward modeling of different combination types of sand bodies, as well as actual drilling, logging, and seismic data. Rock physics research shows that type I sweet spots are characterized by medium to high P-wave impedance and low Vp/Vs, while type II sweet spots are characterized by high P-wave impedance and high Vp/Vs; Through seismic forward modeling and analysis of seismic response characteristics of typical wells, the seismic reflection patterns of various sweet spots are summarized and formed. The results show that single-layer sweet spots with a thickness of more than 3 m are medium to strong amplitude seismic reflections, with obvious seismic response and easy identification; Interbedded sweet spots with a main layer thickness of more than 3 m have single waveform and composite waveform seismic characteristics, and the seismic response of the main layer is weak, making identification difficult; The thin interlayer type with a thickness of 1–3 m and the sweet spots under strong reflection shielding on the top surface of Fuyu have complex seismic response, unclear reflection characteristics, and great difficulty in identification. Based on the research results of tight oil sweet spots seismic response, a matching technology for tight oil sweet spots seismic prediction with the core of “seismic sedimentology interpretation, high-resolution thin reservoir inversion prediction, horizontal well performance tracking and adjustment while drilling, and integrated modeling of in-situ stress and rock mechanics parameters” has been established. The average sandstone drilling rate reaches 82%, and the oil layer drilling rate reaches 70%, playing a key role in increasing the tight oil storage and production of Fuyu reservoir under the source.