Study and application of wide-azimuth seismic anisotropy analysis and correction in shale reservoir in Gulong Sag, Songliao Basin, China

Abstract

The Gulong Sag in the northern Songliao Basin, China, possesses abundant shale oil resources and represents a highly prospective area for shale oil exploration. However, the Qingshankou formation shale oil reservoir within this region exhibits characteristics such as thin longitudinal thickness, pronounced horizontal heterogeneity, limited frequency range, and significant anisotropy that pose difficulties in accurately predicting the “sweet spot” of shale oil within the target interval. The azimuthal anisotropy characteristics of the target layer in the Qingshankou formation are analyzed in this manuscript, utilizing wide-azimuth and small bin seismic data from the Y3 research area. Considering the limitations of existing methods for fitting elliptical velocities in azimuthal anisotropy correction, the influence of azimuthal anisotropy time difference on the non-in-phase superposition of seismic in-phase axis is eliminated by employing a non-rigid dynamic matching method, thereby enhancing the resolution and imaging accuracy of seismic data. The azimuth anisotropy correction effectively broadens the frequency range of the stack profile by 7 Hz, thereby enhancing the reliability of data for shale oil reservoir prediction in the study area.