Fracture prediction for continental shale oil reservoirs based on prestack orthotropic seismic inversion

The Jiyang Depression, a continental fault basin rich in shale oil resources, hosts a well-developed fault system due to multi-phase tectonic movements. Natural fractures provide essential reservoir space and seepage pathways for shale oil and also play a critical role in hydraulic fracturing optimization, which makes accurate fracture prediction vital for efficient shale oil exploration and development in this region. The coupled fracture-shale anisotropy significantly constrains prediction accuracy. To address this issue, this study proposes a multi-parameter inversion method based on the orthorhombic P-wave reflection coefficient equation, which decouples intrinsic shale anisotropy from fracture-related azimuthal anisotropy. Specifically, three VTI parameters are inverted using seismic data acquired along the fracture orientation, and fracture-sensitive parameters are subsequently derived from wide-azimuth seismic data. The methodology is applied to fracture prediction for shale oil reservoirs in the M sag of the Jiyang Depression. Comprehensive comparison and verification with post-stack ant-tracking attributes, image logging interpretations, field fracturing parameters, and microseismic-estimated effective stimulated reservoir volume (ESRV) show that the proposed method can effectively characterize the development of shale fractures and exhibits strong practicability and reliability.