A new fracture detection method based on full-azimuth anisotropic migration and shaping regularization

Fracture detection plays an important role in oil and gas exploration. Azimuth-dependent amplitude anisotropy is a key indicator for fracture characterization. In order to not only retain the azimuthal information but also preserve the genuine amplitude relationships in the common image gathers, an accurate anisotropic migration algorithm is required. A further complication arises when the migrated seismic data are inverted to determine the fracture properties, specifically the challenge posed by the stability of the Rüger equations. In this paper, we derive a fourth-order travel time equation for orthorhombic media that performs the anisotropic migration in the local angle domain. By introducing a new shaping regulator to the conventional fracture inverse problem, we improved the accuracy and convergence of the algorithm. The proposed migration and inversion approaches have been validated with a synthetic and a real dataset from the Tarim basin. The results of this validation suggest that the proposed workflow leads to better preservation of the azimuthal and anisotropic information in the migrated seismic data. A subsequent inversion of the migrated seismic data results in a higher resolution of the fracture density compared to the conventional singular value decomposition approach. (paper)