Research and Application of Anisotropic Prestack Inversion Technology Based on OVT Domain Dimension Reduction in Fracture Prediction-Taking Shahezi Formation of Dsh20 Well Area in Anda Area of Northern Songliao Basin as an Example

The tight sandy conglomerate of the Shahezi Formation in the northern Songliao Basin has the characteristics of deep burial, complex structure, diverse lithological assemblages, and rapid changes in sedimentary facies. The evaluation of gas “sweet spots” is of great significance. P-wave anisotropic fracture prediction technology based on ellipse fitting is a widely used method, but this method fails to fully consider the elastic information in the data. In this paper, the prestack fracture prediction technology based on anisotropic inversion in the OVT domain is proposed. The Thomsen anisotropy parameters are estimated by elastic parameter inversion for data at different azimuth angles. At the same time, in view of the coupling and instability of the 7-parameter inversion in the Ruger equation, the Fourier series expansion is used in the HTI medium according to the isotropic medium at different azimuths. The elastic parameter is used to obtain the B1 parameter that reflects the anisotropy characteristics, and the inversion parameter is reduced by 3, which greatly improves the stability and anti-noise of the inversion. This method has obvious effect in the prediction of deep fractures in the northern Songliao Basin, and provides technical support for the characterization of tight gas “sweet spots”.