Amplitude anisotropy of shear-wave splitting and fluid detection in thin-layer reservoir

Abstract

Thin interbeds are typical reservoirs in eastern China. Thin layers and fractures bring huge challenge to fluid identification in anisotropic reservoir. This study focuses on thin-fractured reservoirs and amplitude attributes of shear-wave splitting, and consequently predicted fluid type in fractured reservoir based on the response of fast and slow S-waves to fluids. 3D HTI viscoelastic equation was employed to analyze amplitudes of split S-waves through fluid-filled and fractured media, including oil- and water-saturated synthetic models. Similar to velocity anisotropy, amplitude anisotropy was proposed to avoid the calculation of S-wave quality factor. Amplitude ratio and substation derived from amplitude anisotropy were used to identify fluid type. Example from the Luojia area of Shengli oilfield was used to demonstrate the effectiveness of the inversion method. Results show that amplitude ratio and amplitude subtraction are useful to distinguish fluids, while the former works better than the latter.