A new AVOZ inversion method for higher precision fracture and its fluid prediction

Usually, conventional azimuthal AVO (AVOZ) inversion method is based on two-term Rüger equation, which might give rise to inaccuracy in estimating fracture properties for large-offset data due to neglecting the third term. Nowadays, the industry is increasingly acquiring large-offset seismic data, which drives us to seek a more accurate fracture prediction method that can make full use of large-offset information. In the paper, a new AVOZ method is developed based on three-term Rüger reflection equation, by which both fracture properties (fracture density and fracture orientation) and Thomsen anisotropic parameters (ε^v and δ^v) can be solved. In addition, based on previous studies, fracture fluid indicator can be obtained as well. Numerical model shows that, fracture density and orientation from the new method is much closer to the real value than that from conventional AVOZ inversion. And the inversion anisotropic parameters are also approximate to the theoretical value. Meanwhile, fracture fluid indicator on the basis of inversion results from the new method can effectively identify different fluid types. In field data application, it is found that the result well agrees with FMI information, which is more accurate than that obtained by conventional AVOZ inversion. The fracture fluid indicator is also in a good agreement with well production, which proves the feasibility of this method.