Understanding Seismic Anisotropy from Fractures Observed in Wells

The description of fracture networks is a critical input for the building of reservoir models and reservoir simulation. This paper presents the integration of the physical characteristics of fractures defined in wells to interpret the azimuthal anisotropy of the amplitude of seismic signals. The proposed method converts the well data into elastic tensors to compute anisotropic reflection coefficients. Synthetic traces are then created by convolving the resulting reflection logs with source wavelet. The comparison of the synthetic seismograms with real azimuthal seismic data is used to evaluate the effect of fractures on these data. It turns out that taking into account the fractures in the forward modelling has only a minor effect on the correlation between synthetic and real traces: the variations observed between azimuthal sectors are strong and inconsistent with an anisotropic behaviour. These variations are probably due to poor seismic quality or to other causes such as layering or stress effects.