Development and application of an effective method for reservoir predication based on seismic diffraction

Carbonate fractured and cavernous reservoirs account for a large proportion in petroleum exploration, for which reservoir prediction is a tough issue. As seismic reflection method assumes the reflection interface to be an infinite smooth plane, its application is restricted by the horizontal and vertical resolutions, which cannot detect geological bodies such as carbonate fractured and cavernous reservoirs. The seismic diffraction method for reservoir prediction only analyzes diffraction information in the seismic wave field after the removal of reflected waves from seismic data. The difficulty in using diffraction is related to the weak signal of diffracted waves which can be masked in the context of strong reflection. Thus, it is required to remove the reflected energy for highlighting the diffraction information. Based on the correlation difference between reflection and diffraction, this study presents a diffraction separation method via a combination of plane-wave destruction filter and medium filter. The proposed method adopts the regularization inversion algorithm to obtain the smooth dip angel filed of reflection, and then implements medium filter along the estimated dip angle to calculate the reflection data with stable wavelet and constant amplitude. Finally, diffraction extraction is accomplished by subtracting the predicted reflected waves from the seismic data. Numerical simulation and practical application demonstrate that the diffraction-based method can effectively extract geological information of interlayer karsts, caves, and vugs, showing a good perspective for studying carbonate fractured and cavernous reservoirs.