A combined Parzen-wavelet approach for detection of vuggy zones in fractured carbonate reservoirs using petrophysical logs

• A combined approach is used for detection of vuggy zones by signal processing (Wavelet) and pattern classification (Parzen) by petrophysical logs.
• Petrophysical logs can detect vugs accurate with lower cast than conventional method (Core and Image Log).
• The detection errors often occurred at the marginal areas of vuggy and non-vuggy zones.
• The accuracy of the method is dependent on the proportion of vuggy to non-vuggy zones.
• High accuracy and low cost of this combining method are benefits of this methodology, comparing to others.

Vuggy porosity which is the most important type of porosity in carbonate rocks, significantly affects permeability, pressure drop and recovery factor of the rocks. As a result, its identification and modeling are essential for reservoir characterization and history matching. Image logs as well as RCAL and SCAL tests are main methods to determine vugs. However, these methods are costly and usually unavailable. Therefore, developing a generalized approach for recognizing vugs appears to be necessary. In this paper, a combined Parzen-wavelet based algorithm is developed for identifying vuggy zones in wavelet coefficient domain using gamma ray (GR), neutron porosity (NPHI), bulk density (RHOB) and sonic (DT) logs. Compatibility between core tests and the results of the developed method revealed the capability of the method.