Comprehensive prediction method of seismic to thin sandstone reservoir in delta-frontal

Key words:  curve reconstruction  geostatistics inversion  attributes analysis  thin reservoir  delta-frontal subfacies

Abstract:

The reservoirs of delta-frontal subfacies are characterized by single thin sandstone and there are no obvious impendence difference between sandstone and shale. Based on curve reconstruction and seismic forward modeling, the seismic inversion and attribute analysis technology suitable to such thin reservoirs were studied respectively. The results indicate that fine prediction of thin reservoirs can be accomplished by two effective methods:pseudo-sonic curve reconstruction with origin sonic and gamma ray curve which can improve the reservoir identification ability of impedance inversion; and the combination of sparse spike impedance and geostatistics stochastic inversion which contributes to decrease uncertainty in reservoir prediction. Due to the scattered relationship between thickness of thin reservoirs and seismic attributes in the delta-frontal subfacies, the spatial distribution of thin sand bodies in sand groups can be qualitatively characterized by optimizing attributes and selecting threshold based on the identification ability of seismic attributes in different scale of sand bodies. Results obtained by the proposed seismic inversion and attributes analysis are cross-validated, and are applied to guide adjustment of well deployment scheme in oilfield, resulting in a significant improvement of drilling success rate from 65% to 82%.