Oil fields in eastern China generally have complex faults,serious interbedding of sand and mudstone,and staggered overlap between river sand bodies.Owing to the limitation of seismic vertical resolution,it is impossible to reliably identify whether there are low-order small faults or sand body overlapping zones,which have a significant impact on the deployment and adjustment of oil field development schemes.In view of this problem,a model
containing small faults with different fault throws and sand bodies with different overlapping ranges and falls was designed.The forward modeling results showed that the sand body overlap zone with thickness less than the tuning thickness that form a “pseudo fault” response on the seismic profile,that is,the distortion or dislocation of seismic event axis was similar to small faults.However,through a comprehensive analysis of seismic multi-attributes,it was found that seismic amplitude and seismic waveform structure attributes have different response characteristics to the overlap of small faults and sand bodies.Combined with the conventional root-mean-square (RMS),amplitude attribute,and waveform variation coefficient (WVC) attribute,two identification criteria were established.①When both the RMS amplitude and WVC attribute suddenly change to low values,the existence of faults can be recognized.②If the RMS amplitude is a low-value mutation and the WVC attribute is a high-value mutation,the overlapping zone of the sand body can be identified.These criteria were applied to the seismic data of the S23 reservoir in the W102 fault block of the Shengli exploration area.The results showed that the abnormal characteristics of the RMS amplitude and WVC attributes of the small fault development area and thin sand body overlap zone are consistent with these two identification criteria.Two thin sand body overlap zones in the north were identified,and they provide a reference basis for the adjustment and deployment of development schemes in this area.
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