Identification of complex intersalt faults in lower Ganchaigou Formation,Yingzhong area,Qaidam Basin
The surface and underground geological conditions in the Yingzhong area of Qaidam basin are com-plex,making it difficult to precisely delineate the intersalt faults in the Lower Ganchaigou Formation with con-ventional data of prestack depth migration.This study utilizes optimized prestack depth migration data based on multi-directional grid tomography to accurately identify the complex faults in that area.The distribution charac-teristics of the complex intersalt fault system are also studied with attribute analysis using azimuthal dip scan-ning.This study provides a basis for the delineation and selection of favorable zones in the Yingzhong area.The results are as follows.①The optimized prestack depth migration data based on multi-directional grid to-mography solves the problems of inaccurate occurrence imaging and unclear fault imaging of the lower Gan-chaigou Formation in the Yingzhong area.The reinterpretation of the new seismic data reveals that in the"in-cluded angle area"formed by the intersection of Fault XI and Fault IV,there are several small detachment faults in the inter salt strata of the lower Ganchaigou Formation,which belong to different fault systems compared to the imbricate thrust faults developed in the sub-salt strata.②Based on the new prestack depth migration data,the azimuthal dip scanning attributes are extracted,which reveals that these small inter salt detachment faults are distributed in an inverse"S"shape in the map.This is consistent with the regional compressive tectonic stress in the NNE direction,indicating that they are formed during the intense compression and stabilization stage from the late Pliocene to the Quaternary.③ The intersalt faults in the lower Ganchaigou Formation have strong control over local structures.Six favorable traps are identified in the"included angle area"and several wells are very productive,indicating that the intersalt faults are key favorable zones for future exploration.
万方数据
维普
