Seismic characteristic of intrusive rock in the Upper Ordivican and its influence on the imaging of reservoir in the Shunbei area,Tarim Basin
Significant breakthrough in petroleum exploration has been obtained recently in the Ordovician strata in the eastern Shunbei area,Tarim Basin,which is benefit from the identification of fault-controlled carbonated fracture-vuggy reservoir and prediction of its distribution.As the exploration moves into westward area,the de-velopment of multiple sets of complex intrusive rock in the Upper Ordovician has caused poor seismic imaging,which has great impact on the identification of fractures and reservoirs in the Middle and Lower Ordovician and restricts the exploration process in this area.Based on the drilling,3D seismic data and regional geological back-ground,this study established a variety of complex intrusions and fracture-vuggy reservoirs model and carried out seismic refection forward modelling of Middle and Lower Ordovician reservoirs on the basis of detailed study of the characteristics of intrusions developed in the Upper Ordovician in the Shunbei area.According to the study,the intrusive rock not only leads to the disjunction of phase at the edge of the intrusion in the seismic profile,but also forms pseudo-faults in the Upper Ordovician underside.In addition,the nearly horizontal thick-bedded,multi-layered intrusions can also cause the formation of multiple waves in the Middle and Lower Ordo-vician.Furthermore,the multiple waves can strength the amplitude of the beaded reflection caused by the frac-tures and cavities,which increase the difficulties in the re-cognization of the favorable reservoirs.By combining forward modeling and seismic attributes,the fault identification method is defined,both of the relationship be-tween intrusive rock thickness and amplitude and the influence degree of intrusive rock on reservoir imaging are quantified,all of which can greatly improve the reliability of fault identification and the accuracy of reservoir de-scription,thus provide a geophysical basis for the next exploration deployment.
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