多道地震成像方法在台西南盆地断层与岩浆侵入体识别中的应用研究

Application of Multichannel Seismic Imaging Methods in the Identification of Faults and Magmatic Intrusions in Southwest Taiwan Basin

台西南盆地是南海北部陆缘上的新生代盆地,其中发育了丰富的断层和岩浆侵入体,对油气成藏和构造研究具有重要意义。利用叠后时间偏移、倾角时差校正后的叠后时间偏移(以下简称:叠前部分偏移)和叠前时间偏移三种成像方法对台西南盆地的多道地震数据进行成像,并对比分析了这3种成像方法对台西南盆地中断层和岩浆侵入体的识别效果。叠后时间偏移可识别规模较大的主要断层,难以识别规模较小的断层。叠前部分偏移对规模较大和规模较小的断层都可以进行识别,较叠后时间偏移识别出的断层数量更多。叠前时间偏移不仅能够识别规模较大和规模较小的断层,还可以对规模更小的断层进行识别,其识别出的断层数量多于叠前部分偏移。叠后时间偏移无法准确识别岩浆侵入体中的透镜状结构特征;叠前部分偏移能识别出岩浆侵入体的透镜状岩块;叠前时间偏移识别出的透镜状岩块较叠前部分偏移的识别结果更加完整。进一步讨论了叠前时间偏移方法中偏移最大倾角参数对成像效果的影响,研究了多道地震成像方法识别台西南盆地断层和岩浆侵入体的效果,希望对该区域进一步的油气与构造研究有所裨益。

The southwest Taiwan Basin is a Cenozoic basin formed on the northern continental margin of the South China Sea,where abundant faults and magmatic intrusions were developed,which is of great significance for the study of oil and gas accumulation and tectonic evolution.In this study,three imaging methods,namely poststack time migration,poststack time migration after dip moveout correction(hereinafter referred to as prestack partial migration)and prestack time migration,were used to image the multichannel seismic data from the southwestern Taiwan Basin,and the recognition effects of these three imaging methods for faults and magmatic intrusions in the southwestern Taiwan Basin were compared and analyzed.Firstly,the method of poststack time migration can identify major faults with large scale,but it is difficult to identify small faults.Secondly,the method of prestack partial migration can identify both large-and small-scale faults,and the number of faults identified by using this method is more than that by using poststack time migration.Thirdly,the method of prestack time migration can not only identify large and small faults,but those smaller faults,and the number of faults identified by using this method is more than that by using prestack partial migration.Poststack time migration can not accurately identify lenticular structural features in magmatic intrusions.Prestack partial migration can identify lenticular blocks of magmatic intrusions.The recognition result of lenticular blocks identified by using prestack time migration is more complete than that by using partial prestack migration.Finally,this study discussed the influence of the maximum migration dip angles on the imaging effect in prestack time migration method,and the effect of multi-channel seismic imaging methods on identifying faults and magmatic intrusions in the southwest basin of Taiwan,which may be helpful to the study of ooil and gas accumulation and tectonic evolution in this area.