青藏高原羌塘盆地二维地震数据采集方法试验研究

Acquisition technique test of 2-D seismic survey in Qiangtang basin of Tibet

羌塘盆地地表地质条件复杂,地震资料信噪比低,取得高质量的地震剖面存在很大困难。为了改善这一问题,我们通过50km长的二维反射地震试验剖面,初步探索出一套适用于羌塘地区地震资料采集的方法技术。研究对比表明,合理加大接收排列,采用有效深井、药量,添加适当大炮与适当延长记录长度等措施能够在该地区获得较丰富的地下反射信息。从试验处理的剖面看,该施工方式是合理的、有效的。

It is difficult to acquire a high quality seismic section for the Qiangtang basin of Tibet because of complex seismic-geological conditions and low signal-noise ratio in this area. In order to determine acquisition methods suitable for the features of this basin, we conducted a test along seismic reflection profile with 50 km long. The seismic profile is a common-depth-point （CDP）stacked section acquired with explosive source using I/O Image 24-places seismograph, 480 receiver-groups, 30 m receiver-group spacing, 2 millisecond samplings. The 16-kilogram explosives were generally placed in a single well, as deep as 18 m, space is 150 m, and 60- fold. To surely increase energy of reflection wave, we had also taken a large explosive weight of 100 kilograms, combined wells at the depth of 18 m. PROMAX data process system was used to process seismic data. The preliminary seismic reflection time profiles reveal fine reflection images and offer a great deal of helpful information for studying the structure of the Qiangtang basin. The result shows that lengthening the array, deploying valid well depth and explosive quantity, adding reasonable shot with a large quantity of explosives and prolonging record time are necessary to acquire abundant reflection in this area. The test processing profiles show that this method is both feasible and effective.