松辽盆地北部深层火山岩地质条件下三维叠前深度偏移速度模型建立

Building of 3D pre-stack depth migration velocity model under deep volcanic environment in northern Songliao Basin

松辽盆地北部徐家围子断陷深层地质条件复杂,虽然常规叠后时间偏移处理的成果,能够识别区域构造与火山岩的复合发育区基本轮廓,但陡倾角地层的反射成像不清晰,火山岩地层边界模糊,其原因在于断陷地层的速度结构复杂,常规叠后时间偏移不能使反射波正确归位,只有三维叠前深度偏移技术才能提高成像精度。分析了兴城地区的地质条件,指出本区准确建立偏移速度模型难点是深层火山岩结构,并给出了基于叠前深度偏移迭代的速度建模对策。结果表明这种速度建模方式行之有效。

For the complex geological structure in Xujiaweizi Depression of northern Songliao Basin, the post stack migration seismic section is of poor imaging in steeper dip structure and it smears the volcanic outlines, although these geological features could be roughly figured out. The reason is that post stack migration can not correctly image for seismic data with steeper dip layers; but 3D pre-stack depth migration is the correct solution. In this paper, the geology in Xingchen area is analyzed, and it is concluded that deep volcanic structure made it difficult to build up velocity model correctly. The pre-stack depth migration loop is the solution for model building. The practical data show this model has better results.