莺歌海盆地模糊带地震资料的成像处理技术

IMAGING PROCESSING OF THE WHITE ZONE SEISMIC DATA IN YINGGEHAI BASIN

莺歌海盆地中央泥底辟构造带是非常有利的含气构造带，由于受深部热流体和浅层气的共同影响，在构造顶部的地震资料存在着不同程度的模糊带。对于由浅层气多次反射屏蔽所造成的模糊带，我们通常先作精细的速度分析，取得可靠的一次波速度，再作Ｆ—Ｋ滤波，在Ｆ—Ｋ域中切除多次波能量，保留一次波能量。Ｆ—Ｋ滤波后，作第二次速度分析，提高速度参数的精度，从而提高叠加效果，使模糊带的有效波得以成像。精细的速度分析表明，模糊带的速度偏低。在时间域的剖面上，同相轴有下弯现象。为得到正确的深度域图像，我们采用了叠前深度偏移，它在深度域中进行剩余时差分析，射线追踪，层析成像反演，对初始速度模型进行修正，这一过程可以反复叠代，使速度模型逐步逼近真实。这一方法提高了速度参数的精度，从而也提高了叠前深度偏移处理的结果———深度剖面的精度。在Ｐｒｏｍａｘ２Ｄ地震资料交互处理系统上完成了上述的两项处理工作，取得了明显的效果，对该区构造带的面貌有了新的认识，扩大了勘探的范围和领域。

The central mud diapir structure belt in Yinggehai Basin is the structural belt quite beneficial to gas accumulation.Under the influence of both deep thermal fluid and shallow gas,a varisized white zone can be found in the seismic data at the top of structure.For the white zone made up by the shallow gas' multiple reflection shielding,a careful velocity analysis is generally made first to acquire the reliable primary wave velocity,then the F—K filtering is carried out.The primary wave energy may be retained through eliminating multiple wave energy in F—K domain.After F—K filtering,the second velocity analysis can be made to increase the accuracy of the velocity parameter,thus raising the stack quality so as to cause the effective wave to be imaged in the white zone.By means of the careful velocity analysis,it is shown that the velocity in the white zone is on the low side and the event is curved downward on time domain section.In order to get a correct depth domain image,the prestack migration was adopted.In the depth domain,the residual moveout analysis,ray tracing and tomographic inversion are carried out and the primary velocity model was corrected.Such a process may be repeatedly iterated so as to make the velocity model approaching to the reality.By use of this method,the accuracy of the velocity parameter may be increased,thus raising the quality of the depth section which is the result of prestack depth migration processing.The two processing works mentioned above have been finished by use of the Promax 2D seismic data interactive process system,an obvious effect being achieved.A new understanding about the structural belt in this basin has been formed and the exploration scope and area are enlarged.