平原地区新近系横向厚度变化对深部目的层地震成像影响分析

在我国东部平原地区，新近系的厚度变化较大，对下部煤层反射波的准确成像产生巨大影响。致使地震解释出现煤层深度误差大、假向斜、假背斜及断层位置严重偏离等问题。通过模拟新近系起伏变化对深部目的层反射波的正演，发现目的层反射波随上覆低速层的起伏而起伏，其中断点的绕射波特征也随之出现较大变化，对此进行常规叠后偏移易出现成像失真。对此采取分时校正方法，计算出不同赋存深度条件下的煤层反射波校正量曲线．将获得的校正量运用叠后偏移处理，能较好地消除深部同相轴不正常的凹凸现象，实现对目的层构造及其形态的正确成像。济宁二号井八采区的实例证明，分时校正后的叠后偏移方法可有效消除新生界横向起伏变化对深部目的层准确成像的影响。

Impacting Analysis of Plain Area Neogene System Transversal Uneven Variation on Deep Part Target Seismic Imaging

In the eastern plain area of China, the thickness of Neogene System is variable, thus causes substantial impact on correct reflection imaging. It brings about larger errors, false syncline, anticline and fault positions seriously departure from real situation in coal seam depth seismic interpretation. Through forward solutions of simulated Neogene System undulation versus deep part target reflection, have found that the target reflection waves undulating along with overlying low velocity layers. Diffracted wave characteristics of faulted points are also present larger variation therewith, thus imaging distortion will be happened after traditional poststack migration. By this, time-sharing correction is used to compute coal seam reflection correcting value curve under different depths. While the poststack migration process of correcting values can preferably eliminate deviant rugged phenomenon of deep part phase axes, and realize target structure configuration correct imaging. The example of No.8 winning district, Jining No.2 coalmine has demonstrated that the poststaek migration after time-sharing correction can effectively eliminate impact on deep part target correct imaging from Cenozoic erathem transversal undulating.