三维弯曲界面炮集P波反射时距特征分析

P-WAVE REFLECTION TIME-DISTANCE CHARACTERISTIC OF SHOT GATHER FROM 3D SEISMIC CURVED-INTERFACE

对于三维反射地震,文中将三维弯曲界面视为倾向和倾角变化的三维倾斜界面的包络,并依据三维倾斜界面反射提出计算三维弯曲界面P波反射时距的一种新方法。该方法基于倾角CDP理论,从界面反射点出发,给出地表CDP网格点,由检波点位置计算炮点位置,得到三维地震的炮点网格和检波点网格的分布关系,最终计算P波的三维反射时距。炮集数值模拟的结果表明,该方法有较高的计算效率,便于分析反射时距随炮点位置的变化,特别能揭示界面反射点位置和时距的关系。三维弯曲界面和三维倾斜界面的反射时距特征对比表明,仅从同一测线方位的时距难以将这两种类型的界面反射区分开来,但比较不同方位的时距差异可以解决这一问题。

It＇s very difficult and time-consuming to calculate the precise location of the reflection points in the reflection time-distance simulation of 3D complex tectonic model. In order to analyze the P-wave reflection time-distance characteristic systematically and accurately, the paper regards 3 D curved interface as the envelope of 3D dipping interface with different tendencies and inclinations, and presents a new method for calculating P-wave reflection time-distance from 3D curved interface, using the princi- ple of reflection from 3D dipping interface. Based on the dip layer CDP theory,the location of shot points and reflection travel times are obtained from the positions of receivers and surface CDPs, finally the 3D P-wave reflection records of shot gather are received, assuming that the distribution of interface reflection points is known. Numerical simulation results of shot gather show that this method has high computing efficiency and can be applied to analysis of the P-wave reflection time-distance characteristic with different positions of shots; especially it can reveal the relation between reflection points and time-distance curve. The reflection timeistance feature comparison of 3D curved interface and 3D dipping interface shows that it＇s very hard to distinguish time-distance characters between two types of interfaces only from the same survey line orientation, and this problem can be solved by comparing time-distance differences from different survey orientations.