﻿ 黏弹性叠前时间偏移:陡倾角构造成像与实际应用
 地球物理学报  2018, Vol. 61 Issue (2): 707-715 PDF

1. 中国科学院地质与地球物理研究所, 中国科学院油气资源研究重点实验室, 北京 100029;
2. 中国科学院大学, 北京 100049

De-absorption prestack time migration: steep dip structure imaging and its application
LIU Wei1,2, ZHANG JianFeng1,2
1. Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;
2. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract: De-absorption pre-stack time migration (PSTM) can compensate absorption and dispersion via an actual wave propagation path using effective Q parameters. Compared with conventional pre-stack time migration, it has higher resolution image. In this paper, we modified the conventional travel time method to a high order one by introducing two non-dimensional parameters. These parameters are obtained by optimizing the travel time equation and the travel time calculated using the Snell's law. To improve the robustness of imaging steep-dip structure and faults, we present a new travel time calculation method useful for graphic process unit (GPU) and a seismic trace split method. Applying the method to the real 3D land seismic data produces significant improvements in resolution especially in steep-dip structure and faults. At the same time, the improved method can reduce the calculation time by more than one third.
Key words: Viscoelastic media    Pre-stack time migration    Steep dip structure    Travel time    GPU speed up
0 引言

1 黏弹性叠前时间偏移及等效Q

 (1)

 (2)

Qeff就是等效Q值，与均方根速度类似，它是替代上覆地层各个不同Q值影响的一个等效参数，等效Q值和均方根速度可共同表达为

 (3)

 (4)

 (5)

2 高精度走时计算

 (6)

 (7)

α=0和β=0，式(7)即退化为式(2)，无量纲参数αβ与均方根速度Vrms同样，仅是成像点的(x, y, T)的函数，改变任一空间位置上的αβ，仅影响该位置处大入(出)射角度的偏移同相轴的聚焦.

 (8)

 图 2 成像点以不同角度向地面发出的射线路径 Fig. 2 Rays shooting at the imaging point with different angle

 (9)

 图 1 某CDP位置的均方根速度和转换层速度 Fig. 1 Root mean square velocity and interval velocity at some CDP position
 图 3 三个不同成像位置的常规走时和高精度走时误差图 Fig. 3 Error graph of conventional and high precision travel time at three different imaging point
3 分时段的频率域成像算法

 (10)

 (11)

 (12)

 (13)

 图 4 时间域子波响应图 Fig. 4 Wavelet Response graph in time domain
 图 5 放大的时间域子波响应图 Fig. 5 Enlarged wavelet response graph in time domain
 图 6 整道成像和分段成像对局部比图 Fig. 6 Comparison of total trace image and two segments image
4 实际三维陆上地震资料的应用效果与对比

 图 7 本文方法成像结果 Fig. 7 The imaging result using the method in this paper
 图 8 商业软件结果本文走时高分辨率结果和常规走时高分辨率结果对比 (a)商业软件结果; (b)本文走时高分辨率成像结果; (c)常规走时高分辨率成像结果. Fig. 8 Comparison of commercial imaging result, the two parameter travel time method high resolution imaging result and conventional travel time method high resolution imaging result (a) Commercial image result; (b) High resolution image using two parameter travel time method; (c) Conventional high resolution imaging result.
 图 9 常规偏移结果和本文高分辨率偏移结果频谱对比 Fig. 9 The spectrum of conventional result and high resolution result

5 结论

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