三维电磁偏移数值滤波器实现及参数分析

Realization and parameter analysis for filter of 3D numerical electromagnetic migration

基于满足扩散方程的电磁偏移场解析式,推导了能够应用于实际数据处理的电磁偏移数值滤波器.为了合理选取滤波器参数,本文基于偏移微分方程,构建了满足偏移微分方程的解析测试场,通过测试场与偏移数值滤波器处理结果比较,重点研究了滤波器窗口大小、采样距离、偏移深度等滤波器参数对数值偏移滤波效果的影响,确定了数值滤波器参数选择原则.考虑到实际应用,在计算偏移电导率时,本文利用背景场定义了反射函数.建立了三维典型地电模型做数值计算,利用电磁偏移数值滤波器处理模拟数据,得到了合理的目标体位置和形态.测试场比较和数值试验证明,电磁偏移成像是一种可靠稳定的电磁资料解释技术.

Based on the theory of electromagnetic migration in which the migration field satisfies electromagnetic diffusion equation, we derived electromagnetic migration numerical filter, and people can use it to process practical data. In order to reasonably choose filter parameters, test analytical field was constructed in this paper using migration differential equation. By contrasting the test field and the results produced by digital migration filter, we studied the filter parameters influence, which include filter window size, sampling space, and migration depth. Then, we determined the criteria how to choose optimized filter parameters. In order that the filter can be easily used in practical data, this paper defined reflectivity function using background field, then migration conductivity was calculated. The numerical modeling was done for 3D typical geo- electric models, and the numerical filter was used to process the numerical data. The tests demonstrated that people can use the migration filter to obtain the reasonable position and shape of targets.