金属矿区多分量地震成像方法研究

Exploration for the large and concealed metal mineral resources in depth 500m to 1500m below the second prospecting space is currently carried out in China. With low SNR and poor traceability, it is rather difficult to stack imaging with the conventional vertical component seismic data of the metallic mineral deposits due to the complex seismic geological conditions, such as small scale, poor continuity, large dip, and varied tendency of the deposit structure as well as the rugged surface. This project intends to study tomography velocity modeling by the first arrivals and reflected waves, focusing on the research of continuation operator in mixed-domain and preserved amplitude migration algorithm for the converted-wave pre-stack wave equation depth migration. We will study the parametric method of the velocity models with rugged surface and steep interface via mixed subdivision of the triangle network and rectangular one. In order to improve mixed-posed problem of the Jacobi matrix during tomography inversion, the multi-scale progressive inversion and optimal Lagrange constraints will be adopted. The P wave and converted SV wave propagation operator that is based on Fourier finite-difference splitting as well as back-propagating downward continuation will be discussed about. The converted wave imaging condition modified by continuation operator will also be studied. And the rules between splitting and modification of the operator, local imaging matrix, weighted stack function and the amplitude-preserved imaging will be researched by means of different seismic gathers. Combining the tomography velocity modeling with the pre-stack depth migration iteratively, the multi-component seismic imaging in depth domain to the complex structure objects in metallic mineral deposit areas will be achieved.

我国正大力发展500-1500m第二找矿空间内大深度、隐伏金属矿产资源的探查工作。由于金属矿床尺度小、连续性差、倾角大、倾向多变、地表起伏等复杂的地震地质条件，其地震资料信噪比低、波组可追踪性差，常规单分量反射地震叠加成像遇到很大困难。 本项目在进行初至波与反射波联合层析速度建模研究的基础上，重点开展转换波叠前波动方程深度偏移的混合域延拓算子及保幅偏移算法研究。将研究三角网与矩形网混合剖分对起伏地表及陡变界面速度模型的参数化方法，利用多尺度渐进反演与最优拉格朗日约束改善层析反演矩阵的混定性问题。对基于Fourier有限差分波场传播算子分裂及波场后向传播的纵、横波下延算子进行研究，研究延拓算子修正的转换波成像条件，研究不同地震道集上算子的分裂、修正、局部成像矩阵、叠加权函数及其与保幅成像的作用规律。将层析速度建模与叠前深度偏移有机结合，实现金属矿区复杂构造目标的多分量地震成像。

由于金属矿集区复杂的地震地质条件，其地震资料信噪比低、波组可追踪性差，本项目针对金属矿多分量地震资料的信噪压制和波场有效分离、转换波偏移成像以及速度建模等关键问题开展研究。. 提出并研究了联合SVD和F-K滤波方法分离地震纵横波技术，通过研究奇异值分解后地震信号相干性差异，联合SVD和F-K实现了地震纵横波分离及噪声压制；引入广义S变换，将时频分析方法和自适应协方差矩阵方法相结合，实现了多分量地震信号时频域自适应极化分析和滤波。提出采用矩形和不规则四边形组成的混合网格对模型进行剖分，提高了网格对起伏地表(界面)的拟合程度，改进基于旅行时线性插值（LTI）法的射线追踪技术，将其推广到起伏地表VTI介质地震波旅行时计算中；研发了基于高阶旋转交错网格得三维各向异性TTI介质/粘弹介质地震波场有限差分数值模拟软件。提出并研究联合多波旅行时层析与ADCIG道集结合的近地表速度建模与转换波偏移速度分析方法，将噪声源面波成像、地震初至波与反射波旅行时层析结果相结合，实现用于偏移的近地表速度建模，基于倾斜地层角道集剩余深度量方程，进行速度更新与迭代的逐层偏移速度分析，研发形成了基于ADCIG的纵波与转换波偏移速度分析软件，实现了基于角度域共成像点道集（ADCIG）的纵波与转换波地震叠前偏移。. 项目研究成果及研发的针对金属矿集区低信噪比多分量地震资料的去噪、波场模拟及深度域偏移成像软件，已用于黄土复杂地表地震地质填图优化设计、煤田地震叠前成像及近地表地质灾害探测，为金属矿集区地震资料处理与解释提供了新的理论与方法支持，为山地环境深部矿产资源地震勘查提供了新的手段。