金属矿多源地震波场重构与联合成像研究

Focus on the characteristics and needs of reflected seismic exploration for deep mineral and hard rock areas, we proposed to generate the full wave field by maximize the acquisition and application of the multi-source seismic wave field (multi-source and multiple similar sources) to achieve high-precision imaging for deep geological structure. The active sources seismic signals would be mainly utilized with the supplement of passive sources. Active source data can be collected by conventional acquisition system. Whereas In our research we will take the newly developed high-efficiency simultaneous seismic acquisition where different sources are shot in an overlapping fashion simultaneously or with certain time delays and blended shot records are acquired, so that both acquisition efficiency and image quality can be significantly improved. In that case, a deblending method is essential for the reconstruction of conventional single source data. In our research, both the inversion separation methods and the filtering deblending methods will be fully studied for the purpose of improving the separation quality and calculation efficiency significantly. While the passive seismic data can be used to generate the virtual reflected records via seismic interferometry, which means the ambient noise could be used to get the useful reflected data with wider frequency bandwidth. The basic idea of seismic interferometry method is retrieval of useful signal from the chaotic disorder seismic signal, new seismic signal is generated by the interference of recorded seismic signal, the new seismic signal not only include the properties of original seismic signal, but also retrieve some important features that the original signal does not have. Finally the multi-source seismic wave field can be achieved by the combination of reconstructed active and passive wave field which is able to fully describe the details of underground media model with more geological information and wider frequency bandwidth. As the key technology of our research, multi-source full waveform inversion can establish a reliable velocity model for the high precision reverse time migration of deep metal mine and hard rock areas.

针对矿集区深部金属矿及硬岩地区反射波地震勘探的特点，本课题提出最大化地采集并应用多震源地震波场信息（主动源、被动源和多个同类震源）实现深部地质构造高精度成像。研究中将以主动源地震信号为主，被动源地震信号为辅助的形式。主动源数据采集可以采用常规的单炮记录方式，也可以采用低成本高效率的混合采集记录并经波场分离技术实现地震记录重构。而被动源地震记录则可以通过地震干涉法形成虚拟反射记录，重构后的主动源和被动源波场可以形成多源地震波场，它信息全、频带宽，能够更加完整精细地描述地下介质模型。高精度频率域全波形反演是本课题的技术关键，能够为金属矿及硬岩地区高精度逆时偏移成像建立精确可靠的速度模型。它既可以单独应用于被动源或主动源地震记录的速度建模，也可用于被动源和主动源混合地震数据的串联或联合的全波场反演处理。课题还将开展主动源共散射点地震全波形反演以及最优化干涉法重构虚拟记录的方法研究。

被动源地震信号广泛存在于自然界中，来自地下的被动源地震波场携带了大量深部介质参数信息。由于被动源地震信号往往较弱且不易识别，常规地震数据处理中往往将其作为噪声而去除。本项目研究的目标就是要提取并利用记录到的被动源地震信号，将其与常规主动源地震信号进行联合重构，并用以提高地震反演和成像的质量，达到优势互补的目的。本项目首先开展了高效的主动源多源地震采集和处理研究，为后期数据的联合处理提供高精度的主动源地震资料。提出了主动源混合采集地震数据分离中插值与去噪的同步处理方法，以及可变频震源混合采集数据的波场分离方法。这两种方法能解决实际中可能遇到的多种复杂采集情况的炮分离问题。提出了基于快速迭代收缩阈值算法的多震源混合数据偏移成像方法，以及基于全变分原理的多震源混合数据直接偏移成像方法。针对被动源地震信号的提取和重构，提出了基于多窗谱方法的被动源地震干涉法，以及被动源数据多域迭代去噪算法，可以得到高质量和保幅性好的被动源重构数据。针对三种不同的情形，提出了主动源与被动源地震数据插值及联合数据成像方法，有效的利用了主被动源地震数据各自的优势。针对被动源地震数据含有丰富的低频信息，提出了利用被动源低频信息重构主动源缺失低频信息的方法。在全波形反演方面，针对常规全波形反演的跳周问题，提出了基于稀疏盲反褶积低频重构的全波形反演方法，以及基于最小平方滤波的全波形反演方法。针对主被动源联合全波形反演，提出了两种策略，分别是基于被动源照明补偿的全波形反演方法和基于地震干涉法的主被动源地震数据联合全波形反演方法。为了适应实际复杂介质的情况，本项目还开展了弹性介质下多源地震数据低频重构以及全波形反演研究，提出了基于各向异性全变分约束的多震源地震数据弹性波全波形反演方法。本项目超额完成了预期目标，提出了一整套针对多源地震联合重构以及联合反演和成像的新方法和新技术，具有重要的理论意义和实际意义。