| 基于可视性分析与能量补偿的金属矿弹性波全波形反演 |
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| 引用本文： | 孙宏宇,韩立国,韩淼,王志强.基于可视性分析与能量补偿的金属矿弹性波全波形反演[J].地球物理学报,2015,58(12):4605-4616. |
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| 作者姓名： | 孙宏宇 韩立国 韩淼 王志强 |
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| 作者单位： | 1. 吉林大学 地球探测科学与技术学院, 长春 130026;2. 国土资源部应用地球物理重点实验室, 长春 130026;3. 中国地质调查局 油气资源调查中心, 北京 100029 |
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| 基金项目： | 国家高技术研究发展计划(863计划)重大项目课题(2014AA06A605)和国家深部探测专项第3项目(SinoProbe-03)联合资助. |
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| 摘 要： | 采用弹性波全波形反演方法精确重建深部金属矿多参数模型,建模过程采用基于地震照明的反演策略.首先给出基于照明理论的观测系统可视性定义,利用可视性分析构建新的目标函数,对反演目标可视性较高的炮检对接收到的地震记录在波场匹配时占有更高的权重,确保了参与反演计算中的地震数据的有效性;其次将给定观测系统对地下介质的弹性波场照明强度作为优化因子,根据地震波在波阻抗界面处的能量分配特点,自适应补偿波场能量分布和优化速度梯度,以提高弹性波全波形反演过程的稳定性和反演结果的精度.理论模型和金属矿模型反演试验结果表明,基于可视性分析和能量补偿的反演策略可以使弹性波全波形反演更快地收敛到目标函数的全局极小值,获得适用于金属矿高分辨率地震偏移成像的多参数模型.
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| 关 键 词： | 金属矿地震 全波形反演 弹性波 可视性分析 能量补偿 |
| 收稿时间： | 2015-11-03 |
Elastic full waveform inversion based on visibility analysis and energy compensation for metallic deposit exploration |
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| SUN Hong-Yu,HAN Li-Guo,HAN Miao,WANG Zhi-Qiang.Elastic full waveform inversion based on visibility analysis and energy compensation for metallic deposit exploration[J].Chinese Journal of Geophysics,2015,58(12):4605-4616. |
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| Authors: | SUN Hong-Yu HAN Li-Guo HAN Miao WANG Zhi-Qiang |
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| Institution: | 1. College of Geo-exploration Science and Technology, Jilin University, Changchun 130026, China;2. Key Laboratory of Applied Geophysics, The Ministry of Land and Resources, Changchun 130026, China;3. Oil and Gas Survey of China Geological Survey, Beijing 100029, China |
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| Abstract: | The weak and discontinuous reflections and scattering features in complex environments make it difficult to construct velocity models suitable for imaging in conventional P-wave seismic exploration for metallic deposits. Multi-wave and multi-component seismic exploration technology may have the advantages in effort to solve this problem. Elastic full waveform inversion (EFWI) exploiting the multi-component and pre-stack seismic data can reconstruct highly accurate multi-parameter models for imaging complex deposit structure in the deep subsurface. The EFWI method based on visibility analysis and adaptive energy compensation is introduced in this paper which can utilize prior information more adequately relevant to vector seismic fields from the target.#br#For a specific geometry in seismic acquisition, only signals from sources and receivers within a certain extent have effect on the inversion and imaging about the objective body. According to the contribution for a single shot-geophone pair to the imaging of the objective body, the statistical analysis method is used to obtain the whole illumination intensity of the target zone which is defined as the visibility of the single source-receiver pair. To improve the inversion result by utilizing the seismic information related to the target zone as much as possible without increasing computation and acquisition costs, we can construct the objective function of EFWI based on geometry visibility to increase the proportion of residuals related to the target zone during wavefield matching. FWI is a data-fitting procedure between observed and calculated data. Wavefields with weaker energy make less contribution to the misfit of objective function even though the velocity contrast is bigger. The uneven distribution of energy due to several cases can be expressed by seismic illumination. So bi-directional illumination intensity of the elastic wavefield is used as a weighting factor to adaptively optimize and balance the gradients of EFWI. Zoeppritz equations control the process of automatic compensation because they describe the energy distribution of seismic waves across the interface of impedance.#br#The EFWI algorithm proposed in this paper is implemented by the finite-difference method to calculate the elastic wavefields in the time domain and LBFGS optimization method to update the initial models. The multi-parameter gradients (density, P-wave and S-wave velocity) are calculated by the cross-correlation between forward and backward wavefields in the time domain. First, the validity of our inversion method is verified on the MarmousiII model. The accuracy of inversion results with visibility analysis and energy compensation is improved compared with conventional EFWI. The model test results based on one metallic model of Luzong Basin also illustrate that our new method makes the inversion converge to global minimum of objective function faster and provides accurate and multi-parameter models which can be applied to high-resolution seismic migration imaging of metallic deposits.#br#The numerical results show that the elastic full waveform inversion algorithm based on visibility analysis utilizes the effective information from the target zone adequately. Introducing the illumination intensity of the elastic wavefield to EFWI by transmission coefficients between two layers can also balance the energy distribution of wavefields adaptively. Both of the two inversion strategies with illumination can improve the accuracy of imaging. The EFWI method can accurately reconstruct deep and multi-parameter models for metallic deposits, including density, P and S wave velocity, which makes it possible to obtain high-resolution migration imaging about deposit structures. |
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| Keywords: | Metallic deposits Full waveform inversion Elastic wave Visibility analysis Energy compensation |
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