基于三维快速正反演的瞬变电磁数据解释技术及其应用方法  

Interpretation and application of three-dimensional fast forward and inversion for transient electromagnetic data

作　　者：程铭 杨迪琨 罗强 韩思旭 CHENG Ming;YANG DiKun;LUO Qiang;HAN SiXu(Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology,Southern University of Science and Technology,Shenzhen Guangdong 518055,China;Guangdong Provincial Geophysical Prospecting Team,Guangzhou 510800,China)

机构地区：[1]南方科技大学广东省地球物理高精度成像技术重点实验室,广东深圳518055 [2]广东省地球物理探矿大队,广州510800

出　　处：《地球物理学报》2025年第1期342-354,共13页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2023YFF0718000);国家自然科学基金(42274102);广东省地球物理高精度成像技术重点实验室基金(2022B1212010002)资助。

摘　　要：瞬变电磁数据三维正反演基本算法已经成熟,但由于非唯一性和计算成本等原因,在实际中并未得到有效应用.本文以接地长导线源瞬变电磁为例,基于先进的快速三维正演和“热启动”反演技术,建立一套具有实用性的瞬变电磁勘探实际资料三维处理与解释流程.首先,在数据分析阶段,通过观测分解方法和大规模并行计算实现了近实时的三维交互式正演建模,可快速获得既匹配地质信息又广泛拟合实测数据的地电模型.观测分解法利用“尺度匹配”和“局部离散化”的概念将接地长导线源分解为许多以电偶极子为源的子问题,每个子问题都使用独立优化的时间和空间离散化方法分别计算,子问题之间互相独立,从而实现快速并行求解.解释人员结合地质先验信息,经过反复正演验证,获得可靠的三维初始模型.最后,将该模型作为初始模型和参考模型,引导反演快速进入稳定的收敛域,经反演程序自动搜索迭代后获得拟合数据的三维解释模型.使用交互式建模获得热启动反演初始模型不仅可以加速三维反演收敛,而且确保所得模型具有地质意义.本文将上述流程应用于广东英德某铅锌矿实测数据,三维反演揭示的高导电性矿体形态与钻孔资料以及地质剖面高度吻合,证明了上述方法的有效性和实用性.这一工作有望推动三维瞬变电磁处理解释在实际找矿生产中的广泛应用.The basic algorithms for three-dimensional(3D)forward and inverse modeling of transient electromagnetic(TEM)data have matured,but practical application has been limited due to non-uniqueness and computational costs.This paper uses the grounded long wire source TEM as a case study to establish a practical 3D processing and interpretation workflow for TEM data.The workflow leverages advanced fast 3D forward modeling and"warm-start"inversion techniques.Survey decomposition and large-scale parallel computing achieve near real-time 3D interactive forward modeling during the data analysis phase.This approach rapidly generates a geoelectric model that aligns with geological information and broadly fits measured data.The survey decomposition method breaks down the grounded long wire source into numerous sub-problems with electric dipoles as sources,employing independently optimized time and space discretization methods for each sub-problem.This enables rapid parallel solving of sub-problems,ensuring efficient computation.By combining geological prior information,interpreters obtain a reliable 3D initial model through repeated forward modeling validations.Finally,this initial and reference model guides the inversion to rapidly enter a stable convergence domain.After automatic search iterations in the inversion process,a 3D interpretative model fitting the data is obtained.The use of interactive modeling to obtain a warm-start inversion initial model not only accelerates the convergence of 3D inversion but also ensures the resulting model has geological significance.This workflow is applied to measured data from a lead-zinc mine in Yingde,Guangdong,revealing a high-conductivity ore body that aligns with drilling data and geological profiles.This demonstrates the effectiveness and practicality of the proposed method.This work is expected to promote the widespread application of 3D transient electromagnetic processing and interpretation in practical mineral exploration.

关 键 词：瞬变电磁 三维正演 观测分解 三维反演 

分 类 号：P631[天文地球—地质矿产勘探]