E-E_(x)广域电磁法横向约束反演  

Lateral constrained inversion of E-E_(x) wide field data

作　　者：张继锋[1] 周光裕 刘最亮 孙乃泉[1] 张富翔 王中圣 ZHANG Jifeng;ZHOU Guangyu;LIU Zuiliang;SUN Naiquan;ZHANG Fuxiang;WANG Zhongsheng(College of Geology Engineering and Geomatics,Chang’an University,Xi’an 710054,China;Huayang New Material Technology Group Co.,Ltd.,Yangquan 045000,China)

机构地区：[1]长安大学地质工程与测绘学院,陕西西安710054 [2]华阳新材料科技集团有限公司,山西阳泉045000

出　　处：《煤炭学报》2022年第7期2698-2707,共10页Journal of China Coal Society

基　　金：国家重点研发计划资助项目(2018YFC0807806);国家自然科学基金资助项目(42174168);陕西自然科学基金基础研究计划资助项目(2021JM-159)。

摘　　要：针对E-E_(x)广域电磁法反演剖面横向不连续性问题,在原有Occam反演的基础上添加了相邻测点约束项,使得在模型反演过程中不仅仅考虑到了反演模型的纵向光滑性,同时尽可能使横向相邻测点反演剖面具有连续性。当存在测井先验资料时,该约束项可实现对钻井附近测点的纵向约束,其余测点则通过上一测点进行约束,从而改善反演剖面的横向连续性。为了充分利用先验资料及减小剖面反演误差积累,采用测井附近的点或电场值较稳定的测点为剖面分割点,对整条剖面进行分段反演,可减小累积误差。采用一维横向约束反演目标函数,先后通过进退法和黄金分割法求取拉格朗日乘子。一维模型测试结果显示,采用参考点约束的反演收敛速度更快,反演电阻率在中间层更趋近于模型本征电阻率。二维模型测试结果表明:采用横向约束反演得到的剖面电阻率连续性好,电阻率剖面更光滑。基于横向约束的反演对于地层的精细分层和定量解释优于广域视电阻率解释断面。实际数据反演时,可首先对实测数据进行预处理和光滑,计算广域视电阻率,以此作为反演的初始模型,能够快速收敛到真实模型。最后,对山西某处广域电磁法野外实测资料进行了反演,结果表明:一维横向约束反演比广域视电阻率在横向上连续性更好,纵向分层能力强,该结果和实际出水点以及已知采空区吻合较好,与实际地质情况符合,表明该方法能够改善实测资料的反演效果,提高广域电磁法在煤矿水文地质方面的勘探精度。In order to solve the problem of lateral discontinuity of inversion profile for E-E_(x)wide field electromagnetic method,the constraint term of adjacent points is added on the basis of the original Occam inversion,so that not only the longitudinal smoothness of inversion model is considered in the inversion process,but also the continuity of cross-section inversion by adjacent points is made as far as possible.When there is logging prior data,this item can realize the vertical direction constraint on the measured points near the drilling well,and the inversion results of the other survey points are considered to be the least different from the previous one,so as to improve the lateral continuity.In order to make full use of prior data and reduce the accumulation of inversion errors,we adopts the method that the adjacent survey points or the measured points with stable field value and wide field apparent resistivity as the section segmentation points,and carries out piece-wise inversion of the whole profile to reduce accumulation error of profile inversion.The objective function of one-dimensional lateral constrained inversion is given,and the Lagrange multiplier is calculated by the combination of advance and backward method and golden section method.The one-dimensional model test results show that the inversion convergence rate with the reference point constraint is faster,and the inversion resistivity is closer to the model intrinsic resistivity in the middle layer,but it has little influence on the calculation error.The two-dimensional model test results show that the cross-section resistivity obtained by inversion with lateral constraints has better continuity and smoother profile.The inversion with lateral constrains is superior to the interpretation of the fine stratification and quantitative interpretation of wide filed apparent resistivity section.In the survey inversion,measured data can be prepossessed and smoothed first to calculate the wide filed apparent resistivity,which can be used to the initial m

关 键 词：广域电磁法 视电阻率 OCCAM反演 横向约束 煤层富水区 

分 类 号：P631[天文地球—地质矿产勘探]