V8方法介绍

EM-tech.ofSystem2000.netFoundation电磁法勘探（system2000.net）基础TechnicalsupportDep.PhoenixgeophysicsLtd.China=EinChinese•E:electricity&telluric(geoelectricE&D)•H:Magnetic(H&B)•EverythingstartfromMaxwellformula传统的电法仅指直流电法，在中国，目前电法包括直流电法和电磁法ldldUE*dUEtDJHtBEBD0EJHBEDJ传导电流dD/dt位移电流SeverMosts•MostParameters(ρ电阻率,η极化率,ε介电常数,c频率相关系数,τ时间常数,m充电率)•Mostdifficulties(Inversion?Models?)•MostInstabilities(1D-3D?Depth?topography)•MostmutationsMT/AMT/CSAMT/CSEM/EMAP/EH4(flatwave)DC(0-frequency)IP/SIP/TDIP/(IntroducePolarity)TDEM(timedomain)GPR(Hi-frequencywaveequation)EM(simple)•Mostfuturedevelopments(seismic?Gravity?)•MostapplicationsinMine/Water/Tunneletc.Tx&Rx•Tx:earth,TXU-30,T-200,AB,Loop•Rx:sensorLoopelectrodeSomekeywords•Apparent-(ρ电阻率,η极化率,ε介电常数,c频率相关系数,τ时间常数,m充电率)•TimeDomain&FrequencyDomain(FT)•Acquisition(earth----tbl,tss,trs)•Processing(tbl,tss,trs----app.ρηεcτm)•Data&Modelsinversion(app.-----“real”ρηεcτm)•InterpretationApp.DataEM-responseModelInversionformulationEM-responseModelgeologicModelsummaryV8DataFlow2003.TBL1987.TBL2.TFS4.TFS….V8RXU-3ERXU-TMRTXU-30APP.DataEMModelGeoModel*.TBL*.TRS*.TSS*.TSnEMFieldAcquisitionConfigureV8V8CFcardThisisOrg.DataTEMProCMTProInversionexplanationCorrectyourexplanationSurvey需求先验地质信息地球物理方法观测系统施工设计解释方案反演方案开挖反馈MainProblemsinSurvey•Precision分辨率•topography地形•Contact接地•Frequencystepping频率表•Noise干扰•Plan计划•Gain增益•Filter滤波器summaryCSAMT(MT/AMT)CS=ControllableSourceMT=megnetelluricsounding(400Hz~0.000001Hz)A=Audio(10000Hz~1000Hz)平面波，垂直入射，阻抗定义场源：太阳风引起地球电离层电性规律分布垂直入射：依据Snell定律阻抗定义：电场/磁场两个模式：TE/TMHxZyxEyTEModeExZxyHyTMModeCSAMT•CSAMT/EMAP/EH4•目前国内一般作标量的TM模式测量，效率高•横向分辨率较好，纵向较差，结合相位•避开近区和过渡带•避免过低频率•远区才满足MT/AMT假设，为频率测深•过渡区为综合效应•近区频率和测深无关，而和极距有关低频直线上升CSAMT6公里之外认为是远区超过60度角非平面波AB长度约2-3km由于是TM模式测线必须垂直断层走向TXU-30AB30°6km2~3kmCSAMTDesign•Depth:Skindepth=δH＝503(ρ/f)0.5mδH有效＝δH/20.5=356(ρ/f)0.5m•1°接收极距a=点距，它与横向分辩力相关；•2°发射长度AB＝1/4～1/3倍收发距长度，2～3km场强大，•信号强；粗线2ohm/Km,AB=2000m较好。•3°收发距，指收发测线之间的线距r•①尽量保证目标探测频段处在远区，r＞6～7倍最大目标探深。•②保证观测信号够强(发射电流要求)Example5015025035045055065075085095010501150125013501350145015501650175018501950501001502003005008001200150020002500大相岭隧道V5辅助剖面V5FK0+000～V5FK1+400段电阻率分布剖面图ρs(Ω·m)0100200300400比例尺：(m)高程(m)Fw6F7Fw7Fw8砂岩CSAMTStatic-Shift0510152025303540-10-50Static-shiftAfterspacefilterInversionsummarySIPpreview•SIP=CR=谱激电=复电阻率•WhatisIP：IPisnotEM•SIP:Freqdomain（FD）256Hz~0.01Hz比较项DC.IPSIPFreq.1or2WideFreq.BandFocus相对强度IP效应全过程Para.FD:Φ,Pa(PFE)TD:ηρ,c,τ,mEMeff.hardeasyApp.扫面定位SIPParameters•ρa视几何电阻率（按电极装置计算）=DCρa•ca视频率相关系数：ca越高，极化物质分布越单一均匀•τa视时间常数：由于勘探体积内极化物质的结构（如粒度、连通性、性状等）的差异，导致的SIP谱在频带上所占有的中心位置的不同，具体表现在视时间常数的变化上。•ma全域视充电率：基本和DCIP相同，ma越高，极化物质体积含量越大.SIPDesignSIPDesignSIPDesign9RXUscheduleSIPExamplessummaryTDEMPreviewTDEMLayoutTDEMDesign粗略确定极限探测深度的表达式：H极限(εz)≈40(Mρ)0.2H极限(Bz)≈28M1/3M=L2×I磁场分量Bz(t)要比感应电压εZ(t)衰减慢中心回线：H极限=0.55(L2Iρ1/η)0.2AB线源装置H极限≈0.48(AB.Irρ1/η)0.2η=0.2~0.5nV/m2V8文档上的经验公式D=(500*ρ*t)0.5TDEMcharacters•1Dor2Dor3D?•Howtoprocessformulation?•Whenthefieldstop?•MaximumDepth?•Highresistivity?•TimeWindow?据水平薄板上推导，采样时间t与薄层纵向电导S、埋深h及探测深度H之间的关系为：t=μ0S[(4H/3)-h]可见，对目标层的探测深度是时间的函数。例：目标层范围hmin～hmax、探测窗口Hmin～Hmax可算出tmin与tmaxTDEMSurveyTDEMExamplesummaryDCResistivity•DCresistivityisanimportantparameter•DCneednotV8•DChasmostcreditability•DCiseasy•DCcanhelpSIP/CSAMT/TDEM•YouneedHDCorVDCinformationtoimproveyouraccuracy.summaryFuture•Multi-results-2000-100001000200030004000500060007000303132333435363738394041424344454647484950303132A1333435363738394041424344454647484950A137317718000177200001772200017724000177260001772800017730000177320001773400017736000177380001774000017742000177440001774600017748000177500001775200017754000177560002000Depth(m)48121620(公里)Future•Multi-TomographyTech.Inversion+migration+other?050100150200250300350400-150-100-500Distance(km)Depth(km)0.511.522.533.544.55Future•Multi-Tech.•Multi-dimension•Multi-dataset•Multi-location:AirborneEM&CSEMThankyouWelcometodiscuss!!!Forserviceandconsultation