发射电流波形对瞬变电磁测量结果影响及校正的研究
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摘要
瞬变电磁法是一种先进的地球物理勘探方法,已成功地应用于多个领域的深部测量,但这一技术由于发射、接收及数据处理各部分存在的问题使其在浅部测量中没有得到成功的应用。国内外学者经过多年研究,认为提高瞬变电磁法浅层分辨能力需要解决三个问题:减小发射电流关断时间;缩短测量回路的过渡过程;减小发射电流波形对测量结果的影响。
本论文主要针对发射电流斜阶跃关断的斜阶跃场源,分析在斜阶跃场源激发下不同地电模型在三种常用测量装置下的瞬变响应,并根据这些瞬变响应进一步分析发射电流波形对测量结果的影响以及浅层测量对发射系统的要求,研究无需关断效应校正的直接计算全程视电阻率的数值计算方法。论文主要做了以下工作:
①从瞬变电磁法原理出发,介绍了这种地球物理勘探方法的应用范围、常用测量装置及其异常特点、方法的优点以及目前还存在的问题。介绍并分析了目前就发射电流波形对测量结果的影响及校正方法的研究现状、“视电阻率”计算方法的研究现状,指出了它们的适用范围和需要改进之处。
②介绍了不同地电模型在三种测量装置下负阶跃响应的由来,根据这些响应推导了各种模型在斜阶跃场源激励下感应段和衰减段的负斜阶跃响应,并从负阶跃响应与负斜阶跃响应的关系和磁场与磁场变化率的关系两方面证明了推导的正确性。分析了发射电流波形平稳性、对称性对二次感应电压的影响;以中心回线装置为例,分析了发射电流波形后沿对二次感应电压的影响,结合发射电流前沿与周期讨论了二者对感应段和衰减段二次感应电压的影响。
③根据三种测量装置的负斜阶跃磁场和磁场变化率的解析表达式,分别讨论了感应段和衰减段的负斜阶跃磁场、感应电压与视电阻率的关系,给出了全程视电阻率的直接计算方法。最后用理论模型和实例计算证明了全程视电阻率直接算法的有效性。
Transient Electromagnetic Method is a kind of advanced geophysics prospect methods, and is successfully applied to various fields of the deep soundings. However, this technology fails in resolving the shallow target in the vertical direction because of imperfectness of the transmitter, receiver and data-processing. After many years of research, scholars at home and abroad point out that enhancing the ability of shallow identification of this method needs to solve three key issues: reducing the turn-off time of the transmmitter current; shortening the the transition process of the receiver loop; eliminating the effect of transmmitter current wave on the sounding results.
Transient response generated by ramp turn-off current is mainly studied in this paper. The transient response of several models under three commonly used measuring devices is analyzed. Based on these responses, the effect of transmitter current wave on sounding and the requirements of transmitter system for shallow measurement is further analyed. A numerical direct method of calculating the apparent resistivity without turn-off effect correction is studied. The main tasks of the thesis are presented as follows:
Beginning with the principle of Transient Electromagnetic Method, the application fields, commonly used measurements devices, typical characteristics, as well as the existing problem of this method is introduced. The research status of the effect of transmitter current wave on sounding, turn-off effect correction as well as apparent resistivity calculation methods are introduced and analyed. The scope of these methods and need for improvement is also pointed out.
The origin of responses generated by step turn-off transmitter current of several models with three commonly used measurements devices is introduced. Based on these responses, the responses generated by ramp turn-off transmitter current in induction stage and decay stage are derived. From two aspects—the limit and the special relationship between magnetic fields and time derivative of magnetic field,the correctness of the derivation is proved. The effect of stableness and symmetry of transmitter current wave on the second induction voltage is analyed. Taking central loop as an example, the effect of turn-off time on the induction voltage is analyed. The effect of forefront and cycle time of transmmitter current on induction voltage in induction stage and decay stage is discussed.
According to the magnetic field and time derivative of magnetic field of three commonly used measuring devices, the relationship among magnetic field, induced voltage and apparent resistivity is discussed. A calculation method for all-time apparent resistivity is proposed. Finally, the practicability of the all-time apparent resistivity direct calculation algorithm is proved with theoretical models and field data experiments.
本论文主要针对发射电流斜阶跃关断的斜阶跃场源,分析在斜阶跃场源激发下不同地电模型在三种常用测量装置下的瞬变响应,并根据这些瞬变响应进一步分析发射电流波形对测量结果的影响以及浅层测量对发射系统的要求,研究无需关断效应校正的直接计算全程视电阻率的数值计算方法。论文主要做了以下工作:
①从瞬变电磁法原理出发,介绍了这种地球物理勘探方法的应用范围、常用测量装置及其异常特点、方法的优点以及目前还存在的问题。介绍并分析了目前就发射电流波形对测量结果的影响及校正方法的研究现状、“视电阻率”计算方法的研究现状,指出了它们的适用范围和需要改进之处。
②介绍了不同地电模型在三种测量装置下负阶跃响应的由来,根据这些响应推导了各种模型在斜阶跃场源激励下感应段和衰减段的负斜阶跃响应,并从负阶跃响应与负斜阶跃响应的关系和磁场与磁场变化率的关系两方面证明了推导的正确性。分析了发射电流波形平稳性、对称性对二次感应电压的影响;以中心回线装置为例,分析了发射电流波形后沿对二次感应电压的影响,结合发射电流前沿与周期讨论了二者对感应段和衰减段二次感应电压的影响。
③根据三种测量装置的负斜阶跃磁场和磁场变化率的解析表达式,分别讨论了感应段和衰减段的负斜阶跃磁场、感应电压与视电阻率的关系,给出了全程视电阻率的直接计算方法。最后用理论模型和实例计算证明了全程视电阻率直接算法的有效性。
Transient Electromagnetic Method is a kind of advanced geophysics prospect methods, and is successfully applied to various fields of the deep soundings. However, this technology fails in resolving the shallow target in the vertical direction because of imperfectness of the transmitter, receiver and data-processing. After many years of research, scholars at home and abroad point out that enhancing the ability of shallow identification of this method needs to solve three key issues: reducing the turn-off time of the transmmitter current; shortening the the transition process of the receiver loop; eliminating the effect of transmmitter current wave on the sounding results.
Transient response generated by ramp turn-off current is mainly studied in this paper. The transient response of several models under three commonly used measuring devices is analyzed. Based on these responses, the effect of transmitter current wave on sounding and the requirements of transmitter system for shallow measurement is further analyed. A numerical direct method of calculating the apparent resistivity without turn-off effect correction is studied. The main tasks of the thesis are presented as follows:
Beginning with the principle of Transient Electromagnetic Method, the application fields, commonly used measurements devices, typical characteristics, as well as the existing problem of this method is introduced. The research status of the effect of transmitter current wave on sounding, turn-off effect correction as well as apparent resistivity calculation methods are introduced and analyed. The scope of these methods and need for improvement is also pointed out.
The origin of responses generated by step turn-off transmitter current of several models with three commonly used measurements devices is introduced. Based on these responses, the responses generated by ramp turn-off transmitter current in induction stage and decay stage are derived. From two aspects—the limit and the special relationship between magnetic fields and time derivative of magnetic field,the correctness of the derivation is proved. The effect of stableness and symmetry of transmitter current wave on the second induction voltage is analyed. Taking central loop as an example, the effect of turn-off time on the induction voltage is analyed. The effect of forefront and cycle time of transmmitter current on induction voltage in induction stage and decay stage is discussed.
According to the magnetic field and time derivative of magnetic field of three commonly used measuring devices, the relationship among magnetic field, induced voltage and apparent resistivity is discussed. A calculation method for all-time apparent resistivity is proposed. Finally, the practicability of the all-time apparent resistivity direct calculation algorithm is proved with theoretical models and field data experiments.
引文
[1] McNeill, J.D, Bosnar, M.C.. Comparison of geoelectric section obtained acrossed a fault with EM39 borehole induction logger and TEM 47 time-Domain system in central loop sounding mode TN-23[J]. Geophysical Journal International , 1988, Vol.142, No.3, pp.: 898–914
[2]嵇艳鞠.浅层高分辨率全程瞬变电磁系统中全程二次场提取技术研究[D].吉林大学博士论文, 2004.
[3]蒋邦远.瞬变电磁法勘探[M].北京:地质出版社, 1998.
[4]牛之琏.时间域电磁法原理[M].长沙:中南工业大学出版社, 1992.
[5]王兴泰.工程与环境物探新方法新技术[M].地质出版社,2003.
[6]郭纯,刘白宙,白登海.地下全空间瞬变电磁技术在煤矿巷道掘进头的连续跟踪超前探测[J].地震地质, 2006.9, 28(3): 456-462
[7] Stefi Krivochieva, Michel Chouteau. Whole-space modeling of a layered earth in time-domain electromagnetic measurements[J]. Journal of Applied Geophysics, 2002, No. 50, pp.: 375– 391.
[8] Niels B?ie Christensen. A generic 1-D imaging method for transient electromagnetic data[J]. Geophysics, April 2002, Vol. 67, No. 2, pp.: 438–447.
[9] Buselli, G., Barber, C., Zerilli, A.. The mapping of groundwater contamination with TEM and DC methods[J]. Explor. Geophys., 1988, Vol. 19, pp.: 240–248.
[10] Christensen, N. B., and S?rensen, K. I.. Surface and borehole electric and electromagnetic methods for hydrogeophysical investigations: Eur. J. Environ[J]. Eng. Geophys., 1998, Vol. 3, No. 1, pp.: 75–90.
[11]钟士模,郑大钟.过渡过程分析[M].北京:清华大学出版社, 1986.
[12] Fitterman D. V., Anderson W L. Effect of transmitter turn-off time on transient soundings[J]. Geoexploration, 1987, No.24, pp.: 131-146.
[13] Levy, G. M.. Correction of measured transient electromagnetic responses for finite transmitter turn-off duration[J]. 1984, Technical note TN-16, Geonics Limited.
[14]白登海, Maxwell A M.瞬变电磁法中两种关断电流对响应函数的影响及其应对策略[J].地震地质, 2001, 23(2): 245-251.
[15] A. P. Raiche. The Effect of Ramp Function Turn-off on the TEM Response of Layered Earth[J]. Exploration Geophysics, 1984, No. 15, pp.: 37-41.
[16] Spies B. R., Eggers D. E.. The use and misuse of apparent resistivity in electromagnetic methods[J]. Geophysics, 1986, No. 51, pp.: 1462-1471.
[17] Raiche A P, Spies B. R…Coincident loop transient electromagnetic master curves forinterpretation of two-layer earths[J]. Geophysics, 1981, Vol. 46, No. 1, pp.: 53-64
[18]白登海, Maxwell A M,卢健,等.时间域瞬变电磁法中心方式全程视电阻率的数值计算[J].地球物理学报, 2003, 46(7): 697-704.
[19] (美)米萨克N.纳比吉安.勘查地球物理:电磁法第一卷理论[M].赵经祥,王艳君译.北京:地质出版社, 1992.
[20] Ward S. H., Hohmann G W. Electromagnetic theory for geophysical applications[M]. In: Nabighian, M N, Ed. Electromagnetic methods in applied geophysics-theory. Soc Explor Geophys, 1988, No. 1, pp.: 131-311.
[21] (美)G. A..科恩,T. M..科恩.数学手册[M].周明强译.北京:工人出版社, 1987.
[22]黄忠霖,黄京. Matlab符号运算及其应用[M].北京:国防工业出版社,2004.
[23] Tatsuoki Nagaishi, Hajime Ota and Eiichi Arai, et al. High Tc SQUID System for Transient Electromagnetic Geophysical Exploration[J]. IEEE Transaction on Applied Superconductor, June 2005, Vol. 15, No. 2, pp.: 749-752.
[24] G. Panaitov, M. Bick, Y. Zhang, and H.-J. Krause. Peculiarities of SQUID magnetometer application in TEM[J]. Geophysics, June 2002, Vol. 67, No. 3, pp.: 739–745.
[25] Richard S. Smith, A. Peter Annan. Using an induction coil sensor to indirectly measure the B-field response in the bandwidth of the transient electromagnetic method[J]. Geophysics, September 2000, Vol. 65, No. 5, pp.: 1489–1494.
[26]陈明生,田小波.电偶源瞬变电磁测深研究(五)—实测感应电压转换成垂直磁场[J].煤田地质与勘探, 1999, 27(5): 63-65.
[27]嵇艳鞠,林君,于生宝,等. ATTEM系统中电流关断期间瞬变电磁场响应求解的研究[J].地球物理学报, 2006, 49(6): 1884-1890.
[28]罗国平,魏凤英.瞬变电磁法磁场及其视电阻率研究[J].中国煤田地质, 2000, 12(2): 60-62.
[29]张秉仁,林君.TEM-II型发射机换相过程及无功功率释放回路的研究[J].国外电子测量技术, 2002(3): 17-19.
[30]付志红,周雒维,苏向丰.瞬变电磁发射机中的电流脉冲整形技术[J].电力电子技术, 2006.2, 40(1): 58-60.
[31]付志红,周雒维,苏向丰,杜雄.两种新颖的准谐振型电流陡脉冲整形电路[J].中国电机工程学报, 2006.3, 26(5): 70-75.
[32] Auken E, Nebel L, S?rensen KI, et al. EMMA—A geophysical training and education tool for electromagnetic modeling and analysis[J]. Journal of Environmental & Engineering Geophysics, 2002, (7): 57-68.
[2]嵇艳鞠.浅层高分辨率全程瞬变电磁系统中全程二次场提取技术研究[D].吉林大学博士论文, 2004.
[3]蒋邦远.瞬变电磁法勘探[M].北京:地质出版社, 1998.
[4]牛之琏.时间域电磁法原理[M].长沙:中南工业大学出版社, 1992.
[5]王兴泰.工程与环境物探新方法新技术[M].地质出版社,2003.
[6]郭纯,刘白宙,白登海.地下全空间瞬变电磁技术在煤矿巷道掘进头的连续跟踪超前探测[J].地震地质, 2006.9, 28(3): 456-462
[7] Stefi Krivochieva, Michel Chouteau. Whole-space modeling of a layered earth in time-domain electromagnetic measurements[J]. Journal of Applied Geophysics, 2002, No. 50, pp.: 375– 391.
[8] Niels B?ie Christensen. A generic 1-D imaging method for transient electromagnetic data[J]. Geophysics, April 2002, Vol. 67, No. 2, pp.: 438–447.
[9] Buselli, G., Barber, C., Zerilli, A.. The mapping of groundwater contamination with TEM and DC methods[J]. Explor. Geophys., 1988, Vol. 19, pp.: 240–248.
[10] Christensen, N. B., and S?rensen, K. I.. Surface and borehole electric and electromagnetic methods for hydrogeophysical investigations: Eur. J. Environ[J]. Eng. Geophys., 1998, Vol. 3, No. 1, pp.: 75–90.
[11]钟士模,郑大钟.过渡过程分析[M].北京:清华大学出版社, 1986.
[12] Fitterman D. V., Anderson W L. Effect of transmitter turn-off time on transient soundings[J]. Geoexploration, 1987, No.24, pp.: 131-146.
[13] Levy, G. M.. Correction of measured transient electromagnetic responses for finite transmitter turn-off duration[J]. 1984, Technical note TN-16, Geonics Limited.
[14]白登海, Maxwell A M.瞬变电磁法中两种关断电流对响应函数的影响及其应对策略[J].地震地质, 2001, 23(2): 245-251.
[15] A. P. Raiche. The Effect of Ramp Function Turn-off on the TEM Response of Layered Earth[J]. Exploration Geophysics, 1984, No. 15, pp.: 37-41.
[16] Spies B. R., Eggers D. E.. The use and misuse of apparent resistivity in electromagnetic methods[J]. Geophysics, 1986, No. 51, pp.: 1462-1471.
[17] Raiche A P, Spies B. R…Coincident loop transient electromagnetic master curves forinterpretation of two-layer earths[J]. Geophysics, 1981, Vol. 46, No. 1, pp.: 53-64
[18]白登海, Maxwell A M,卢健,等.时间域瞬变电磁法中心方式全程视电阻率的数值计算[J].地球物理学报, 2003, 46(7): 697-704.
[19] (美)米萨克N.纳比吉安.勘查地球物理:电磁法第一卷理论[M].赵经祥,王艳君译.北京:地质出版社, 1992.
[20] Ward S. H., Hohmann G W. Electromagnetic theory for geophysical applications[M]. In: Nabighian, M N, Ed. Electromagnetic methods in applied geophysics-theory. Soc Explor Geophys, 1988, No. 1, pp.: 131-311.
[21] (美)G. A..科恩,T. M..科恩.数学手册[M].周明强译.北京:工人出版社, 1987.
[22]黄忠霖,黄京. Matlab符号运算及其应用[M].北京:国防工业出版社,2004.
[23] Tatsuoki Nagaishi, Hajime Ota and Eiichi Arai, et al. High Tc SQUID System for Transient Electromagnetic Geophysical Exploration[J]. IEEE Transaction on Applied Superconductor, June 2005, Vol. 15, No. 2, pp.: 749-752.
[24] G. Panaitov, M. Bick, Y. Zhang, and H.-J. Krause. Peculiarities of SQUID magnetometer application in TEM[J]. Geophysics, June 2002, Vol. 67, No. 3, pp.: 739–745.
[25] Richard S. Smith, A. Peter Annan. Using an induction coil sensor to indirectly measure the B-field response in the bandwidth of the transient electromagnetic method[J]. Geophysics, September 2000, Vol. 65, No. 5, pp.: 1489–1494.
[26]陈明生,田小波.电偶源瞬变电磁测深研究(五)—实测感应电压转换成垂直磁场[J].煤田地质与勘探, 1999, 27(5): 63-65.
[27]嵇艳鞠,林君,于生宝,等. ATTEM系统中电流关断期间瞬变电磁场响应求解的研究[J].地球物理学报, 2006, 49(6): 1884-1890.
[28]罗国平,魏凤英.瞬变电磁法磁场及其视电阻率研究[J].中国煤田地质, 2000, 12(2): 60-62.
[29]张秉仁,林君.TEM-II型发射机换相过程及无功功率释放回路的研究[J].国外电子测量技术, 2002(3): 17-19.
[30]付志红,周雒维,苏向丰.瞬变电磁发射机中的电流脉冲整形技术[J].电力电子技术, 2006.2, 40(1): 58-60.
[31]付志红,周雒维,苏向丰,杜雄.两种新颖的准谐振型电流陡脉冲整形电路[J].中国电机工程学报, 2006.3, 26(5): 70-75.
[32] Auken E, Nebel L, S?rensen KI, et al. EMMA—A geophysical training and education tool for electromagnetic modeling and analysis[J]. Journal of Environmental & Engineering Geophysics, 2002, (7): 57-68.