【摘要】：本論文以海洋可控源電磁法(Marine Controlled-source Electromagnetic Method,MCSEM)中的經(jīng)典一維層狀地電模型為基礎,深入討論了電偶極子場各分量的正演響應特征,研究了在不同發(fā)射-接收裝置方位、不同場分量和不同頻點下的正演模擬數(shù)據(jù)對理論模型反演的分辨率影響,最后仿真模擬出了實際海水層和海底地層電阻率變化情況下的反演特征。在電磁場的正演計算中,使用TE、TM模式分解的方法,引入謝昆諾夫勢分別對不同方位電偶極子產(chǎn)生的電磁場進行了計算;綜合分析場分量得到:無論何種發(fā)射-接收方位下,五層含油氣層模型與三層模型振幅對比時,Ey、Ez和Bx分量的異常都比Ex、By和Bz的異常大;分析了空氣波影響因素,海水的深度對空氣波的壓制起到了很大的作用,相同的海水深度下海底電阻率不同時,空氣波開始影響的臨界收發(fā)距不變,而海底地層電阻率越高,空氣波占優(yōu)的臨界收發(fā)距越大;研究了覆蓋層厚度的影響,對于1 Hz的電磁波,覆蓋層大于3000m時海底高阻產(chǎn)生的異常開始消失;驗證了振幅-收發(fā)距(Magnitude Value Offset,MVO)曲線的T等值現(xiàn)象,在固定厚度和電阻率的乘積不變時,MVO曲線幾乎重合;最后正演計算了淺層薄層高阻屏蔽的情況發(fā)現(xiàn):加大收發(fā)距可以得到深層的異常體信息。在反演的計算中,引入了高斯-牛頓反演法和奧克姆反演法進行對比,然后利用奧克姆反演法分別分析各發(fā)射方位、各分量和不同頻點組合的一維反演效果發(fā)現(xiàn):HED-Y模式下的數(shù)據(jù)反演效果最好;使用Ey和Bx分量進行反演效果最好,z分量的電磁場的反演效果較差,聯(lián)合反演Ey、Ez和Bx的數(shù)據(jù)對反演效果沒有更好的提升,反演經(jīng)典五層模型時,0.1 Hz和1 Hz的頻點組合進行反演就達到了良好的效果,繼續(xù)增加頻點來反演也沒有提高反演效果。在最后仿真模擬海洋地層的反演時發(fā)現(xiàn):海水電阻率分層對反演效果影響很大,測量海水電阻率分層是必要的,海底地層電阻率小尺度變化時,反演結(jié)果能反映出海底地層電阻率變化的趨勢。
[Abstract]:Based on the classical one-dimensional layered geoelectric model of ocean controllable source electromagnetic method (Marine Controlled-source Electromagnetic Method,MCSEM), the forward response characteristics of each component of electric dipole field are discussed in depth, and the azimuth of different transmitter-receiver devices are studied. The effect of forward modeling data at different field components and different frequencies on the resolution of the theoretical model inversion is obtained. Finally, the inversion characteristics of the actual seawater layer and submarine strata are simulated. In the forward calculation of electromagnetic field, using the method of TE,TM mode decomposition, the electromagnetic field generated by electric dipole with different azimuth is calculated by introducing Shikhunov potential. It is concluded by comprehensive analysis of field components that the anomalies of Ey,Ez and Bx components are larger than those of Ex,By and Bz when the amplitudes of the five-layer oil-bearing gas reservoir model and the three-layer model are compared with those of the three-layer model under any emission-receiver azimuth; The influence factors of air wave are analyzed. The depth of sea water plays a great role in the suppression of air wave. The larger the critical transceiver distance of air wave is; The influence of overburden thickness is studied. For the electromagnetic wave of 1 Hz, the anomaly caused by high resistivity of seabed begins to disappear when the overburden is larger than 3000m. The T-equivalent phenomenon of amplitude-transceiver distance (Magnitude Value Offset,MVO) curve is verified. When the product of constant thickness and resistivity is invariant, the MVO curve almost coincides. Finally, the forward calculation shows that the deep abnormal body information can be obtained by increasing the transceiver distance. In the calculation of inversion, Gao Si Newton inversion method and Oakham inversion method are introduced to carry out the comparison, and then each launch azimuth is analyzed by using the Oakham inversion method. The results of one-dimensional inversion of different components and different frequency points show that the data inversion effect of HED-Y model is the best; The inversion effect of Ey and Bx components is the best, the electromagnetic field inversion effect of z component is poor, and the inversion effect of Ey,Ez and Bx data is not improved better. The combination of 0. 1 Hz and 1 Hz has achieved a good result, and the inversion effect has not been improved by increasing the frequency points. When simulating the inversion of marine strata, it is found that the resistivity stratification of sea water has a great influence on the inversion effect, it is necessary to measure the stratification of resistivity of sea water, and when the resistivity of seabed strata changes on a small scale, The inversion results can reflect the trend of the resistivity variation of the submarine strata.
【學位授予單位】：東華理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P631.325

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本文編號：2303291