發(fā)布時間：2018-04-26 16:31

  本文選題：電性各向異性 + 大地電磁��； 參考：《中國地質大學》2016年博士論文

【摘要】：電性各向異性,即介質電導率隨方位變化的現象,已被證實廣泛存在于地球地殼和上地幔中,對觀測電磁場有不可忽視的影響。大地電磁方法通過測量地球表面天然電磁場的變化量,能探測地球深部電性結構,可用于研究地下介質電性各向異性特征。本文首先使用基于非結構網格的自適應有限元法來求解對角各向異性情況下大地電磁正演控制方程,非結構三角網格的應用既有利于起伏地形和復雜地質構造的建模,又便于模擬包含多種尺寸結構的地電模型；網格的自動細化則可避免人為網格劃分導致的計算誤差并提高計算效率。對經典四層層狀模型和二維各向異性塊體模型進行了正演模擬試算,并分別與一維準解析解、二維有限差分數值解結果進行對比,驗證了正演算法的準確性。接著構建了包含模型結構懲罰項和各向異性懲罰項的反演目標函數,反演算法則采取了經典模型空間Occam策略,使得模型的搜索過程非常穩(wěn)定,能在較少的迭代次數內獲得合理的反演結果。反演試驗對象為海底起伏各向異性復雜模型,反演結果準確反映了各向異性體的存在,并還原了真實模型的主要電性特征。同時探討了相關反演參數對反演的影響,發(fā)現反演并不依賴初始模型和初始正則化參數的選取,但結構懲罰項和各向異性懲罰項顯著影響了反演過程和結果。探討了羌塘地塊的地質構造概況和主要地質和地球物理特征,分析了羌塘地塊的天然氣水合物發(fā)育和儲存條件。對天然氣水合物的音頻大地電磁各向異性響應特征進行了詳細討論,證明了音頻大地電磁方法能準確顯示天然氣水合物各向異性體空間位置和分布情況,并對天然氣水合物的飽和度變化以及多個賦存巖層的存在都有所反映。結合相關測井資料和已探明的天然氣水合物儲層相關物性參數,對青藏高原北部祁連山木里地區(qū)的音頻大地電磁實測資料進行了帶先驗信息約束的各向異性反演解釋。反演結果反映了天然氣水合物儲層的各向異性特征,并說明了天然氣水合物儲存的有利條件。最后對羌塘地塊三條南北走向的大地電磁測線進行了各向異性處理解釋。反演結果表明羌塘地塊地下介質電性分層明顯,上地殼存在延展廣的高阻層,表明印度巖石圈的俯沖前緣應該并沒有越過班公湖-怒江縫合帶。中下地殼普遍發(fā)育高導層,其中南、北羌塘地塊下方均發(fā)育了位置相對固定的高導體,彼此被羌中隆起區(qū)的相對高阻區(qū)域分隔。南、北羌塘地塊下方高導體沿東西構造走向電阻率相較于沿南北測線走向電阻率小很多。中下地殼高導體與部分熔融有關,高導體區(qū)域的各向異性特征佐證了物質向東運移的可能性。
[Abstract]:The phenomenon of electrical anisotropy, that is, the variation of dielectric conductivity with azimuth, has been proved to exist widely in the earth's crust and upper mantle, which can not be ignored in the observation of electromagnetic fields. The magnetotelluric method can be used to study the electrical anisotropy of underground media by measuring the variation of natural electromagnetic field on the surface of the earth. In this paper, an adaptive finite element method based on unstructured meshes is first used to solve the magnetotelluric forward control equations under diagonal anisotropy. The application of unstructured triangular meshes is beneficial to the modeling of undulating terrain and complex geological structures. It is also convenient to simulate the geoelectric model with various sizes, and the automatic mesh refinement can avoid the calculation error caused by artificial meshing and improve the computational efficiency. The forward simulation of the classical four layer model and the two dimensional anisotropic block model is carried out, and the results are compared with the results of one dimensional quasi-analytical solution and two dimensional finite difference numerical solution, respectively. The accuracy of the forward algorithm is verified. Then the inversion objective function including structural penalty term and anisotropic penalty term is constructed, and the classical model space Occam strategy is adopted in the inversion algorithm, which makes the searching process of the model very stable. Reasonable inversion results can be obtained in fewer iterations. The object of inversion experiment is the complex model of seafloor undulating anisotropy. The inversion results accurately reflect the existence of anisotropic bodies and restore the main electrical characteristics of real models. It is found that the inversion does not depend on the selection of initial model and initial regularization parameters, but the structural penalty term and anisotropic penalty term significantly affect the inversion process and results. The geological structure and main geological and geophysical characteristics of Qiangtang block are discussed, and the development and storage conditions of natural gas hydrate in Qiangtang block are analyzed. The characteristics of the acoustic magnetotelluric anisotropy response of gas hydrate are discussed in detail. It is proved that the audio magnetotelluric method can accurately display the spatial position and distribution of the anisotropic body of natural gas hydrate. It also reflects the change of gas hydrate saturation and the existence of several rock formations. Based on the correlation logging data and the proven physical parameters of gas hydrate reservoirs, the anisotropic inversion interpretation with prior information constraints on the audio frequency magnetotelluric field data in Muli area of Qilian Mountains in the northern Qinghai-Tibet Plateau is carried out. The inversion results reflect the anisotropic characteristics of gas hydrate reservoirs and illustrate the favorable conditions for gas hydrate storage. Finally, the anisotropic interpretation of three magnetotelluric lines with north and south strike in Qiangtang block is given. The inversion results show that the electrical stratification of the underground media in the Qiangtang block is obvious, and the upper crust has a high resistivity layer with wide extension, indicating that the subduction front of the Indian lithosphere should not have crossed the Bangonghu-Nujiang suture zone. The upper and lower crust generally developed high conductance layer, in which the south and north Qiangtang blocks developed relatively fixed high conductors, which were separated by the relatively high resistivity area of the middle and middle Qiang uplift area. The resistivity of the high conductors along the east-west strike of the Qiangtang block in the south and north is much smaller than that along the north-south line of the Qiangtang block. The high conductors in the middle and lower crust are related to partial melting, and the anisotropic characteristics of the high conductor regions confirm the possibility of eastward migration of matter.
【學位授予單位】：中國地質大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：P631.3

【相似文獻】

相關期刊論文 前7條

1 郝守玲,趙群;裂縫介質對P波方位各向異性特征的影響——物理模型研究[J];勘探地球物理進展;2004年03期

2 劉殿明;巖石聲學各向異性特征研究[J];中國煤田地質;1992年03期

3 李國權;閆長斌;齊菊梅;秦建甫;;南水北調西線工程板巖強度的各向異性特征[J];工程地質學報;2011年06期

4 史艷輝;李發(fā)榮;;確定儲層各向異性特征的方法[J];國外油田工程;2007年09期

5 林為人;高橋學;;稻田花崗巖單軸拉伸強度和變形各向異性特征(英文)[J];巖石力學與工程學報;2008年12期

6 高新勃;強小科;趙輝;陳艇;;風成紅黏土序列磁化率各向異性特征對區(qū)域應力變化的響應[J];地球科學進展;2014年03期

7 ;[J];;年期

相關會議論文 前6條

1 詹林森;沈金松;王鵬飛;馬超;連福明;;裂隙參數的各向異性特征分析[A];中國地球物理學會第二十七屆年會論文集[C];2011年

2 葉為民;楊林德;黃雨;唐益群;董炳炎;;上海軟土微觀空隙各向異性特征及其成因分析[A];第七屆全國工程地質大會論文集[C];2004年

3 姜枚;薛光琦;董英君;A.Hirn;;青藏高原地震剪切波各向異性特征及解釋[A];1999年中國地球物理學會年刊——中國地球物理學會第十五屆年會論文集[C];1999年

4 郝守玲;趙群;;利用物理模型模擬影響P波方位各向異性特征的因素[A];油氣地球物理實用新技術——中國石化石油勘探開發(fā)研究院南京石油物探研究所2004年學術交流會論文集[C];2004年

5 郝守玲;趙群;;利用物理模型模擬影響P波方位各向異性特征的因素[A];中國地球物理第二十一屆年會論文集[C];2005年

6 陳大元;修濟剛;安金珍;陳峰;;巖石不同變形階段電阻率變化各向異性特征研究[A];1996年中國地球物理學會第十二屆學術年會論文集[C];1996年

相關博士學位論文 前1條

1 黃一凡;羌塘地塊地殼電性各向異性特征研究[D];中國地質大學;2016年

，

本文編號：1806791