(1. 中南大學(xué) 有色金屬成礦預(yù)測教育部重點實驗室，長沙 410083；
2. 中南大學(xué) 地球科學(xué)與信息物理學(xué)院，長沙 410083；3. 北京礦產(chǎn)地質(zhì)研究院，北京 100012；
4. 中國石油長慶油田分公司 勘探開發(fā)研究院，西安 710018；
5. 低滲透油氣田勘探開發(fā)國家工程實驗室，西安 710018)
摘 要: 采用偽隨機信號源的廣域電磁法具有探測深度大、精度高、抗干擾能力強、效率高等優(yōu)點，正成為新的研究熱點。E-Ex廣域電磁法已經(jīng)實現(xiàn)了一維和二維正反演。但地球介質(zhì)是復(fù)雜的三維結(jié)構(gòu)，所采集到的數(shù)據(jù)需要進(jìn)行三維反演和解釋，為了進(jìn)一步提高廣域電磁法的數(shù)據(jù)處理和解釋精度，迫切需要進(jìn)行廣域電磁法三維正反演研究。采用積分方程法實現(xiàn)E-Ex廣域電磁法三維正演，首先對均勻半空間中存在低阻異常體進(jìn)行了數(shù)值模擬，發(fā)現(xiàn)廣域視電阻率不僅具有比CAGNIARD視電阻率更優(yōu)的分辨能力，且廣域視電阻率的場源陰影效應(yīng)相對CAGNIARD視電阻率有所減弱；然后對均勻半空間中存在高阻異常體進(jìn)行了數(shù)值模擬，結(jié)果表明CAGNIARD視電阻率對高阻體響應(yīng)不明顯，而廣域視電阻率有良好反映。研究表明，無論是高阻還是低阻異常體，廣域視電阻率的分辨能力都優(yōu)于CAGNIARD視電阻率。
關(guān)鍵字: 廣域電磁法；廣域視電阻率；積分方程法；數(shù)值模擬
（1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education,
Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
3. Beijing Institute of Geology for Mineral Resources, Beijing 100012, China;
4. Research Institute of Exploration and Development, PetroChina Changqing Oilfield Company,
Xi’an, 710018, China;
5. National Engineering Laboratory for Exploration & Development of Low-Permeability Oil＆Gas Fields,
Xi’an 710018, China）
Abstract:In the study of E-Ex wide field electromagnetic method, one-dimensional (1-D) forward modeling and inversion has been achieved, there are only a few number of publications related to the three-dimensional (3-D) forward modeling and inversion study. In the field work, the geological situation is complex, and the data needs 3-D inversion and interpretation, so 3-D forward modeling, inverse and interpretation become the bottleneck of wide field electromagnetic method. There is an urgent need for 3-D modeling of wide field electromagnetic method. Integral equation method was applied to achieve E-Ex wide field electromagnetic method 3-D modeling. Firstly a single low resistivity anomalous target body within homogeneous half-space was simulated, and it was found that not only the wide field apparent resistivity has better resolution capability than CAGNIARD apparent resistivity, but also the effect of the source and non-plane wave effect was weakened for wide field apparent resistivity. Then, a single high resistivity anomalous target body within homogeneous half-space was simulated, and it was found that, for the high resistivity body response, the CAGNIARD apparent resistivity is hard to distinct, but the wide field apparent resistivity has great resolution capability. The analysis shows that no matter the anomalous has high resistivity or low resistivity, the resolution of wide field apparent resistivity is better than that of the CAGNIARD apparent resistivity.
Key words: wide field electromagnetic method; wide field apparent resistivity; integral equation method; numerical simulation
