發(fā)布時(shí)間：2018-06-23 15:08

  本文選題：瞬變電磁法 + 全程視電阻率　； 參考：《東華理工大學(xué)》2015年碩士論文

【摘要】：隨著礦產(chǎn)開發(fā)力度的加大,淺部礦產(chǎn)資源,已大幅減少。開展第二深度空間(500m~2000 m)礦產(chǎn)資源的精細(xì)勘探已成為一項(xiàng)緊迫和長(zhǎng)期的任務(wù)。我國(guó)找礦的主體也正在向深部礦、隱伏礦發(fā)展,地球物理勘探成為隱伏礦產(chǎn)資源調(diào)查越來(lái)越重要的手段,開展大深度、高精度地球物理探測(cè)研究是當(dāng)前物探所面臨的主要科學(xué)問題。近年來(lái),瞬變電磁法在礦產(chǎn)勘探領(lǐng)域得到廣泛應(yīng)用。但回線源瞬變電磁法僅對(duì)低阻異常敏感,對(duì)高阻異常的探測(cè)能力較弱,且勘探深度有限。LOTEM雖然可以觀測(cè)磁場(chǎng)垂直分量和電場(chǎng)水平分量,對(duì)低阻和高阻異常都有較好的反映,但因收發(fā)距離較大,信噪比降低,不利于高效、精細(xì)探測(cè)。根據(jù)瞬變電磁場(chǎng)基本理論,當(dāng)選擇適當(dāng)?shù)陌l(fā)射波形激發(fā)電磁場(chǎng)時(shí),接地導(dǎo)線源可以實(shí)現(xiàn)近源觀測(cè)。在此基礎(chǔ)上提出的電性源短偏移距瞬變電磁法(SOTEM)是一種探測(cè)深度大、精度高、施工高效的瞬變電磁工作形式。視電阻率作為電磁法數(shù)據(jù)解釋的主要甚至唯一參數(shù),在SOTEM系統(tǒng)中具有舉足輕重的作用。由于SOTEM觀測(cè)全場(chǎng)區(qū)信號(hào),因此精確的全程視電阻率計(jì)算方法對(duì)于充分展現(xiàn)SOTEM的探測(cè)能力是十分重要的。本文從麥克斯韋方程出發(fā),借助輔助位函數(shù),求取電性源在均勻大地表面及層狀大地表面產(chǎn)生的響應(yīng)。將長(zhǎng)接地導(dǎo)線源響應(yīng)分成線源項(xiàng)和接地項(xiàng)分別計(jì)算,大大節(jié)省了計(jì)算時(shí)間。其次,通過擴(kuò)散場(chǎng)平面?zhèn)鞑シ植紙D、單點(diǎn)衰減曲線對(duì)電性源激發(fā)的二次電磁場(chǎng)各分量進(jìn)行研究,為實(shí)際工作選取合適的觀測(cè)分量和觀測(cè)范圍提供了理論支持。運(yùn)用分段級(jí)數(shù)逼近法、二分法、平移算法分別對(duì)磁場(chǎng)垂直分量及其隨時(shí)間的導(dǎo)數(shù)進(jìn)行了全程視電阻率求取,并對(duì)三種全程視電阻率提取方法的優(yōu)劣以及基于磁場(chǎng)強(qiáng)度和感應(yīng)電動(dòng)勢(shì)計(jì)算的全程視電阻率的對(duì)薄層的分辨能力進(jìn)行了分析。全程視電阻率曲線特征,與早、晚期視電阻率相比,對(duì)電性目標(biāo)體反映更準(zhǔn)確,能較準(zhǔn)確地反映地電斷面的信息。另外,全程視電阻率僅與地層的電性結(jié)構(gòu)有關(guān),與收發(fā)距、方位角無(wú)關(guān),便于野外進(jìn)行接地源瞬變電磁近源測(cè)量。最后將本文提出的全程視電阻率計(jì)算方法應(yīng)用于某金屬礦探測(cè),取得了較好的地質(zhì)成果。通過理論分析和實(shí)例應(yīng)用,證明本文提出的電性源瞬變電磁全程視電阻率計(jì)算方法的有效性。全程視電阻率消除了淺部的假高值現(xiàn)象,明顯優(yōu)于傳統(tǒng)晚期視電阻率,相對(duì)真實(shí)地反映出地層的電性變化規(guī)律。
[Abstract]:With the intensification of mineral exploitation, shallow mineral resources have been greatly reduced. It has become an urgent and long-term task to carry out fine exploration of mineral resources in the second depth space (500m~2000 m). The main body of prospecting in our country is also developing towards deep ore and hidden ore. Geophysical exploration has become an increasingly important means for the investigation of hidden mineral resources and has been carried out in a large depth. High-precision geophysical exploration is the main scientific problem in geophysical exploration at present. In recent years, transient electromagnetic method has been widely used in the field of mineral exploration. However, the transient electromagnetic method of loop source is only sensitive to low resistivity anomalies and weak in detecting high resistivity anomalies. Although the exploration depth is limited, the vertical and horizontal components of magnetic field can be observed, and both low resistivity and high resistivity anomalies can be well reflected. However, because of the large transceiver distance and the lower signal-to-noise ratio, it is unfavorable to high efficiency and fine detection. According to the basic theory of transient electromagnetic field, the near-source observation can be realized by grounding wire source when proper transmitting waveform is selected to excite the electromagnetic field. On this basis, the short offset transient electromagnetic method (SOTEM) for electrical source is proposed, which is a kind of transient electromagnetic working form with high detection depth, high precision and high construction efficiency. As the main or even the only parameter in the interpretation of electromagnetic data, apparent resistivity plays an important role in SOTEM system. Due to the whole field signal observed by SOTEM, it is very important to calculate the whole apparent resistivity of SOTEM accurately in order to fully demonstrate the detection ability of SOTEM. Based on Maxwell's equation and auxiliary potential function, the response of electrical source on homogeneous and stratified geodetic surface is obtained in this paper. The response of long grounding wire source is divided into line source term and grounding term, which greatly saves calculation time. Secondly, through the plane distribution of diffusion field and the single point attenuation curve, the components of the secondary electromagnetic field excited by the electric source are studied, which provides theoretical support for the practical work to select the appropriate observation component and observation range. Using the piecewise series approximation method, the dichotomy method and the translation algorithm, the whole apparent resistivity of the vertical component of the magnetic field and its derivative with time are obtained, respectively. The advantages and disadvantages of three methods for extracting the whole process apparent resistivity and the resolution ability of the whole process apparent resistivity based on magnetic field intensity and induction electromotive force are analyzed. Compared with the early and late apparent resistivity, the characteristics of the whole apparent resistivity curve are more accurate to reflect the electrical target body, and can accurately reflect the information of the geoelectric section. In addition, the whole apparent resistivity is only related to the electrical structure of the formation, independent of the transceiver distance and the azimuth, so it is convenient to measure the earthing source transient electromagnetic near source in the field. Finally, the whole apparent resistivity calculation method proposed in this paper has been applied to a certain metal ore exploration, and good geological results have been obtained. Through theoretical analysis and practical application, it is proved that the proposed method for calculating the whole apparent resistivity of transient electromagnetic source is effective. The whole apparent resistivity eliminates the false height phenomenon in the shallow area and is obviously superior to the traditional late apparent resistivity and reflects the electric change law of the formation.
【學(xué)位授予單位】：東華理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P631.325

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相關(guān)期刊論文 前2條

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本文編號(hào)：2057533