發(fā)布時(shí)間：2018-06-07 07:31

  本文選題：模型約束項(xiàng) + 先驗(yàn)信息　； 參考：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：大地電磁法是一種高效的地球物理勘探方法,經(jīng)多年的發(fā)展,該方法理論體系逐漸完善,而且不斷引進(jìn)新的數(shù)學(xué)計(jì)算方法,故大地電磁法的應(yīng)用空間愈加廣泛。目前在油氣勘查、地?zé)豳Y源勘探和金屬礦產(chǎn)勘查中大地電磁法都有廣闊的發(fā)揮空間,實(shí)踐證明該方法是一種不可或缺的地球物理勘查方法,有必要對其進(jìn)行更加深層次的學(xué)習(xí)與研究。大地電磁法的目標(biāo)函數(shù)由數(shù)據(jù)擬合項(xiàng)及模型約束項(xiàng)組成。在目標(biāo)函數(shù)中,數(shù)據(jù)擬合項(xiàng)控制反演所得結(jié)果的正演響應(yīng)與理論模型的正演響應(yīng)之間差值在一個(gè)可接受的范圍內(nèi);模型約束項(xiàng)控制模型光滑約束,此外,該項(xiàng)還能夠改變反演結(jié)果中的異常形態(tài),其靈活多變,可以在其中添加多種先驗(yàn)信息。本論文主要介紹了通過修改模型約束項(xiàng)來引入傾角信息、界面信息,充分地利用了先驗(yàn)信息已到達(dá)改善反演結(jié)果的目的。地質(zhì)體一般具有清晰的走向或傾角信息,有必要建立一種新的目標(biāo)函數(shù)來將這些信息加入到電磁法反演中。用一個(gè)旋轉(zhuǎn)矩陣對水平方向及垂直方向?qū)?shù)做旋轉(zhuǎn)運(yùn)算,使得其導(dǎo)數(shù)方向可以任意改變。將這個(gè)旋轉(zhuǎn)矩陣代入到模型約束項(xiàng)中創(chuàng)建一個(gè)新的目標(biāo)函數(shù),使得新目標(biāo)函數(shù)可以在結(jié)構(gòu)體的走向或者傾角方向上起到拉伸的作用。本文在大地電磁法二維的情況下討論了該方法,列舉了理論模型及實(shí)測數(shù)據(jù)加以驗(yàn)證,對比新方法與普通方法的反演結(jié)果,證明新方法的有效性。在地球物理勘探方法中,地震勘探對界面信息比較敏感,可以通過反射波劃分地下界面信息。本論文建立一種新的目標(biāo)函數(shù)將界面信息引入到電磁法反演中,分別采用了添加交叉梯度項(xiàng)進(jìn)行分區(qū)域反演及修改拉普拉斯算子控制邊界導(dǎo)數(shù)這兩種方法,令新的目標(biāo)函數(shù)可以更加準(zhǔn)確地劃分地層界面。在大地電磁法二維的情況下,建立理論模型以及實(shí)測數(shù)據(jù)分別對改進(jìn)后的算法進(jìn)行驗(yàn)證分析,證明該方法的正確性。引入傾角信息、界面信息這兩種方法都取得了良好的效果,說明在反演中先驗(yàn)信息的引入是至關(guān)重要的,通過引入先驗(yàn)信息可以減弱反演多解性、改善反演結(jié)果。
[Abstract]:Magnetotelluric method is an efficient geophysical exploration method. With the development of many years, the theoretical system of this method has been gradually improved and a new mathematical calculation method has been introduced, so the application space of magnetotelluric method has become more and more extensive. At present, magnetotelluric method is widely used in oil and gas exploration, geothermal resources exploration and metal mineral exploration. It has been proved by practice that this method is an indispensable geophysical exploration method. It is necessary to carry on the deeper level study and research to it. The objective function of magnetotelluric method consists of data fitting term and model constraint term. In the objective function, the difference between the forward response of the inversion result and the forward response of the theoretical model is within an acceptable range, and the model constraint term controls the smooth constraint of the model, in addition, the difference between the forward response of the inversion result and the forward response of the theoretical model is within an acceptable range. This method can also change the abnormal shape in the inversion result, and it can add a variety of prior information to it. This paper mainly introduces the introduction of inclination information and interface information by modifying the constraint terms of the model, and makes full use of the prior information to improve the inversion results. Geological bodies generally have clear information of strike or inclination, so it is necessary to establish a new objective function to add these information to electromagnetic inversion. A rotation matrix is used to rotate the horizontal and vertical derivatives so that the derivative direction can be changed arbitrarily. The rotation matrix is added to the constraint term of the model to create a new objective function so that the new objective function can stretch in the direction of structure direction or inclination. This paper discusses the magnetotelluric method under the condition of two-dimensional magnetotelluric method, enumerates the theoretical model and the measured data to verify it, compares the inversion results of the new method with the common method, and proves the validity of the new method. In geophysical exploration, seismic exploration is sensitive to interface information and can be divided into underground interface information by reflection wave. In this paper, a new objective function is established to introduce the interface information into the electromagnetic inversion. Two methods are used to inverse the boundary derivatives by adding the cross gradient terms and modifying the Laplace operator to control the boundary derivatives. The new objective function can be used to divide the stratigraphic interface more accurately. In the case of two dimensional magnetotelluric method, the theoretical model and the measured data are established to verify and analyze the improved algorithm, and the correctness of the method is proved. The introduction of dip information and interface information shows that the introduction of prior information is very important in inversion. The introduction of prior information can weaken the multi-solution of inversion and improve the inversion results.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P631.325

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本文編號：1990362