本文選題：CSAMT + 域分解�。� 參考：《中國(guó)地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：可控源音頻大地電磁法(CSAMT)是一種人為建立場(chǎng)源并觀測(cè)電磁反射信號(hào),同時(shí)能夠加強(qiáng)抗干擾、增強(qiáng)信噪比的電磁勘探方法。通過不同頻率對(duì)地下不同深度信息的靈敏度不同,且具有較好的垂向分辨能力,因此該方法被廣泛應(yīng)用于礦產(chǎn)資源、水文地質(zhì)和油氣資源等領(lǐng)域,還在地質(zhì)普查、地?zé)峥辈楹铜h(huán)境工程等領(lǐng)域上發(fā)揮了重要作用。CSAMT在數(shù)值模擬與反演中,有限元法在計(jì)算精度上較高,但是有限元法正演求解過程中對(duì)于邊界條件應(yīng)用性較高;積分方程法僅對(duì)異常體剖分,但在計(jì)算并矢格林函數(shù)積分上效率低下;有限差分法計(jì)算效率較高,但對(duì)于網(wǎng)格的剖分要求嚴(yán)格,并且還要進(jìn)行散度校正。隨著社會(huì)的發(fā)展,計(jì)算效率和計(jì)算精度深受重視,因此要基于各種數(shù)值模擬方法的優(yōu)缺點(diǎn),本文將研究區(qū)域剖分為由積分方程法計(jì)算的邊界區(qū)域和利用有限元法計(jì)算的內(nèi)部區(qū)域。利用整體積分方程法和局部微分方程法的聯(lián)用方法(GILD)來進(jìn)行CSAMT三維正演,由于積分方程法進(jìn)行三維正演無需邊界條件的優(yōu)點(diǎn),讓該方法應(yīng)用在邊界區(qū)域,繼而為有限元法提供邊界條件;由于有限元法在剛度矩陣和荷載矩陣合成高效的特點(diǎn)替換內(nèi)部區(qū)域應(yīng)用積分方程法的并矢格林函數(shù)積分的大量計(jì)算,這樣減少了正演計(jì)算時(shí)間,降低了硬件內(nèi)存需求,同時(shí)提高了計(jì)算精度。利用內(nèi)部區(qū)域各自互不關(guān)聯(lián)的獨(dú)立性大大提高了 GILD算法的可并行性,本文采用OpenMP并行加速,在計(jì)算并矢格林函數(shù)積分和剛度矩陣大幅度提高了三維正演計(jì)算效率。三維反演采用傳統(tǒng)的阻尼最小二乘法,針對(duì)觀測(cè)點(diǎn)范圍內(nèi)區(qū)域進(jìn)行三維反演,在反演過程中不斷改進(jìn)阻尼因子,最終在同時(shí)滿足擬合差和模型的光滑度上,達(dá)到較好的反演結(jié)果;反演低阻體的效果比反演高阻體的要好。本文通過對(duì)同一觀測(cè)數(shù)據(jù),進(jìn)行不同大小區(qū)域進(jìn)行反演,結(jié)果表明,反演區(qū)域的大小對(duì)反演本身毫無影響,剖分的越多,僅在計(jì)算系數(shù)矩陣的耗時(shí)上越長(zhǎng)。
[Abstract]:The controllable source audio magnetotelluric method (CSAMT) is a kind of electromagnetic exploration method, which can establish the field source and observe the electromagnetic reflection signal, at the same time, it can strengthen the anti-interference and enhance the signal-to-noise ratio (SNR). The sensitivity of different frequencies to different depth of underground information is different, and the method has good vertical resolution. Therefore, this method is widely used in mineral resources, hydrogeology and oil and gas resources, and is also in geological survey. CSAMT has played an important role in the fields of geothermal exploration and environmental engineering. In the numerical simulation and inversion, the finite element method has a higher accuracy, but the application of the finite element method to the boundary conditions is higher in the forward modeling process. The integral equation method is not efficient in the computation of dyadic Green's function, but the integral equation method is efficient only for abnormal bodies, but the finite difference method is more efficient, but it is strict for mesh generation, and the divergence correction should be carried out. With the development of society, the efficiency and precision of calculation are paid more attention to, so we should base on the merits and demerits of various numerical simulation methods. In this paper, the study area is divided into the boundary region calculated by the integral equation method and the internal region calculated by the finite element method. The global integral equation method and the local differential equation method are used to carry out the three-dimensional forward modeling of CSAMT. Because the integral equation method has the advantage of no boundary condition, the method is applied in the boundary region. Then the boundary conditions are provided for the finite element method, because the finite element method is efficient in the combination of stiffness matrix and load matrix, it replaces a large number of calculations of the dyadic Green's function integral by the integral equation method in the internal region, thus reducing the forward calculation time. The requirement of hardware memory is reduced and the calculation precision is improved. The parallelism of the GILD algorithm is greatly improved by using the independence of the internal regions. In this paper, the parallelism of the GILD algorithm is improved by using the OpenMP parallel acceleration, and the efficiency of 3D forward modeling is greatly improved in the computation of dyadic Green's function integral and stiffness matrix. The traditional damped least square method is used in the 3D inversion, and the damping factor is improved continuously in the inversion process for the region within the range of the observation point. Finally, the fitting error and the smoothness of the model are satisfied at the same time. The result of inversion is better than that of high resistivity. In this paper, the inversion of the same observed data is carried out in different regions. The results show that the size of the inversion region has no effect on the inversion itself. The more the division is, the longer the computation time of the coefficient matrix is.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P631.325

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相關(guān)期刊論文 前10條

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本文編號(hào)：1959583