本文選題：疊前深度偏移 + VTI介質(zhì)�。� 參考：《長(zhǎng)安大學(xué)》2017年碩士論文

【摘要】：隨著現(xiàn)今油氣勘探中勘探目標(biāo)的日趨復(fù)雜,以往基于各向同性簡(jiǎn)單介質(zhì)基本假設(shè)的基本成像理論越來越不能滿足現(xiàn)階段油氣勘探的實(shí)際需求,這就使得研究符合地下實(shí)際地質(zhì)模型的復(fù)雜介質(zhì)的成像方法變得非常迫切。另一方面,各向異性普遍存在于地殼介質(zhì),因此在現(xiàn)階段的地球物理研究中,開展地震各向異性的研究對(duì)于認(rèn)知地球內(nèi)部構(gòu)造、油氣田的勘探與開發(fā)以及地質(zhì)災(zāi)害防治等方面都具有重要意義�；诟飨虍愋越橘|(zhì)的疊前深度偏移技術(shù)是現(xiàn)階段對(duì)復(fù)雜地質(zhì)情況成像效果最好的技術(shù)。在復(fù)雜構(gòu)造區(qū)和更深部的地震勘探中應(yīng)用疊前深度偏移技術(shù),可以獲得較為精細(xì)的成像效果。論文首先對(duì)各向同性介質(zhì)聲波方程進(jìn)行單程波解耦,獲得可直接進(jìn)行波場(chǎng)上、下外推的單程波延拓算子。針對(duì)復(fù)雜介質(zhì),對(duì)延拓過程中的垂向波數(shù)利用不同的數(shù)學(xué)展開式進(jìn)行近似展開,分別推導(dǎo)出裂步傅里葉(SSF)、廣義屏(GSP)與切比雪夫傅里葉(CF)波場(chǎng)傳播算子。針對(duì)VTI介質(zhì),結(jié)合地震疊前深度偏移的基本理論以及波場(chǎng)在VTI介質(zhì)中傳播的頻散特性,分別推導(dǎo)了可適用于VTI介質(zhì)的SSF、GSP、CF延拓算子。然后對(duì)比分析這三種算子的相對(duì)誤差曲線和脈沖響應(yīng)特征,總結(jié)了它們的優(yōu)缺點(diǎn)。再借助于偏移成像理論,編程實(shí)現(xiàn)完整的VTI介質(zhì)單程波疊前深度偏移。最后利用SEG VTI-HESS模型驗(yàn)證這三種偏移方法的成像效果及成像效率。對(duì)比分析裂步傅里葉(SSF)、廣義屏(GSP)與切比雪夫傅里葉(CF)波場(chǎng)傳播算子的相對(duì)誤差、脈沖響應(yīng)效果,對(duì)于橫向速度差異較大、大傾角的介質(zhì),SSF算子將產(chǎn)生較大的誤差,GSP算子效果優(yōu)于SSF算子,CF算子誤差最小、脈沖響應(yīng)也更符合實(shí)際的波場(chǎng)傳播過程。理論模型試算結(jié)果表明:要在復(fù)雜介質(zhì)區(qū)獲得較好、較精細(xì)的成像效果時(shí),應(yīng)選擇切比雪夫傅里葉疊前深度偏移方法;在構(gòu)造相對(duì)簡(jiǎn)單的地質(zhì)區(qū)域,選擇裂步傅里葉偏移方法可以大大節(jié)約計(jì)算成本;廣義屏方法的效果是這兩種偏移方法的一個(gè)折中。
[Abstract]:With the increasing complexity of exploration targets in the present oil and gas exploration, the basic imaging theory based on the basic assumption of isotropic simple medium is more and more unable to meet the actual demand of oil and gas exploration at the present stage. This makes it very urgent to study the imaging methods of complex media in accordance with the actual underground geological model. On the other hand, anisotropy exists generally in crustal media, so in the present geophysical research, the study of seismic anisotropy is of great importance to the cognition of the inner structure of the earth. The exploration and development of oil and gas fields and the prevention of geological disasters are of great significance. Prestack depth migration based on anisotropic media is the best technique for imaging complex geological conditions at present. The application of prestack depth migration technique in the seismic exploration of complex structural areas and deeper areas can obtain more precise imaging results. In this paper, we first decouple the acoustic wave equation of isotropic medium by one-pass wave decoupling, and obtain the one-pass wave extension operator which can be extrapolated directly from the wave field. For complex media, the vertical wavenumber in the extension process is approximated by different mathematical expansions, and the wave field propagation operators are derived, respectively, for the split-step Fourier transform (SSF) and the Chebyshev Fourier transform (CFF). For VTI medium, combined with the basic theory of seismic prestack depth migration and the dispersion characteristics of wave field propagating in VTI medium, the VTI GSP CF continuation operator suitable for VTI medium is derived respectively. Then, the relative error curves and impulse response characteristics of these three operators are analyzed, and their advantages and disadvantages are summarized. With the help of migration imaging theory, complete VTI medium prestack depth migration is realized by programming. Finally, the SEG VTI-HESS model is used to verify the imaging effect and efficiency of the three migration methods. By comparing and analyzing the relative errors of the propagation operators of split step Fourier transform (SSF), generalized screen (GSPs) and Chebyshev Fourier transform (CFD), the effect of pulse response is quite different for transverse velocity. The effect of SSF operator is better than that of SSF operator and the impulse response is more consistent with the actual wave field propagation process. The experimental results of theoretical model show that the Chebyshev Fourier prestack depth migration method should be chosen in order to obtain better and more precise imaging effect in complex media regions, and in geological areas with relatively simple structure, the method of Chebyshev Fourier prestack depth migration should be selected. The computational cost can be greatly saved by choosing the split step Fourier migration method, and the effect of the generalized screen method is a compromise between the two migration methods.
【學(xué)位授予單位】：長(zhǎng)安大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P631.4

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本文編號(hào)：1940765