【摘要】：速度是反映地下構(gòu)造和巖石物性的一個(gè)重要參數(shù)。地球物理問題歸根到底是速度估計(jì)的問題。如何準(zhǔn)確重建地下速度場(chǎng)信息就成了地震波勘探的核心問題,而近地表速度建模問題又是地球物理建模普遍存在的重點(diǎn)及難點(diǎn)問題。近地表速度的精度直接影響勘探區(qū)域的地震資料靜校正、整個(gè)速度場(chǎng)的建模以及最終成像的效果。目前常用的近地表建模方法和技術(shù),如折射波法、面波法以及常規(guī)的走時(shí)層析方法等多基于高頻近似的射線理論,不能滿足當(dāng)前近地表精細(xì)建模的需求。因此更精確的近地表速度反演方法越來越為大家所關(guān)注。全波形反演是基于波動(dòng)方程的非線性反演理論,利用了地震全波場(chǎng)信息,在理論上被認(rèn)為是建模精度最高的手段,已經(jīng)實(shí)現(xiàn)了海上實(shí)際資料應(yīng)用,但陸上實(shí)際資料應(yīng)用受低頻數(shù)據(jù)缺失,觀測(cè)系統(tǒng)限制,陸上隨機(jī)干擾嚴(yán)重和近地表?xiàng)l件諸多因素的影響還存在諸多困難。論文聯(lián)合初至走時(shí)層析與全波形反演的建模優(yōu)勢(shì),引入早至波的概念,基于全波形反演思想,介紹了一種特征波波形反演方法—早至波波形反演。將速度建模問題轉(zhuǎn)化為求解目標(biāo)函數(shù)極值問題,即利用觀測(cè)記錄和模型正演記錄之間的最佳匹配建立地下模型,僅使用早至波信息,避開基于射線理論高頻假設(shè)的最短路徑原理弊端和全波形反演對(duì)大偏移距和低頻的要求,利用早至波的運(yùn)動(dòng)學(xué)和動(dòng)力學(xué)信息,填補(bǔ)常規(guī)建模手段的‘盲區(qū)’,完成近地表及中淺層的高精度速度建模。論文從波形反演基本理論出發(fā),引入早至波波形反演流程,通過模型測(cè)試,直觀的展示了早至波波形反演處理精細(xì)速度建模的能力,反演結(jié)果的精度和分辨率比初至波走時(shí)層析反演的結(jié)果要高,該方法非線性程度較低,反演過程相對(duì)穩(wěn)定,計(jì)算效率較高,收斂效果相對(duì)較好,即使在初始模型精度較低的情況下,仍然可以同時(shí)分辨低波數(shù)和高波數(shù)成分。最后,將早至波波行反演應(yīng)用到實(shí)際資料,考慮整個(gè)反演過程需要關(guān)注的細(xì)節(jié),根據(jù)處理理論模型與實(shí)際資料的經(jīng)驗(yàn),展示了方法的正確性,可行性和實(shí)用性。提出一套對(duì)于速度橫向變化大和表層構(gòu)造比較復(fù)雜的情況下的表層速度建模策略。與此同時(shí),該方法與其他非地震方法的結(jié)合在近地表的礦產(chǎn)普查,工程物探,油氣勘探等領(lǐng)域具有廣泛的應(yīng)用前景。
[Abstract]:Velocity is an important parameter reflecting underground structure and petrophysical properties. The problem of geophysics is, in the final analysis, the problem of velocity estimation. How to accurately reconstruct the information of underground velocity field has become the core problem of seismic wave exploration, and the problem of near-surface velocity modeling is an important and difficult problem in geophysical modeling. The accuracy of near-surface velocity directly affects the static correction of seismic data in exploration area, the modeling of the whole velocity field and the effect of final imaging. At present, the commonly used near-surface modeling methods and techniques, such as refraction wave method, surface wave method and conventional travel-time tomography method, are based on high-frequency approximation ray theory, which can not meet the needs of the current fine modeling near the surface. Therefore, more and more accurate near-surface velocity inversion method has attracted more and more attention. Full wave inversion is a nonlinear inversion theory based on wave equation, which uses seismic full wave field information. It is considered to be the most accurate method of modeling in theory, and has realized the application of practical data on the sea. However, there are still many difficulties in the application of practical data on land due to the lack of low frequency data, the limitation of observation system, the serious random disturbance on land and the near surface conditions. This paper combines the modeling advantages of first arrival time tomography and full waveform inversion, and introduces the concept of early arrival wave. Based on the idea of full wave inversion, this paper introduces a characteristic wave inversion method-early arrival wave inversion. The velocity modeling problem is transformed into solving the objective function extremum problem, that is, using the best match between the observation record and the model forward record, the underground model is established, and only the early wave information is used. Avoiding the defects of the principle of the shortest path based on the high frequency hypothesis of ray theory and the requirement of large offset and low frequency for full waveform inversion, and using the kinematics and dynamics information of the early arrival wave to fill the 'blind zone' of the conventional modeling methods, The high precision velocity modeling of near surface and medium shallow layer is completed. Based on the basic theory of waveform inversion, the paper introduces the inversion process of early to early wave waveform, and through model testing, shows the ability of precision velocity modeling of early to early wave inversion processing. The accuracy and resolution of the inversion results are higher than those of the first arrival wave travel time tomography inversion results. This method has lower nonlinearity, the inversion process is relatively stable, the computational efficiency is higher, and the convergence effect is relatively good. Even if the accuracy of the initial model is low, the low wavenumber and the high wavenumber components can still be distinguished at the same time. Finally, the early wave inversion is applied to the actual data, considering the details of the whole inversion process, the correctness, feasibility and practicability of the method are demonstrated according to the experience of processing the theoretical model and the actual data. A set of surface velocity modeling strategies for large lateral velocity variation and complex surface structure is proposed. At the same time, the combination of this method and other non-seismic methods has a broad application prospect in the near surface mineral survey, engineering geophysical exploration, oil and gas exploration and other fields.
【學(xué)位授予單位】：中國(guó)石油大學(xué)(華東)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P631.4

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