【摘要】：地震偏移成像是一種優(yōu)秀數(shù)據(jù)處理技術(shù),它將地表接收到的地震記錄投影到其源頭從而構(gòu)建地下結(jié)構(gòu)圖像。在現(xiàn)有的各種偏移成像技術(shù)中,由于其相對(duì)于其他傳統(tǒng)偏移技術(shù)所的具有優(yōu)異性能,逆時(shí)偏移(RTM)是被當(dāng)今勘探工業(yè)界以及學(xué)術(shù)界所公認(rèn)的標(biāo)準(zhǔn)成像技術(shù)。盡管逆時(shí)偏移計(jì)算量大所需計(jì)算時(shí)間長(zhǎng),但是它能有效地綜合應(yīng)對(duì)復(fù)雜地質(zhì)情況、陡傾角反射面以及強(qiáng)橫向速度擾動(dòng)。逆時(shí)偏移將地表記錄到的地震信號(hào)視作邊界條件,然后將這些信號(hào)在時(shí)間上進(jìn)行反傳直至滿足成像條件。這個(gè)方法可以使用與波場(chǎng)正演模擬相同的模擬算法。傳統(tǒng)的地震波場(chǎng)外推理論假設(shè)地表是水平的,而在模擬地震波傳播的時(shí)候必須考慮到不規(guī)則地表的影響,這并不總是一項(xiàng)簡(jiǎn)單的工作,但是我們能夠通過(guò)我們的正演模擬算法正確地處理起伏地表的問(wèn)題。這項(xiàng)工作采用了曲線網(wǎng)格有限差分方法(CG-FDM)來(lái)模擬起伏地表?xiàng)l件下的彈性地震波傳播。其中,貼體網(wǎng)格的被用來(lái)避免人為散射同時(shí)使網(wǎng)格與自由地表相一致。我們使用高階優(yōu)化的同位網(wǎng)格DRP/opt MacCormack算法來(lái)求解一階速度應(yīng)力方程組,因?yàn)檫@種算法使得計(jì)算效率和計(jì)算精度達(dá)到最好的平衡。在解決了正演模擬問(wèn)題后,通過(guò)在時(shí)間上對(duì)地表記錄進(jìn)行翻轉(zhuǎn)并最終利用反轉(zhuǎn)后的記錄做逆時(shí)外推,進(jìn)而完成波場(chǎng)的逆時(shí)外推。成像準(zhǔn)則和成像條件是逆時(shí)偏移的核心,震源歸一化的互相關(guān)成像條件被用來(lái)對(duì)下行以及上行波場(chǎng)在相對(duì)應(yīng)時(shí)刻進(jìn)行互相關(guān)。我們用過(guò)以Marmousi模型作為真實(shí)模型的合成數(shù)據(jù)實(shí)驗(yàn)來(lái)研究我們方法的優(yōu)缺點(diǎn),與此同時(shí),其他的一些簡(jiǎn)單模型也被用于測(cè)試。我們用垂直方向有限差分圖像處理技術(shù)來(lái)消除互相關(guān)結(jié)果中的低頻噪音,這個(gè)方法對(duì)水平結(jié)構(gòu)的成像是非常有用的,由它得到的消除低頻噪音后的結(jié)果非常顯著。我們重點(diǎn)關(guān)注彈性波傳播而不是聲波是因?yàn)榈厍虮旧肀憩F(xiàn)出彈性體的特征。各種模型測(cè)試得到的逆時(shí)偏移結(jié)果令人滿意,我們的偏移算法能完美應(yīng)用于商業(yè)用途。另一方面,對(duì)位于巴基斯坦Punjab地臺(tái)的Nandpur氣田潛在反射層的實(shí)際地震數(shù)據(jù)的解釋工作已經(jīng)完成。出于這個(gè)目的,在巴基斯坦政府的官方批準(zhǔn)下,Nandpur氣田的實(shí)際數(shù)據(jù)被用來(lái)更加清晰實(shí)際地闡述地震數(shù)據(jù)解釋。我們用地震和地球物理測(cè)井資料用來(lái)做結(jié)構(gòu)解釋并最終通過(guò)地球物理測(cè)井技術(shù)評(píng)估該區(qū)域碳?xì)浠锎嬖诘目赡堋＝Y(jié)果表明,這片區(qū)域具有很大的油氣開(kāi)發(fā)前景。
[Abstract]:Seismic migration imaging is an excellent data processing technology, which projects the seismic records received from the surface to its source to construct the underground structure image. Among the existing migration imaging techniques, because of their excellent performance compared with other traditional migration techniques, inverse time migration (RTM) is a standard imaging technology recognized by the exploration industry and academia. Although the computation time of inverse time migration is long, it can effectively deal with complex geological conditions, steep dip reflection surface and strong lateral velocity disturbance. Inverse time migration regards seismic signals recorded on the surface as boundary conditions and then transmits them back in time until the imaging conditions are satisfied. This method can use the same simulation algorithm as the forward simulation of the wave field. The traditional extrapolation theory of seismic wave field assumes that the surface of the earth is horizontal, but the influence of irregular surface must be taken into account when simulating the propagation of seismic wave. This is not always a simple task. But we can deal with the problem of undulating surface correctly through our forward simulation algorithm. A curved grid finite difference method (CG-FDM) is used to simulate elastic seismic wave propagation under undulating surface conditions. Among them, the body-fitted grid is used to avoid artificial scattering and make the mesh consistent with the free surface. We use the high-order optimization DRP/opt MacCormack algorithm to solve the first-order velocity stress equations because the algorithm achieves the best balance between computational efficiency and accuracy. After solving the forward modeling problem, the inverse time extrapolation of the wave field is accomplished by flipping the surface record in time and finally making use of the inverted record to do inverse time extrapolation. Imaging criteria and imaging conditions are the core of inverse time migration. The normalized cross-correlation imaging conditions are used to cross-correlate the downlink and uplink wave fields at the corresponding time. We have used the Marmousi model as the real model to study the advantages and disadvantages of our method. At the same time, some other simple models have also been used for testing. We use the vertical finite-difference image processing technique to eliminate the low frequency noise in the cross-correlation result. This method is very useful for the imaging of horizontal structure, and the results obtained from the method are very significant after the elimination of low frequency noise. We focus on the propagation of elastic waves rather than sound waves because the Earth itself exhibits the characteristics of elastic bodies. The results of inverse time migration obtained by various model tests are satisfactory, and our migration algorithm can be used perfectly for commercial purposes. On the other hand, the interpretation of the actual seismic data of the potential reflectors of the Nandpur gas field at the Punjab platform in Pakistan has been completed. To this end, actual data from the Nandpur gas field, with the official approval of the Pakistani government, have been used to explain the seismic data more clearly and practically. We use seismic and geophysical logging data for structural interpretation and ultimately evaluate the possibility of the presence of hydrocarbons in the region through geophysical logging techniques. The results show that this area has great prospects for oil and gas development.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：P631.4

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 王祥春;劉學(xué)偉;;起伏地表三維聲波方程地震波場(chǎng)模擬(英文)[J];Applied Geophysics;2007年01期

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