本文選題：AVO效應(yīng)　切入點(diǎn)：AVO反演　出處：《中國地質(zhì)大學(xué)(北京)》2017年博士論文

【摘要】：海底沉積物彈性參數(shù)的獲取對于天然氣水合物勘探、海底冷泉探測等有著重要意義。在海洋地震勘探研究中,研究目標(biāo)往往集中在海底以下目標(biāo)體的探測。AVO (Amplitude Variation with Offset)技術(shù)作為一種從疊前地震數(shù)據(jù)中提取地下介質(zhì)物性參數(shù)的有效手段,主要關(guān)注了海底以下地層物性參數(shù)的反演,對于與海水交界的海底沉積物彈性參數(shù)的反演往往被忽略。本文研究目的在于利用海底反射的AV0效應(yīng)進(jìn)行海底沉積物彈性參數(shù)的反演。海底反射界面可視為一個(gè)流體-固體界面,該界面處滿足法向應(yīng)力連續(xù)、法向位移連續(xù)、切向應(yīng)力為零三個(gè)邊界條件。本文基于該界面處的邊界條件推導(dǎo)了描述平面縱波入射海底時(shí)透反射效應(yīng)的Zoeppritz方程。海底反射界面是一個(gè)強(qiáng)彈性差異界面,常規(guī)的弱彈性差異假設(shè)下的近似方程不適用于海底反射。本文利用級數(shù)展開的方法在不對界面兩側(cè)彈性參數(shù)做任何假設(shè)的情況下推導(dǎo)了反射系數(shù)隨入射角變化關(guān)系的近似方程。描述海底反射系數(shù)隨入射角變化關(guān)系的精確方程和近似方程構(gòu)成了本文的理論基礎(chǔ)�；诤５追瓷湎禂�(shù)隨入射角變化關(guān)系的精確方程和近似方程,給出了一種海底沉積物三彈性參數(shù)的兩步線性反演方法。該方法在第一步反演中利用近角度區(qū)間內(nèi)反射系數(shù)隨入射角正弦平方之間的一次函數(shù)關(guān)系,求取反射系數(shù)的梯度和截距信息;在第二步反演中利用大入射角區(qū)間內(nèi)的反射系數(shù)求取海底橫波速度與縱波速度之比;最后由梯度、截距和橫縱波速度之比求取海底沉積物的縱波速度、橫波速度和密度。在該方法的基礎(chǔ)上進(jìn)一步討論了子波準(zhǔn)確性對反演結(jié)果的影響,并給出了一種基于巖石物理約束的直接利用反射振幅進(jìn)行海底沉積物彈性沉積物參數(shù)反演的策略。最后通過模型例子分析了兩步線性反演方法中近角度區(qū)間估計(jì)準(zhǔn)確性對反演結(jié)果的影響。針對兩步線性反演方法的不足,本文基于無約束優(yōu)化算法,直接利用精確的反射系數(shù)方程對海底沉積物彈性參數(shù)進(jìn)行反演。從常步長梯度算法入手,詳細(xì)研究了包括最速下降法、牛頓法、共軛梯度法在內(nèi)的各種無約束優(yōu)化算法在海底沉積物彈性參數(shù)反演中的表現(xiàn)。這類方法直接利用全角度范圍內(nèi)的反射系數(shù)信息進(jìn)行反演,不需要事先對近角度區(qū)間進(jìn)行估計(jì),這大大提高了反演結(jié)果的穩(wěn)定性。最后對南海實(shí)際地震資料進(jìn)行了反演與初步分析。
[Abstract]:The acquisition of elastic parameters of seabed sediment is of great significance for gas hydrate exploration and submarine cold spring exploration. As an effective method to extract the physical parameters of underground media from pre-stack seismic data, the research object is usually focused on the detection of the subsea target. The technique of AVO amplitude Variation with Offsetts, as an effective means to extract the physical parameters of underground media, mainly pays attention to the inversion of the physical parameters of the strata below the sea floor. The inversion of the elastic parameters of seafloor sediments at the interface with sea water is often ignored. The purpose of this paper is to use the AV0 effect of sea floor reflection to retrieve the elastic parameters of seabed sediments. The seabed reflection interface can be regarded as a. Fluid-solid interface, The interface satisfies the continuity of normal stress and normal displacement. The tangential stress is zero three boundary conditions. Based on the boundary conditions at this interface, the Zoeppritz equation is derived to describe the permeable reflection effect when the plane longitudinal wave is incident to the seafloor. The submarine reflection interface is a strongly elastic differential interface. The conventional approximation equation under the assumption of weak elastic difference is not suitable for submarine reflection. In this paper, the relation between reflection coefficient and incidence angle is derived without any assumption of elastic parameters on both sides of the interface by using series expansion method. The exact equation and approximate equation describing the relation of submarine reflection coefficient with incident angle form the theoretical basis of this paper. Based on the exact equation and approximate equation of submarine reflection coefficient varying with incident angle, In this paper, a two-step linear inversion method for three elastic parameters of seafloor sediment is presented. In the first step, the first step inversion is based on the first order function between the reflection coefficient and the sinusoidal square of the incident angle in the near angle interval. The gradient and intercept information of reflection coefficient are obtained. In the second step, the ratio of sea bottom shear wave velocity to longitudinal wave velocity is obtained by using the reflection coefficient in the range of large incidence angle. The ratio of intercept to shear wave velocity is used to calculate the velocity, shear wave velocity and density of seafloor sediment. Based on this method, the influence of wavelet accuracy on inversion results is discussed. A direct inversion strategy of elastic sediment parameters using reflection amplitude based on the physical constraints of rock is presented. Finally, the near angle interval estimation in the two-step linear inversion method is analyzed by a model example. The effect of accuracy on inversion results. Based on the unconstrained optimization algorithm, the elastic parameters of seafloor sediment are inversed directly by using the exact reflection coefficient equation. Starting with the constant step size gradient algorithm, the most rapid descent method and Newton method are studied in detail. The performance of various unconstrained optimization algorithms, including conjugate gradient method, in the inversion of elastic parameters of seafloor sediments. This kind of method directly uses the reflection coefficient information in the whole angle range for inversion, and does not need to estimate the near-angle interval in advance. This greatly improves the stability of the inversion results. Finally, the inversion and preliminary analysis of the actual seismic data in the South China Sea are carried out.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：P631.4

【相似文獻(xiàn)】

相關(guān)期刊論文 前10條

1 陳潔;桂志先;朱凡求;王寧;齊虹;;蘇25區(qū)塊含水飽和度變化所引起的AVO響應(yīng)分析[J];長江大學(xué)學(xué)報(bào)(自然科學(xué)版);2011年12期

2 傅文敏;AVO模擬分析泥盆系礁體勘探的困難和可能性[J];重慶石油高等專科學(xué)校學(xué)報(bào);1997年01期

3 朱兆林,王永剛,曹丹平;裂縫性儲層AVO檢測方法綜述[J];勘探地球物理進(jìn)展;2004年02期

4 胡曉麗;譚大龍;;孔隙形狀對AVO響應(yīng)影響的研究[J];巖性油氣藏;2010年03期

5 李中元;北極地區(qū)天然氣水合物的AVO屬性研究[J];石油物探;2004年S1期

6 何濤;史，

本文編號：1670121