伪波阻抗反演和频谱成像技术在琼东南盆地储层预测中的应用

我国琼东南盆地深水区勘探程度低,工区内只有一口刚打到研究层段黄流组顶部的探井,针对该情况,介绍了一种在无井或少井情况下利用速度谱资料进行地震反演的方法.该方法首先利用离工区较近的井进行有井反演,然后结合有井反演过程的认识,利用速度谱资料提取伪井信息进行伪波阻抗反演,并充分利用已有的地质信息来完善无井反演的结果,最后利用频谱成像技术对反演结果进行验证.结果表明,为了获取准确的伪波阻抗数据,需要准确的速度谱数据,且在构造比较平缓、能量集中、质量较好的道集提取伪井资料,并充分利用已知地震、地质信息和频谱成像分析结果,可以减小无井反演结果的多解性.     

地震逆散射偏移与反演综述

随着油气勘探领域逐渐向深层、复杂型、隐蔽性油气藏转移,油气资源的勘探难度越来越大,传统反射地震勘探技术难以满足日益增长的油气勘探需求,亟需发展适合复杂地质构造的地震波偏移反演新技术.针对地球深部非均匀结构体引起的地震散射波,发展地震逆散射偏移反演理论和技术将有可能解决复杂构造成像反演的技术难题.本文回顾地震波逆散射偏移反演理论的发展历史和基本原理,以逆广义Radon变换求解线性化逆散射问题为基础,介绍逆散射理论在介质结构成像、物性参数反演、多次波衰减等方面的技术延伸,同时将其应用到合成数据和实际数据资料,探讨地震勘探逆散射方法的技术优势和应用潜力.     

基于共炮偏移的AVO反演

常规AVO多是利用CMP道集的振幅进行反演。主要有三个方面影响其精度:首先,CMP道集假设地下为水平层状介质,但是实际地下介质多为倾斜地层,地层倾角越大CMP道集的振幅所反映地下介质的位置与实际位置差距就越大。其次,NMO、DMO和反褶积等常规处理流程,都会造成振幅值失真。第三,反演所用的反射系数公式是与入射角有关的量,而欲从CMP道集得到准确的入射角与振幅之间的对应关系,则十分困难。波动方程叠前深度偏移除对复杂介质和陡倾角地层具有较强的成像能力,还可以最大限度的减少常规处理所带来的误差并使振幅归位。本文综合了保幅偏移、角度道集提取以及AVO反演等前人的工作,提出直接从炮集数据反演AVO属性的方法,以期显著减少上述三个因素对AVO反演精度的影响。     

叠前逆时深度偏移中的激发时间成像条件

与其他偏移方法相比,逆时偏移基于精确的波动方程而不是对其近似,用时间外推来代替深度外推.因此,它具有良好的精度,不受地下构造倾角和介质横向速度变化的限制.激发时间成像条件的求取是叠前逆时偏移的难点之一,本文采用求解程函方程的方法得到地下各点的初至波走时,以此作为叠前逆时偏移的成像条件.基于任意矩形网格和局部平面波前近似的有限差分初至波走时计算方法精度较高并适用于强纵横向变速的复杂介质.试算结果表明,在复杂介质模型中利用叠前逆时深度偏移收到了很好的成像效果.     

地震偏移成像不确定性分析初探

勘探地球物理领域存在大量宏观动力学过程的物理数学表达及尚待深入探索的不确定性事实,其中一类是源自对偶量的不可交换性或不可对易性.本文从地震偏移成像中的不确定性分析入手,探讨偏移成像中受到波场延拓过程不确定性的影响.文中给出了若干深度偏移算法对Marmousi模型的偏移不确定度分布表达及图像显示;文中还对若干波场延拓方法,从不确定性估计的角度进行了比较.笔者认为对应用技术领域中的宏观不确定性分析,将有益于深化对宏观动力学过程的理性认识,也为偏移算法评价提供一种途径;重要的是,进行不确定性分析将有利于把握所用偏移算法的不确定度分布,继而有针对性地采取相应的改善措施,以期提高算法的整体确定性程度.     

Smooth constraint inversion technique in genetic algorithms and its application to surface wave study in the Tibetan Plateau

IntroductionThe dispersion phenomena, which can be observed when surface wave travels through the Earth interior, has been extensively applied in investigating the velocity structure of the Earth interior. Usually, the dispersion curve is a nonlinear function of the thickness, S and P wave velocities and density of each layer. Because surface wave inversion is a multiple-minima problem, the result strongly depends on the initial model in traditional linear inversion. Genetic algorithm (GA) …     

A new technique for moment tensor inversion with applications to the 2008 Wen-chuan M_s8.0 earthquake sequence

A MS8.0 earthquake occurred in Wenchuan County, Sichuan Province, China, on May 12, 2008, and subsequently, numerous aftershocks followed. We obtained the moment tensor solutions and source time functions (STFs) for the Wenchuan earthquake and its seven larger aftershocks (MS5.0~6.0) by a new technique of moment tensor inversion using the broadband and long-period seismic waveform data from the Global Seismic Network (GSN). Firstly, the theoretical background and technical flow of the new technique was brie...     

一种矩张量反演新方法及其对2008年汶川Ms 8.0地震序列的应用

本文利用全球地震台网（GSN）的宽频带与长周期地震波形资料,采用矩张量反演的新方法,反演得到了2008年5月12日四川省汶川县MS8.0地震及其7个较大余震（MS5.0-6.0）的矩张量解与震源时间函数等震源参数.文章首先简要叙述矩张量反演新方法的理论背景和技术途径,并以汶川大地震的一个余震为例阐述了具体的实现过程;然后给出包括主震在内的8次地震的矩张量解和震源时间函数;最后分析探讨这些结果的构造意义.本文提出的矩张量反演新方法,不但与全球矩心矩张量（GCMT）一样,可以给出点源矩张量解,而且还可以给出点源的震源时间函数. 反演得到的汶川大地震的7个较大余震的震源时间函数表明,即使是中等强度的地震也可能有复杂的震源过程;汶川大地震的多数余震发生在以逆冲为主、兼具小量走滑分量的龙门山断裂带的主断裂上,但很可能有些余震则发生在主断裂附近的次级走滑断裂上.      

叠前时间偏移技术在深层断陷区地震成像中的应用

Kirchhoff积分叠前时间偏移应用波动方程的Kirchhoff积分解实现地下反射层的偏移问题,该技术应用所有偏移距的地震资料,能适应纵横向速度变化较大的情况,是复杂地区地震资料成像的较理想的方法.叠前时间偏移是对偏移处理和偏移速度修改的一个迭代过程,偏移速度的精度直接影响到偏移效果.对大庆油田古龙断陷某工区的三维地震资料,应用叠前时间偏移技术进行成像处理,对于埋深较大的目的层,断陷结构复杂,介质的各向异性较为严重,所以应用考虑各向异性参数的速度修改公式,得到较为精确的偏移速度体,进而保证偏移CRP道集拉平,得到成像良好的偏移数据体.实际地震数据偏移处理结果表明叠前时间偏移技术可对复杂构造的地震数据准确成像,可在古龙地区断陷地层勘探中推广应用.     

表层多次波成像方法技术研究

在处理表层多次波比较发育的地震数据资料时,和常规将多次波作为噪音进行压制和去除的思路不同,本文提出利用表层多次波来进行地震构造成像的方法技术流程.首先基于互相关技术将表层多次波转化为准一次波,在利用准一次波进行偏移成像之前,提出应用局部倾斜叠加变换的方法,压制由于其特殊的构建过程而常常伴随准一次波的背景干涉噪音,提高准一次波数据的信噪比;然后应用扩展的分步傅里叶偏移方法对去噪后的准一次波数据进行成像,此偏移成像方法在实现分步傅里叶方法时选取多个背景参考速度,不仅继承常规分步傅里叶偏移方法稳定高效,没有有限差分计算存在的频散影响的特点,而且可以增强常规分步傅里叶偏移方法处理复杂陡倾构造的能力.通过数值模拟数据测试,说明本文提出的这一套利用表层多次波进行复杂地下构造成像的方法技术的可行性和有效性.     

Vp和Vp/Vs联合反演:在日本东北地区深部结构成像(英文)

本文提出了一种新的反演方法:通过采用纵、横波走时数据对(从相同的震源产生的P和S波被同一台站记录)来联合反演纵波速度(Vp)和纵、横波速度比(Vp/Vs),然后单独反演横波速度Vs,在反演过程中同时对地震参数进行定位。该方法不需要假设P和S波的射线路径一致,它是沿着P和S波射线路径计算相对慢度扰动值。该方法直接把Vp/Vs作为一个模型参数,由此能获得比采用从独立反演获得的Vp和Vs计算出Vp/Vs的方法更精确的速度比值。该新方法被应用到反演日本东北地区的壳幔速度及波速比结构的研究中,获得了较好的效果。反演结果表明,在日本东北地区,太平洋俯冲板块为一高Vp,高Vs和低Vp/Vs异常区,而在活火山下方的浅部地幔楔以及背弧深部地区为低Vp,低VS和高Vp/VS异常。虽然这些特征在前人的研究中已经报道过,但与前人的研究结果相比,本次研究所获得的Vp/Vs的空间分布具有较小的分散性,同时,它的分布特征能较好的与地震波速度结构相吻合。     

等效偏移距偏移方法在声波反射成像测井中的应用研究(英文)

声波反射成像测井能够获得井眼周围构造的重要信息,然而,由于接收到的反射波信号远小于井眼模式波、信噪比较低,且每次发射只有8道接收,因此应用常规的偏移成像处理方法成像效果不好。本文应用一种基于散射理论的等效偏移距偏移方法,对声波反射成像测井模拟数据及现场数据进行偏移处珲。结果表明,与常规叠后深度偏移方法相比,等效偏移距方法可以有效提高覆盖次数,对于低信噪比的声波反射测井资料可以获得较好的井旁构造成像效果。     

Some elements of mathematical information theory and total inversion algorithm applied to travel time inversion

The total inversion algorithm and some elements of Mathematical Information Theory are used in the treatment of travel-time data belonging to a seismic refraction experiment from the southern segment (Sardinia Channel) of the European Geotraverse Project. The inversion algorithm allows us to improve a preliminary propagating model obtained by means of usual trial and error procedure and to quantify the resolution degree of parameters defining the crust and upper mantle of such a model. Concepts related to Mathematical Information Theory detect some seismic profiles of the refraction experiment which give the most homogeneous coverage of the model in terms of number of trajectories crossing it. Finally, the efficiency of the inversion procedure is quantified and the uncertainties regarding knowledge of different parts of the model are also evaluated.     

An overview of surface wave methods and a reliability study of a simplified inversion technique

Following a brief overview of the history and the development of the Surface Wave Method—with a focus on techniques for processing and inverting field data—a Simplified Inversion Method (SIM) is described, which constitutes an improvement of the Satoh et al. (1991) [1] method. The SIM is a direct inversion method of surface wave dispersion data, making use of a penetration depth coefficient, a_R, whose value is a function of Poisson's ratio and the overall shape of the dispersion curve. In the present study the coefficient a_R has been evaluated using data from (a) an extensive database compiled from the technical literature and containing results of inverted surface wave measurements and nearby cross-hole/down-hole measurements, (b) results of side by side surface wave and cross-hole measurements, performed at five sites in the course of this study, (c) finite element analyses simulating the performance of surface wave measurements and thus providing “virtual” data, and (d) applying a current advanced inversion code, available on the Web. Based on all the above data, optimum values of a_R (and of the corresponding uncertainty of the derived V_so vs. depth profile) have been estimated. These values were found to be independent of depth from ground surface. The results of all analyses and comparisons indicate that for the majority of realistic soil profiles (including cases of normal and inverse dispersion conditions) the proposed SIM provides very reliable V_so vs. depth profiles when a value of a_R=0.63–0.67 is used in the inversion process. It is concluded that the SIM can be used with confidence as a direct inversion method of surface wave dispersion data.     

用地震波波形拟合方法研究中小地震的震源机制

采用网格搜索方法,利用区域地震三分量全波形资料,对中小地震震源机制的反演方法进行了研究。反演采用初动约束、分段求相关系数,以及幅值加权的混合方法计算误差函数,通过格点搜索法确定震源深度。理论模型试验表明,反演结果具有较好的稳定性和可靠性。云南地区区域数字地震台网的观测资料反演表明,该方法可以合理地拟合观测波形资料。将2001年7月9日(24.93°N,101.47°E)发生的MS 5.3地震的震源机制解与哈佛大学CMT进行了对比,结果表明,Z分量波形拟合略比CMT拟合的好,R分量和T分量的波形拟合明显好于CMT的对应分量。 我们对2001年4月5日在(25.77°N,102.30°E)发生的mb 4.8地震进行了震源机制反演。结果表明,该地震主要表现为走滑断层,震源机制解为(180°,80°,11°)。根据这两个地震震源机制推断的主应力轴,与该地区现代构造应力场特征基本一致。     

A new technique for moment tensor inversion with applications to the 2008 Wenchuan M S8.0 earthquake sequence

A MS8.0 earthquake occurred in Wenchuan County, Sichuan Province, China, on May 12, 2008, and subsequently, numerous aftershocks followed. We obtained the moment tensor solutions and source time functions (STFs) for the Wenchuan earthquake and its seven larger aftershocks (MS5.0~6.0) by a new technique of moment tensor inversion using the broadband and long-period seismic waveform data from the Global Seismic Network (GSN). Firstly, the theoretical background and technical flow of the new technique was briefly introduced, and an aftershock of the Wenchuan earthquake sequence was employed to illustrate the real procedure for inverting the moment tensor; secondly, the moment tensor solutions and STFs of the eight events, including the main shock, were presented, and finally, the interpretation of the results was made. The agreement of our results with the GCMT results indicates the new approach is efficient and feasible. By using this approach, not only the moment tensor solution can be obtained but also the STF can be retrieved; the inverted STFs indicate that the source rupture process may be com-plicated even for the moderate earthquakes. The inverted focal mechanisms of the Wenchuan earthquake sequence show that the most of the aftershocks occurred in the main faults of the Longmenshan fault zone with predomi-nantly thrustingwith minor right-lateral strike-slip component, but some of them may have occurred in the sub-faults with strike-slip faulting in the vicinity of the main faults.     

基于波场分离理论的逆时偏移成像条件研究及应用

逆时偏移成像方法与其它算法的成像方法相比,由于算法不受地层倾角的限制,因此针对陡倾角构造和复杂地质模型地区的成像有着无可比拟的优越性,特别是在盐丘发育的地区优势更加明显.实际应用过程中,逆时偏移通常是应用互相关成像条件构建成像,然而,这种成像条件会产生低频、强振幅的噪音,如果不能彻底消除这些噪音,那它就会严重影响甚至淹没有效信号,特别是在浅层的强反射界面上方往往会出现大量的低频噪音,从而使得浅层构造基本无法识别.基于传统互相关成像条件的这一局限,本文提供了一个新的成像条件,它能在有效成像的同时消除这些低频、强振幅的干扰噪音;其具体实现思路就是将炮点及检波点波场分离成它们的单程波传播分量,然后采用互相关成像条件对分离后的波场进行成像,从而实现逆时偏移成像.通过对模型数据和实际野外数据的实测,证明了该方法的有效性和适用性.     

鄂尔多斯盆地西缘地区偏移成像技术研究

鄂尔多斯盆地西缘地区地质构造发育,构造类型的多样化有利于油气的运移和储存,具有较好的勘探前景.由于构造的复杂性,静校正问题突出,准确建立速度场困难,深层成像精度差;绕射波、回转波发育,成像归位不准确.本文综合层析静校正技术和初至波剩余静校正技术计算静校正量,在精细速度分析的基础上建立偏移速度场模型,采用基于共炮检距域的...     

Research on the imaging of concrete defect based on the pulse compression technique

When the synthetic aperture focusing technology (SAFT) is used for the detection of the concrete, the signal-to-noise ratio (SNR) and detection depth are not satisfactory. Therefore, the application of SAFT is usually limited. In this paper, we propose an improved SAFT technique for the detection of concrete based on the pulse compression technique used in the Radar domain. The proposed method first transmits a linear frequency modulation (LFM) signal, and then compresses the echo signal using the matched filtering method, after which a compressed signal with a narrower main lobe and higher SNR is obtained. With our improved SAFT, the compressed signals are manipulated in the imaging process and the image contrast is improved. Results show that the SNR is improved and the imaging resolution is guaranteed compared with the conventional short-pulse method. From theoretical and experimental results, we show that the proposed method can suppress noise and improve imaging contrast, and can also be used to detect multiple defects in concrete.