【作者】 杨城增；

【导师】 刘学伟；

【作者基本信息】 中国地质大学(北京) ， 地球物理学， 2012， 硕士

【摘要】 由于解决地质问题的复杂化程度和精细程度的进一步提高，常规反射波地震勘探技术不能很好地应用在山前断裂带、盆地边缘破碎带、岩浆侵入型的勘探问题，且难以取得精确的成像效果；因此，针对构造或岩性复杂区油气勘探、隐伏金属矿等复杂勘探问题，提出了散射波地震方法。它是基于地震波散射理论，并且是使用更广义的散射波描述多种尺度非均匀地质体形成的复杂地震波场的勘探方法。散射波成像是依赖地震散射波理论，属于叠前时间偏移的一种成像方法，为地震成像以及速度分析提供了独特的研究思路。在前人工作的基础上，详细理解了地震散射波场理论，了解散射波场与反射波场的本质区别，明确了散射波的运动学特征，即散射波时距曲面是一个Choeps金字塔；散射波成像的核心是等效偏移距理论，依据等效偏移距原理形成共散射点(CSP)道集，其本质是按照等效偏移距的大小重新选排地震道信息的过程；此道集具有更大的偏移距覆盖范围和更高的信噪比，提高了速度分析的精度，为后续的改善成像奠定了基础。本文的基本目的是在地震散射波主能量理论基础上，探索能否利用散射波场主能量信息改善散射成像效果，这也是论文的价值所在。当地下散射体与背景介质满足不同的尺度关系时，产生不同机制类型的散射；系统分析了纵波入射到地质体时，形成前向散射和背向散射的图样，在一些假设和忽略一些因素的前提下，寻找到散射波主能量方向与地质体倾角的规律，而后依据主能量方向的权系数为一、其他方向的权系数按照散射衰减图样逐渐减小的原则进行加权成像，以突出主能量对成像的影响，编程实现了主能量权系数的计算和共散射点道集的形成过程。对理论模型数据及实际资料进行了处理，并将得到的结果与前人不加权成像的效果进行了比对，对比发现加权后提高了信噪比，有效压制了多次波和空间假频，散射波的同相轴更加趋于双曲线，突出了主能量信息，削弱非主能量信息；叠加剖面增强了地下地质体的连续性，改善了成像效果。该方法能有效处理低信噪比、不规则地震资料以及改善小尺度的地质体成像，尤其是浅层效果会更明显。最后总结了该方法的优势和缺陷，给出了本人对此方法的期望。更多还原

【Abstract】 Due to the enhancement of the degree of complexity and sophistication aboutthe solution of geological problems, the conventional reflection seismic explorationtechnology can’t be well applied in the exploration, include the piedmont fault zone、the basin margin fracture zone and the concealed metal ore, and it is difficult to obtainaccurate imaging effect; Therefore, the scattering wave seismic methods is proposedwith the complex exploration of the tectonic or lithology complex oil and gasexploration and the buried metal mine. It is a exploration method that is based on theseismic wave scattering theory, and uses more generalized scattering wave to describecomplex seismic wave field from variety of scale non-uniform geological. Thescattered wave imaging is a migration method that dependent on the seismicscattering wave theory, and belongs to pre-stack time migration, which provides aunique research idea for seismic imaging and velocity analysis.On the basis of previous work, I particularly understand the seismic scatteredwave field theory and find out the essential difference of between the scattered wavefield and the reflected wave field, have a clear about the kinematic characteristics ofthe scattered wave, that the traveltime-offset surface form scattered wave is a Choepspyramid; according to the principle of equivalent offset, forming the commonscattering point (CSP) gathers is the committed step of scattered wave imaging,which’s essence is the process of re-choose seismic trace information in accordancewith the size of the equivalent offset. this gather have greater offset coverage andhigher signal to noise ratio, and improve the accuracy of velocity analysis, which isthe foundation for the improvement in imaging.The basic purpose of this paper is that confirm the possibility of using the mainenergy information of scattered wave to improve the scattering imaging, based on thetheory of the main energy of seismic scattered wave, which is the value of the paper.The scatterers and the background media meet different scale relations, which resultin the different types of scattered mechanisms; When the compressional wave isincident on the geological body, I systematically analysis of the pattern of forward scattering and backscattering; in the premise of some assumptions and ignore somefactors, I find the discipline between the direction of scattered wave main energy andinclination of the geological, then do the weighted imaging according to theprinciples that the weight coefficient of the main energy direction is one, the weightedcoefficient of others direction gradually reduce in accordance with scatteringattenuation pattern,which highlight the affection of main energy to imaging, andachieve the calculation of main energy weight coefficient and forming the commonscattering gathers by programming. Processing the model data and filed data, what’sresult have a comparison with the effect of the previous unweighted imaging whichimprove the signal to noise ratio, and effectively suppress the multiple reflections andspatial aliasing, meanwhile the scattered wave events become more hyperbolic,highlighted the main energy information, and weaken the non-primary energyinformation. the stacked section enhance the continuity of the subsurface geologicbody, and improve the imaging effect. This method can effectively deal with lowsignal to noise ratio and irregular seismic data and can improve the imaging ofsmall-scale geological body, especially used in shallow data. Finally I summarize theadvantages and disadvantages of this method, and give my expectation of it.更多还原