井间层析成像分辨率影响因素研究及应用

发布时间：2018-02-24 22:24

本文关键词： 井间层析成像分辨率走时成像振幅成像　出处：《中国矿业大学》2017年硕士论文　论文类型：学位论文

【摘要】：浅地表地质问题,主要包括溶洞、废弃采空区和断层等地质异常区,严重威胁着工程建设和人民生命财产的安全,其后期的治理工作尤为重要。地球物理勘探主要应用电法勘探和地震勘探的方法探测异常位置、范围和埋深,可为后期的治理工作提供参考依据。常规地震勘探基于连续均匀的、光滑的反射界面,横向上具有不均匀性,使得异常区不能得到全面直观的体现。层析成像技术,利用地震波的走时和振幅等信息进行反演成像,进而得到探测范围内波速分布的规律图像,它的分辨率高于常规的地震勘探,同时具有可靠性好、图像直观和信息量大的特点。层析成像方法包括井地层析成像、井间层析成像和联合层析成像,井间层析成像将激发和接收全部在井中完成,比井地层析成像具有更好的信噪比和分辨率,在探测浅地表地质问题具有明显的优势,是本文的主要研究内容。本文首先对井间层析成像的数学理论基础以及正反演算法进行概述,基于最短旅行时正演算法和SIRT反演算法,通过正演数值模拟,分析了有、无地质异常体情况下的波场特征,其中包括井间直达波旅行时和直达波振幅特征,阐述了走时层析成像和振幅衰减成像的基础。随后,通过建立正演模型,着重从观测系统角度研究了影响层析成像分辨率的三个因素,包括观测角、射线密度和震源频率,并分别进行了走时层析成像和振幅衰减成像,得到了以下三点结论:(1)观测角越大,层析成像的结果越准确,分辨率越高,但是观测角增加到一定范围后,角度的增加对成像结果影响不大;(2)射线越密,穿过异常区的射线条数越多,层析成像的分辨率越高,但是过密的射线密度对成像效果提升很有限;(3)震源频率直接影响地震波的波场,频率越高,波长越小,走时层析成像的效果越好,但是对于振幅衰减成像而言,频率增加到一定范围后,对成像效果的提升有限。最后,本文将井间地震直达波走时层析成像方法应用于溶洞、断层走向的探测之中,经过现场验证,该方法取得了良好的探测效果。
[Abstract]:Geological problems on the shallow surface, including karst caves, abandoned goaf and fault and other geological anomalies, pose a serious threat to engineering construction and the safety of people's lives and properties. Geophysical exploration mainly uses the methods of electrical exploration and seismic exploration to detect the abnormal position, scope and depth. The conventional seismic exploration is based on the continuous uniform and smooth reflection interface, and the horizontal heterogeneity, which makes the abnormal area not fully and intuitively reflected. By using the information of travel time and amplitude of seismic wave, inversion imaging is carried out, and the regular image of velocity distribution in the range of detection is obtained. Its resolution is higher than that of conventional seismic exploration, and it has good reliability. The methods of tomography include well ground tomography, cross well tomography and combined tomography. Cross-well tomography will excite and receive all of them in the well. It has better signal-to-noise ratio and resolution than well-ground tomography, and has obvious advantages in detecting geological problems on shallow surface. It is the main research content of this paper. Firstly, the mathematical theory foundation and forward and inverse algorithms of cross-well tomography are summarized in this paper. Based on the shortest travel time forward algorithm and SIRT inversion algorithm, through forward numerical simulation, we analyze the existence of, The characteristics of wave field in the absence of geological anomalies, including the travel time and amplitude characteristics of direct wave between wells, the basis of travel time tomography and amplitude attenuation imaging are expounded. Three factors affecting the resolution of tomography, including the angle of observation, the density of ray and the source frequency, are studied from the viewpoint of observation system, and the traveling time tomography and amplitude attenuation imaging are carried out respectively. The three conclusions are as follows: the larger the observation angle is, the more accurate the tomography result is and the higher the resolution is. However, when the observation angle is increased to a certain range, the increase of angle has little effect on the imaging result. The higher the number of ray strips passing through the abnormal area, the higher the resolution of tomography, but the higher the frequency of the source directly affects the wave field of the seismic wave, the smaller the wavelength is, but the more dense the ray density is to the enhancement of the imaging effect, the more limited the source frequency is. The better the effect of traveling time tomography is, but for amplitude attenuation imaging, the improvement of imaging effect is limited when the frequency increases to a certain range. Finally, this paper applies the method of cross-well seismic direct wave traveling time tomography to the cave. In fault strike detection, the method has been proved to be effective in detecting fault strike.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631.4

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