【作者】 喻振华；

【导师】 汤井田；

【作者基本信息】 中南大学 ， 地球探测与信息技术， 2008， 博士

【摘要】 井间地震由于具有多波接收、高精度、高分辨率、能量传播距离短、接近探测目标、避开低速带等一系列优点,在工程中得到了越来越广泛的应用。但是由于井间地震波的多样性和复杂性,为了更有效了解不同波场分量在均匀半空间的分布情况,分析井间波场中的反射、透射、绕射、散射以及能量的衰减等运动学和动力学的各种细节特征,更好地指导地质解释,本论文开展了基于典型工程地质模型的井间地震波的交错网格正演模拟;并在作者多年从事水利水电工程地震层析成像技术研究和应用的基础上,总结了工程应用中的一些重要技术措施,可为工程井间地震层析成像技术的推广应用,提供了科学依据,具有指导意义。本论文就工程井间地震波正演和层析成像技术两大内容,开展了以下工作:(1)在水利水电工程勘察中进行井间地震层析成像时,不同于油气田的井间地震勘探,其井深度较小,大多在100米深度内,当震源、检波器接近地表或井中水位面顶部时,地表面和井中水位面的影响不可忽略。为此,作者在本文中,结合水利水电工程的特点,建立了包含地表和井水位面的井间地震模型,并对其进行了正演模拟,得到了模拟的井间地震记录和水平粒子分量波场快照。(2)作者系统地总结了前人的研究成果及当前主要的地震波场正演算法的基础上,推导了二、三维的一阶速度-应力弹性波方程及其任意阶时间和空间精度的交错网格差分格式。在正演计算过程中,为节约内存空间和模拟计算时间,作者采用了非规则的可变有限差分网格和变化的时间步长理论,在保证计算精度的前提下,较大地提高了计算速度。(3)详细地探讨了交错网格差分法正演计算时的稳定性条件,得出了偶阶精度差分的时间和空间采样步长须满足的稳定性条件;分析了地震波数值频散产生的原因,阐述了通量校正传输(FCT)和提高差分精度两种频散压制方法;归纳了几种经典吸收边界条件的分类方法及这些吸收边界条件的优缺点,着重介绍了完全匹配层(PML)吸收边界条件,并导出了二、三维各向同性介质一阶应力-速度弹性波方程的相应的PML边界条件的差分格式,为跨孔地震波场的差分法正演模拟及其相应的程序编制打下基础。(4)结合Visual C++可视化程序设计语言,编制了井间交错网格的差分法地震波正演程序,把该自制程序应用于典型工程地质模型的正演计算中,得到了相应模型的波场快照和地震记录,记录中可以清晰观测到初至波、反射波、透射波及多次波的运动学和动力学特征。通过分析这些正演记录和波场快照,可更深刻地理解地震波场的传播规律,可加深对井间地震波场快照的认识,提高井间地震资料处理的解释精度。此外,对不同力源(水平方向单力源与水平方向力偶源)在快、慢地层产生的地震波,进行了全波场正演模拟,得到了压力、水平应力、水平粒子速度、垂直粒子速度的地震记录及波场快照,通过这些跨孔地震全波场的模拟,可全面把握不同场源、不同粒子速度的特征。(5)详细分析了走时(速度)层析成像技术的原理,总结了不同层析成像射线追踪技术的优缺点,并应用ART算法和SIRT通过对数字化模型分别进行重构,比较了两种算法的优劣。在此基础上编制了层析成像正反演处理系统软件,通过对四侧和两侧观测系统下的正方形缺陷模型和十字裂隙模型进行正演模拟和反演成像,深入地研究了观测系统对成像精度的影响。综合利用地质地球物理资料、速度测井、孔内摄像和地震记录,提出了建立初始速度模型和反演边界约束条件的综合方法,耿得了更准确和清晰的反演成像效果。然后,深入探讨了地震波吸收层析成像的机理,得知地震吸收层析成像方法,它可为地震波速层析成像提供有益补充。针对这两种层析成像技术的优缺点,提出了利用多参数(波速、吸收系数)综合地震层析成像的想法,使波速层析成像与吸收层析成像两者能相互印证、互为补充。作者把它们应用于工程实践中,有效地提高地震层析成像技术在工程应用中的解释精度,为地质解释与工程诊断提供更充分的依据。更多还原

【Abstract】 Cross-hole seismic has been applied in project extensively because of many advantages, such as multi-wave receiving, high accuracy, high resolution, short of energy propagation length, approach detecting object, avoiding low speed zones. But because of the complexity and diversity of cross-hole seismic wave, for understanding the distributing instance of different wave field component in homogeneous half space effectively, analysis diversified detailed characteristics of kinematics and dynamics of reflection, transmission, diffraction, scattering and power attenuation in cross-hole seismic, and for better geological explanations, this text develops the forward simulation based on the cross-hole seismic wave equation and the seismic tomography technology. Based on the long time research and application of seismic tomography technology in water resources and hydropower project, the author sums up some important technology measures in project application, which could provide scientific basis and guiding meaning for the development and application of tomography technology of project cross-hole seismic. For the forward simulation and tomography technology of project cross-hole seismic wave, this text develops the below works:(1)When doing the cross-hole seismic tomography in water resources and hydropower project, the depth of the hole is small, and most of them are less than 100 meters. when the seismic source, wave detector are close to the ground or the top of water level surface in the hole, the influence of ground and the water level surface could not be ignored. So, in this text, combining with the characteristic of water resources and hydropower project, the author establishes cross-hole seismic model including ground and water level surface in the hole, does the forward simulation to it, calculate and completely analysis the propagation rule and characteristic of wave field in different field source and different particle velocity.(2)Based on systematically summing up the previous author’s research and the mainly seismic wave field forward calculation method, the author derives first-order coupled elastic equations of 2D and 3D particle velocity and stress and the any order accurate time and space formulation of staggered-grid, finite-difference scheme. During the forward simulation calculation, the author takes irregular variable finite grids and variable time step theory. This would improve the calculation speed while guarantee the accuracy.(3)The author discusses detail the stability condition of staggered-grid, finite-difference method, and gets the stability condition which the time and space sampling step of high order accuracy difference must be satisfied. Analysis the reason of seismic wave numerical dispersion, and discusses the two dispersion compacting methods which are FCT and improving finite-difference accuracy. Conclude the classify method of some classical absorbing boundary condition and the advantages and disadvantages of them, then mainly introduces the basic theory used in forward simulation of PML absorbing boundary condition, and derives 2D or 3D PML absorbing boundary condition of first-order coupled elastic equations of particle velocity and stress in isotropic media. This could set the foundation for the cross-hole seismic wave field and the according program compiling.(4)Combining with Visual C++ visual program design language, compiles difference seismic wave forward program of cross-hole staggered-grid. Then apply this program into the forward simulation calculation of typical project geological models, and get the wave field snapshot and seismic record of the according model. In these results, it could clearly observe the kinematics and dynamics characteristics of primary wave, reflection wave, transmission wave and multiple wave of reflection. By analysis these forward record and wave field snapshot, it could understand the propagation regulation of seismic wave field more profundity, improve the comprehension to cross-hole seismic wave field snapshot and provide the technology support to the inversion interpretation. Moreover, do the whole wave field forward simulation to the seismic wave produced in quick, slow formation of different force source (level direction single force source and level direction double force source). It could get the seismic record and wave field snapshot of pressure, level stress, level particle velocity and vertical particle velocity. By the whole wave field simulation of this cross-hole seismic, it could grasp the characteristic of different field source and particle velocity completely.(5)analysis in detail the theory of travel-time tomography, sum up the advantages and disadvantages of different tomography ray tracing technology, and compare the advantages and disadvantages of ART and SIRT by applying them to rebuilding the numerical model separately. Based on this, the author compiles the inversion tomography process systematic software. By the forward simulation and inverse imaging of square defect model and cross fracture model in four sides and two sides observing system, it could research the influence of observing system to the imaging accuracy deeply. Comprehensively utilizing the geologic geophysical data, velocity logging, hole imaginary and seismic record, put forward the comprehensive method of setting up the initial velocity model, and gets the more accuracy and clearly inversion imaging effect.Then, deeply discuss the mechanism of seismic wave absorbing tomography; get the seismic absorbing tomography method, which could provide the useful supplement for the seismic wave absorbing tomography. According to the advantages and disadvantages of these two tomography technology method, the author puts forward utilizing multi-parameter to integrate the seismic tomography, which could make the wave velocity tomography and absorption tomography to makeup and confirm each other. The author applies these to project practice, which could improve the interpretations accuracy of seismic tomography technology in project, and provide more abundant basis to geological interpretations and project diagnose.更多还原