【作者】 葛利华；

【导师】 姜弢；

【作者基本信息】 吉林大学 ， 仪器科学与技术， 2014， 博士

【摘要】 在噪声较强或者复杂地区进行地震勘探时，获得的原始地震记录信噪比经常无法满足勘探需求。研究表明，源端波束形成（beam-forming）技术，即相控震源系统（PAVS，Phased Array Vibrator System）通过激发定向地震波，明显改善地震记录信噪比，能够实现高分辨率及远距离的地下信息探测。但是， PAVS应用过程中，由于需要多台震源同时工作，搬运困难，工作量大；且由于震源间的非一致性，影响了PAVS的地震波定向精度，针对目标体的信噪比改善难以达到要求；同时，PAVS实验采集到的地震数据仅能提高某一方向的信号质量，对于地下情况未知的勘探区域，需要多次PAVS实验，工作效率低，以上因素制约了PAVS的应用和推广。为解决源端地震波束形成技术应用中存在的问题，本文提出接收端地震波束形成方法－基于接收阵列的时域地震波束形成方法（TSBBRA，Time-domainSeismic Beam-forming Based on Receiver Array），提取来自勘探目标的定向地震波数据，达到改善接收数据质量的目的。TSBBRA方法能提取任意方向的地震波，且当方向参数与来自勘探目标的反射波方向一致时，能有效改善反射地震数据质量，以较低的成本，达到等同于源端地震波束形成的应用效果。本文围绕理论、方法、数值模拟、观测系统优化设计和野外实验五个方面，展开对TSBBRA方法的研究，主要研究内容如下：首先，理论方面，阐述了TSBBRA工作原理。从波束形成原理入手，理论推导了TSBBRA方法的地震波场强分布及方向因子，分析了合成地震波束的主要特性：主波束方向、主波束宽度、波束零点位置及波束副瓣，分析了影响地震波束特性的主要参数：震源数量、震源间距、地震波速度和延时参数，并研究了各参数对形成地震波束的影响。另外，从理论角度对比了源端地震波束形成与TSBBRA方法的异同，并分析了TSBBRA方法的优势。然后，方法方面，结合TSBBRA工作原理，提出了适于TSBBRA的数值模拟方法：基于交错网格有限差分的时域地震波束形成数值模拟（NSTSBBSFD，Numerical Simulation of Time-domain Seismic Beam-forming Based on Staggered-mesh Finite Difference）。建立了单震源点的波动方程及其交错网格有限差分格式，给出了其他限定因素，包括稳定条件、边界条件及震源函数。给出了TSBBRA方法地震波场数据合成方程，其中包括TSBBRA方法波场快照数据合成方程，TSBBRA方法单炮记录数据合成方程及TSBBRA方法方向特性数据合成方程。其次，数值模拟方面，研究了TSBBRA方法在典型速度模型中的地震响应。根据TSBBRA数值模拟方法，通过对比单个可控源和TSBBRA方法在均匀介质模型中的模拟结果，说明了TSBBRA方法能够实现地震波束定向。针对复杂介质条件下TSBBRA方法波束形态复杂问题，研究了TSBBRA方法在典型介质模型的地震响应，包括水平层介质模型和倾斜模型、背斜模型和向斜模型、高速体模型和低速体模型。结果给出了几种速度模型下TSBBRA方法合成的波场快照、方向特性图及单炮记录，通过与单个可控源对比，理论上证明了TSBBRA在复杂介质条件下应用的有效性，及提高地震记录信噪比的可行性。提出角度域能量分布密度的概念，对地震波场进行角度域分解，分析了地震波场角度域能量分布，探明地震波在不同介质中传播时，反射波主波束的方向变化。另外，对比不同速度模型，根据数值模拟结果，阐述了TSBBRA方法针对不同类型勘探目标的应用方法。再次，观测系统优化设计方面，研究了倾斜矿区模型下，针对三个不同深度目标反射层位，实现了TSBBRA方法延时参数优化设计，论证了延时参数优化设计对进一步提高反射波数据质量的有效性。提出接收阵列内能量最强和能量分布密度均衡相结合的最优延时参数设计原则，并给出设计方法。利用单震源点数据合成具有方向性的TSBBRA数据，针对不同反射层位，分析了TSBBRA方法不同延时时间的反射波地震记录，通过绘制接收阵列内反射波能量随延时参数的变化曲线，获得适于不同目标层的最优延时参数。分析了TSBBRA方法最优延时参数时的地震波场，定量计算了针对不同反射层最优延时参数时的反射波主波束方向，并定量分析了延时参数优化设计对反射信号信噪比和分辨率的改善。最后，野外实验方面，利用自主研发的电磁驱动式可控震源进行了TSBBRA方法野外实验。结果给出了相同勘探区域的单个可控源、TSBBRA方法不同延时时间的单炮记录和叠加剖面，对比单个可控源发现，合适延时参数下，TSBBRA方法提高了地震记录质量，增加了勘探深度，从实践角度证明了TSBBRA方法的有效性。综上所述，论文从理论、数值模拟和实践角度说明了TSBBRA方法在提高地震记录信噪比的重要意义。回顾围绕基于接收阵列的地震波束形成方法所做的研究，取得的主要成果有如下几个方面：1）通过理论研究，论证了TSBBRA方法在接收端实现地震波束定向的可行性，研究了地震波主波束特性，分析了影响主波束特性的参数；2）阐述了TSBBRA工作方法，并给出TSBBRA方法波场快照、单炮记录及方向特性数据的合成方法；3）通过数值模拟，得到从简单到复杂6种典型速度模型TSBBRA方法地震数据，分析了不同模型地震数据的波场快照、单炮记录和方向特性数据，阐述了针对不同类型勘探目标的TSBBRA应用方法；4）根据观测系统设计需要，针对倾斜矿区模型不同目标层位，对TSBBRA方法延时参数进行优化设计，研究了延时参数优化后接收阵列内地震波能量分布，及地震波场的角度域能量分布，定量分析了TSBBRA方法对目标层位反射信号信噪比的改善；5）完成了TSBBRA方法的野外试验，从实践上证明了TSBBRA方法实现地震波束定向、提高地震记录信噪比的有效性。论文主要创新点：1）理论上证明了TSBBRA方法在接收端实现地震波束定向的可行性，分析了地震波束特性及影响因素；2）提出TSBBRA数值模拟方法，实现了模拟区域内方向性数据的形成，并阐述了针对不同类型勘探目标的TSBBRA应用方法；3）提出利用地震波场方向特性图，分析地震波在不同介质中传播的方向特性；4）提出了接收阵列内反射波能量最强与能量密度分布均衡相结合的选取原则，针对不同深度目标层位，进行了TSBBRA方法延时参数优化设计，并定量分析了延时参数优化设计对目标层反射信号信噪比的改善。更多还原

【Abstract】 When noise is strong or seismic exploration is used in the complex area, SNR ofthe obtained seismic data is usually unable to meet the demand. Research shows thatstimulate directional seismic waves by the phased source system (PAVS, Phased ArrayVibrator System) can significantly improve signal to noise ratio of seismic records,which can form directional seismic beam, was developed.However, PAVS application process has a new problem in recent years. Becauseof the need for multiple source simultaneously, it is difficulty in handling and highcost. Since the non-uniformity between the source affects the seismic directionalprecision of PAVS，SNR improvement is difficult to meet the requirements for targets;and it requires multiple PAVS experiments to explore the case of unknownunderground area for the low efficiency，because of the seismic experimental datacollected by PAVS only improving the signal quality in one direction Meanwhile.These factors restrict the PAVS application and promotion.In order to solve the problems that exist in earthquake beamforming technologyof the source, this paper presents the seismic beamforming method of receiver-Time-domain Seismic Beam-forming Based on Receiver Array（TSBBRA） to extractthe data from the beam directional seismic exploration targets and improve receptionObjective data quality. TSBBRA method can extract any direction of seismic waves,and when the parameters of direction are consistent with the reflected wave directionfrom exploration targets, it can effectively improve the quality of seismic data atlower cost to achieve the same application effect as the seismic source beamforming.This paper focuses on the theory, methods, numerical simulation, observationsystem optimization design and field experiments, and expands research contents forTSBBRA methods，the main research work are as follows:First, this paper expounds the working principle of TSBBRA. We derivedseismic wave field intensity distribution and the direction factor of TSBBRA methodtheoretically from the Forming principle of beam, and analyze the main characteristicsof synthetic seismic beams: the main beam direction, the main beam width, beam zeroposition and beam sidelobes；also analyze the main parameters affecting of theseismic beam characteristics: source number, source spacing, seismic wave velocityand delay parameters. And we do some research for the effects of various parameterson the formation of the earthquake beam， and propose the similarities anddifferences earthquake beamforming methods of seismic source and TSBBRA from atheoretical point, and analyze the strengths of TSBBRA methods.Then, methods, combined with TSBBRA theory we propose (NSTSBBSFD),Numerical Simulation of Time-domain Seismic Beam-forming Based onStaggered-mesh Finite difference), which is applied to numerical simulation ofTSBBRA. We establish the wave equation and staggered-mesh finite differencescheme of single source point, and give the other limited factors, including the stability conditions, boundary conditions and the source function. NSTSBBSFD givesTSBBRA seismic wave field data synthesis equation, including data synthesisequation of TSBBRA wave field synthesis snapshots, TSBBRA shot record datasynthesis equation and TSBBRA direction characteristic data synthesis equation.Secondly, we study the TSBBRA seismic response in a typical velocity model atnumerical simulation. According TSBBRA numerical simulation method, illustratethe TSBBRA method can achieve seismic beam orientation by comparing the singlecontrolled source and TSBBRA simulation results in a homogeneous medium models.For the complex problems of TSBBRA beam shape in complex media conditions, westudy TSBBRA seismic response in typical medium model, Including horizontallayer media model, tilt media models anticline,syncline media model,high-speedmodel and low-speed model. In several media model, we give TSBBRA synthesizedwave field snapshots,directional characteristics and shot record. By comparison with asingle controlled source, we demonstrate the effectiveness of TSBBRA conditions incomplex media, and that improve signal to noise ratio of seismic records isfeasibility. We propose the concept of angle domain energy density distribution，conducted a seismic wave field angle domain decomposition, analysis the angledomain energy distribution of seismic wave field, and measure changes of the mainbeam direction of the reflected wave in different media. In addition, compare ofdifferent velocity model, and based on the simulation results, we describe a methodTSBBRA application methods for different types of exploration targets.Again, in the observation system optimization design, Achieve optimizationdesign of TSBBRA delay parameter for three different bit depth of the target reflectorlayer in tilt mining model, and demonstrate the effectiveness of the delay parameteroptimization to further improve the quality of the reflected wave data. We proposethe optimal delay parameter design principles based on the strongest energy andenergy density in the receive array，and give the design method. Using single sourcedata Synthesis directivity TSBBRA data, We analyze the reflected wave seismogramsat different TSBBRA delay for different reflective layers，and obtain optimal delayparameter is applied to different target layers by plotting the receiving array reflectedwave energy(Curve Fitting). Analysis the seismic wave field at TSBBRA optimaldelay parameter, quantitatively calculate the main beam direction at optimal delayparameter for different reflective layer, and quantitatively analyze the delay parameteroptimization to improve the signal to noise ratio and resolution of reflected wave.Finally, we utilize self-development electromagnetic vibrator in filedexperiments with method of TSBBRA in the aspect of field experiments.The resultsshow that the stacked section of shot record in a signal controlled source and usingdifferent delay time with TABBRA method in the same exploration area. Compared itwith signal controlled source, we find that the TSBBRA method improves the qualityof seismic records, and increase the depth of exploration with appropriate delayparameters. From a practical point of view, we prove the effectiveness of TSBBRAmethod.Summary, papers from theory, numerical simulation and practical perspectiveillustrates the importance of TSBBRA method of improving SNR of seismic records. Review of that based on seismic studies around doing the receive array beamformingmethod has the following major achievements in several areas:1) Through theoretical research, we prove the feasibility of TSBBRA methodthat the receiving end to realize the seismic beam directed and study the seismic mianbeam characteristics and analyze the parameters that affect the characteristics of themain beam.2) We elaborate the working method of TSBBRA, and give a synthetic methodof that snapshot of the wave field TSBBRA method, single recording data anddirectional characteristics of a single shot.3) Through numerical simulation, we get6typical methods of seismic datawhich from simple to complex velocity models of TSBBRA. Analysis of the wavefield snapshot of different models of seismic data, shot records and directionalcharacteristics of the data.We elaborated the TSBBRA application methods fordifferent types of exploration.4) According the needs of the observation system design, we aim at tilt miningmodel for different target horizons, we optimize the design of methods for TSSBBRAdelay parameters.We study the the energy distribution of receiving array seismic afteroptimized delay parameters, and the angle domain of seismic wave field.We alsoquantily analysis of the TSBBRA ways to improve SNR of the reflected signal intarget horizon.5) Completed a field test using the method of TSBBRA, the method ofTSBBRA proves the effectiveness that the realization of the seism from thedirectional beam and improve the SNR of seismic records.The main innovtion of the paper:1) Theoretically prove the feasibility of TSBBRA method at receiving end torealize the orientation of seismic beam, and analysis of the seismic beamcharacteristics and influencing factors.2) We propose a method of numerical simulation, and realize the forming ofdirectional data in a simulation region.And elaborate the TSBBRA applicationmethods for different types of exploration.3) We propose that using the directional characteristics of seismic wave fielddiagram,and anlaysis the directional characteristics of seismic wave propagation indifferent media.4) We propose a selecting principle that using the combination of the strongestreflected wave energy density of receving array and the blance of energy density.Forthe target layers at different depths, we optimize the delay parameter of TSBBRAmethod. And we also quantily analysis of the TSBBRA ways to improve SNR ofthe reflected signal in target horizon.更多还原