VSP数据成像方法研究

发布时间：2018-03-29 15:54

本文选题：VSP　切入点：数值模拟　出处：《东北石油大学》2015年硕士论文

【摘要】：为了满足如今油气勘探和开发对高精度处理复杂地下构造的迫切需求,VSP技术以其高信噪比、高分辨率,能够识别井旁小断层、微裂隙等精细构造的优势,正在成为目前地震勘探中解决精细成像地下构造和精细描述油气储层等问题的一项有力技术。随着地震设备性能的逐步提升,VSP数据的采集也越来越完善,因此有效的VSP数据成像方法也逐渐成为地震资料处理中的一个研究热点。本文简述了VSP观测系统及其波场特征,在VSP数据的数值模拟、波场分离以及逆时偏移方面进行了研究探索。本文采用有限差分法数值模拟VSP数据,利用泰勒级数展开式推导了波动方程的时间二阶、空间高阶有限差分格式,并讨论了正演模拟的稳定性条件和震源函数。详细分析了完全匹配层吸收边界条件对人工边界产生的反射干扰进行吸收和衰减的原理及效果。针对有限差分法数值模拟中的频散问题,应用通量校正传输法对其做有效压制。VSP资料包含丰富的波场信息,上下行波的能量差异为处理工作带来了难度。通过分析传统波场分离方法的缺点和局限性,对f-k滤波法和中值滤波法分别进行优化。优化f-k滤波法解决了传统方法输出波场中的Reiber混合问题,优化中值滤波法突破了传统方法滤波方向和滤波窗长单一的局限,提高了波场分离精度。叠前逆时偏移基于双程波动方程,被认为是目前精度最高的地震资料偏移算法。本文详细介绍了逆时偏移的计算过程,针对边界和存储问题,在应用PML边界条件的基础上提出优化存储方式,实现了在不引入随机噪音的同时大大节约存储的逆时偏移算法,保证了偏移剖面的精度。关于逆时偏移中成像条件的应用,本文分析和比较了互相关成像条件、归一化成像条件和上下行波振幅比成像条件三种方法的原理和应用。对逆时偏移结果中的低频噪音干扰,采用拉普拉斯算子噪音压制法进行处理,提高成像精度。综合分析表明,高精度的逆时偏移方法可有效成像VSP地震数据,对精细刻画井旁小断层、大倾角、井旁局部构造具有一定优势,作为一项地震勘探新技术具有深远的研究意义和广阔的应用前景。
[Abstract]:In order to meet the urgent need of oil and gas exploration and development to deal with complex underground structures with high precision, VSP technology has the advantages of high signal-to-noise ratio (SNR), high resolution, and the ability to identify fine structures such as small faults and micro-fractures near wells. It is becoming a powerful technique in seismic exploration to solve the problems of fine imaging underground structure and fine description of oil and gas reservoir. With the gradual improvement of seismic equipment performance, the acquisition of VSP data is becoming more and more perfect. Therefore, the effective imaging method of VSP data has gradually become a research hotspot in seismic data processing. In this paper, the VSP observation system and its wave field characteristics are briefly described, and the numerical simulation of VSP data is presented. The wave field separation and inverse time migration are studied. In this paper, the finite difference method is used to simulate the VSP data, and the Taylor series expansion is used to derive the second order and high order finite difference schemes of the wave equation. The stability condition and source function of forward modeling are discussed. The principle and effect of absorbing and attenuating the reflection interference caused by artificial boundary by perfectly matched layer absorbing boundary condition are analyzed in detail. The dispersion problem in value simulation, The effective suppression of VSP data by flux correction transmission method contains abundant wave field information, and the energy difference between up-and-down waves brings difficulties to the processing work. This paper analyzes the shortcomings and limitations of traditional wave field separation methods. The f-k filtering method and the median filtering method are optimized respectively. The optimized f-k filtering method solves the Reiber mixing problem in the output wave field of the traditional method, and the optimized median filtering method breaks through the limitation of the traditional filtering direction and the single window length of the filter. The accuracy of wave field separation is improved. Pre-stack inverse time migration is based on two-way wave equation and is considered to be the most accurate migration algorithm for seismic data at present. In this paper, the calculation process of inverse time migration is introduced in detail, aiming at boundary and storage problems. Based on the application of PML boundary condition, an optimized storage method is proposed to realize the inverse time migration algorithm without introducing random noise, which can ensure the accuracy of migration profile. The application of imaging conditions in inverse time migration is discussed. This paper analyzes and compares the principle and application of three imaging methods: cross correlation imaging condition, normalized imaging condition and up / down wave amplitude ratio imaging condition. The Laplace operator noise suppression method is used to improve the imaging accuracy. The comprehensive analysis shows that the high precision inverse time migration method can effectively image VSP seismic data, and can accurately depict small faults near wells with large dip angle. As a new seismic exploration technique, the local structure near the well has some advantages, which has profound research significance and broad application prospect.
【学位授予单位】：东北石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.4;P618.13

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