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基于应用网格环境的复杂地表波动方程基准面静校正研究
Research of Wave Equation Datum Static Correction for Complex Topography Based on Grid
【作者】 刘素芹；
【导师】 仝兆岐；
【作者基本信息】 中国石油大学 ， 地质资源与地质工程， 2008， 博士
【摘要】 静校正技术一直是复杂地表区勘探的“瓶颈”,目前生产中广泛使用的静校正方法都基于地表一致性假设,复杂地表区往往不满足这种假设,波动方程基准面静校正被公认为是复杂地表区最好的静校正方法之一。本论文对波动方程基准面静校正进行了深入的研究,包括波动方程基准面静校正的流程、初至波拾取及近地表模型的建立、波场延拓算法等。设计了更合理的实现流程,建立了较准确的近地表速度模型,提出了高精度的波场延拓算法,使得波动方程基准面静校正适应于地表起伏剧烈、近地表速度纵横向变化剧烈的复杂地表区。在对波动方程基准面静校正原理深入分析的基础上,设计了一套波动方程基准面静校正流程。实现流程主要包括9个步骤:①利用自动和人工相结合的方式进行初至拾取;②利用初至旅行时层析成像技术,获取近地表速度模型;③把炮集记录分为共炮点道集和共检波点道集;④在共炮点道集上,利用近地表速度模型,将所有检波点从地表向下延拓到高速层顶界面;⑤采用替换速度,将检波点波场从高速层顶界面向上延拓到水平基准面;⑥将延拓后的数据重排,生成共检波点道集;⑦在共检波点道集上,利用近地表速度模型,将所有炮点向下延拓到高速层顶界面;⑧采用替换速度,将炮点从高速层顶界面向上延拓到水平基准面;⑨将延拓后的数据重排,生成共炮点道集。从波动方程基准面静校正的实现流程可以看出,波动方程基准面静校正需要准确的地表结构和精确的延拓方法。本论文采用自动拾取和人工修正相结合的方式进行初至拾取,利用初至旅行时层析成像技术重建地表介质速度分布,对层析成像模型测试的结果证明,初至旅行时层析反演方法能获得较合理的近地表速度模型。波动方程波场延拓方法主要有Kirchhoff积分法、有限差分法和频率-波数域法,Kirchhoff积分法和有限差分法是一种近似解,波动方程在频率-波数域变换不会带来波的畸变,可以得到精确解。频率-波数域内的相移法和相移插值法都不能适应速度横向变化剧烈的地质条件,为了解决这一问题,本论文提出了“相移-时移法”,通过修改Stolt公式,使得波动方程基准面静校正不受校正量的限制,从而能适应地表起伏剧烈、近地表速度纵横向变化剧烈的地质条件。为了检验“相移-时移法”在频率-波数域进行波动方程基准面静校正的有效性,对建立的理论模型进行了试算,并对某复杂地表区的实际地震资料进行了处理。实验结果证明,所用的方法和建立的模型是正确有效的。用“相移-时移法”在频率-波数域进行波动方程基准面静校正消除了起伏地表和复杂地表结构对数据的影响,同时,还消除了由于地表起伏对地下构造形态产生的畸变,为后续处理的速度分析和同相叠加奠定了良好的基础。由于波动方程基准面静校正计算量巨大,要想投入工业化应用,需要在高性能计算环境下进行。在对高性能计算深入研究的基础上,本论文建立了一个适合地震资料处理的松耦合微机计算集群和一个石油应用网格,对建立的集群做了性能测试,并把波动方程基准面静校正程序移植到石油应用网格环境中。
【Abstract】 As we all know, static correction is the bottleneck in complex near-surface structure area all the time. The static correction methods broadly used in practice are all base on the Surface Consistency Hypothesis. But complex topography can’t accord with the Hypothesis. So wave equation datum static correction is considered one of the best static correction method .In this paper, wave equation datum static correction is researched deeply, including implement flow, establishing near-surface velocity model and wavefield continuation. A reasonable implement flow is designed. An accurate velocity model is established. A high precision arithmetic of wavefield continuation is put forward. These makes wave equation datum static correction suitable for more complex topography, including rugged topography and velocity varying severely.Through deep analysis on the principle of wave equation datum static correction, a set of implement flow is designed. The flow includes nine steps:①Picking up refraction first break;②Obtaining near-surface structure by first break tomographic mothod;③Dividing seismic data into CSP gather and CRP gather ;④In CSP gather, continuating all receive points to the top of high velocity layer;⑤Continuating receive points to datum plane;⑥Resorting these data into CRP gather;⑦In CRP gather, continuating all shot points to the top of high velocity layer;⑧Continuating shot points to datum plane;⑥Resorting these data into CSP gather.The implement flow shows that wave equation datum static correction needs accurate near-surface structure and exact wavefield continuating arithmetic.First break can be picked through combinative method of automation and manual. Near-surface velocity model can be established through travel time inversion by shortest path ray tracing. The test result indicates that this method is correct and effective. Wave equation can be continuated by Kirchhoff approximation, finite-difference and method based on frequency-wavenumber field. Kirchhoff approximation and finite-difference aren’t exact arithmetic. Exact result can be obtained in frequency-wavenumber field. Phase shift and phase shift with interpolating can’t be used in most complex near-surface area, such as horizontal velocity varying acutely. In order to solve this problem,“phase-shift time-shift”arithmetic is proposed. The arithmetic modifies Stolt formula. Then, wave equation datum static correction can have arbitrary size correction.Many tests about the model and arithmetic are done, and practical seismic data of complex topography is processed. The result indicates that this implement project is correct. It can eliminate the bad influence of rugged topography and complex near-surface structure. Thus, it can establish a good foundation for velocity analysis and in-phase stacking.Wave equation datum static correction needs large computing resource. If the technology is applied into seismic data industry process, high computing environment is necessary. A computing cluster and a petroleum grid are built. Test result indicates this cluster has high efficiency. The program of wave equation datum static correction is migrated in grid.