起伏地表地震波旅行时混合网格线性插值射线追踪

发布时间：2018-06-23 08:52

本文选题：射线追踪 + 旅行时线性插值法　；参考：《长安大学》2017年硕士论文

【摘要】：简单地表条件下的地震勘探已不能满足人们日益增长的需求,因此需要向具有复杂地表条件的地区或更深的区域进行,同时为了进一步开发我国西部地区油气藏,那么研究地震波在起伏地表地质模型中的传播规律就显得尤为重要。然而,在起伏地表地区利用地震勘探工作进行油气藏的开发和利用会面临各种各样复杂难以处理的问题,例如:地震数据采集困难、采集到的地震数据质量差不能用于研究、散射干扰严重、成像效果不好甚至不成像等。因此,本文在前人研究的LTI的基础上,研究地震波在起伏地表地下介质中的传播情况。为了提高起伏地表和复杂构造条件下LTI法对地表和速度界面的处理能力以及地震波旅行时的计算精度和效率。本文对完全矩形网格剖分的LTI方法进行了改进,提出用矩形网和不规则四边形网相结合的方法离散速度模型,即采用不规则四边形网剖分起伏地表和起伏界面附近的速度模型,而速度模型的其他部分则采用矩形网剖分,分别对矩形网和不规则四边形网采用适用于矩形网和适用于不规则四边形网的局部旅行时计算公式。通过全矩形网格剖分模型LTI法和混合网格剖分模型LTI法对同一均匀速度模型进行模型试算及误差分析,其结果表明,本文提出的网格剖分方法计算效率和计算精度更高;通过使用混合网格LTI法追踪Marmousi模型中地震波的传播情况,由获得的地震波的射线路径说明此方法正确可靠。本文将分区多步思想应用于起伏地表多类波传播路径的LTI射线追踪中,用此方法计算多波的旅行时同时追踪其射线路径。通过模拟起伏地表层状模型中的多次反射波和多次透射反射转换波并进行误差分析,验证了分区多步LTI法在追踪多类地震波时具有误差收敛、数值稳定等特点;同时模拟了人为划定剧烈起伏地表的Marmousi模型中的一次反射波和多次反射波,从获得的多次波的射线路径和波前扩展过程图可以看出起伏地表分区多步LTI法具有准确可靠的特点。
[Abstract]:Seismic exploration under simple surface conditions can no longer meet the increasing needs of people, so it is necessary to carry out seismic exploration in areas with complex surface conditions or deeper areas, and in order to further develop oil and gas reservoirs in the western part of China. So it is very important to study the propagation law of seismic wave in undulating surface geological model. However, the exploitation and utilization of oil and gas reservoirs by seismic exploration in undulating surface areas will face a variety of complex and difficult problems, such as the difficulty of seismic data acquisition, the poor quality of collected seismic data can not be used for research, The scattering interference is serious, the imaging effect is not good or even does not appear. Therefore, on the basis of LTI, the propagation of seismic waves in undulating surface and underground media is studied in this paper. In order to improve the processing ability of the LTI method to the surface and the velocity interface under the undulating surface and complex tectonic conditions, the calculation accuracy and efficiency of the seismic wave travel time are improved. In this paper, the LTI method of complete rectangular mesh generation is improved, and a discrete velocity model is proposed by combining rectangular mesh with irregular quadrilateral mesh, that is, the irregular quadrilateral mesh is used to divide the velocity model near the undulating surface and the undulating interface. The other parts of the velocity model are divided into rectangular mesh and irregular quadrilateral network respectively. The local travel time formulas suitable for rectangular network and irregular quadrilateral network are used respectively. By using LTI method and LTI method, the model of uniform velocity is calculated and the error is analyzed. The results show that the mesh generation method proposed in this paper is more efficient and accurate. The propagation of seismic waves in the Marmousi model is tracked by using the mixed grid LTI method. The ray paths of the obtained seismic waves show that this method is correct and reliable. In this paper, the idea of partition multistep is applied to the LTI ray tracing of multi-wave propagation paths on undulating surface. The method is used to calculate the travel time of multi-waves and track their ray paths simultaneously. By simulating and analyzing the multi-reflection and multi-transmission converted waves in the layered model of undulating surface, it is verified that the multi-step LTI method has the characteristics of error convergence and numerical stability in tracking multi-type seismic waves. At the same time, the primary and multiple reflection waves in the Marmousi model are simulated. From the ray paths and wavefront propagation process of the multiple waves obtained, it can be seen that the multistep LTI method has the characteristics of accuracy and reliability.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631.4

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