The Ray Tracing Of Seismic Wave With The Hybrid Grid Travel-time Linear Interpolation In The Undulating Surface Model

Seismic exploration in simple surface conditions has been unable to meet the growing needs of people,so it is necessary to be carried out in the region with the more complex surface conditions or the deeper areas.At the same time,in order to further develop the oil and gas reservoirs in China's western region,it is very important to study the propagation law of seismic wave in the undulating surface geological model.However,We will face a variety of complex problem when using seismic exploration work to develop and use the oil and gas reservoirs in the undulating surface area.such as: data collection difficult,poor quality of data collected not to research,severe clutter,the imaging result is bad and even not imaging,etc.Therefore,based on the predecessors' research of linear travel-time interpolation ray tracing method(LTI),we are to research seismic wave travel-time ray tracing under the condition of undulating surface.In order to improve both the ability to deal with topography and velocity interfaces and the accuracy to calculate travel-time under complex structures with topographical conditions,the author presents a new method of LTI based on hybrid meshes,that consisting of rectangle meshes and irregular quadrilateral meshes instead of which on single rectangle meshes.That is,using irregular quadrilateral meshes near the undulating surface and interface,and using rectangular meshes away from the undulating surface and interface.The author,respectively,gives the new formulas to calculate the local travel-time which is suitable for rectangular meshes and irregular quadrilateral meshes.The results of the model calculation and error analysis to the same uniform velocity model using LTI method with rectangular grid and LTI method with hybrid grid shows that the hybrid grid method is more efficient and accurate in this paper.By using the LTI method with hybrid grid to trace the propagation of seismic waves in the Marmousi model,The ray path of the obtained seismic waves indicates that the method is correct and reliable.In this paper,We use the multi-stage LTI method to track the multiple waves in the undulating surface geological model to calculate the time of multiple waves while tracking its ray path.By simulating the multiple reflections and multiple transmission waves in the simple layered model of undulating surface and performing the error analysis,It is proved that the multi-stage LTI method has the characteristics of error convergence and numerical stability.At the same time,we simulate the single reflection waves and multiple reflection waves in the classical Marmousi model with undulating surface,it is obtained that the multi-stage LTI method has the features of accuracy and reliability from the ray path and wavefront expansion process of the multiple waves.