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地震走时层析成像在油气田勘探和开发中的应用日益广泛。主要用于速度分析,为其它的地震资料处理方法提供精确的速度模型。逆垂直地震剖面RVSP(Reversed Vertical Seismic Profile)层析成像的关键是求解一个大型稀疏的线性方程组。求解方程组常用的迭代法,需要一个比较合理的初始猜测解,也即是初始速度模型。初始模型关系到反演的效率甚至成像的正确性。提出了一种自动求取层析成像初始速度模型的方法。该方法假定激发点到接收点间的射线是直射线,并利用最小路径法射线追踪得到初至走时来求取初始速度模型。通过建立数学模型验证了自动生成速度初始模型的可行性及可靠性,并对出现的问题进行探讨。
Earthquake Traveltime Tomography is increasingly used in the exploration and development of oil and gas fields. It is mainly used for velocity analysis to provide accurate velocity models for other seismic data processing methods. The key of inverse vertical seismic profile RVSP (Reversed Vertical Seismic Profile) tomography is to solve a large and sparse linear system of equations. The iterative method commonly used to solve equations requires a more reasonable initial guess solution, that is, the initial velocity model. The initial model is related to the efficiency of inversion and even the correctness of imaging. A method of automatically calculating the initial velocity model of tomography is proposed. The method assumes that the ray between the excitation point and the receiving point is a direct ray, and the initial velocity model is obtained by using the minimum-path ray ray tracing to obtain the first-strike velocity. The feasibility and reliability of the auto-generated initial velocity model are verified by establishing mathematical models, and the problems that arise are discussed.