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在地层物性参数完全未知的情况下，如何利用反射波信号提取速度参数，是反射波能否正确成像的前提。由于井间地震方法特殊的观测系统，给速度参数的求取带来很大的困难。为此，本文在分析了井间地震反射波叠加速度概念和误差规律的基础上，提出了近似叠加速度的概念。该速度的求取方法有两种：第一种是采用同地面地震常速扫描相似的方法拾取to—叠加速度对，这种方法简单、准确，但比较费时；另一种方法是用插值加相关的方法求取叠加速度谱。该速度谱同时考虑了速度、深度、地层倾角三个因素的影响，对于平层和单斜层都能较好地确定t0—叠加速度对。本文讨论了井间地震反射波成像的方法原理及存在的问题，提出了反射波绕射成像方法，即利用上面所述的方法求取的to—叠加速度对，对输入的共炮点道集（CSG）或共接收点道集（CRG）的每一条记录做水平动校和垂直动校，把数据从Ω（Zs，Zg，t）域映射到（x，to）域，形成to叠加剖面。该剖面既能反映排列之间地层的形态，也能反映排列之上和之下地层的变化情况。
How to use the reflected wave signal to extract the velocity parameter is a prerequisite for whether the reflected wave can be correctly imaged when the physical parameters of the formation are completely unknown. Due to the special observing system of crosswell seismic method, it is very difficult to get the speed parameters. Therefore, based on the analysis of the concept and error of superimposed speed of cross-well seismic reflection wave, this paper proposes the concept of approximate stacking velocity. There are two ways to get the velocity: the first method is to pick up the stacking velocity pair by the method similar to the ground-based seismic velocity scanning. This method is simple and accurate, but it is time-consuming. The other method uses interpolation The related method finds the superposition velocity spectrum. The velocity spectrum considers the influence of three factors of velocity, depth and dip angle simultaneously, and the t0-stacking velocity pair can be well determined for both flat and monoclinic layers. This paper discusses the principle and existing problems of cross-well seismic reflection imaging, and proposes a reflection diffraction imaging method, that is, using the above-mentioned method to calculate the to- (Zs, Zg, t) to the (x, to) domain for each record of the CSG or CRG to form a to-stack profile . The profile reflects both the formation morphology and the changes in the formation above and below the alignment.