Ellipse Development Velocity Analysis And Application

The improvement of the seismic velocity's efficiency and precision is the key technique of seismic data processing.Ellipse development velocity analysis is based on ellipse development theory.This method dosent require the horizontal layer hypothesis.It can show the real dip information of the layer.Through it,we can get the correct RMS velocity.But in real data processing,we use all CSP gathers' information and this will reduce the efficiency of velocity analysis..It cannot fulfill the requirement of 3D real data processing.Accordingly,we carried out a study to overcome the low efficiency and precision problems.According to improve the velocity analysis efficiency,based on CSP gathers,we carried out a method with angle constrain.In this paper,we derived the equation between layer dip and the emergence point.Then established a flow of CSP ellipse development velocity analysis with angle constrain: First of all,considered the geological characteristics and offset aperture,we can get the maximum constrain angle.Then we calculate the range of the emergence point with the angle.Secondly,choose the range of the scanning velocity,calculate the zero offset section of every scanning velocity based on CSP gathers.Thirdly,arrange the constant velocity zero-offset sections and extract the RMS velocity spectrums.Finally,pick the final RMS velocity.To solvethe problem of the 3D real data velocity analysis' s presicion,we learn from ProMAX and Omega,choose a scanning range from 90%-110% for the picked RMS velocities.Then we can get the different stack segments of the same common normal emergence point and find the best stack segments to pick the RMS velocity in the way of human-computer interaction.In this way we developed the 3D ellipse development velocity analysis method based on common normal emergence point gathers.The flow is as follow: Firstly,choose the bin of the emergence point and then extract the common normal emergence point gathers.Secondly,expand the data into zero offset section with 3D ellipse development equation.Thirdly,pick the initial RMS velocity,then calculate the stack segments with the velocity range to get different stack segment groups of different velocities.Finally,find the best stack segments and pick the RMS velocity to get the high precision velocity.With the methods we carried out,we conducted model test and real data test.Their results show some conclusions: Ellipse development velocity analysis with angle constrain is effective in improving the velocity efficiency without reducing the precision.By observing the stack segments' effect of different velocities,we can pick the better RMS velocities,improve the precision of RMS velocity.